Technological samples of metals and alloys. Mechanical properties of metal and technological testing of pipes

Technological tests are used to assess the ability of a material to withstand a certain deformation under conditions as close as possible to production conditions. Such assessments are qualitative in nature. They are necessary to determine the suitability of a material for the manufacture of products using technology that involves significant and complex plastic deformation.

To determine the ability of sheet material up to 2 mm thick to withstand cold stamping (drawing) operations, the spherical dimple drawing test method is used using special punches having a spherical surface (GOST 10510). The test diagram is shown in Fig. 9.3.

Rice. 9.3. Schematic of the Erichsen spherical dimple drawing test

During the test, the pulling force is recorded. The design of the device provides for automatic termination of the drawing process at the moment when the force begins to decrease (the first cracks appear in the material). A measure of the ability of a material to draw is the depth of the drawn hole.

A sheet or tape with a thickness of less than 4 mm is tested for bending (GOST 13813). The test is carried out using the device shown in Fig. 9.4.

Rice. 9.4. Bend test scheme

1 – lever; 2 – replaceable leash; 3 – sample; 4 – rollers; 5 – sponges; 6 - vice

The sample is first bent to the left or to the right by 90 0, and then each time by 180 0 in the opposite direction. The criterion for completing the test is the destruction of the sample or the achievement of a specified number of kinks without destruction.

Wire made of non-ferrous and ferrous metals is tested for torsion (GOST 1545) with determination of the number of full turns before failure of samples, the length of which is usually (– wire diameter). The bend test (GOST 1579) is also used according to a scheme similar to testing sheet material. A winding test is carried out (GOST 10447). The wire is wound in tightly fitting turns onto a cylindrical rod of a certain diameter (Fig. 9.5).

Fig.9.5. Wire winding test

The number of turns should be within 5...10. A sign that the sample has passed the test is the absence of delamination, peeling, cracks or tears in both the base material of the sample and its coating after winding.

For pipes with an outer diameter of no more than 114 mm, a bend test is used (GOST 3728). The test consists of smoothly bending a piece of pipe in any way at an angle of 90 0 (Fig. 9.6. a) so that its outer diameter in no place becomes less than 85% of the initial one. GOST sets the bend radius value R depending on pipe diameter D and wall thickness S. The sample is considered to have passed the test if, after bending, no violations of metal continuity are detected on it. Samples of welded pipes must withstand testing in any position of the seam.

The flange test (GOST 8693) is used to determine the ability of the pipe material to form a flange of a given diameter (Fig. 9.6.b). A sign that the sample has passed the test is the absence of cracks or tears after flanging. Flanging with preliminary distribution on a mandrel is allowed.

The expansion test (GOST 8694) reveals the ability of the pipe material to withstand deformation when expanding into a cone up to a certain diameter with a given cone angle (Fig. 9.6.c). If after distribution the sample has no cracks or tears, then it is considered to have passed the test.

For pipes, a flattening test to a certain size is provided (Fig. 9.6.d), and for welded pipes GOST 8685 provides for the position of the seam (Fig. 9.6.d), and a hydraulic pressure test.

To test wire or rods of round and square cross-section intended for the manufacture of bolts, nuts and other fasteners by the upsetting method, the upset test (GOST 8817) is used. The standard recommends a certain degree of deformation. The acceptance criterion is the absence of cracks, tears, or delaminations on the side surface of the sample.

Rice. 9.6. Pipe testing schemes:

a – on the bend; b – on board; c – for distribution; g, e – for flattening

For rod materials, the bend test is widely used: bend to a certain angle (Fig. 9.7.a), bend until the sides are parallel (Fig. 9.7.b), bend until the sides touch (Fig. 9.7.c).

Rice. 9.7. Bending test schemes:

a – bend to a certain angle; b – bend until the sides are parallel; c – until the sides touch

GOST 7564-97

Group B09

INTERSTATE STANDARD

RENTAL

General rules for sampling, blanks and specimens for mechanical and technological tests

Rolled products. General rules of sampling, rough specimens and test pieces selection for mechanical and technological testing

MKS 77.040
OKSTU 0908

Date of introduction 1999-01-01

Preface

1 DEVELOPED by the Russian Federation, Interstate Technical Committee for Standardization MTK 120 "Cast Iron, Steel, Rolled Products"

INTRODUCED by Gosstandart of Russia

2 ADOPTED by the Interstate Council for Standardization, Metrology and Certification (Minutes No. 12 of November 21, 1997)

The following voted for adoption:


State name	Name of the national standardization body
The Republic of Azerbaijan	Azgosstandart
Republic of Armenia	Armgosstandard
Republic of Belarus	State Standard of Belarus
Georgia	Gruzstandart
The Republic of Kazakhstan	Gosstandart of the Republic of Kazakhstan
Kyrgyz Republic	Kyrgyzstandard
The Republic of Moldova	Moldovastandard
Russian Federation	Gosstandart of Russia
The Republic of Tajikistan	Tajikgosstandart
Turkmenistan	Home State Inspectorate of Turkmenistan
The Republic of Uzbekistan	Uzgosstandart
	State Standard of Ukraine

3 The standard complies with the international standard ISO 377-1-89 "Sampling and preparation of samples and specimens from pressure-treated steel. Part 1: Samples and specimens for mechanical testing" regarding sampling and preparation of specimens for mechanical testing

4 By Decree of the State Committee of the Russian Federation for Standardization, Metrology and Certification dated April 13, 1998 N 118, the interstate standard GOST 7564-97 was put into effect directly as the state standard of the Russian Federation from January 1, 1999.

5 INSTEAD GOST 7564-73

6th EDITION (September 2009) with Amendment (IUS 3-2002)

1 AREA OF USE

This standard establishes general rules for the selection of samples, blanks and specimens for testing tensile, impact bending, upset, cold bending of long, shaped, sheet and wide rolled products.

2 REGULATORY REFERENCES

This standard uses references to the following standards:

GOST 1497-84 (ISO 6892-84) Metals. Tensile Test Methods

GOST 7268-82 Steel. Method for determining the susceptibility to mechanical aging by impact bending test

GOST 8817-82 Metals. Slump test method

GOST 9454-78 Metals. Impact bending test method at low, room and elevated temperatures

GOST 9651-84 (ISO 783-89) Metals. Tensile test methods at elevated temperatures

GOST 11701-84 Metals. Tensile testing methods for thin sheets and strips

GOST 14019-2003 (ISO 7438:1985) Metallic materials. Bend test method

3 TERMS AND DEFINITIONS

3.1Rental unit- a product selected from a batch for the purpose of cutting samples for the manufacture of test specimens.

3.2 Try- part of the product intended for the manufacture of sample blanks for testing.

In some cases, the breakdown may be the rental unit itself.

3.3 Blank- part of the sample, processed or unprocessed mechanically, subjected, if necessary, to heat treatment, intended for the manufacture of test samples.

3.4 Test samples- a part of a sample or workpiece of a certain size, processed or unprocessed mechanically and brought to the condition required for a specific test.

In some cases, the sample may be a sample or a blank.

3.5Control condition- a condition in which a sample, workpiece or test piece can be subjected to heat treatment and (or) mechanical treatment and differs from the delivery condition.

In such cases, the sample, blank or test piece is called a control sample, control blank or control sample.

3.6 Equivalent terms in Russian, English, French and German are given in Appendix A.

4 GENERAL REQUIREMENTS FOR THE SELECTION OF SAMPLES, PREPARATIONS AND SPECIMENS

4.1 Samples, blanks and test samples, selected in accordance with the requirements of Appendices B, C and D, must characterize the type of rolled product. Requirements for sampling, blanks and specimens can be specified in other regulatory documents for rental.

4.2 Identification of samples, blanks and specimens

Samples, blanks and test specimens must be marked. If during the manufacturing process of a sample, workpiece and (or) sample it is impossible to avoid the removal of markings, the marking is transferred before it is removed.

4.3 The number of samples and specimens taken for testing must be established in the regulatory document for rental.

4.4 When taking samples and workpieces, conditions must be provided to protect the samples from the effects of heating and work hardening.

Allowances from the cutting line to the edge of the finished sample must correspond to Table 1.

Table 1 - Allowances from the cutting line to the edge of the finished sample


Diameter (thickness) of rolled products, mm	Allowance, mm, for the method of cutting samples and blanks, not less
	fire or thermal effects	without thermal influence

		Rolled thickness

(Amendment).

5 SELECTION AND PREPARATION OF SAMPLES AND PREPARATIONS. SELECTION LOCATION AND ORIENTATION OF SAMPLES FOR MECHANICAL TESTS

5.1 Sampling location and sample size

The sample is taken in such a way that the location of the sample and the orientation of the test specimens taken from it in relation to the product comply with the requirements of the rental standard or, in the absence of one, the requirements of Annex B.

In case of disagreement between the manufacturer and the consumer, samples are taken from the end of the rental at the distance given in Appendix D, unless otherwise specified in the regulatory document for rental.

The sample size must be sufficient to obtain the samples required for the particular test.

If necessary, sufficient material should be available to carry out repeated tests.

5.2 Sampling location, dimensions and orientation of test specimens

The location of sampling (sampling option) and, if necessary, the dimensions of the samples, the orientation of the sample in the rolling direction (lengthwise and transversely) must be specified in the regulatory document for rolling.

In the absence of such requirements, use the directions specified in Appendix B.

Note - In order to reduce metal losses and taking into account established practice, the rolling standard, if acceptable from a technical point of view, may regulate the possibility of using transverse samples instead of longitudinal ones (for reforged samples) in order to control the specified values for longitudinal samples.

On the specimen for impact bending testing, the longitudinal axis of the notch should be perpendicular to the rolling direction.

5.3 Sampling and preparation

5.3.1 The rental regulation shall specify whether the test is intended to determine properties in the as-delivered condition (5.3.2) or in the control condition (5.3.3).

5.3.2 Test as delivered

Unless otherwise specified in the regulatory document for rental, the sample must be taken from rolled products that have undergone all stages of plastic and (or) heat treatment to which the rental must be subjected before delivery.

If the sample cannot remain attached to the rolled unit until the end of production (for example, sheets cut before annealing, samples for testing of which are taken from the scrap generated during cutting), the rolling regulations must specify the stage of sampling from the rolled unit. The processing modes to which the sample is then subjected must be similar to the processing modes of the rolled product itself. In particular, heat treatment should be carried out in the same modes in which rolled products are processed and, if possible, simultaneously.

Sampling should be carried out in such a way as not to change the characteristics of the part of the sample from which the samples are made.

If it is necessary to edit a sample to obtain high-quality samples from it, the edit should be in a cold state, unless otherwise specified. Straightening is not considered mechanical processing (5.3.3.2) if it does not cause strain hardening that can change the mechanical properties of the rolled product.

Note - After cold straightening of specimen blanks, heat treatment may be required. In this case, heat treatment modes should be determined by agreement between the manufacturer and the consumer. In exceptional cases, when editing causes a significant change in the shape of the sample, the method of sample preparation should be established by agreement between the manufacturer and the consumer.

The sample must not be subjected to any other mechanical or thermal treatment.

5.3.3 Control test

5.3.3.1 Sample

The sample must be taken from the product at the manufacturing stage, determined by the regulatory document for rental.

Sampling may be carried out by any method, provided that it does not involve changes in the metal.

If the sampling method entails changes in the metal, then there must be a sufficient amount of metal in the sample to eliminate this influence when making samples. Before any heat treatment, if necessary, straightening should be carried out in a hot or cold state.

5.3.3.2 The workpiece (sample), if necessary, is subjected to:

a) pressure treatment, in which the rental regulations must define the conditions of any pressure treatment (for example, forging, rolling) to which the sample must be subjected, and indicate, in particular, the initial and final dimensions of the sample;

b) preliminary turning before heat treatment.

If the sample must be reduced for heat treatment, the rolling standard shall specify the dimensions to which the sample must be reduced. If necessary, the rental standard should also stipulate the method of reducing the sample;

c) heat treatment in an environment with guaranteed temperature stability, measured by a device that has passed metrological certification.

The type of heat treatment must comply with the requirements of the regulatory document for rolled metal.

The workpiece should not be subjected to a specified heat treatment more than once, with the exception of tempering, which can be repeated within a specified temperature range. For any retest, a new workpiece must be selected.

For steel with a tensile strength of 1270 N/mm (130 kgf/mm) and more, samples made with an allowance for grinding are subjected to heat treatment.

5.4 Selection and preparation of samples for testing mechanical properties

5.4.1 Cutting and machining

Cutting samples should be done cold and with precautions taken to avoid surface hardening and overheating of the rolled product, which can change its mechanical properties.

Marks left by the tool after machining, which may affect the test results, must be removed by grinding (with a generous supply of coolant) or polishing, provided that the selected surface finishing method maintains the dimensions and shape of the sample within the tolerances regulated by the relevant test standard.

5.4.2 The shape, dimensions and permissible deviations in the dimensions of the samples must comply with GOST 1497, GOST 7268, GOST 9454, GOST 9651 and GOST 11701.

5.4.3 For tensile testing of long rolled products of round, square and hexagonal profiles, cylindrical samples are used.

5.4.4 For tensile testing of strip and sheet products with a thickness of up to 25 mm inclusive, flat samples are used, over 25 mm - cylindrical samples. Testing of rolled products with a thickness of 7-25 mm can be carried out on both flat and cylindrical samples. The type of sample is indicated in the quality document.

5.4.5 To test shaped rolled products with a thickness of up to 25 mm inclusive, flat samples are used with the surface layers of the rolled product retained on them, and with non-parallel sides of the flange - with the surface layers of the rolled stock retained on one side; when the thickness of the rolled product is more than 25 mm, it is allowed to process a flat sample to a thickness of 25 mm while maintaining the rolled surface on one side of the sample or to produce cylindrical samples.

Note - For profile flange thicknesses from 7 to 25 mm, the test can be carried out on both flat and cylindrical samples.

5.4.6 Rolled round, square and hexagonal profiles, for which the selection of blanks and samples is carried out according to option 1, with a diameter or square side of up to 25 mm, rolled strip with a thickness of up to 25 mm and a width of up to 50 mm, shaped profiles with a flange thickness of up to 4 mm can be tensile tested on non-machined specimens.

5.4.7 To test the impact bending of rolled products with a diameter of up to 16 mm inclusive, square with a square side of up to 10 mm inclusive, and strip and sheet rolled products with a thickness of up to 10 mm inclusive, samples measuring 5x10x55 mm are used, for rolled products with a diameter of more than 16 mm and a thickness of more than 10 mm - samples measuring 10x10x55 mm.

5.4.8 Specimens for impact bending tests from shaped rolled products are cut so that one of the side faces coincides with the surface of the rolled product. The axis of the cut must be perpendicular to the surface of the rolled product.

5.4.9 In the case of heat treatment of samples, the requirements must be the same as for workpieces (5.3.3.2, subparagraph c).

6 SAMPLING AND PREPARATION OF SAMPLES FOR SETTLEMENT TEST

6.1 Samples for slump tests are taken from either end of the rod or strip. For rolled products supplied in coils, the sample is taken at a distance of at least 1.5 m from the end when the coil weighs up to 250 kg and at a distance of at least 3.0 m when the coil weighs more than 250 kg.

6.2 Test conditions, the state of the surface of the samples and the procedure for assessing the results must comply with the requirements of GOST 8817.

7 SAMPLING AND PREPARATION OF SPECIMENS FOR COLD FLEXURAL TEST

7.1 Place of sample cutting in relation to the rolling direction and length of the rolled product - in accordance with Appendix B.

7.2 When taking samples and workpieces, conditions must be provided to protect the samples from the effects of heating and work hardening, as set out in 4.4 of this standard.

7.3 The minimum distance from the end of the product for sampling or samples for testing in case of disagreement is in accordance with Appendix D.

7.4 Sampling scheme for cold bending tests - in accordance with Appendix D.

7.5 Methods of sampling, types of samples and other requirements for cold bending testing must meet the requirements of GOST 14019.

APPENDIX A (for reference). EQUIVALENT TERMS DEFINED IN SECTION 3 IN RUSSIAN, ENGLISH, FRENCH AND GERMAN

APPENDIX A
(informative)

Table A.1 - Equivalent terms


Designation					Standard item
	Russian	English	French	German
	Rental unit		Product echantillon

	Blank	Rough specimen
	Test sample

Figure A.1

APPENDIX B (recommended). PLACE OF CUT-OUT OF SAMPLES, BLANKS AND SPECIMENS IN RELATION TO THE DIRECTION OF ROLLING AND LENGTH OF THE ROLLER

Table B.1 - Place of cutting samples, blanks and specimens


Type of rental	Position of the longitudinal axis of the sample relative to the rolling direction	Place for cutting samples, blanks and specimens to length
Varietal round, square, hexagonal and rectangular sections		From either end of a rod or coil. For rolling in coils, samples are taken at a distance of at least 1.5 m from the end when the coil weighs up to 250 kg and at a distance of at least 3.0 m when the coil weighs more than 250 kg
Shaped (channels, tees, corner, z-beams, I-beams, wide-flange beams, special interchangeable profile for support of mine workings - SVP)		From any end
Sheet, roll, broadband up to 600 mm wide, incl. after longitudinal dissolution
Sheet, roll, broadband with a width of 600 mm or more		From any end of sheet and wide rolled products. For rolled products at a distance of at least 1 m from the end of the roll
Note - For wide-band rolled products with a width of 600-1000 mm, by agreement between the manufacturer and the consumer, it is allowed to use longitudinal samples.

APPENDIX B (recommended). SCHEME FOR SELECTION OF BLANKS FROM SAMPLES TO DETERMINE THE MECHANICAL PROPERTIES OF ROLLED STEEL

B.1 Scheme for selecting blanks from samples to determine the mechanical properties of rolled products in the delivered state (option 1)

B.1.1 Selection of blanks from samples of long products

______________

Figure B.1 - Schemes for selecting blanks from samples from rolled products of round and polygonal sections

______________
* It is allowed to make selections until 01/01/2001.

Figure B.2 - Schemes for selecting blanks from samples from rolled square and rectangular sections

Beveled strip

Figure B.3 - Schemes for sampling blanks from strips with beveled edges

(Amendment).

B.1.2 Selection of blanks from samples from shaped rolled products*
_____________
* For unequal angles, the workpiece is cut from a larger flange.

Figure B.4 - Schemes for selecting blanks from samples from shaped rolled products

B.1.3 Sampling of rolled sheets and strips

Rolled width; and - sampling location

Figure B.5 - Sampling schemes for sheet and wide rolled products

Table B.1 - Position of the sample relative to the rolled surface


Type of test	Rolled thickness, mm	Position of the longitudinal axis of the sample in relation to the rolling direction at the rolled width, mm		Sample position relative to the surface, mm
		150<<600
Tensile at normal temperature

Control of yield strength at elevated rolling temperatures for products operating under pressure	From 3 to 10		Transversely, next to a tensile specimen at normal temperature


For impact bending	From 5 to 10
			Across or along in accordance with the standard or specifications for rental

Rolled thickness
Note - By agreement between the manufacturer and the consumer, it is allowed to use: - transverse samples during tensile testing of wide-band rolled products with a width of 400-600 mm; - longitudinal samples during tensile testing and impact bending of rolled products with a width of 600-1000 mm.

B.2 Scheme for sampling blanks to determine the mechanical properties of rolled steel from improved steel in the delivery state (normalized or improved) or in the control state (option 2)

B.2.1 Selection of blanks from samples of long products

Rolled round and polygonal sections

Figure B.6 - Schemes for selecting blanks from samples from rolled products of round and polygonal sections

Rental of square and rectangular sections

Figure B.7 - Schemes for selecting blanks from samples from rolled square and rectangular sections

B.2.2 Selection of blanks from samples from strips with beveled edges of sheet and wide rolled products - similar to option 1

APPENDIX D (recommended). MINIMUM DISTANCE FROM THE END OF THE PRODUCT FOR SAMPLING, BLANKETS AND TEST SPECIMENS IN CASE OF DISAGREEMENT

Table D.1 - Minimum distance from the end of the product for sampling, blanks and specimens


Type of rental				Minimum distance from the end of the product
Rolled products in coils with rolled ends, diameter*, mm:






Rolled bars
Rolled products with rolled ends				1 turn, but not more than 2 turns from the outer end of the roll
Rolled products with hardened and tempered ends				0.5 x roll diameter, but not less than 160 mm
Sheets with hot or cold cut ends
* For rolling square and hexagonal sections, the diameter of a circle is taken, the cross-sectional area of which is equivalent to the cross-sectional area of a square or hexagon.

APPENDIX E (recommended). SAMPLING SCHEME FOR COLD FLEXURAL TESTS

D.1 Sampling of long products

Rolled round and polygonal sections

Figure E.1 - Schemes for sampling from rolled products of round and polygonal sections

Rolled square section

Figure E.2 - Scheme for sampling from square rolled products

Rolled rectangular section

Figure D.3 - Schemes for sampling from rolled products of rectangular section

D.2 Sampling from shaped steel*
_____________
* For unequal angles, sampling is carried out from the larger shelf.

Figure D.4 - Schemes for sampling from shaped rolled products

E.3 Sampling of sheet and wide rolled products- anywhere along the width for rolled products of thickness:

Figure E.5 - Schemes for sampling from sheet and wide rolled products

Electronic document text
prepared by Kodeks JSC and verified against:
official publication
Ordinary carbon steel
quality and low alloy: Sat. GOST. -
M.: Standartinform, 2009

Mechanical properties are revealed when the metal is exposed to tensile, bending or other forces. The mechanical properties of metals are characterized by: 1) tensile strength in kg/mm 2; 2) relative elongation in %; 3) impact strength in kgm/cm 2; 4) hardness; 5) bend angle. The listed basic properties of metals are determined by the following tests: 1) tensile; 2) on a bend; 3) for hardness; 4) on impact. All these tests are carried out on metal samples using special machines.

Tensile test. The tensile test determines the tensile strength and elongation of the metal.

The tensile strength is the force that must be applied per unit cross-sectional area of a metal sample in order to break it.

For tensile testing, samples are prepared, the shape and dimensions of which are established by GOST 1497-42. tests are carried out on special tensile testing machines. The sample heads are secured in the grips of the machine, after which a load is applied that stretches the sample until it fails.

To test sheet metal, flat samples are made. Low-carbon steels have a tensile strength of about 40 kg/mm 2, high-strength steels and special ones - 150 kg/mm 2.

The elongation of mild steel is approximately 20%.

Relative elongation characterizes the plasticity of the metal; it decreases with increasing tensile strength.

Hardness test. To determine the hardness of a metal, a Brinell or Rockwell device is used.

Brinell hardness is determined as follows. A solid steel ball with a diameter of 10.5 or 2.5 mm is pressed under a press into the metal being tested. Then, using a binocular tube, measure the diameter of the imprint that was made under the ball on the test metal. The Brinell hardness is determined by the diameter of the indentation and the corresponding table.

The hardness of some steels in Brinell units:

Low carbon steel......IV 120-130

High strength steel.... IV 200-300

Hard hardened steels.....IV 500-600

As hardness increases, the ductility of the metal decreases.

Impact test. This test determines the ability of a metal to withstand impact loads. The impact test determines the impact strength of a metal.

Impact strength is determined by testing samples on special pendulum impact testers. The lower the impact strength, the more fragile and the less reliable such a metal is. The higher the impact strength, the better the metal. Good low-carbon steel has an impact strength of 10-15 kgm/cm2.

Bend test. Reinforcement for reinforced concrete structures must have hooks at the ends with a bend angle of up to 180° and bends along the length of the reinforcement at 45 and 90°. Therefore, reinforcing steel is subjected to a cold bend test.

Technological tests establish the ability of reinforcing steel to absorb deformations without compromising its integrity, i.e. without the appearance of cracks, tears, or delaminations.

The ability of a metal to undergo various types of deformation is usually revealed during technological tests of samples. The results of technological tests of metals are judged by the condition of their surface. If after testing no external defects, cracks, tears, delaminations or fractures are found on the surface of the sample, then the metal has passed the test.

The extrusion test is used to determine the ability of sheet metal to be cold formed and drawn. I place the sample in a special device, in which a hole is squeezed out with a punch with a spherical surface until the first crack appears in the metal.

A characteristic of the plasticity of a metal is the depth of the hole before the metal fractures.

The bend test of welds is carried out to determine the toughness of a butt welded joint. The sample is freely mounted on two cylindrical supports and subjected to bending until the first crack appears. A characteristic of fluidity is the bending angle.

A bend test in a cold or heated state is carried out to determine the ability of sheet metal to accept a bend of a given size and shape. Test samples are cut from the sheet without treating the surface layer.

When the sheet metal thickness is more than 30 mm, bending testing is usually not carried out. To carry out the bending test, presses or a vice are used.

The cold upset test is used to determine the ability of a metal to accept a compressive deformation of a given size and shape. The tests are carried out on rods directed into the dig and intended for the manufacture of bolts, rivets, etc. The sample must have a diameter equal to the diameter of the rod being tested and a height equal to two diameters of the rod. In this sample, the sample is deposited with blows of a sledgehammer to a height specified by the technical conditions.

The flattening test is necessary to determine the ability of strip, bar or sheet metal to accept a given flattening.

A wire winding test with a diameter of up to 6 mm is intended to determine the ability of a metal to withstand a given number of turns. The wire is wound onto a mandrel of a certain diameter. After winding, there should be no surface defects on the wire.

The wire bend test is used to determine the ability of the metal to withstand repeated bending and unbending. Round wire and rods with a diameter of 0.8-7 mm are tested at a speed of about 60 bends per minute until the sample is destroyed. Sample length 100-150 mm.

The double roof lock test is designed to determine the ability of sheet metal with a thickness of less than 0.8 mm to accept deformation of a given size and shape. When testing, two sheets are connected with a double lock. The bend angle, number of bends and extensions of the lock are indicated in the technical specifications.

A bend test for a pipe with a diameter of no more than 115 mm in a cold or hot state is needed to determine the ability of the metal to accept a bend of a given size and shape. A pipe sample with a length of at least 200 mm, filled with dry sand or filled with rosin, is bent 90° around a mandrel, the radius of which is indicated in the technical specifications.

The pipe flattening test is necessary to determine the ability of the metal to undergo flattening deformation. A sample with a length approximately equal to the outer diameter of the pipe is flattened with blows of a hammer (hammer, sledgehammer) or under a press to the dimensions specified in the technical specifications.

Test

on metal processing technology

topic: Sheet metal processing

1. Determination of the suitability of sheet material for deep drawing by testing according to the Eriksen method

2. Beading round holes

3. Punching with an elastic tool

4. Determination of parameters of superplasticity of metals

Literature

1. Determination of the suitability of sheet material for deep drawing by testing according to the Eriksen method

The suitability of a metal for drawing can be established by ductility indicators determined from the results of linear tensile testing of samples: the ratio of the yield strength to the tensile strength y/yv, the hardening index P, anisotropy coefficient R b.

Metals having

y t / y v = 0.65 - 0.75, P > 0,2, R b? 1.0.

Carrying out tensile tests and determining the above indicators of metal ductility requires special equipment, highly qualified personnel, and also a significant investment of time. Therefore, such tests are carried out in laboratory conditions. In production, simpler and less labor-intensive technological tests are carried out. One of these tests is the spherical hole drawing test according to GOST 10510-80 (Eriksen method) on the MLT-10G device.

Testing sheet material using the Eriksen method refers to technological tests, which mean identifying the ability of sheet metal to undergo plastic deformations similar to those that it experiences during technological processing.

To establish the suitability of a material for sheet metal drawing operations, three main types of tests are used:

v tests for the depth of extrusion of a spherical hole;

v tests on the drawing depth of the cap;

v stretching the hole.

The MLT-10G device allows you to carry out all three of the above types of tests.

The Eriksen method consists of drawing out a spherical hole in a sample clamped along the contour using a punch 3 with a spherical working surface (Fig. 1.1).

The sample is clamped between the matrix 1 and a clamping ring 2 . The criterion for completing the test is the moment of crack formation on the surface of the sample. A measure of the ability of a metal to draw is depth. h elongated hole. Depending on the depth of the elongated hole, the metal is classified into one or another drawing category (Table 1.1).

Figure 1.1 - Scheme of drawing a spherical hole: 1 - matrix; 2 - pressure ring, 3 - punch

Table 1.1 - Standards for testing materials using the Eriksen method

In accordance with GOST 10510--80 clamping force Q of the sample to the matrix should be 10 - 11 kN.

In addition to the main test indicator - the depth of drawing of a spherical hole - the quality of the metal can be judged by the nature of destruction and the condition of the surface of the drawn hole. Rupture of the sample along a circular arc (Fig. 1.2, A) indicates the isotropy of the metal. Break in a straight line (Fig. 1.2, b) indicates a banded microstructure of the metal. A smooth surface of the hole indicates a fine-grained structure, while a rough surface (“orange peel”) indicates a coarse-grained structure of the metal.

Figure 1.2 - Types of destruction of workpieces during drawing (forming) of a spherical hole

Material support

v testing machine MTL-10G (Fig. 1.3);

v a set of equipment for drawing (forming) a spherical segment: a punch with a diameter of 20 mm, a matrix, a clamping ring, a caliper, a micrometer;

v samples made of sheet carbon or structural steel with a thickness of 0.8 - 2.0 mm in the form of cards with dimensions of (70-100) x (70-100) mm or circles with a diameter of 70-100 mm.

Figure 1.3 - Diagram of the MTL-10G testing machine: 1 - steering wheel; 2 - washer with markings; 3 - bushing with a clamping ring; 4 - spherical punch; 5 - exhaust point; 6 - mirror; 7 - spring-loaded stopper; 8 - screw.

The MLT-10G machine works as follows. By rotating the steering wheel 1, the sleeve 3, connected to the body with a threaded connection, is moved to the right, as well as the screw 8, locked in the sleeve 3 by a spring-loaded stopper 7. In this case, the workpiece is firmly clamped between the clamping ring of the sleeve 3 and the extraction point 5.

Next, by compressing the spring, the stopper 7 is released from the blind groove in the screw 8. With further rotation of the steering wheel 1, the screw 8 along the thread in the hole of the sleeve 3 moves to the right with the sleeve 3 stationary. The spherical punch 4, moved together with the screw 8, deforms the clamped workpiece into the exhaust cavity glasses 5. The formation of a crack in the molded workpiece is recorded visually using a mirror 6.

2. Beading round holes

metal hole stamping superplasticity

Hole flanging is widely used in stamping production, replacing the operations of drawing with subsequent cutting of the bottom. Flaring of holes is used especially effectively in the manufacture of parts with a large flange, when drawing is difficult and requires several transitions. Currently, holes with a diameter of 3 x 1000 mm and a material thickness of 0.3 x 30 mm are produced by flanging.

By flanging we mean the operation of cold sheet stamping, as a result of which a flange is formed along the internal (internal flanging) or external (external flanging) contour of the workpiece. Basically, internal flanging of round holes is performed. In this case, the formation of a bead is carried out by pressing into the hole of the matrix a part of the workpiece with a previously punched hole or simultaneously with the beading. The flanging pattern for round holes is shown in Figure 2.1. A type of flanging is flanging with a thinning wall.

Figure 2.1 - Schemes for flanging round holes: a) with a spherical punch; b) cylindrical punch

Round holes are flanged using a spherical one (Figure 2.1 A) or a cylindrical punch (Figure 2.1 b). In the latter case, the working end of the punch is made in the form of a retainer (catcher), ensuring centering of the workpiece along the hole, with a conical transition to the working part of the diameter d P.

Metal deformation during flanging is characterized by the following changes: elongation in the tangential direction and a decrease in the thickness of the material, as evidenced by the radial-ring mesh applied to the workpiece (Figure 2.2). The distances between the concentric circles remain without significant changes.

Figure 2.2 - Workpiece before and after flanging

The degree of deformation when flanging holes is determined by the ratio between the diameter of the hole in the workpiece d and side diameter D or the so-called flanging coefficient:

TO = d/D,

Where D determined by the midline (see Figure 2.2).

If the flanging coefficient exceeds the limit value TO before, cracks form on the side walls.

The limiting flanging coefficient for a given material can be calculated analytically using the formula:

where h is the coefficient determined by the flanging conditions;

d is the relative elongation determined from tensile tests.

The value of the maximum flanging coefficient depends on the following factors:

1) the nature of the processing and the condition of the edges of the holes (drilling or punching, the presence or absence of burrs);

2) relative thickness of the workpiece s/D;

3) the type of material and its mechanical properties;

4) the shape of the working part of the punch.

There is a direct dependence of the maximum permissible flanging coefficient on the relative thickness of the workpiece, i.e., with a decrease d/s value of the maximum permissible flanging coefficient TO pre decreases and the degree of deformation increases. In addition, the value TO pre depends on the method of obtaining the flanged hole, which is shown in Table 2.1 for low-carbon steel. Table 2.2 shows the limit values of the flanging coefficient for non-ferrous materials.

The permissible value of thinning of the bead wall during flanging due to defects in the edge of the hole (burrs, work hardening, etc.) is significantly lower than the value of transverse narrowing during tensile testing. The smallest thickness at the edge of the side is:

Table 2.1 - Calculated values TO pre for mild steel

Punch type

Method for making a hole

Values TO before depending on d/s

spherical

punching in a stamp

cylindrical

drilling with deburring

punching in a stamp

Calculation of technological parameters for flanging round holes is carried out as follows. The initial parameters are the internal diameter D internal flanged hole and side height N, specified by the drawing details. Based on the specified parameters, the required diameter is calculated d technological hole.

Table 2.2 - Values TO pred for non-ferrous metals and alloys

For a relatively high side, diameter calculation d performed based on the equality of the volumes of the workpiece before and after flanging:

Where D 1 = d n + 2( r m + s).

In this formula, the geometric parameters are determined according to Figure 2.1.

For a low side, the calculation can be performed from the condition of conventional bending in a radial section:

d = D + 0,86r m - 2 N - 0,57s.

Then they check the possibility of flanging in one transition. To do this, compare the flanging coefficient (see page 14) with the limit value TO prev: TO > TO prev

The force of flanging round holes with a cylindrical punch can be approximately determined by the formula

where s T is the yield strength of the material.

The nature of the change in force during flanging is shown in Figure 2.3 depending on the shape of the outline of the working part of the punch.

Figure 2.3 - Force diagrams and transitions for flanging round holes with different punch shapes: A) curvilinear; b) spherical; V) cylindrical

3. Punching with an elastic tool

The use of traditional methods of sheet stamping is associated with the production of expensive stamping equipment and is effective only for large-scale and mass production. In small-scale and pilot production, cold sheet stamping in the case of using conventional die designs is not economically profitable, that is, the costs of stamping equipment do not pay off.

One of the cost-effective stamping methods in small-scale and pilot production is stamping with an elastic tool, when one of the working tools is made of rubber or polyurethane. At the same time, the design of the tool is significantly simplified and its production is reduced in cost, the need to manufacture and fit a second working tool is eliminated, and the lead time for production preparation is reduced.

Stamping with an elastic tool is used both for separation operations - cutting and punching, and for form-changing operations - bending, drawing and forming.

Rubbers and polyurethanes are used as elastic media for stamping. Rubbers are less wear-resistant and operate at relatively low pressures, usually not exceeding 20 h 30 MPa.

Recently, polyurethane has been increasingly used instead of rubber. Polyurethanes are more wear-resistant and can withstand pressures of about 1000 MPa (in closed volumes). The strength of polyurethane is 6 hours 8 times higher than that of rubber, and reaches 600 MPa. The most commonly used polyurethanes are the SKU-6L, SKU-7L, and SKU-PFL brands. The latter grade is usually used for separation operations.

Elastic media are used especially effectively when performing separation operations. Using polyurethane, you can cut parts from aluminum alloys up to 3 mm thick; made of steel (alloy and carbon), brass and bronze up to 2 mm thick.

Typical universal equipment for cutting and punching is shown in Figure 3.1. In one press stroke, the part is cut out along the contour and holes and grooves are punched in accordance with the configuration of the cutting template. The container in which the elastic tool is located is usually made of 40X steel with a hardness after normalization H.R.C. 28 h 32.

Cut-out templates of a simple configuration and a thickness of more than 2 x 3 mm are made of carbon steel grades U 8, U 8A, U 10, U 10A. Templates that are thinner and more complex in contour are made from alloy steel grades X 12, X 12M, X 12F 1. The hardness of the template after hardening is H.R.C. 56 h 60, roughness of the working surface after grinding Ra 0.25 h 1.00.

When cutting parts, the height of the cutting template is of great importance, on which the amount of material waste and the quality of the part depend. Optimal template height N(in mm), ensuring high-quality cutting of a workpiece from a plastic material, can be determined by the formula

where d r is the relative uniform elongation of the material;

s- material thickness, mm.

Figure 3.1 - Stamp for cutting and punching with elastic media: 1 - container; 2 - washer; 3 - elastic tool; 4 - workpiece; 5 - cut-out template; 6 - die plate

Elastic block height N e (mm) is selected from the condition

N e 3 H + 10, (3.2)

Where N taken in millimeters.

Required material allowance L(mm) when cutting parts with a simple contour is determined by the formula

Where f- coefficient of friction between the workpiece and the die plate.

When cutting parts with a curved contour, the amount of allowance L(mm) is determined by:

Where R- where is the radius of curvature of the contour of the part (the plus sign is taken for a convex contour, the minus sign for a concave contour).

The pressure required to cut out a part along the contour depends on the mechanical properties of the material, its thickness and the height of the cutting template. For a convex (plus sign) or concave (minus sign) curved section, cutting pressure q determined by the formula

and for a straight section according to the formula

q = s s in / H. (3.6)

For punching small diameter holes d pressure is:

q = 3s s in / d, (3.7)

and for cutting small grooves with dimensions A b

When simultaneously cutting out a part along the contour and punching holes and grooves, the required pressure should be determined by the maximum value q max, which, as a rule, corresponds to punching holes and grooves with the smallest area.

Press force R, necessary to carry out the separation operation, is determined taking into account the coefficient of losses due to friction and compression of the elastic tool according to the formula

R = 1,2Fq max , (3.9)

Where F- area of the working surface of the elastic tool.

4. Determination of parameters of superplasticity of metals

Superplasticity is the state of a deformable material with a special structure that occurs at a high homologous temperature and is characterized by abnormally high extreme degrees of deformation without breaking the continuity of the material under the influence of stresses, the magnitude of which is very low and strongly depends on the rate of deformation and the structure of the material.

Thus, three conditions are necessary to transfer materials to a superplastic state:

1. The special structure is an ultra-fine equiaxed grain with a size of no more than 25 microns. Such a structure provides a different deformation mechanism at the superplasticity temperature - intergranular sliding.

2. Optimal temperature T = 0.7…0.85 Tm. (Tmelt is the melting temperature of the metal). At T< 0,7 Тпл диффузионная подвижность зерен невелика для реализации межзеренного скольжения. При Т >At 0.85 Tmel, intensive grain growth occurs, inhibiting the processes of intergranular sliding, which leads to the disappearance of the effect of superplasticity in the metal.

3. Strain rate d: low enough for complete diffusion processes to occur and high enough to prevent grain growth under high temperature conditions; for materials with an ultrafine-grained structure of 1-10 μm in size d = 10 -5 ... 10 -3 s -1 , for materials with submicron grain 0.1-1 μm d = 10 -0 ... 10 -3 s -1 , for materials with nanocrystalline structure 100-10 nm = 10 -1 ...10 1 s -1 , for amorphous materials 10 3 ...10 5 s -1 .

Signs of a state of superplasticity:

1. Increased sensitivity of flow stress S to changes in strain rate d, i.e. increased tendency to rapid hardening. The rate sensitivity of flow stress to strain rate is determined by the coefficient

m = dlnS /dln th > 0.3.

2. Large resource of deformability (quasi-uniform deformation of hundreds and thousands of percent according to the principle of a running neck).

3. The flow stress in the SP state is several times less than the yield strength of materials during plastic deformation.

The relationship between the force and strain-rate parameters of metals and alloys processed by pressure is generally as follows:

S = Ce n th m , (4.1)

where e and d are the logarithmic degree and rate of deformation;

C is a coefficient depending on the temperature and structure of the metal.

For superplastic materials, strain hardening is practically absent, that is, n = 0, e n = 1 and equation (1) takes the form:

S = Kj m, (4.2)

at the same time K? WITH.

All methods for determining the parameter m are based on a comparison of the flow stress S at at least two strain rates d.

From formula (2), the indicator m can be determined by the equation:

m = dlnS /dln th (4.3)

The procedure for determining m is that the sample is stretched or compressed to the maximum force, and then in the section of steady flow (under constant or decreasing load) the deformation rate is sharply increased from v 1 to v 2 (Fig. 4.1.).

Figure 4.1 - Scheme of the force-time curve for determining the indicator m by the method of abrupt change in the speed of the traverse

Upon reaching a new maximum of effort and the beginning of a steady flow, the speed of the traverse is changed again, decreasing or increasing it.

The desire to more fully satisfy the requirements of the same preliminary deformation and invariance of the structure led to the development of different calculation methods using different points of the curve in Fig. 4.1. Let's look at some of them.

1. According to the Bekofen method:

where P A is the maximum force at v 2, and P B is the force obtained by extrapolating the section CD at speed v 1 to a deformation equal to the deformation at a point at speed v 2. The value m obtained from equation (4.4) is assigned to a certain average strain rate calculated from v 1 and v 2 under the condition of uniform deformation.

Bacophen's method is inaccurate due to extrapolation errors.

2. Morrison's method does not require extrapolation, since m is determined by the equation:

where S A and S C are the true stresses at the points of maximum effort for the compared speeds;

S A = 4Р А/р(D 2 А), D А = DovНо/(Н о - Д А);

S С = 4Р С /р(D 2 С), D С = DovНо/(Н о - Д С),

D o and H o are the original dimensions of the samples;

D A, D C - absolute deformation of samples at points A and C.

th A and th C - true strain rates,

th A = V A /(N o - D A), s -1;

th C = V C /(N o - D C), s -1,

where V A and V C are the deformation rates at points A and C, mm/s.

However, points A and C correspond to different deformations, and the values of m obtained when increasing and decreasing speed are different.

3. According to the third method, the value of m is related to the strain rate before the shock:

Here, a reverse extrapolation of the section of steady flow at speed v 2 is carried out to the deformation (points E and E!) at which the speed was switched.

The method gives good reproducibility of results, but its physical meaning is not clear.

4. The Hedworth and Stowell method assumes that in the straight section DF the structure of the metal has not yet had time to change and then

It is believed that of the above, the Hedworth and Stowell method is the most acceptable.

Literature

1. Novikov I.I. Superplasticity of alloys with ultrafine grains / I.I. Novikov, V.K. Tailor. - M.: Metallurgy, 1981. - 168 p.

2. Smirnov O.M. Pressure processing of metals in a state of superplasticity / O.M. Smirnov. - M.: Mechanical Engineering, 1979. - 189 p.

3. Karabasov Yu.S. New materials / Yu.S. Karabasov [and others]. - M.: MISIS, 2002. - 736 p.

4. Tikhonov A.S. Effect of superplasticity of metals and alloys / A.S. Tikhonov. - M.: Nauka, 1978. - 142 p.

5. Chumachenko E.N. Mechanical tests and construction of analytical models of the behavior of materials under conditions of superplasticity. Part 1 / E.N. Chumachenko, V.K. Portnoy, I.V. Logashina // Metallurg. - 2014. - No. 12. - P. 68-71.

6. Chumachenko E.N. Mechanical tests and construction of analytical models of the behavior of materials under conditions of superplasticity. Part 2 / E.N. Chumachenko, V.K. Portnoy, I.V. Logashina // Metallurg. - 2015. - No. 1. - P.76-80.

7. SSAB. Sheet steel stamping: a reference book. Cutting to specified sizes and plastic shaping: transl. from English / ed. R.E. Gleaner. - Gothenburg: SSAB, 2004. - 153 p.

8. Belyaev V.A. Cold stamping and die design: methodological recommendations for performing laboratory work / V.A. Belyaev. - Biysk: AltSTU im. Polzunova, 2007. - 37 p.

9. Anishchenko A.S. Progressive technological solutions in metal forming: Lecture notes in 3 parts. Part 1. Sheet stamping with moving media. Pressure processing of metals in a state of superplasticity / A.S. Anishchenko. - Mariupol, Perm State Technical University, 2013. - 58 p.

10. Belyaev V.A. Cold stamping and die design: methodological recommendations for performing laboratory work / V.A. Belyaev. - Biysk: AltSTU im. Polzunova, 2007. - 37 p.

11. Grigoriev L.L. Cold stamping: reference book / L.L. Grigoriev, K.M. Ivanov, E.E. Jurgenson. - St. Petersburg: Politekhnika, 2009. - 665 p. : ill.