301 stainless steel belt production process and equipment

The production process of 301 stainless steel strip has very high requirements on production equipment and production technology. The production line is a systematic production line optimized and run-in from rolling mill to bright annealing furnace, flattening equipment, tension and straightening equipment, slitting equipment, shearing equipment and other equipment. Any problem in any link will affect the finished product quality of 301 stainless steel strip. The following is a brief overview of the production process and equipment selection of 301 stainless steel strips.

Stainless steel 301 stainless steel strips generally use conventional cold-rolled and annealed steel coils as raw materials, and the 2B surface can be used. According to product specifications and raw material conditions, one or two rolling passes can be used. According to the process flow, the main units selected include: preparation unit, multi-roller rolling mill, degreasing unit, bright annealing unit, stretch straightening machine, slitting/cross-cutting unit, etc.

(1) Preparation unit: In order to improve the cold rolling yield of stainless steel, it is necessary to weld the lead strips at both ends of each coil of steel strip before rolling. For this purpose, a preparation unit is required.

(2) Multi-roller rolling mill: Stainless steel is severely work-hardened and difficult to roll. The use of small-diameter work rolls and large-tension multi-roller reversing mills is a distinctive feature of cold rolling of stainless steel strips. For rolling precision stainless steel strips less than 0.3mm, twelve-roller, fourteen-roller (domestic), eighteen-roller (domestic), twenty-roller and other rolling mills are generally used.

(3) Degreasing unit: In order to strengthen the rolling process and improve the surface finish of the rolled parts during the rolling of stainless steel strips, the rolling mill needs to use mineral oil for cooling and lubrication. The oil products generally use MobilGenrex 26, Shell Somentor N60, KB-Sendzimir, etc., after rolling, through the action of the rolling mill oil scraper, the rolling oil remaining on the surface is about 150mg/m2 ~ 200mg/m2 (each side). Since the bright annealing unit in the next process generally uses a muffle furnace, the muffle furnace cannot directly burn the residual rolling oil through the flame. In order to prevent the residual oil on the surface of the strip from being brought into the bright furnace, affecting the atmosphere and strip in the furnace The quality of the steel surface, so the rolled stainless steel strip must be chemically degreased to remove the rolling oil remaining on the strip surface during the rolling process, and then enter the bright annealing furnace (muffle furnace) with protective gas for brightening annealing. For those delivered in hard condition, the rolling oil on the surface of the strip must be removed before finishing, and degreasing is also required. A separate degreasing unit also needs to add decoilers, welders, slitting shears, coilers and other equipment to achieve continuous production.

(4) Bright annealing unit: There are mainly two types of bright annealing units: vertical and horizontal. In order to produce precision stainless steel strips with high surface quality, vertical bright annealing units are generally used. At present, the more popular vertical muffle bright annealing furnaces in the world generally include three types: vertical full-muffle upward heating type, vertical full-muffle downward heating type, and vertical muffle + bricklaying electric heating hybrid type. The hybrid bright furnace consists of three parts: the heating section (muffle heating section + electric heating section), the slow cooling section, and the cooling section. The muffle heating section, slow cooling section, and cooling section are basically the same as the full muffle type. The electric heating section has a square structure and is lined with high alumina bricks to build the furnace lining. It takes 30 hours to lift the entire muffle furnace and replace the muffle, excluding the time for stopping the furnace, cooling, exhausting, charging, and heating. The hybrid muffle furnace only takes about 24 hours to lift and replace the muffle. In hybrid bright furnaces, the furnace temperature of the muffle furnace is lower than that of electric heating. For the same output, if an electric heating furnace is used, the heating section can be shorter. The hybrid bright furnace has the characteristics of high output and good energy saving effect. However, the electric heating section is a muffle-less heating section, using molybdenum wire for heating, and using high-alumina bricks to build the furnace lining. The refractory grade is high and expensive, and the quality of the BA board may be affected by refractory problems. If it is required to produce high-quality BA boards, the full-muffle bright furnace can ensure the quality, and the equipment maintenance is convenient and the operating cost is relatively low; if the manufacturer focuses on the output of BA boards, it is more suitable to choose a hybrid bright furnace suitable.

(5) Leveling unit: The conventional 2-roller or 4-roller leveling process is used for annealing materials in a soft state. This process can be used for industrial strip production. This process uses large-size work rolls to apply a small reduction cold rolling process to the steel strip that has been brightly annealed. However, the steel strip produced in this way is not ideal and often exhibits instability. When the strip steel is further processed, such as cold stamping and molding production, some defects will be scattered and cause deformation. The tensile bending and straightening method is the only process that can meet the requirements of softening and hardening flattening of strip steel. During this process, the strip is subjected to controlled tension while being bent out of shape by a set of small free rollers. This kind of processing makes the strip only slightly elongated and has good shape in the length, width and thickness directions. After straightening, the stress distribution on the strip is uniform. Even after the plate is slit, punched, forged, formed and ground, the stress distribution is still ideal. For ultra-thin precision stainless steel strips, stretching and straightening units are generally used, and can be adapted to both hard and soft materials.

(6) Slitting/cross-cutting unit: Stainless steel finishing includes slitting or cross-cutting units. For ultra-thin precision stainless steel, almost all users need tapes of different widths, which can be cut according to customer requirements. sizes.