High-purity spring flat steel and smelting method thereof

Abstract

The invention discloses high-purity spring flat steel and a smelting method thereof. The production process comprises the steps of combined blown converter smelting, slag dredging behind a converter, ladle refining, vacuum treatment and continuous casting. The steel comprises the following chemical components in percentage by weight: 0.45%-0.49% of C, 1.20%-1.30% of Si, 1.35%-1.45% of Mn, less than or equal to 0.010% of P, less than or equal to 0.015% of S, 0.60%-0.70% of Cr, 0.02%-0.03% of Nb, 0.10%-0.20% of Ni, 0.0010%-0.0020% of B, 0.020%-0.030% of Al, 0.0095%-0.012% of N, 0.0010%-0.0020% of Ca, less than or equal to 0.0025% of Ti and the balance of Fe and inevitable impurities. The high-purity spring flat steel continuous casting billet produced through the method is uniform in component, the macrosegregation carbon range of the section of the casting billet is controlled within 0.03%, the content of inclusions is extremely low, distribution of the inclusions is uniform, the content of harmful elements and gas is extremely low, P is smaller than or equal to 0.008%, Ti is smaller than or equal to 0.002%, and total oxygen is smaller than or equal to 8 ppm.

Description

technical field [0001] The invention belongs to the technical field of ferrous metal smelting, and relates to a high-purity spring flat steel and a smelting method thereof. Background technique [0002] Spring flat steel is an important part of steel for transportation vehicles, railway vehicles, tractors and other transportation tools and construction machinery and equipment. Those parts produced with spring flat steel mainly bear the weight of the upper part of vehicles and mechanical equipment or play a buffering role, and their use environment is harsh, which is directly related to the performance and driving safety of motor vehicles. Therefore, the strength, fatigue limit and impact toughness of spring flat steel are required to be higher. With the rapid development of the economy, the problem of energy shortage has become a prominent problem restricting the sustainable development of the automobile industry. Low fuel consumption, low emission transportation vehicles a...

AI Technical Summary

Problems solved by technology

Although the comprehensive mechanical properties and fatigue life of spring flat steel have been greatly improved, the economy of spring flat steel has not been significantly improved. To some extent, the production cost and control difficulty of spring flat steel have increased, such as The design cost of 52CrMoV4 steel is relatively high, and it also has high strength and fatigue performance in theory. When we produced this steel, all performance indicators met the standard requirements, but the fatigue life was not ideal

Through UT flaw detection, it was found that there was a defect in the core of the product. Further metallographic analysis found that there was a microcrack defect in the core of the product, and there was a martensitic structure. It was finally determined that the root cause of the problem was the continuous casting used for rolling the product. There is segregation in the center of the slab, and the carbon content in the center of the slab is relatively high. After rolling, due to the formation of a martensitic structure with poor plasticity in the center and the failure to release the residual stress reasonably, delayed cracks in the center will occur

[0004]Based on the above analysis, the steel composition design and production of the existing spring flat steel have not fully considered its economic performance, and the cost of steel billets used for rolling spring flat steel And internal quality control is not enough attention, the fatigue life of spring flat steel can be improved by reducing the inclusion content, inclusion size, harmful element content, macro segregation and improving the low-fold structure of the slab

Images