Some standard content:
GB/T4338—1995
This standard is equivalent to the international standard ISO783:1989 "High-temperature tensile test of metallic materials". This standard has slight differences in technical content from ISO783:1989 in combination with the domestic test equipment situation, but does not affect the main contents commonly used internationally.
This standard is revised this time. While revising GB4338—84 "Metal High-temperature Tensile Test Method", GB3652-83 "Metal Pipe High-temperature Tensile Test Method" is also revised and incorporated into this standard. The following important technical aspects have been revised: applicable temperature range, definition, specimen measurement accuracy, minimum specimen gauge length, temperature allowable deviation, temperature measurement accuracy, temperature holding time, tensile test rate, performance result numerical rounding and specimen machining requirements. This standard shall be implemented from March 1, 1996. From the date of implementation, this standard will replace GB4338—84 "Metal High-temperature Tensile Test Method" and GB3652—83 "Metal Pipe High-temperature Tensile Test Method". Appendix A of this standard is the appendix of the standard.
This standard was proposed by the National Technical Committee on Steel Standardization. This standard is under the jurisdiction of the Information Standards Research Institute of the Ministry of Metallurgical Industry. The responsible drafting unit of this standard is the Iron and Steel Research Institute of the Ministry of Metallurgical Industry. The participating drafting units of this standard are Fushun Steel Plant of the Ministry of Metallurgical Industry and the First Branch of Changcheng Steel Plant of the Ministry of Metallurgical Industry. The main drafters of this standard are Liang Xinbang, Wang Yaoqun, Tong Zhandong and Gu Fangxin. This standard was first issued in April 1984 and revised for the first time in July 1994. 252
GB/T4338-1995
ISO Foreword
ISO (International Organization for Standardization) is a federation of national standards bodies (ISO members) worldwide. International standards are usually formulated and revised by ISO technical committees. Members interested in a subject for which a technical committee has been established have the right to participate in that committee. International organizations, both governmental and non-governmental, that collaborate with ISO also participate in the work. ISO works closely with the International Electrotechnical Commission (IEC) in the field of electrotechnical standardization. The draft international standard adopted by the technical committee is distributed to all member cities for review before being accepted as an international standard by the ISO committee. According to the ISO procedure, at least 75% of the members agree to pass it. International Standard ISO783 was developed by ISO/TC164 Technical Committee on Metal Mechanical Properties Testing. This standard replaces the recommended standard ISO/R783:1968. Appendices A to G are part of this international standard. Appendix H is for reference only. 243
1 Scope
National Standard of the People's Republic of China
Metallic Materials
Elevated Tensile Test
Metallic Materials-Tensile Testing at Elevated TemperatureGB/T 4338--1995
eqv iso 783:1989
GB 433881
G365283
This standard specifies the principles, definitions, symbols, specimens, specimen size measurement, test equipment, specimen heating and temperature measurement, test conditions, property determination, rounding of property result values, test result processing and test report of elevated temperature tensile test method for metals. This standard is applicable to the determination of one or more tensile mechanical properties of metallic materials at test temperatures ranging from above room temperature to 1100℃. 2 Referenced Standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. The versions shown are valid when this standard is published. All standards are subject to revision. Parties using this standard should explore the possibility of using the latest versions of the following standards: GB2975-82 Sampling regulations for mechanical and process performance tests of steel materials GB8170—87 Rules for numerical rounding off
JJG139—91 Verification procedures for tension, compression and universal testing machines JJG141~83 Verification procedures for working platinum 10-platinum thermocouples JJG157—83 Verification procedures for small load material testing machines JJG351-84 Verification procedures for working nickel-chromium-nickel silicon, nickel-chromium-copper thermocouples JJG475-86 Verification procedures for electronic universal testing machines JJG762--92 Verification procedures for extensometers
3 Principle
The test is to stretch the specimen with tensile force at the test temperature, generally stretching it to fracture in order to determine the tensile mechanical properties. 4 Definitions
This standard adopts the following definitions.
4.1 Parallel length (.): The parallel length between the two heads or two clamped parts (headless specimens) of the specimen. 4.2 Gauge length: The length between the two marks used to measure the elongation of the specimen at any time during the tensile test. 4.2.1 Original gauge length (L,): The gauge length of the specimen at room temperature before heating and force application. 4.2.2 Post-fracture gauge length (L): After the specimen is broken, the gauge length when the broken parts are butt-jointed at room temperature so that their axes are in the same straight line 1.
4.3 Extensometer gauge length (L): The length of the parallel length portion of the specimen used to test the specimen with an extensometer. This length is different from L but should be less than Lr and greater than bgvd. or D, (see Table 1). 4.4 Stress: The force at any time during the tensile test divided by the original cross-sectional area of the specimen 4.5 Specified non-proportional elongation stress (α): The stress when the non-proportional elongation of the specimen gauge length reaches the specified percentage of the original gauge length Note: The symbol representing this stress should be accompanied by a corner note, for example, 0po.2 represents the stress when the specified non-proportional elongation is 0.2%. The State Administration of Technical Supervision approved 251
1996-0301 on October 10, 1995 for implementation
GB/T4338-—1995
4.6 Specified residual elongation (ε): The percentage of the residual elongation of the gauge length of the specimen after the tensile force is removed to the original gauge length. 4.7 Yield point (c): The stress of a metal material that exhibits the kitchen yield phenomenon, when the specimen can continue to elongate without increasing the force (maintaining a constant) during the test. If the force decreases, the upper and lower yield points should be distinguished. 4.7.1 Upper yield point (αsu): The maximum stress before the specimen yields and the force decreases for the first time. 4.7.2 Lower yield point (osl): The minimum stress in the yield stage when the initial transient effect is ignored. 4.8 Tensile strength (α): The stress corresponding to the maximum force during the breaking of the specimen. 4.9 Elongation after fracture (8): The ratio of the elongation of the gauge length to the original gauge length after the specimen is broken. 4.10 Reduction of area (minimum): The maximum reduction in the cross-sectional area at the neck after the specimen is broken as a percentage of the original cross-sectional area. 5 Symbols
The symbols, names and units are listed in Table 1.
Original thickness of the specimen or tube wall
Original width of the specimen
Original diameter of the specimen or the distance from the opposite sides of the polygonal cross section Minimum diameter of the specimen after fracture
Parallel length of the specimen
Original gauge length of the specimen
Total length of the specimen
Original outer diameter of the tube
Original cross-sectional area of the specimen
Minimum cross-sectional area of the specimen after fracture
Specified non-proportional elongation force
Force at service point|| tt||Upper yield point force
Lower yield point force
Maximum force
Specified non-proportional elongation stress
Windfall point
Upper yield point
Lower yield point
Tensile strength
Elongation after fracture
Reduction of area
Specified non-proportional elongation
Specified residual elongation
Circular ratio
Elongation magnification
Note; 1 N/mm-- 1 MPa
6 Test specimen
6.1 Test specimen shape and size
GB/T4338--1995
The shape and size of the test specimen depend on the shape and size of the metal product to be tested for mechanical properties. The shape of the test specimen cross section can be circular, rectangular, or shaped, or other shapes in special cases. 6.1.1 Proportional specimens and non-proportional specimens
6.1.1.1 The specimen whose original gauge length L and original cross-sectional area S have the relationship L. =KVS. is called a proportional specimen. K in the formula is the proportional coefficient, and its value is preferably 5.65. The original gauge length should be no less than 20mm. When the proportional coefficient value of 5.65 cannot meet the requirement of the original gauge length of 20mm, the proportional coefficient value of 11.3 can be used. 6.1.1.2 Any specimen whose original gauge length L. and original cross-sectional area S. do not have the proportional relationship described in 6.1.2.1 is called a non-proportional specimen. 6.1.2 Sample cutting and sample preparation
6.1.2.1 The location, direction and number of sample cutting shall comply with the requirements specified in GB2975 or product standards or agreements. 6.1.2.2 When cutting samples and machining samples, prevent the mechanical properties of the material from being changed due to cold working or heating. 6.1.2.3 The specimens that need heat treatment shall be heat treated before the last machining process or finishing. 6.1.2.4 The specimens that have been machined shall be straight, free of burrs, mechanical damage, rust and visible defects on the surface. 6.1.2.5 For materials with low elongation after fracture (≤5%), the diameter or width in the middle of the parallel length may be slightly smaller than the diameter or width at both ends, but the difference shall not exceed 0.5% of the diameter or width. The change from the smaller in the middle to the larger at both ends shall be continuous and smooth. And it shall be noted in the report.
6.1.2.6 Plates with a thickness greater than 8mm and pipes with a wall thickness greater than 8mm may be machined into longitudinal circular specimens as large as possible if there is no provision in the product standard or agreement.
6.1.2.7 For products with equal cross-sections, whether the specimens are machined or not shall be specified by the product standard or agreement. If there is no provision, the specimens without final machining and T shall be tested, and the specimens without machining shall retain the original surface. 6.1.2.8 When plates and thin plates are machined into rectangular cross-section specimens, the two wide surfaces shall retain their original surfaces unless otherwise specified in the relevant standards. 6.1.2.9 For pipes, full-section pipe section specimens shall be used as much as possible if the testing machine capacity permits. 6.1.2.10 Full-section pipe section specimens shall be equipped with plugs at both ends for clamping. The shape of the plugs shall not affect the deformation within the gauge range of the specimen. The shape, size and position of the plugs on the full-section pipe section specimens are shown in A3.3. 6.2 Commonly used specimens
Commonly used specimens are shown in Appendix A. Product standards or agreements may specify other suitable specimens. 7 Measurement of specimen dimensions
7.1 Determination of the original cross-sectional area of the specimen
7.1.1 The cross-sectional diameter of the circular specimen shall be measured at both ends and in the middle of the gauge length in two mutually perpendicular directions, and the arithmetic half mean shall be taken. The minimum value of the average diameters measured three times is used to calculate the original cross-sectional area of the circular specimen, and is calculated according to formula (1): So a Rdi
. (13
7.1.2 The width and thickness of the cross-sectional area of the rectangular specimen shall be measured at both ends and the middle of the gauge length. The minimum value of the cross-sectional area measured at two locations is taken. The cross-sectional area of the rectangular specimen is calculated according to formula (2): Sa-a,be
(2)
7.1.3 The wall thickness and width of the cross-sectional area of the longitudinal arc specimen of the pipe shall be measured at both ends and the middle of the gauge length. The minimum value of the cross-sectional area measured at two locations is taken. The cross-sectional area of the longitudinal arc specimen of the pipe is calculated according to formula (3): S. - abo[1 + 6D,(D- 2a,
7.1.4 The outer diameter of the cross section of the full-section pipe section specimen should be measured once in two mutually perpendicular directions at one end, and the arithmetic mean value should be taken. The wall thickness of the pipe should be measured at four mutually perpendicular directions at the same end, and the arithmetic mean value should be taken. The cross-sectional area calculated by the average outer diameter and the average wall thickness is taken as the original cross-sectional area within the gauge length. Calculate according to formula (4): Se = na(D, an)
7.1.5 The determination of the original cross-sectional area of the specimen should be accurate. For specimens with circular, rectangular, and polygonal cross sections, the accuracy should be ±1%; for specimens with a thickness of 0.1mm~~3.0mm, the accuracy should be ±2%. For convenience, the measuring tool can be selected according to the requirements of Table 2. Table 2
Cross-sectional dimensions
0. 1~0. 5
≥0. 5~2. 0
>2. 0~- 10. 0
7.2 Marking of the original gauge length of the specimen
The minimum graduation value of the measuring tool shall not be greater than
7.2.1 The original gauge length can be marked on the parallel length of the specimen with a small punch or a thin line. The marking should be clear and should not affect the fracture of the specimen. If the parallel length is much longer than the original gauge length, several sets of overlapping original gauge lengths can be marked. 7.2.2 The calculated value of the original gauge length of the proportional specimen should be rounded to the nearest multiple of 5mm; if it is an intermediate value, round it to the larger value. 7.2.3 The marking of the original gauge length should be accurate to ±0.5% or 0.15mm, whichever is larger. 8 Test equipment
8.1 Testing machine
8.1.1 The testing machine shall be calibrated in accordance with JJG139, JJG157 or JJG475, and shall not be lower than level -1. 8.1.2 The force application system of the testing machine shall be able to apply axial force to the specimen, and the coaxiality error between the center line of force action and the specimen axis shall be expressed as a percentage of the ratio of the maximum bending strain to the average axial strain, and shall not exceed 15%. The coaxiality error calibration method shall be in accordance with JJG139, and the calibration shall be carried out at room temperature.
8.1.3 The testing machine shall be equipped with a speed indicating device, which can be flexibly adjusted within the speed range specified in this standard during the test. 8.1.4 The testing machine shall be equipped with a device for recording or displaying force, and its function shall meet the requirements of this standard for determining mechanical properties. 8.2 Extensometer
8.2.1 Select an extensometer of the corresponding level according to Table 3, and the extensometer shall be calibrated in accordance with JJG762. 252
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Specified non-proportional elongation
or specified residual elongation
8.2.2 It is recommended to use an extensometer that can measure the elongation on both sides of the specimen. 8.3 Heating device
The heating device should be able to heat the specimen to the specified temperature, and the temperature deviation should meet the requirements specified in Table 4: Table 4
Test temperature
>600~~800
≥800～1100
8.4 Temperature measurement device
Minimum level of extensometer
Temperature allowable deviation
8.4.1 The resolution of the temperature measuring instrument should not be greater than 1C. The error should not exceed 2℃, and it should be calibrated regularly. 8.4.2 Thermocouples and compensation wires should be calibrated in accordance with JJG141 or JJG351. 8.4.3 The temperature of the reference end of the thermocouple should be kept constant, and the deviation should not exceed ±0.5℃. 9 Sample heating and temperature measurement
9.1 When the original gauge length of the sample is less than or equal to 50mm, tie a thermocouple at each end; when it is greater than 50mm, tie a thermocouple at each end and in the middle. The measuring end of the thermocouple should have good thermal contact with the sample mounting surface, and the influence of direct heat radiation from the furnace wall should be avoided. 9.2 After the sample is loaded into the furnace, it should generally be heated to the specified test temperature within 1H, and the temperature should be avoided from exceeding the specified temperature upper limit. 9.3 The sample must be kept at the specified test temperature for at least 10 minutes before the test can begin. During the temperature maintenance period and the test until the sample breaks, the temperature deviation should meet the requirements specified in Table 4.
10 Test conditions
10.1 Test rate
10.1.1 Unless otherwise specified in the product standard or agreement, the test rate shall comply with the following requirements: 10.1.1.1 Determine the specified non-proportional secondary stress and yield point, upper and lower yield points. From the beginning of the test to the end of the test cage or service stage of the specified non-proportional secondary stress, the strain rate of the parallel length of the specimen shall be kept as constant as possible within the range of 0.001min-10.005min.
In the case that the testing machine does not have the ability to control the strain rate, the test machine chuck no-load movement rate of 0.02L.min1 is used. The intermediate strain rate 1} is used for the stretching 218
test.
GB/T4338--1995
10.1.1.2 When only tensile strength is measured or after saturation, the strain rate should be as constant as possible between 0.02min-1 and 0.20min-1.
If the testing machine cannot meet such a rate requirement, the no-load moving rate of the testing machine chuck can be 0.1Luin-1. The arbitration test adopts an intermediate strain rate".
10.1.1.3 The change from one test rate to another should be continuous and without impact. 11 Performance measurement
11.1 Determination of non-proportional elongation stress
11.1.1 Graphic method: The force-elongation curve is recorded by automatic recording method during tensile test. When recording the curve, the stress represented by each millimeter of the force axis is generally not more than 10MPa, and the height of the curve should make the required F more than 1/2 of the force axis range. The selection of the elongation magnification should make the length of the oc segment in Figure 1 not less than 5mm. ||tt| |On the recorded curve, from the intersection point O of the elastic straight line segment and the elongation axis, intercept the C segment corresponding to the specified non-proportional elongation (OC-n·Ls,), and draw a parallel line CA of the elastic straight line segment through point C to intersect the curve at point A. The force F. corresponding to point A is the measured specified non-proportional elongation force (see Figure 1). The specified non-proportional elongation stress is calculated according to formula (5): Gp
n·ipn
Figure 1 Graphical method for determining the specified non-proportional elongation force (5)
Instructions for use
1] The provisions of the second paragraph of this article are consistent with 8.3. of the international standard 1S0783-1989.1 The second paragraph of the provisions are somewhat different. The latter provision is: "If the testing machine is unable to obtain the required strain rate, the stress rate should be adjusted so that the strain rate within the elastic range is less than 0.003min1. In any case, the stress rate within the elastic range should not exceed 300N/mm2·min)\. 2! There is no provision for the second paragraph of this article in 8.3.2 of the international standard IS0)783-1989. 259
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11.1.2 If the force-elongation curve of the metal material has no obvious elastic straight line segment, so that it is difficult to determine the corresponding specified non-proportional elongation force, the following method can be used:
Hysteresis loop method: Select the force axis ratio and elongation magnification according to 1.1, 1. During the test, the specimen is continuously subjected to force corresponding to the expected specified non-proportional elongation stress, Divide it to about 10% of the previously applied force, and then apply force at least until it enters the envelope range. Normally, a hysteresis loop will be drawn. Draw a straight line through the two end points of the hysteresis loop. Intercept the OC segment from the true origin O of the curve (OC=n·L.e,). Draw a straight line CA through point C parallel to the above-drawn straight line. The force F corresponding to the intersection A of line CA and the curve is the measured specified non-proportional elongation force (see Figure 2a). If line (A) is located on the right side of the hysteresis loop, the force corresponding to the intersection of line (A) and the envelope is taken as the specified non-proportional elongation force F (see Figures 2b and 2c).
If there is no obvious elastic straight line segment in the force-elongation curve, the arbitration test must make line (CA) located on the left side of the hysteresis loop. Force!
Figure 2 Determination of specified non-proportional elongation force by hysteresis loop method 260
GB/T4338--1995
ne ep
Continued Figure 2
11.1.3 Production inspection allows the use of recorded force-chuck (beam) displacement curves to determine the specified non-proportional elongation stress (see Figure 3) when the specified non-proportional elongation is greater than or equal to 0.2%. The selection of the force axis ratio is in accordance with 11.1.1, and the selection of the displacement magnification should make the length of the 0C section ((C.n·L·ep) in Figure 3 not less than 5mm.
Figure 3 Force-chuck displacement method to determine the specified non-proportional elongation force 11.1.4 In the absence of an automatic recording curve, the specified non-proportional elongation can be determined by the manual point drawing method of step-by-step force application 261
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—19 95
The specified non-proportional elongation stress with a rate greater than or equal to 0.2%. However, at least 8 levels of force corresponding to the elongation should be read, and the dwell time for each level of force should not exceed 3s.
11.1.5 When using an automatic device (such as a microprocessor, etc.) to determine the specified non-proportional elongation stress, it is not necessary to draw a tensile curve. 11.2 Verification test of specified residual elongation
During the test, first apply a pre-stretching force corresponding to a stress of about 10MPa to the specimen, and adjust the zero reading of the extensometer. Then continuously apply force to the specimen to the force corresponding to the specified stress, maintain this force for 10 to 12s (or as specified by relevant standards or agreements), remove the full pre-stretching force, and verify that the residual elongation does not exceed the specified value.
11.3 Determination of yield point, upper yield point and lower yield point 11.3.1 For metal materials that show obvious yielding phenomenon, their yield point, upper yield point or lower yield point should be determined. When there is no specific provision in the relevant standards or agreements, generally only the yield point or the next service point is measured and reported. For metal materials that show no obvious yield phenomenon, unless otherwise specified, the specified non-proportional elongation stress pm.2 should be measured. 11.3.2 Graphic method: During the tensile test, an automatic recording device is used to record the force-elongation curve or the force-chuck displacement curve. The ratio of the force axis should be in accordance with 11.1.1. The elongation (or chuck displacement) magnification should be appropriately selected according to the material characteristics. The curve is recorded at least to the end of the service stage. Determine the constant force F of the yield platform on the curve graph. Or the maximum force F before the first drop in force in the yield stage or the minimum force F when the initial transient effect is not allowed (see Figure 4). The yield point, upper yield point and lower yield point are calculated according to formula (6), (7) and (8) respectively: F
Initial transient effectbZxz.net
Initial transient effect
Figure 4 Graphical method for determining yield force, upper yield force and lower yield force 262
GB/T4338--1995
Continued Figure 4
11.3.3 Pointer method: Production inspection allows the use of the pointer method to determine the yield point, upper yield point and lower yield point. During the test, the constant force at which the pointer of the force dial stops rotating for the first time, or the maximum force before the pointer rotates for the first time, or the minimum force when the initial transient effect is ignored, is measured. The corresponding stresses are the yield point and the upper and lower yield points respectively. The arbitration test adopts the graphical method. 11.4 Determination of tensile strength
The specimen is stretched to fracture, and the maximum force reached during the test is determined from the recorded tensile period graph (see Figure 5), or the maximum force is read from the force dial. The tensile strength is calculated according to formula (9): Q =
Figure 5 shows the method for determining the maximum strength
17.5 Determination of the elongation at break
.. (9)1.1 stipulates that the elongation (or chuck displacement) magnification should be appropriately selected according to the material properties, and the curve should be recorded at least to the end of the service stage. Determine the constant force F of the yield platform on the curve graph. Or the maximum force F before the force drops for the first time in the yield stage or the minimum force F when the initial transient effect is not allowed (see Figure 4). The yield point, upper yield point and lower service point are calculated according to formulas (6), (7) and (8) respectively: F
Initial transient effect
Initial transient effect
Figure 4 Graphic method for determining yield force, upper yield force and lower yield force 262
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Continued Figure 4
11.3.3 Pointer method: Production inspection allows the use of the pointer method to determine the service point, upper service point and lower yield point. During the test, the constant force when the pointer of the force dial stops rotating for the first time, or the maximum force before the pointer rotates for the first time, or the minimum force when the initial transient effect is ignored, the corresponding stresses are the yield point and the upper and lower yield points respectively. The arbitration test adopts the graphical method. 11.4 Determination of tensile strength
The specimen is stretched to fracture, and the maximum force reached during the test is determined from the recorded tensile period graph (see Figure 5), or the maximum force is read from the force dial. The tensile strength is calculated according to formula (9): Q =
Figure 5 Graphic method for determining the maximum force
17.5 Determination of elongation at break
.. (9)1.1 stipulates that the elongation (or chuck displacement) magnification should be appropriately selected according to the material properties, and the curve should be recorded at least to the end of the service stage. Determine the constant force F of the yield platform on the curve graph. Or the maximum force F before the force drops for the first time in the yield stage or the minimum force F when the initial transient effect is not allowed (see Figure 4). The yield point, upper yield point and lower service point are calculated according to formulas (6), (7) and (8) respectively: F
Initial transient effect
Initial transient effect
Figure 4 Graphic method for determining yield force, upper yield force and lower yield force 262
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Continued Figure 4
11.3.3 Pointer method: Production inspection allows the use of the pointer method to determine the service point, upper service point and lower yield point. During the test, the constant force when the pointer of the force dial stops rotating for the first time, or the maximum force before the pointer rotates for the first time, or the minimum force when the initial transient effect is ignored, the corresponding stresses are the yield point and the upper and lower yield points respectively. The arbitration test adopts the graphical method. 11.4 Determination of tensile strength
The specimen is stretched to fracture, and the maximum force reached during the test is determined from the recorded tensile period graph (see Figure 5), or the maximum force is read from the force dial. The tensile strength is calculated according to formula (9): Q =
Figure 5 Graphic method for determining the maximum force
17.5 Determination of elongation at break
.. (9)
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