GB/T 6397-1986 Metallic materials — Test pieces for tensile testing English
This standard specifies the general requirements for test pieces for tensile testing of various metal products at room temperature. Test pieces shall be selected in accordance with relevant standards or the requirements of the agreement between both parties.
This standard is applicable to general test pieces for tensile testing of steel and non-ferrous metal materials. Unless otherwise specified, the test pieces of bars, profiles, sheets (strips), tubes, wires, castings, die castings and forgings shall all be carried out in accordance with this standard.
1 Cutting of the sample billet, preparation and marking of test pieces
1.1 The position and direction for cutting the sample billet from the product shall be carried out in accordance with the relevant standards of GB 2975-82 Rules for sampling in mechanical and technological testing of steel products or the requirements of the agreement between both parties.
1.2 Both the cutting sample billets and the machined test pieces shall be strictly prevented from affecting the mechanical properties of the metal due to cold working or heating. Generally, it is advisable to perform them on the cutting machine tool. When cutting the sample billets by flame cut or cold shearing, sufficient machining allowance shall be left on the edge, generally not less than the thickness of the product, and at least not less than 20mm. However, thin sheets (strips) and the like are exceptions. For details, please refer to GB 2975-82. When machining test pieces, the cutting and grinding depths as well as the lubricating (cooling) agent shall be appropriate. The final cutting and grinding depths shall not be too large to avoid affecting performance. It is recommended to retain the machining center hole for re-dressing when necessary.
1.3 Rectangular billets cut from plates, flat materials or strips that have passed visual inspection shall generally retain their original surface layers without any damage. Burrs on the test pieces must be removed, sharp edges shall be rounded, and the radius of the arc should not be too large. For the wire and sheet (strip) test pieces cut from the reel, straightening or leveling is permissible. However, the correction shall be free of obvious impact on the mechanical performance of the test pieces. For the test pieces with elongation not determined, they may be directly tested without correction.
1.4 For the single-cast test pieces that have not been machined, any sand inclusions, slag inclusions, burrs, flash, etc. on the surface must be removed.
1.5 All test pieces that do not meet the requirements specified in this standard, and have obvious transverse knife marks, grinding marks or mechanical damage on the surface, obvious quenching deformation or cracks, and visible metallurgical defects to the naked eye are not allowed to be used for the test.
1.6 The marking of test pieces shall generally be placed on the end face or side of the head (for small cross-section test pieces, a signboard can be hung) to facilitate identification during the test.
2 Symbols, names and units of test pieces (see Table 1)
Table 1
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3 General specifications for the shape and size of test pieces
3.1 Test pieces for tensile testing are classified into two types: proportional and fixed gauge length test pieces. Generally, they are machined test pieces and unmachined full-section test pieces. Their cross-sections are usually circular, rectangular, irregular, and unmachined full-section shapes. The original cross-sectional area Fo of full-section test piece can be calculated based on the nominal or measured dimensions as per the regulations.
3.2 Parallel length l of test pieces: For circular test pieces, it shall not be less than lo + do; for rectangular specimens, it shall not be less than lo + bo/2. When conducting arbitration tests, they shall be lo + 2do and lo + bo respectively.
3.3 For machined leading circular and rectangular test pieces, the transition from the parallel part to the head must be gentle. The size of the arc radius, r, can be determined according to the dimensions, materials and machining processes of each part of the test piece. For brittle materials, r shall be appropriately increased. Shape and dimension of test piece head shall be designed based on the size of test piece, material properties, test purpose and the structure of testing machine fixture, but it is necessary to ensure the axial tensile force. For circular or rectangular test pieces with and without heads, the length of the clamping part shall be at least 3/4 of the length of wedge-shaped fixture.
1 Cutting of the sample billet, preparation and marking of test pieces
2 Symbols, names and units of test pieces (see Table 1)
3 General specifications for the shape and size of test pieces
4 Classification and shape dimensions of test pieces for tensile testing
Additional explanation:
