Small-caliber steel pipe lateral impact sample flattening method

Abstract

The invention provides a small-aperture steel pipe horizontal shock sample flattening method which includes the following steps: cushion block making: each cushion block is tempered and quenched into a martensitic structure, the range of which is HRC35 to 40; mould making: a plurality of cushion blocks are subsequently laminated and numbered from narrow to wide, used together or singly, and form flattening moulds; two cushion blocks with the first numbers form a first set of mould which is arranged on a chuck below a flattening test machine; and then a sample to be tested is arranged on the first set of mould; the inner surface of the sample to be tested contacts the first set of mould; the center lines of the sample to be tested and the mould are aligned; and then the flattening test machine starts to pressurize and load on the upper part of the sample to be tested, until a flat part appears and the sample to be tested is flattened. The method has the advantages that each cushion block can be independently removed, is convenient in use and simple to be processed; the materials are widely available and the consumption is small. The method can make the horizontal shock power of small pipes possible, bring convenience for follow-up testing and improve production efficiency.

Description

technical field [0001] The invention relates to a sample flattening method, in particular to a small-diameter steel pipe transverse impact sample flattening method. Background technique [0002] In general, due to the small size of the pipe (smaller outer diameter and wall thickness), the lateral impact performance is usually not tested during performance testing, because it is very difficult to prepare such experimental samples. However, due to the anisotropy of metal materials, sometimes it is necessary to test the lateral impact performance, especially the development trend of smaller and smaller product specifications and stricter performance requirements, which has led people to pay more and more attention to the lateral impact performance. impact performance. [0003] In the process of preparing the seamless steel pipe impact energy test sample, its length is required to be 55mm long, and for the other two dimensions of the sample, it can be made into a rectangle acco...

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Problems solved by technology

[0004] For such size requirements, the problem that is likely to occur in the preparation of pipe transverse impact energy samples is: when the size of the pipe is very small, the outer diameter and wall thickness are not large, especially when the outer diameter is not large, due to The direct transverse length is difficult to meet the length of 55mm, so the transverse impact specimen cannot be directly prepared, and the material sample needs to be flattened in advance

like figure 1 As shown, the general steel pipe performance testing laboratory in the industry will be equipped with such a pressure flattening test machine. This method is efficient, but it is also prone to problems: due to the poor bending performance of the material of the pipe body itself (or the rigidity is biased) Low) or the size is small, after flattening by this method, it is easy to appear that it is not really flattened, and there will be a wavy section, such as figure 2 As shown, or further loading and flattening the inner surface of the tube, cracks on the inner surface will appear. In both cases, the transverse impact energy cannot be measured according to the user's requirements, so that the quality assurance provided to the user cannot be filled. This performance, so that it is not clear whether this performance can meet the customer's requirements, and the failure of the test sample due to flattening and cracking caused the production plant to repeat sampling and wait for the test results, resulting in the problem of reducing production efficiency from time to time

[0008] The advantage of this method is that it can generally ensure that the impact sample will not be cracked, but it has the following disadvantages: first, it is relatively difficult to process such a mold, and the size is relatively large; second, the sharp angle in the width direction of the mold is not easy to pour out, It is easy to cause indentation on the first contact part of the inner surface of the pipe, and then cracks; the third is that the mold has only one height. If the height is not enough, the sample has already contacted the lower pressure head of the flattening test machine when it is not flattened, which is easy to cause as shown in Figure 3 ( a), uneven development shown in Figure 3(b)

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