High-strength toughness low-medium carbon micro-alloyed air-cooled hardened spring steel and its forming and heat treatment process

Abstract

The invention discloses a high-strength toughness low-medium carbon micro-alloy air-cooled hardened spring steel and its forming and heat treatment process. The composition of the existing spring steel leads to high production costs. The chemical composition of the spring steel of the present invention is calculated as: C : 0.15% to 0.50%, Si: 0.30% to 2.00%, Mn: 0.60% to 2.50%, S: ≤0.020%, P: ≤0.025%, B: 0.0005% to 0.0035%, and the balance is iron. The steel of the present invention can be obtained by controlled cooling after being heated to 900-1050°C for heat preservation. Pearlite and upper bainite) metallographic structure. Then low-temperature tempering can further improve the performance, so that the mechanical properties of the material can reach Rm≥1350MPa, yield strength Rp0.2≥1050MPa, elongation after fracture A≥10%, and reduction of area Z≥35%. Adopting the steel of the invention can simplify the manufacturing process of the spring, save energy and reduce cost.

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...

AI Technical Summary

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

Images