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High-hardenability medium-carbon low-alloy round steel for fastener and manufacturing method of high-hardenability medium-carbon low-alloy round steel

A technology of high hardenability and fasteners, applied in the direction of manufacturing tools, furnace types, furnaces, etc., can solve the problems that cannot meet the hardness distribution and strength and toughness matching requirements of the core quenched structure, so as to improve hardenability and reduce The effect of production costs

Active Publication Date: 2017-03-22
JIANGYIN XINGCHENG SPECIAL STEEL WORKS CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

At present, steels such as 32CrB4 or 42CrMo are usually used to produce fasteners with specifications below 45mm. For fastener products with specifications ≥ 45mm, steels such as 40CrNiMo and 4140MOD with higher content of precious metals such as Mo and Ni are usually used, otherwise the core cannot be satisfied. Quenching structure, cross-sectional hardness distribution and matching requirements for strength and toughness

Method used

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  • High-hardenability medium-carbon low-alloy round steel for fastener and manufacturing method of high-hardenability medium-carbon low-alloy round steel
  • High-hardenability medium-carbon low-alloy round steel for fastener and manufacturing method of high-hardenability medium-carbon low-alloy round steel
  • High-hardenability medium-carbon low-alloy round steel for fastener and manufacturing method of high-hardenability medium-carbon low-alloy round steel

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0023] The steel used for fasteners involved in this example has a diameter of 64mm and is heat-treated according to the requirements of grade 10.9 fasteners. Its chemical composition is calculated by mass percentage: C: 0.42%, Si: 0.25%, Mn: 0.95%, Cr: 1.10%, Mo: 0.10%, Ni: 0.12, Cu: 0.12%, Al: 0.018%, B: 0.0020%, Ti: 0.025%, and the balance is iron and unavoidable impurity elements.

[0024] Process flow: The main raw materials are smelted in an electric furnace, LF refining, and VD degassing to produce molten steel in sequence. After refining, titanium wire and ferroboron are fed; the molten steel is poured into a continuous casting slab with argon protection at a low superheat of 15-30°C throughout the process. , the continuous casting slab is slowly cooled for 32 hours; the continuous casting slab is heated to 1250°C, and kept for 4 hours; after descaling by high-pressure water, it is rolled at a temperature of 1150°C and rolled into round steel bars; The roller hearth fu...

Embodiment 2

[0031] The diameter of the fastener steel involved in this example is 54 mm, and it is heat-treated according to the requirements of grade 10.9 fasteners. Its chemical composition is calculated by mass percentage: C: 0.37%, Si: 0.22%, Mn: 0.95%, Cr: 1.10%, Mo: 0.08%, Ni: 0.10, Cu: 0.10%, Al: 0.022%, B: 0.0023%, Ti: 0.028%, and the balance is iron and unavoidable impurity elements.

[0032]The above round steel is sequentially smelted by electric furnace, LF refined, and VD degassed to produce molten steel. After refining, titanium wire and ferroboron are fed into the molten steel; The slab is heated at 400°C; the continuous casting slab is heated to 1200°C and held for 4 hours; after being descaled by high-pressure water, it is rolled at a temperature range of 1100°C and rolled into round steel bars; the bars are rolled into round steel bars on the induction line After austenitization at 880°C / 5 minutes, it is quenched with a quenching ring, then tempered at 550°C / 5 hours in a...

Embodiment 3

[0039] The diameter of the fastener steel involved in this embodiment is 48 mm, and it is heat-treated according to the requirements of grade 8.8 fasteners. Its chemical composition is calculated by mass percentage: C: 0.36%, Si: 0.21%, Mn: 0.92%, Cr: 1.08%, Mo: 0.08%, Ni: 0.06, Cu: 0.08%, Al: 0.023%, B: 0.0025%, Ti: 0.026%, and the balance is iron and unavoidable impurity elements.

[0040] The above-mentioned round steel is sequentially processed by KR pretreatment, converter smelting, LF refining, and RH degassing to produce molten steel. After refining, it is fed with titanium wire and ferroboron; Casting slab, continuous casting slab is heated at 400°C; the continuous casting slab is heated to 1200°C, held for 4 hours and released from the furnace; after descaling by high-pressure water, it is rolled at a temperature range of 1100°C, and rolled into round steel bars; rods The material is austenitized at 950°C / 4 minutes on a continuous induction line, quenched with a quenc...

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Abstract

The invention relates to high-hardenability medium-carbon low-alloy round steel for a fastener. Chemical ingredients of the high-hardenability medium-carbon low-alloy round steel comprise, by mass, 0.36-0.44% of C, 0.15-0.40% of Si, 0.80-1.00% of Mn, 1.00-1.15% of Cr, 0.05-0.25% of Mo, 0.05-0.25% of Ni, 0.05-0.25% of Cu, 0.015-0.050% of Al, 0.0010-0.0050% of B, 0.020-0.050% of Ti and the balance Fe. The largest diameter of the round steel is 65 mm. The production process comprises converter steel making, LF refining, RH / VD degassing, Ti wire and ferroboron feeding, continuous casting, bar rolling, and quenching and tempering treatment, and therefore the quenched and tempered round steel is obtained. The quenched and tempered round steel can be directly used for machining fasteners such as 10.9-level bolts which meet the ISO 898-1 standards.

Description

technical field [0001] The invention belongs to the technical field of manufacturing special round steel, and in particular relates to a medium-carbon low-alloy round steel with high hardenability that can meet the mechanical performance requirements of 65mm fasteners after quenching and tempering and a manufacturing method thereof. Background technique [0002] Most of the fastener products currently on the market are produced according to ISO898-1: mechanical properties of fasteners-bolts, screws and studs. Table 3 in this standard puts forward very strict mechanical and physical properties of fasteners. Requirements, the difficulties are: ① After quenching, the core martensitic structure of the steel must reach more than 90%; ② On the basis of meeting the strength and hardness range of each strength level, it is also necessary to meet the surface and core Vickers hardness HV0. The difference between 3 ≤ 30HV; ③Using the overall tensile sample with 75% of the diameter of t...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/02C22C38/04C22C38/44C22C38/42C22C38/06C22C38/54C22C38/50C21D8/06C21D1/18
CPCC21D1/18C21D8/065C22C38/02C22C38/04C22C38/06C22C38/42C22C38/44C22C38/50C22C38/54C21D2211/008C21D6/004C21D6/005C21D6/008C21D9/0093C21D9/525
Inventor 冀鸰许晓红胡绍鑫邵淑艳孔祥伟朱云海聂爱诚黄镇
Owner JIANGYIN XINGCHENG SPECIAL STEEL WORKS CO LTD
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