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High-strength bolt steel with excellent delayed fracture resistance and preparation method thereof

A technology of high-strength bolts and delayed fracture resistance, applied in the field of bolt steel, can solve the problems of deteriorating delayed fracture resistance and not using microalloying elements to refine grains, etc.

Active Publication Date: 2021-08-31
BAOSHAN IRON & STEEL CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This invention does not take advantage of the grain refinement effect of microalloying elements, and does not specify the grain size of the material. Since the delayed fracture of high-strength materials often occurs on the grain boundaries of coarse grains, excessive grain size will significantly deteriorate Delayed Fracture Resistance

Method used

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  • High-strength bolt steel with excellent delayed fracture resistance and preparation method thereof
  • High-strength bolt steel with excellent delayed fracture resistance and preparation method thereof
  • High-strength bolt steel with excellent delayed fracture resistance and preparation method thereof

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Embodiment Construction

[0050] The present invention will be further described below in conjunction with embodiment.

[0051] The chemical compositions of the high-strength bolt steel examples A1~A10 of the present invention and three comparative examples steels B1~B3 are as shown in Table 1, and Table 2 shows the examples A1~A10 of the present invention and the comparative examples B1~B3. The preparation process of B3.

[0052] The specific preparation method is as follows:

[0053] The alloys of Examples A1-A5, B2, and B3 of the present invention are smelted in an electric furnace, the alloys of Examples A6-A10, and B1 are smelted in a converter, and then refined outside the furnace, and the alloys of Examples A1-A4, A8-A10, and B1 are smelted in LF Furnace plus VD refining, and embodiment A5~A7, B2, B3 alloy adopts LF to add RH treatment, optimizes synthetic slag structure and alkalinity, embodiment A1~A6, B1 vacuum degassing time 35 minutes, embodiment A7-10# , B2, B3 vacuum degassing time is 4...

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Abstract

The invention provides high-strength bolt steel with excellent delayed fracture resistance and a preparation method thereof. The high-strength bolt steel comprises the following components in percentage by weight: 0.35-0.50% of carbon, 0.20-0.70% of manganese, 0.75-1.35% of chromium, 0.55-1.45% of molybdenum, 0.10-0.50% of vanadium, 0.005-0.10% of aluminum, 0-0.005% of sulfur, 0.02-0.05% of silicon, 0.005-0.15% of titanium, 0.0005-0.003% of oxygen, 0.001-0.007% of nitrogen, and the balance iron and other inevitable impurities; the content of titanium is not less than 3.5 times of the content of nitrogen; the sum of the contents of chromium, molybdenum and vanadium is not lower than 1.75%; and the sum of the contents of sulfur, oxygen and nitrogen is not higher than 0.01%. The high-strength bolt steel is high in purity and refined in grains, can be used for manufacturing high-strength bolts with tensile strength not lower than 1400MPa, has a section shrinkage rate not lower than 50%, is excellent in delayed fracture resistance, and can be applied to automobiles and mechanical parts.

Description

technical field [0001] The invention relates to steel for bolts, in particular to a steel for high-strength bolts with excellent delayed fracture resistance and a preparation method thereof. Background technique [0002] Threaded and bolted connections are one of the most common connections between automotive and mechanical components. Threaded connection has the advantages of convenient disassembly and assembly, simple structure and reliable connection. According to the national standard GB / T3098.1 "Mechanical Properties of Fasteners Bolts, Screws and Studs", most of the commonly used fasteners are grade 8.8~12.9 (equivalent to 800MPa~1200MPa tensile strength level). In the latest revision of the standard, the applicable highest strength grade for high-strength fasteners is grade 12.9, and fasteners with higher strength grades have not yet formed standards. At present, various steel mills and fastener manufacturers generally use 35CrMo (SCM435) and 42CrMo (SCM440) for the...

Claims

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Application Information

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IPC IPC(8): C22C38/02C22C38/04C22C38/06C22C38/22C22C38/24C22C38/28C21D8/06C21D1/74C21D1/32C21D1/25
CPCC22C38/04C22C38/22C22C38/24C22C38/06C22C38/02C22C38/28C22C38/001C22C38/002C21D8/065C21D1/32C21D1/74C21D1/25C21D2211/009C21D2211/005C21D2211/002
Inventor 金峰赵浩洋翟瑞银姚赞
Owner BAOSHAN IRON & STEEL CO LTD
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