Understand the current situation of spring steel production processes at home and abroad:
Pure steel smelting, alloying and microalloying, and controlled rolling and cooling technology support the development of domestic spring steel, but the two key indicators of surface defects and decarburization of domestic spring steel are difficult to reach the level of similar foreign products, and comparative research is needed. The comparison production process is as follows:
A. Domestic Baosteel
The production process is: scrap steel + molten iron-150t electric furnace-refining-continuous casting-billet surface peeling-heating-high-speed wire rolling-Stermore cooling-inspection and delivery; in addition, the process is blast furnace ironmaking –Pretreatment of molten iron – converter steelmaking – secondary refining – die casting – blooming – billet finishing – wire rod rolling – inspection and delivery.
Features: Strengthen the refining operation, adopt electromagnetic stirring of the crystallizer, improve the deoxidation process, and control the rolling. The spring wire has pure steel, small segregation, shallow decarburization, and good surface quality. Dongguan Spring
B. Shagang Huaigang
Shagang Group’s Huaigang production springs are typical and representative.
The process flow is: electric furnace/100t converter-refining furnace (LF, RH)-continuous casting-billet heating-bar and profile continuous rolling production.
Process characteristics: In addition to the use of electromagnetic stirring in the mold to strengthen the secondary refining, the deoxidation process and the continuous casting speed adjustment should be introduced to continuously reduce the superheat of the tundish under the premise of ensuring the purity of the molten steel, and greatly improve the quality of continuous casting. .
C. Kobe Steel Corporation, Japan
Japan’s Kobe Steel Company adopts surface modification technology, nitriding treatment and surface shot peening technology of spring steel wire for valves to improve the strength of valve springs.
The process flow is: billet-hot rolling-deburring-lead bath quenching-drawing-oil quenching-tempering-eddy current testing-cold coil-stress relief-coil end grinding- Nitriding treatment-shot peening treatment-stress aging-storage.
It is known that most of the suspension springs and valve springs used by well-known high-end brands at home and abroad are produced by wire rods or bar round steel from Japan’s Kobe Steel Company.
Process flow: 100t UHP electric furnace-LF-VD vacuum furnace-five-machine five-strand continuous casting-cooling-heating furnace-rolling-cooling-cut to length-packaged and put into storage.
Process characteristics: The electric furnace in the smelting adopts a large carbon content, a low-aluminum clean steel process and a high-basicity slag, vacuum degassing, and protective casting. The calcium metamorphism technology is used to reduce the size of non-metallic inclusions. The online top forging test is used to prevent Surface defects.
Recently, Nanjing Iron & Steel has made a big breakthrough in the development of high-speed spring steel series wire rods, and its ф13mm38Si7 high-speed spring steel base material has been exported to Germany.