Posted 28 Dec 2010 19:00
Stainless steel production, the current general use of conventional slab caster + semi-continuous rolling mill, the conventional slab caster + Steckel mill or a medium thickness of the thin slab and thin slab casting and rolling and other methods. Seeking low-cost production technology, the past two decades, international and domestic are carried out with the twin-roll strip casting process of production of stainless steel. Twin-roll strip casting technology is characterized by two counter-rotating liquid steel in the rapid solidification of water-cooled rollers, so that grain refinement, inhibit the precipitation of second phase, which greatly improve the material performance. With the twin-roll strip casting process in stainless steel, the solidification speed and direct shaping the characteristics of a significant reduction in equipment investment, energy consumption and production costs, to solve some of the special stainless steel plastic poor and difficult processing problems. However, in the production process in order to improve the surface quality of stainless steel and cast with internal quality, must be based on stainless steel and twin roll strip casting process is characterized by, take the following measures: (1) Select low cost, long life cast of small roll diameter roller. Diameter size and roll casting materials and thin with the quality and production costs are closely related. Earlier research had thought that the roll diameter large pool of high altitude, surface width, flow casting pool help to reduce the impact of a smooth steel surface to improve the strip quality. However, recent studies have found that a small roll diameter can reduce the wear of the side dam to bring the loss, so that investment in equipment and operating costs. U.S. Crawfordsville plant built a casting roll diameter 500mm stainless steel twin-roll strip casting machine, and achieved success. (2) The protection of casting, molten steel to prevent oxidation. Stainless steel fluid contains a variety of easily oxidized elements. In the casting process, if properly cast flow protection, easily with oxygen in the air the second reaction of oxides, the formation of the conjunctiva, crust, turn the skin defects. Double-roll strip casting of stainless steel production process, in order to prevent the oxidation of liquid steel strip inclusion of quality need to be N2, Ar and other gases which leads to all parts of the meniscus, the liquid steel and the air is completely isolated to prevent Secondary steel surface oxidation and heat loss. (3) improve the side seal technology. Side of the closure is to prevent the twin-roll strip casting machine steel fluid leakage from the ends of rollers designed to seal, side seal a direct relationship to the thin strip casting process can proceed smoothly. Side of the dam structure and material on the thin edge with the quality, production costs are both breakout and a great influence. Such as the hydraulic cylinder in the form of solid top tight side-seal, due to the side dam casting roll and the relative sliding between the side dam caused by wear and tear, the side dam erosion by the molten steel side dam melting loss, not only pollute the liquid steel, and reduced life expectancy. Foreign developed a magnetic closure device side, through the liquid steel surface applied to the alternating magnetic field, so that the internal liquid and steel interact to inhibit induced eddy current flow of liquid steel. Results show that: using this device can achieve the lower part of seamless steel bath non-contact side of the seal, and the edge of the cast with no adverse effects, can reduce the subsequent processing of pre-cast with cutting edge content. (4) cloth flow system designed to optimize the molten pool of molten steel flow field. Reduce the volatility of bath surface, the meniscus can be kept stable to prevent longitudinal cracks. Within a reasonable pool of molten steel flow, can guarantee the uniform solidification of ribbon, so cast with a uniform crystal structure. (5) the control of process parameters should be based on the performance of different types of organizational characteristics of stainless steel for a targeted whole.