Method for evaluating sensitivity of edge crack of high-strength thin steel plate

A technology for edge cracks, evaluation methods, applied in directions such as testing material strength using applied stable tension/compression

Active Publication Date: 2014-12-17
SHOUGANG CORPORATION
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, there is no unified evaluation method for the early cracking of the edge accompanying the stamping bulging process. The early cracking of the edge in the bulging process is not only related to the material properties, but also related to the die clearance of blanking or trimming.

Method used

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  • Method for evaluating sensitivity of edge crack of high-strength thin steel plate
  • Method for evaluating sensitivity of edge crack of high-strength thin steel plate
  • Method for evaluating sensitivity of edge crack of high-strength thin steel plate

Examples

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Effect test

Embodiment 1

[0027] When using the evaluation method for edge crack sensitivity of high-strength thin steel plate of the present invention, a certain HC420 / 780DPD+Z dual-phase steel is selected as an example, and the edge crack sensitivity is evaluated by the method of the present invention.

[0028] The thickness of the steel plate is selected to be 1.2mm. Firstly, wire cutting is used and the edge is milled with a milling cutter. The edge is polished with No. 800 sandpaper to obtain a standard sample, and the steel ball mold is bulged on a plate forming test machine. A non-contact three-dimensional strain analyzer is used to track the strain of the sample during the bulging process. Such as image 3 As shown, the necking strain state indicated by point A is obtained. see image 3 , the forming limit curve of the steel grade and the strain state (point B) at the rupture point of the single tensile specimen are given as a reference, which is not necessary in this test.

[0029] Five sam...

Embodiment 2

[0031] Select HC340LA low-alloy high-strength steel with a thickness of 1.6mm, first use wire cutting and mill the edge with a milling cutter, and polish the edge with No. 800 sandpaper to obtain a standard sample, and perform steel ball mold bulging on a plate forming test machine. Use a non-contact three-dimensional strain analyzer to obtain the principal strain of the standard sample when it necks and the principal strain when it ruptures (reference, not necessary). Then, five samples with different edge states were prepared by trimming die, and the steel ball die bulging was carried out on the plate forming test machine. A non-contact three-dimensional strain analyzer was used to obtain the principal strain at the point where the sample just broke. see Figure 5 , gives the comparison of the principal strains of rupture obtained by the specimens in different edge states and the principal strains of the standard specimens during necking and rupture. Necking principal stra...

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Abstract

The invention discloses a method for evaluating the sensitivity of an edge crack of a high-strength thin steel plate, belonging to the technical field of thin steel plate formability indexes. The method comprises the following steps: firstly, establishing a steel ball die bulging test; then performing the steel ball die bulging test on a test sample in a one-way tensile strain state; then, carrying out edge milling on the edges of the test sample and polishing to remove burrs to obtain a standard test sample; afterwards, performing the steel ball die bulging test on the standard test sample to obtain a surface main strain value of a part in which necking just appears; trimming a plate, and carrying out steel ball die bulging on the sample, thereby obtaining a surface main strain value of a part, in which cracking just appears, of the sample; and finally, comparing the surface main strain value of the part, in which necking just appears, of the standard test sample with that of the part, in which cracking just appears, of the sample, thereby judging the sensitivity of the edge crack of the steel plate. The sensitivity of the edge crack of a material can be accurately evaluated by the method provided by the invention.

Description

technical field [0001] The invention relates to the technical field of steel rolling, in particular to an evaluation method for edge crack sensitivity of high-strength thin steel plates. Background technique [0002] The demand for lightweight automobiles has led to an increasing use of high-strength steel sheets. During the use of high-strength steel, in addition to being prone to stamping cracks, there will also be cracks at the edge of parts in the early stage of stamping. This is caused by hardening and burrs at the edge of the high-strength steel sheet during blanking or trimming. [0003] The forming limit diagram can be used to evaluate the bulging performance of thin steel sheet. For the simple flanging forming method, the evaluation of hole expansion rate can be used. However, there is no unified evaluation method for the early cracking of the edge accompanying the stamping bulging process. The early cracking of the edge in the bulging process is not only related...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N3/08
Inventor 邝霜韩赟刘华赛姜英花朱国森王勇围齐秀美刘广会陈连峰
Owner SHOUGANG CORPORATION
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