High strength weldable ageing hardening steel and its production method

Abstract

A weldable high-strength steel hardened by ageing contains proportionally C, Si, Mn, P, S, Nb, Mo, Ni, Ti, Cu, Cr and Fe. Its preparing process includes smelting, desulfurizing, top blowing, converting, vacuum treating, casting and rolling. Its advantages are excellent mechanical performance and low-temp toughness, and high resistance to atmosphere and seawater corrosion and fatigue.

Description

technical field [0001] The invention relates to the field of micro-alloyed steel manufacturing, in particular to a high-strength, easy-to-weld age-hardening steel especially suitable for ocean ships and oil drilling platforms and a production method thereof. Background technique [0002] With the increasingly tense use of energy in the world, my country has turned its attention to oil exploration from land to sea, and large-scale offshore oil drilling platforms must be built to exploit oil at sea, which requires steel to have excellent welding performance and formability. It also has high strength, high toughness and good seawater corrosion resistance. Before the application of the present invention, the publication specification of Chinese invention patent application with the application number of 85103631 introduced a marine zero-nine-manganese-niobium low-alloy steel. The production method, the production cost is higher. Moreover, the content of ...

AI Technical Summary

Problems solved by technology

Before the application of the present invention, the publication specification of Chinese invention patent application with the application number of 85103631 introduced a marine zero-nine-manganese-niobium low-alloy steel. The production method, the production cost is higher

Moreover, the content of P and S in the steel produced by injection molding steel ingot is relatively high, and the steel plate is brittle, and its impact energy in the transverse direction at -40°C is only 24J; in addition, this low-alloy steel mainly uses C and Mn as strengthening elements. The improvement of steel strength is very limited, and its yield strength is only 370MPa; therefore, the strength and low-temperature toughness of this low-alloy steel plate are obviously insufficient. When used in a very harsh environment such as the ocean, it is prone to fracture and damage, and its safety performance is poor

The Chinese Invention Patent Application Publication No. 98812446.7 describes a super-high-strength austenitic aging steel with excellent low-temperature toughness. The disadvantage of its process system is: to make the steel plate have an austenite content of about 2 to 10 vol%. The thin-film layer and about 90-98vol% of the micro-layered structure of the lath mainly composed of fine-grained martensite and fine-grained lower bainite are very difficult to operate, which will inevitably lead to a failure rate of product performance. The production cost is relatively high; and the performance of its embodiment is not clearly proposed in the patent application publication, so it can be considered that the possibility of its implementation is not large

It can be seen that the steel plate manufactured by using the above-mentioned zero-nine-manganese-niobium low-alloy steel for marine use cannot have high strength, high toughness, good seawater corrosion resistance and good economic performance at the same time, and it is difficult to meet the requirements of large-scale offshore oil drilling. Platform or marine vessel steel material needs; while using ultra-high strength austenitic aging steel as mentioned above, it is probably not practical