Stainless steel bar detailed Production Process Inspection and cleaning of ingot
Cleaning lines include: shot blasting, infrared surface inspection, ultrasonic flaw detection and grinding grinders. As the level of continuous casting increases, if continuous casting can produce a defect-free billet, the billet cleaning line can be omitted.
Austenitic stainless steel is stable when heated and cannot be strengthened by quenching. This type of steel has good strength and toughness, excellent low temperature toughness, no magnetism, good processing, forming and welding properties, but it is easy to produce work hardening. At the same time, this type of steel has a very low thermal conductivity and is very ductile at low temperatures, so the heating rate can be faster than that of ferritic stainless steel, slightly lower than the heating rate of plain carbon steel.
Roll hole design
When producing stainless steel bars, the roll hole type generally adopts an elliptical-round hole type system. When designing the hole type, it is considered that the hole type has strong adaptability, and the replacement hole type and the rolling mill restart are minimized, that is, the hole type can be Adapted to a variety of products, allowing the hole type to have a larger gap adjustment, so that the entire product range to minimize the hole shape change of the pre-finishing mill.
Rolling temperature control
When stainless steel is rolled, its deformation resistance is quite sensitive to temperature changes. Especially in rough rolling, due to the low rolling speed, the temperature rise caused by deformation work is not enough to compensate the temperature drop of the rolling stock itself, resulting in a large head-to-tail temperature difference. Product tolerances have an adverse effect and surface defects and internal defects can also occur on the rolled stock, affecting the uniformity of the final product performance. In order to solve the above problems, the heated billet is subjected to rough rolling, and then enters a fuel (or gas) holding furnace or an induction reheating furnace which is disposed between the rough rolling and the intermediate rolling, and the temperature is uniformized before entering the medium rolling unit. Rolling. In order to control the excessive temperature rise of the rolled parts during the finish rolling and pre-finishing, a water-cooling device (water tank) is generally provided between the two sets of rolling mills and between the finishing mill stands. Therefore, reasonable control of the grain size can be achieved in order to improve the technical performance of the final product.
Online heat treatment of stainless steel
In the past, the heat treatment of stainless steel bars was carried out offline. With the development of science and the deepening of rolling process research, modern stainless steel heat treatment is also carried out online. When producing bar, for austenitic and ferritic stainless steel, it is not easy to produce cold cracking and self-pointing, air cooling or stack cooling after rolling, or water cooling device before flying shear to achieve residual heat quenching; production In the case of martensitic stainless steel, it is easy to produce cold cracking, and cannot be directly cooled into the cooling bed by water cooling. The structure of the cooling bed is different from the cold bed for producing carbon steel. One method is to adopt an improved stepped rack. A cold bed, such as the cold bed of the US Teledyne AIIvac plant, which was designed by Danieli in Italy in 1989, protrudes into a tank on the high temperature side. The tank can be filled with water to submerge the cold bed in the water, so that the austenitic stainless steel can be carried out. Water quenching, but not water quenching, directly enters the cooling bed. The cooling bed can also be equipped with a heat-insulating hood to delay the cooling of the rolling stock. When the insulating cover is used for delayed cooling, the cooling rate is half of the natural cooling rate. The lower cooling rate is very important to ensure the hysteresis brittle crack of the martensitic stainless steel; the other method is: design one half of the cooling bed into a chain type, and the other half is a common rack type cooling bed. The roller conveyor is provided with a heat preservation cover. When the martensite stainless steel is produced, the flying shears cut the rolled piece into a double ruler or a fixed length. If it is a multiple ruler, the chain type cold bed is quickly pulled into the heat preservation cover, and cut into a cover in the cover. The ruler is then sent to the thermal insulation pit, and the fixed ruler is directly pulled into the thermal insulation pit for slow cooling.