Process optimization and upgrading of weathering steel SPA-H

More than 90% of the world's containers are produced in China. In the past two years, there has been a significant increase in the import and export of containers. Hot-rolled weathering steel for container production has a good market. The main weathering steel used in the production of containers are SPA-H, Q355NH, and the specifications are mainly 1.6~ 6.0mm hot rolled plate. In order to ensure that the steel plate used for container has good mechanical properties and corrosion resistance, a certain amount of Cu, Ni, P, Cr and other alloy elements are added in the process of hot rolled plate production, among which Ni element is the most expensive alloy.

Due to the high alloy content of the weathering steel plate used in container, the large temperature drop of the billet and the thin specifications of the hot rolling, the problems of cold bending cracking often occur.

There are a series of technical difficulties in cost optimization of weathering steel SPA-H in CSP production line. The main problems in the steel zone are the longitudinal crack defects of the casting billet, which will cause steel leakage accidents in serious cases. In order to ensure the normal casting of the casting machine, the composition design of SPA-H steel is in accordance with nickel > 0.10% group production.

By carrying out the process composition optimization test, the Ni element in weathering steel SPA-H steel was cancelled and replaced by Ti element. The influence of casting stability and billet quality on the casting machine was tracked and verified to ensure that the finished product performance met the technical standards.

In order to improve the competitiveness of the product market, on the premise of satisfying the stability of continuous casting production and mechanical properties of the product, the feasibility of using the design idea of adding Ti component to reduce the Ni content in weathering steel SPA-H was studied, so as to achieve the purpose of improving quality and reducing cost and increasing efficiency. 

After the process optimization and performance analysis of the CSP process of weathering steel SPA-H, the low-cost weathering steel SPA-H products were successfully trial-produced and evaluated in the downstream container industry. The performance of the products met the requirements of customers.