A heat treatment method for improving the impact toughness of the core of large-section low-alloy high-strength steel forgings

Abstract

The invention discloses a heat treatment method for improving the impact toughness of the core of a large-section low-alloy high-strength steel forging. The steps include: high-temperature normal tempering→low-temperature quenching and tempering pretreatment→high-temperature quenching+sub-temperature quenching+high-temperature tempering. The method of the invention breaks through the traditional heat treatment method of realizing core performance by hardenability, studies the characteristics of structure transformation, and the relationship between structure and performance, and achieves the purpose of improving performance by realizing a specific metallographic structure. Its advantages are: it does not need to increase the addition of alloy components, which reduces production costs; it has lower requirements for production equipment and reduces equipment investment.

Description

technical field [0001] The invention belongs to the technical field of alloy manufacture, and in particular relates to a heat treatment method for improving the impact toughness of the core of a large-section low-alloy high-strength steel forging. Background technique [0002] Low-alloy high-strength steel forgings have high strength, good plastic toughness, low brittle transition temperature, good thermal stability, weldability and other process properties after quenching and tempering treatment, and have a wide range of applications in petrochemical, energy equipment and other fields. Applications. However, for some parts with large cross-section and high performance requirements, due to the limitation of hardenability, the performance requirements can only be achieved near the surface, and the performance of the core, especially the impact toughness, varies greatly. Moreover, due to the requirements of weldability, there is a strict limit on the carbon equivalent of the ...

AI Technical Summary

Problems solved by technology

However, for some parts with large cross-section and high performance requirements, due to the limitation of hardenability, the performance requirements can only be achieved near the surface, and the performance of the core, especially the impact toughness, varies greatly.

And due to the requirements of weldability, there is a strict limit on the carbon equivalent of the material, and the hardenability cannot be improved by increasing the alloy composition. Therefore, how to improve the impact toughness of the core of large forgings has always been an important research for the development of low-alloy high-strength steel large-section forgings. topic

[0003] S500Q steel is the above-mentioned type of steel. For pie forgings made of this steel with a diameter of more than 1m and a thickness of more than 350mm, the sampling position is 180mm from the outer diameter and at the center of the thickness (drawing can be made), which completely exceeds this steel. Hardenability depth range, relying on conventional quenching and tempering process, the average impact energy of the sampling position is ≤40J, which cannot meet the standard requirement of 47J

Images