12.9-grade delayed-fracture-resistant weather-proof bolting steel and production method

A technology of delayed fracture and bolt steel, applied in the direction of manufacturing tools, heat treatment equipment, furnace types, etc., can solve the problems of increased delayed fracture risk, high notch sensitivity, brittle fracture of thread roots, etc., and achieve excellent atmospheric corrosion resistance and resistance. Delayed fracture performance, excellent toughness and excellent performance

Inactive Publication Date: 2021-04-23
NANJING IRON & STEEL CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The delayed fracture of high-strength bolts is mainly caused by the hydrogen existing in the raw material itself, the hydrogen entering during the bolt manufacturing process, and the hydrogen intruding during the bolt service process. It is easy to produce sudden brittle fracture at the root of the thread or the transition between the screw and the head, which will bring serious safety hazards
At present, since there are no industrial dehydrogenation standards and testing standards, the development of high-strength bolts resistant to delayed fracture at home and abroad is mainly concentrated in the field of material research. Studie

Method used

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  • 12.9-grade delayed-fracture-resistant weather-proof bolting steel and production method
  • 12.9-grade delayed-fracture-resistant weather-proof bolting steel and production method
  • 12.9-grade delayed-fracture-resistant weather-proof bolting steel and production method

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Experimental program
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Effect test

Embodiment 1

[0026] Embodiment 1 adopts electric furnace smelting, through LF refining+vacuum smelting, after vacuum treatment, hydrogen [H]=1.8ppm, continuous casting produces 150mm square continuous casting slab;

[0027] The heating temperature in the soaking section of the continuous casting slab is 990-1050°C, and the total heating time is 130 minutes. The bar factory rolls it into 22mm round steel, and adopts the same heat treatment process as the bolt processing for the round steel sample: the quenching temperature is 860°C, and the heat preservation is 40 minutes. , oil quenching, tempering temperature 550 ℃, heat preservation 80min, water cooling.

Embodiment 2

[0028] Example 2 is also smelted in an electric furnace, through LF refining + vacuum smelting, after vacuum treatment, hydrogen [H] = 1.6ppm, and continuous casting to produce a 150mm square continuous casting billet;

[0029] The heating temperature in the soaking section of the continuous casting slab is 1010-1060°C, and the total heating time is 135 minutes. The bar factory rolls it into 25mm round steel. The round steel sample adopts the same heat treatment process as the bolt processing: the quenching temperature is 890°C, and the heat preservation is 40min. , oil quenching, tempering temperature 580 ℃, heat preservation 80min, water cooling.

Embodiment 3

[0030] Embodiment 3 adopts electric furnace smelting, through LF refining + vacuum smelting, after vacuum treatment, hydrogen [H] = 1.5ppm, continuous casting to produce 150mm square continuous casting billet;

[0031] The heating temperature in the soaking section of the continuous casting slab is 1020-1070°C, and the total heating time is 140min. The bar factory rolls it into a 30mm round steel. The round steel sample adopts the same heat treatment process as the bolt processing: the quenching temperature is 920°C, and the heat preservation is 40min. , oil quenching, tempering temperature 620 ℃, heat preservation 80min, water cooling.

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Abstract

The invention discloses 12.9-grade delayed-fracture-resistant weather-proof bolting steel and a production method. The steel comprises the following components according to the mass percentages: 0.35-0.45% of C, 0.10-0.40% of Si, 0.50-0.90% of Mn, less than or equal to 0.012% of P, less than or equal to 0.005% of S, 0.80-1.20% of Cr, 0.20-0.50% of Cu, 0.80-1.20% of Ni, 0.10-0.50% of V, Nb and Ti, 0.10-0.50% of Mo, 0.015-0.045% of Alt and the balance Fe and inevitable impurities. By designing the components and production technology parameters, the strength of the steel reaches a 12.9 grade, and meanwhile, the steel has excellent atmospheric corrosion resistance performance and delayed fracture resistance performance.

Description

technical field [0001] The invention relates to a bolt steel and a preparation method thereof, in particular to a 12.9-grade delayed-fracture-resistant and weather-resistant bolt steel and a preparation method thereof. Background technique [0002] In the process of manufacturing and installing steel structure bridges and buildings, high-strength bolts are widely used in bridges and buildings because of their technical characteristics such as simple construction technology, convenient installation and disassembly, large bearing capacity, and not easy to loosen. The consumption of buildings has reached hundreds of thousands to millions of sets. Therefore, the design of high-strength bolts, the production of raw materials and the manufacture of high-strength bolt products have all received great attention worldwide. [0003] Highway bridges at home and abroad use up to 8.8 grade bolts, and railway bridges use up to 10.9 grade bolts. In the last century, Japan used 11.9 and 13...

Claims

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Application Information

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IPC IPC(8): C22C38/02C22C38/04C22C38/42C22C38/46C22C38/48C22C38/50C22C38/44C22C38/06C22C33/04C21D8/06C21D1/25C21D9/00
CPCC21D1/25C21D8/065C21D9/0075C22C33/04C22C38/02C22C38/04C22C38/06C22C38/42C22C38/44C22C38/46C22C38/48C22C38/50
Inventor 张瑞徐乐李英奎文辉朱思远
Owner NANJING IRON & STEEL CO LTD
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