Steel material surface quality examining method

A technology of surface quality and inspection method, applied in the field of surface quality inspection, can solve problems such as poor coating

Inactive Publication Date: 2006-01-18
TOYOTA JIDOSHA KK
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

There is also a risk of poor coating as follows: After the coating is carried out, as the scale

Method used

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  • Steel material surface quality examining method
  • Steel material surface quality examining method
  • Steel material surface quality examining method

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0087] Using a fixed spot welder as figure 1 The shown pressurization device 1 is used to carry out the method of the present invention. In addition, the measurement terminals 2 and 3 are insulated by removing the copper cable connecting the measurement terminals 2 and 3 and the transformer (not shown). and, if figure 1 As shown, the copper wire of the current generating device 5 and the copper wire of the voltage measuring device 7 are connected to the measuring terminals 2 and 3 .

[0088] set conditions

[0089] Measuring terminal: Cr-Cu electrode, dome radius (dome radius) type

[0090] Base end diameter 16mm Front end diameter 6mm (Front end 40R)

[0091] Pressure: 87N / mm 2 (250kgf)

[0092] Current: DC current 2A

[0093] The "critical value" used as the evaluation standard of the surface quality of the steel sheet is set by repeating operations (a) to (d) as follows: As a sample, a hot-pressed member 4 using a cold-rolled steel sheet with a thickness of...

Embodiment 2

[0101] The difference between this embodiment and the above-mentioned embodiment 1 is that a hot-pressed member obtained by hot-pressing a hot-rolled steel plate with a plate thickness of 1.4 mm was used as a sample. This example is the same as Example 1 except for that.

[0102] The results are shown in Table 2.

[0103]

Sample No

R scale (mΩ)

According to resistance

test result

actually welded

verify results

1

84.2

NG

NG

2

105.3

NG

NG

3

64.3

NG

NG

4

32.5

NG

NG

5

20.7

NG

NG

6

14.0

OK

OK

7

5.1

OK

OK

8

0.4

OK

OK

[0104] The hot-press member 4 judged as "NG" in the inspection result tends to be welded by spot welding. Therefore, it was confirmed that the method of the present invention can accurately inspect spot weldability.

[01...

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Abstract

A method for simply and reliable examining the weldability of a steel material, for example the oxidization scale of a hot-press steel material. (i) Two measurement terminals that can be pressed under a constant pressing pressure of 8.7 to 208 N/mm<2> are pressed against a member made by a hot-pressing a hot-rolled steel sheet (cold-rolled steel sheet), a constant current of 30 A or less is made to flow between the measurement terminals to measure the voltage between the measurement terminals. (ii) The steel material is subjected to a spot-welding test, and it is judged that this welding is acceptable or not. (iii) With reference to the voltage between the measurement terminals measured about the steel material judged as acceptable, a range of the voltage or resistance between the measurement terminals leading to favorable result of the spot-welding test is determined. (iv) The voltage between the measurement terminals about a steel material is measured in spot welding of actual operation, the spot weldability of this steel material is predicted and judged according to whether the measured voltage value is within the range.

Description

technical field [0001] The invention relates to a method for checking the surface quality of steel materials. Background technique [0002] Hot pressing is a technology that applies oil pressure to a steel plate that is loaded into a heating furnace and heated to about 900°C with a water-cooled metal mold, thereby quenching and pressing it into various parts made of high-strength steel. In particular, recently, this hot pressing has been widely applied to various steel materials including thin steel sheets. Thereby, high-strength hot-pressed parts can be produced. [0003] The steel material to be hot-pressed is heated to a high temperature of about 900°C before stamping. Therefore, scale is inevitably generated on the surface of the heat-pressed member accompanying this heating. [0004] If spot welding is performed directly after hot pressing on such a hot-pressed part with scale on its surface, the Joule heat generated at the scale-forming part in contact with the elec...

Claims

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Application Information

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IPC IPC(8): G01N27/04G01N33/20
CPCG01N33/20G01N33/207
Inventor 富士本博纪福井清之铃木干治
Owner TOYOTA JIDOSHA KK
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