Hot rolling process of stainless steel coil production

2025-07-23

Billet preparation

Bill acceptance: After the stainless steel billets produced by the steel mill are transported to the hot rolling workshop, they must first undergo strict quality inspection. Check the surface quality of the billets (such as whether there are defects such as cracks and scars), size specifications (length, width, thickness, etc.) and chemical composition to ensure that the billets meet production requirements.

Pre-heating treatment: If there are impurities or oxide scales on the surface of the billet that affect the heating and rolling quality, it may be necessary to clean it. Common cleaning methods include mechanical cleaning (such as shot peening) or chemical cleaning (such as pickling).

Heating

Heating in the furnace: Qualified billets are sent to the heating furnace (commonly used are pusher heating furnaces, walking beam heating furnaces, etc.) for heating. The purpose of heating is to improve the plasticity of the billet and reduce the deformation resistance so that it can be deformed smoothly during the subsequent rolling process. The heating temperature generally varies according to the type of stainless steel, usually between 1100-1250℃.

Temperature control: During the heating process, the temperature distribution and heating time in the heating furnace need to be accurately controlled to ensure uniform heating of the billet and avoid defects such as overheating, overburning, and decarburization.

Rough rolling

Descaling: The heated billet first enters the descaling machine, where high-pressure water is used to remove the iron oxide scale produced on the billet surface during the heating process to prevent the iron oxide scale from being pressed into the stainless steel surface during the rolling process and affecting the product quality.

Rolling deformation: The descaled billet enters the rough rolling unit, which is generally composed of multiple rolling mills. Common layouts include two-roller reversible type and four-roller reversible type. The billet undergoes multiple rolling passes in the rough rolling unit and is gradually rolled into an intermediate billet with a thinner thickness and appropriate width. Each rolling will cause the billet to deform to a certain extent, gradually approaching the shape and size requirements of the finished product.

Finishing rolling

Head and tail trimming: The intermediate billet after rough rolling needs to be trimmed and the irregularly shaped, low-temperature, and unstable-quality parts of the head and tail are removed to ensure uniform quality of the billet entering the finishing mill.

Finishing rolling: The intermediate billet after head and tail trimming is sent to the finishing mill. The rolling mill of the finishing mill has higher precision and usually adopts a multi-stand continuous rolling method, generally consisting of 6-8 rolling mills. During the finishing rolling process, by accurately controlling the rolling pressure, rolling speed, roll gap and other parameters of each stand, the intermediate billet is rolled into a stainless steel strip that meets the requirements of the finished product size accuracy and plate shape. The thickness tolerance can be controlled within a small range, while ensuring that the strip shape is good, such as flatness, sickle bend and other indicators meet the standards.

Laminar cooling

Rapid cooling: The temperature of stainless steel strip after finishing is high, and rapid cooling is required to control its structure and performance. Laminar cooling is to quickly cool the strip by spraying cooling water with a certain pressure and flow rate on the surface of the strip. The cooling rate and cooling end temperature will be precisely controlled according to different steel grades and product performance requirements to obtain the required microstructure and mechanical properties, such as strength, toughness, etc.

Coiling

Tension-controlled coiling: After laminar cooling, the temperature of the stainless steel strip is reduced to a suitable range (generally between 50 - 200℃) and enters the coiler for coiling. During the coiling process, the coiling tension is controlled so that the strip is tightly and neatly wound on the coiler drum to form a stainless steel coil. After coiling, the stainless steel coil is unloaded and weighed, bundled, numbered, and other finished product processing procedures are carried out for easy storage, transportation, and sales.

Quality Control in the Hot Rolling Process

In the production of stainless steel coils, quality control in the hot rolling stage is of utmost importance. Here are several key points:
Temperature Control: The temperature throughout the hot rolling process needs to be precisely regulated, especially during the heating and cooling stages, to prevent damage to the material's properties.
Equipment Maintenance: Rolling mills, heating furnaces, etc. require regular maintenance to ensure stable operation and processing accuracy.
Surface Treatment: The oxide scale produced during the rough and fine rolling processes needs to be promptly removed to ensure the smoothness of the sheet surface.
Dimensional Inspection: Through online inspection equipment, the thickness and width of the sheet are monitored in real time to ensure that the products meet the specifications.