The difference between cold rolled steel and hot rolled steel

Cold Rolled Steel:

Cold rolled sheet is a product made of hot rolled coil as raw material and rolled at room temperature below the recrystallization temperature. Mostly used in automobile manufacturing, electrical products, etc. 

Hot Rolled Steel:

By definition, steel ingots or billets are difficult to deform at room temperature and difficult to process. Generally, they are heated to 1100-1250 °C for rolling, This rolling process is called hot rolling.

Production Line Introduction

In Baosteel, there are three modern cold rolling mill plants producing automotive sheets, i.e. No.1 cold rolling mill plant (2030mm), No.3 cold rolling mill plant (1550mm) and 1800mm cold rolling mill plant built jointly with NSC and Arcelor. 

Cold Rolled Steel Plate Product Category:

Low carbon and ultralow carbon steel 

Continuous cold rolled carbon structural steel plates and strips

Continuous cold rolled high-strength bake hardening steel plates and strips

Continuous cold rolled high-strength dual-phase steel plates and strips

Continuous cold rolled high-strength low-alloy steel plates and strips

Applications:

Cold-rolled strips are widely used, such as automobile manufacturing, electrical products, rolling stock, aviation, precision instruments, and canned food. Cold-rolled thin steel plate is the abbreviation of ordinary carbon structural steel cold-rolled plate. Cold-rolled steel plate is made of ordinary carbon structural steel hot-rolled steel strip, which is further cold-rolled into a steel plate with a thickness of less than 4mm. Due to rolling at room temperature, no scale is produced. Therefore, the cold plate has good surface quality and high dimensional accuracy. Coupled with annealing treatment, its mechanical properties and process properties are better than those of hot-rolled steel sheets. In many fields, it has been gradually Use it to replace hot rolled sheet steel.

The difference between hot rolling and cold rolling:

1. Appearance and surface quality: Since the cold plate is obtained after the cold rolling process of the hot plate, and some surface finishing is carried out at the same time, the cold plate is better than the hot plate in terms of surface quality (such as surface roughness). It came well, so if there is a higher requirement for the coating quality of the product, such as the subsequent painting, generally choose the cold plate, and the hot plate is divided into the pickling plate and the non-pickling plate. Normal metallic color, but not cold rolled, so the surface is not as high as the cold plate. The surface of the non-pickling plate usually has an oxide layer on the surface, which is black, or there is a black layer of iron tetroxide. , and if the storage environment is not good, it will usually bring some embroidery.

2. Performance: In general, the mechanical properties of the hot plate and the cold plate are considered to be indistinguishable in the project, although the cold plate has a certain degree of work hardening during the cold rolling process, (but it does not rule out that the mechanical properties are strictly required. , then it needs to be treated differently), the yield strength of the cold plate is usually slightly higher than that of the hot plate, and the surface hardness is also higher, depending on the degree of annealing of the cold plate. But no matter how annealed, the strength of cold plate is higher than that of hot plate.

3. Forming performance, since the performance of cold and hot plates is basically not too different, the influencing factors of forming performance depend on the difference in surface quality. Since the surface quality is better from cold plates, generally speaking, the same material is used. Steel plate, cold plate has better forming appearance than hot plate.