Air cooling hardened spring steel with high obdurability, low-medium-carbon and microalloy and forming and heat treatment process thereof

Abstract

The invention discloses an air cooling hardened spring steel with high obdurability, low-medium-carbon and microalloy and a forming and heat treatment process thereof. Existing spring steel is high in cost due to components. The air cooling hardened spring steel with the high obdurability, low-medium-carbon and the microalloy comprises, by weight, 0.15%-0.50% of C, 0.30%-2.00% of Si, 0.60%-2.50% of Mn, 0-0.020% of S, 0-0.025% of P, 0.0005% ~ 0.0035% of B, and the balance Fe. After the steel is heated to 900-1500 DEG C and the temperature is kept, metallographic structure containing the major bainite and martensite, a small amount of retained austenite, and no other non-martensitic structures (free ferrite, pearlite and upper bainite) can be obtained by adopting controlled cooling. Then properties can be further improved through low temperature tempering treatment; material mechanical property Rm>=1350 MPa; yield strength Rp0.2>=1050MPa; percentage elongation after fracture A>=10%; section shrinkage Z>=35%. The air cooling hardened spring steel with the high obdurability, the low-medium-carbon and the microalloy is adopted, so that the manufacturing process of springs is simplified, energy is saved, and cost is reduced.

Description

technical field [0001] The invention relates to a high-strength toughness low-medium carbon micro-alloy air-cooled hardened spring steel and its forming and heat treatment process, which is used to manufacture elastic parts such as coil springs with a material diameter of Φ10mm to Φ60mm, automobile stabilizer bars, and torsion bars. Background technique [0002] Generally, the process of making spring products with traditional spring steel is mainly divided into two categories: one is to use hard state, that is, materials that reach high strength and high elastic limit after heat treatment, and usually only need to carry out low temperature stress relief treatment after processing and forming It can meet the requirements of use. At present, it is mostly used for springs made of materials with smaller specifications. The other type is that springs with large specifications are mostly made of soft materials that have not been strengthened by heat treatment. Usually, there are t...

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Problems solved by technology

[0009] The purpose of the present invention is to address the technical problems introduced by the above background technology. Based on the characteristics that the cross-section of spring products is not too large and uniform, it is possible to reduce the cost of spring steel through the optimization of composition design from the perspective of obtaining bainite structure. When the increase is not much, the spring is directly cooled with air (air-cooled or air-cooled) after high-temperature heating to obtain a quenched structure mainly composed of bainite and martensite, and then tempered at a low temperature to obtain excellent mechanical properties. Provide a high-strength toughness low-medium carbon micro-alloy air-cooled hardened spring steel and its forming and heat treatment process

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