High-weather-resistant cold heading steel for 10.9 grade fastener and production method of high-weather-resistant cold heading steel

Abstract

The invention discloses a high-weather-resistant cold heading steel for a 10.9 grade fastener and a production method of the high-weather-resistant cold heading steel, and belongs to the technical field of cold heading steel production. The main chemical composition of the high-weather-resistant cold heading steel comprises, by mass percentage content, 0.33-0.43% of C, 0.20-0.50% of Si, 0.35-0.55%of Mn, 0.60-1.00% of Cr, 0.50-0.80% of Ni, 0.20-0.40% of Cu, 0.01-0.10% of V, 0.015-0.040% of Alt, 0.01-0.10% of Re, 0.010-0.030% of P, no greater than 0.0015% of O, no greater than 0.006% of N and the balance Fe and unavoidable impurities. The tensile strength Rm of the high-weather-resistant cold heading steel is less than or equal to 1040 MPa, the yield strength R<p0.2> is less than or equal to 940 MPa, the post-break elongation A is less than or equal to 9%, the area shrinkage Z is less than or equal to 48%, the yield ratio is less than or equal to 0.9, the requirements of the 10.9 gradefastener steel are met, the high weather resistance is achieved, and the production and use are facilitated.

Description

technical field [0001] The invention belongs to the technical field of cold heading steel production, and more specifically relates to a high weather resistance cold heading steel for 10.9 grade fasteners and a production method thereof. Background technique [0002] Cold heading steel is mainly used for the production of fasteners such as bolts, screws, and nuts. my country's railway construction maintains rapid development. The new high-standard railways and the transformation of existing lines into high-speed EMUs, high-power locomotives, and heavy-duty trucks are the most urgent activities. Firmware provides new market demand, and the replacement of in-service equipment on railway lines also provides market space for fasteners. China has a vast territory and complex natural climate environment. With the development of rail transit, higher requirements are put forward for cold heading steel for fasteners. There is an urgent need to develop cold heading steel materials with...

AI Technical Summary

Problems solved by technology

Fasteners made of steel produced by the method of the invention have good oxidation resistance and corrosion resistance, yield strength reaches 320-370MPa, tensile strength is 490-520MPa, and has good cold drawing, cold heading and hot upset processing. Process performance, good anti-oxidation and anti-corrosion performance at the same time, can meet the working requirements of high stress and high relaxation conditions in corrosive environments; but its tensile strength is below 520MPa, it cannot be used to make high-strength fasteners

[0005] The Chinese patent application number is: 201711215120.3, and the publication date is: 2018.05.25 "A 1040MPa weather-resistant bolt with delayed fracture resistance". The mass percentage of its chemical composition is: C: 0.21~0.32, Si: 0.10~0.50, Mn: 0.60~1.00, P: 0.008~0.020, S: ≤0.005, Cr: 0.82~1.20, Ni: 0.25~0.50, Cu: 0.25~0.50, Mo: 0.05~0.20, Nb: 0.015~0.060, V: 0.015~0.090 , Ti: 0.008~0.035, B: 0.0008~0.0035, Al: 0.015~0.040, Ca: 0.003~0.007, Zr: 0.015~0.045, Re: 0.010~0.045, the balance is Fe and unavoidable impurities; Prepare the steel material for anti-delayed fracture and weather-resistant bolts, which can resist delayed fracture and atmospheric corrosion; but the weather resistance index I value of the steel in this method is basically below 7.0, and only has general weather resistance

The material has the effect of atmospheric corrosion resistance, and has the characteristics of good mechanical properties, corrosion resistance, and good formability; but its weather resistance index I value cannot reach 7.0 or above

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