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Delayed fracture prevention method for steel structure and steel structure manufacturing method

A manufacturing method and steel structure technology, applied in the direction of manufacturing tools, welding equipment, metal processing equipment, etc., can solve the problems of reduced toughness, prevention of delayed damage by undisclosed ultrasonic vibration, delayed damage, etc.

Active Publication Date: 2005-12-21
NIPPON STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0010] In this case, since the hydrogen remaining in the steel during the casting process is not sufficiently removed, the rolling is performed to form a thick steel plate shape, so if the hydrogen is released during the cooling process after rolling when the temperature is high And if the amount of hydrogen is reduced, the toughness caused by hydrogen generation will decrease, or the risk of delayed failure will increase
[0011] As a result, problems in the process cannot be avoided, such as the position for slow cooling of the rolled steel plates, heating and heat preservation equipment, and the increase in the time required for them (for example, refer to JP Patent No. 3298519).
[0012] In addition, for example, in the US6171415 patent specification, there is disclosed a method of improving the fatigue strength by applying ultrasonic vibration to the welded joint part, but this document does not disclose the content of using ultrasonic vibration for delayed fracture prevention.

Method used

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  • Delayed fracture prevention method for steel structure and steel structure manufacturing method
  • Delayed fracture prevention method for steel structure and steel structure manufacturing method
  • Delayed fracture prevention method for steel structure and steel structure manufacturing method

Examples

Experimental program
Comparison scheme
Effect test

no. 1 Embodiment

[0028] figure 1 An example in which the delayed failure prevention method of the present invention is applied to a high tension bolt is shown.

[0029] For example, if 1000N / mm 2 If the level of high tension bolts acts on repeated loads, fatigue damage will occur.

[0030] The starting point of this fatigue failure is the area called "fish eye". In this area, due to the internal stress located around the inclusions, the hydrogen present in the steel concentrates around the inclusions, and the local damage resistance deteriorates. Crack formation under small repeated stresses.

[0031] This phenomenon is generally 800N / mm 2 The phenomenon shown in the above high-strength steel materials, however, in welded joints containing a large amount of hydrogen, sometimes even 600N / mm 2 The intensity level of the level also causes problems.

[0032] In steel materials, there are many inclusions, and there are inclusions that form the starting point of fish eyes and inclusions that do...

no. 2 Embodiment

[0038] figure 2 Examples are shown of steel sheets to which the method for preventing delayed failure of the present invention is applied to tensile stress.

[0039] For example, there is a tensile stress of 800N / mm in the action 2 level steel plate, provided with figure 2 In the case of openings as shown, stress concentration occurs at the edge of the opening indicated by the lattice pattern, and hydrogen concentrates at the inclusions where the stress concentration exists as in the first embodiment, thereby deteriorating the local fracture resistance. , Even under the action of small repeated stress, cracks still occur and fish eyes are formed.

[0040] So, in figure 2 In this method, ultrasonic impact treatment is performed on the edge of the opening at the position indicated by the grid pattern, which is impacted with an ultrasonic vibration terminal with a diameter of 1 to 5 mm at the front end. The surrounding area of ​​the TiN precipitates with high internal stre...

no. 3 Embodiment

[0042] image 3 An example in which the method for preventing delayed failure of the present invention is applied to an intersection of a plurality of welding lines is shown.

[0043] For example, in welded structures such as ship hulls, such as image 3 As shown, a portion where a plurality of welding lines of A and A' intersect occurs.

[0044] Since the heating input of welding overlaps, the intersection of the plurality of welding lines becomes the highest residual stress, and the stress concentration is remarkable.

[0045] If tensile stress acts on the stress-concentrated portion, hydrogen will concentrate in the surrounding inclusions, and similar to the first and second examples, the local fracture resistance will deteriorate, and cracks will still occur even under small repeated stresses. , forming a fisheye.

[0046] Figure 4 to represent image 3 A detailed view of the intersection of the welding lines.

[0047] exist Figure 4 In this method, ultrasonic sho...

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Abstract

The present invention provides a method for preventing delayed failure of a steel structure and a method for manufacturing the steel structure. A method for preventing delayed failure of a steel structure. The steel structure includes steel with a tensile strength greater than or equal to 600N / mm2 and / or welded joints of the steel. Ultrasonic impact treatment is performed on the surface of the stress concentration part of the steel structure. The ultrasonic impact treatment is impacted with an ultrasonic vibration terminal having a diameter of 1 to 5 mm at the front end.

Description

technical field [0001] The present invention relates to the tensile strength greater than or equal to 600N / mm 2 A method for preventing delayed failure of a steel structure formed by a steel material and / or a welded joint of the steel material, and a method for manufacturing a steel structure using the method. Background technique [0002] Hydrogen present in steel structures such as high tensile bolts, crankshafts and other components, ships, bridges, buildings and other structures reduces the toughness of steel structures. [0003] In particular, the hydrogen present in the steel structure is a cause of delayed fracture where stress concentration tends to occur due to bending stress and tensile stress. Therefore, a dehydrogenation method for steel sheets has been proposed in the past. [0004] As methods for reducing the hydrogen concentration in steel, degassing treatment of molten steel and heat preservation of cast slabs are carried out, and heating and heat preservati...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B23K31/00C21D7/04
CPCC21D7/04B23K31/00
Inventor 石川忠中岛清孝野濑哲郎
Owner NIPPON STEEL CORP
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