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Method for measuring critical strain of continuous casting billet corner crack propagation

A technology of critical strain and corner cracks, applied in the direction of applying stable tension/pressure to test the strength of materials, measuring devices, instruments, etc., to achieve the effect of simple test process and accurate test results

Active Publication Date: 2021-05-25
NORTHEASTERN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Moreover, the determination method for the test temperature of the middle crack is not applicable to the corner crack.

Method used

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  • Method for measuring critical strain of continuous casting billet corner crack propagation
  • Method for measuring critical strain of continuous casting billet corner crack propagation
  • Method for measuring critical strain of continuous casting billet corner crack propagation

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0056] A method for measuring the critical strain of crack propagation at the corner of a continuous casting slab, comprising the following steps:

[0057] (1) Sampling

[0058] In order to avoid central segregation and serious porosity, samples were taken from the area formed between the thickness 1 / 4 line, the width 1 / 4 line and the distance from the surface of 10mm to obtain continuous casting slab samples; and the continuous casting slab samples were lined Cutting and turning to obtain the thin-section standard tensile specimen for the corner crack test (standard: the length of the specimen is 57mm, the thickness is 1.5mm, the gauge length is 17mm, the diameter of the sheath hole is Φ5, and the chamfer is Φ10). The schematic diagram of the sampling position is as follows figure 1 As shown, the obtained standard tensile specimens are prepared for tensile experiments;

[0059] (2) Prefabricated cracks

[0060] Because the obtained standard tensile specimen is thin-sheet ty...

Embodiment 2

[0075] A method for measuring the critical strain of crack propagation at the corner of a continuous casting slab, comprising the following steps:

[0076] (1) Sampling

[0077] In order to avoid central segregation and areas where porosity is more serious, the sample is sampled from the area formed between the thickness, width 1 / 4 line and the distance from the surface to 10mm to obtain the continuous casting slab sample. In this embodiment, the distance from the surface to the Sampling within 15mm;

[0078] Carry out wire cutting and turning processing on the continuous casting slab sample to obtain the standard tensile sample;

[0079] (2) Prefabricated cracks

[0080] It is used on a fatigue testing machine to prefabricate a V-shaped notch on a standard tensile sample by controlling the load or controlling the displacement. The depth is 0.5mm, and the notch angle is 35°. In order to understand the influence of sample surface roughness and small defects in the processing...

Embodiment 3

[0091] A method for measuring the critical strain of crack propagation at the corner of a continuous casting slab, the same as in Example 2, the difference is that:

[0092] (5) In the stress-strain curve of the specimen broken at the tensile temperature, the strain corresponding to the peak stress is the critical strain for crack propagation at the corner of the continuous casting slab.

[0093] By comparing the strain (Example 2) corresponding to the crack propagation in the metallographic photograph obtained during in-situ stretching and the strain value (Example 3) corresponding to the peak stress in the obtained stress-strain curve for consistency comparison, There is a difference of 0.005 between the two methods for determining the critical strain of crack propagation at the corner of the continuous casting slab, and the agreement is good.

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Abstract

The invention discloses a method for measuring critical strain of continuous casting billet corner crack propagation, and belongs to the technical field of continuous casting. The method comprises the following steps: sampling on a continuous casting billet, and setting reasonable notch depth and angle to prefabricate cracks; then simulating a corner temperature field of the casting blank in the continuous casting process, judging a crack sensitive area, and determining a heating schedule and a deformation speed; and finally, carrying out an in-situ tensile test in combination with the actual strain rate of the crack sensitive area, dynamically observing and analyzing the microscopic deformation morphology and fracture mechanism of the material, and recording the change condition of the metallographic structure during stretching in real time; and determining the critical strain of the corner crack propagation by combining the tensile length when the crack propagation phenomenon occurs and a stress-strain curve obtained in the test. The method for measuring the critical strain of the corner crack propagation of the continuous casting billet is more universal, is not limited by components, and is simple in test process and accurate in test result.

Description

technical field [0001] The invention relates to the technical field of continuous casting, in particular to a method for measuring the critical strain of crack propagation at the corner of a continuous casting slab. Background technique [0002] Cracks are one of the main quality problems of continuous casting slabs, and cracks account for about 50% of all kinds of defects. In the continuous casting process, microalloying elements such as Nb, V, Ti in steel form fine dispersed carbides, nitrides and carbonitrides with C and N, and form thin film ferrite at austenite grain boundaries or grain boundaries. Particles precipitate out, which makes the high-temperature thermoplasticity of steel worse, and cracks are prone to occur on the surface of continuous casting slabs, especially the incidence of transverse cracks and transverse cracks at corners is significantly higher than that of ordinary steel slabs. During the continuous casting process, the corners of the slab are coole...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N3/08G01N3/18G01N3/06
CPCG01N3/08G01N3/18G01N3/068G01N2203/0017G01N2203/0641
Inventor 祭程朱苗勇胡鑫陈天赐
Owner NORTHEASTERN UNIV
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