30CrMnSiNi2A belongs to low-alloy ultra-high-strength steel, which is obtained by adding 1.4% to 1.8% Ni on the basis of high-strength steel 30CrMnSiA. Due to the addition of Ni, the toughness and plasticity of steel are improved, and the hardenability of steel is greatly improved. Parts with a cross-sectional diameter of less than 50mm can be completely hardened in oil. The raw materials and manufacturing costs of this low-alloy ultra-high-strength steel are relatively low, and my country is used to manufacture various missile engine shells.

▶ In the mid-1940s, the United States used AISI4340 structural steel to reduce the tempering temperature to increase the tensile strength of the steel to 1600~1900 MPa.

▶ After the 1950s, various countries have successfully developed a variety of low-alloy and medium-alloy ultra-high-strength steels, such as 300M, D6AC and H-11 steels.

▶ Successfully developed maraging steel in the 1960s, and gradually formed 18Ni maraging steel series.

▶ In the mid-1970s, the United States successfully developed high-purity HP310 steel with a tensile strength of 2200MPa. The 35NCDl6 steel developed by France has a tensile strength greater than 1850MPa, and the fracture toughness and stress corrosion resistance have been significantly improved.

▶ In the early 1980s, the United States successfully developed AFl410 secondary hardening ultra-high-strength steel. When the tensile strength was 1860 MPa, the fracture toughness of the steel reached 160 MPa or more. AFl410 steel is currently being promoted and applied in the aviation and aerospace industry. Kind of new material.

In the early 1950s, my country successfully developed 30CrMnSiNi2A ultra-high strength steel with a tensile strength of 1700 MPa. In the early 1970s, combined with China's resource conditions, it was successfully developed:
● 32Si2Mn2MoVA
● 40CrMnSiMoVA

Since 1980, the introduction of new technologies from abroad and the use of new vacuum smelting processes have successively developed:
● 45CrNiMoVA (D6AC)
● 34Si2MnCrMoVA (406A)
● 35CrNi4MoA
● 40CrNi2Si2MoVA (300M)
● 18Ni maraging steel
And successfully used in the manufacture of aircraft landing gear, solid fuel rocket engine housing and enriched uranium centrifuge housing, etc. At present, ultra-high-strength steel has formed a series of different strength levels, playing an important role in the national defense industry and economic construction.

At present, it is very difficult to improve the strength and toughness of the steel by changing the alloy composition. To develop a more practical and larger 30CrMnSiNi2A steel, it is necessary to develop new processes and new technologies to improve metallurgical quality, such as vacuum smelting technology. Starting to limit the content of gas and impurity elements in steel, through multi-directional forging, thermomechanical heat treatment and the addition of various new processes, China has successfully trial-produced 30CrMnSiNi2A high-strength steel with a diameter of more than 800 mm and an ultra-large size of over 800 mm. The product indicators have reached Standard requirements will be applied to the field of ships. The successful development of this product has filled the domestic gap and further enhanced the market competitiveness in this field.

The large diameter 30CrMnSiNi2A bar also has excellent hardenability, toughness, tempering resistance, and good fatigue resistance and fracture toughness. It is mainly used to make important load-bearing structural components. It was previously used in China's aviation industry. Is widely used.

It is very difficult to produce the super large size 30CrMnSiNi2A bar with a diameter of 800 mm. There is no precedent for successful production in China. Researchers understand that the ship industry has a certain demand for large diameter 30CrMnSiNi2A rods with a diameter of 800 mm. Combining existing smelting equipment and technology, plus the special requirements and use experience of users, they have formulated China's large diameter 30CrMnSiNi2A rod production standards. And technical specifications.

In order to ensure the smooth progress of the first trial production, the researchers of Fushun Special Steel have carefully planned the smelting, processing and heat treatment processes of 30CrMnSiNi2A steel. During the trial production process, the scientific research personnel carried out the whole process tracking calibration. With the joint efforts of relevant units, the composition of the electrode smelted by 30CrMnSiNi2A reached the control requirement. After remelting and smelting, the steel ingot has qualified composition and good surface quality, and finally forged into a bar with a diameter of 800 mm. After inspection, the product chemical composition, high- and low-magnification structure and other performance indicators meet the standard requirements.