Hot Rolled Coil

    Hot rolled coils are made of slabs ( mainly continuous casting slabs ) as raw materials, which are heated and made into strip steel by rough rolling mills and finishing mills . The hot steel strip coming out of the last rolling mill of finishing rolling is cooled to the set temperature by laminar flow , and then rolled into steel strip coils by coilers .

concept

The hot steel strip coming out of the last rolling mill of the finishing rolling mill is cooled to the set temperature through laminar flow and rolled into a steel strip coil by the coiler. The cooled steel strip coil is processed into steel plates, flat coils and longitudinally cut steel strip products through different finishing lines (flattening, straightening , cross-cutting or longitudinal cutting , inspection, weighing, packaging and marking, etc.) according to different user needs.

Production steel plant

Steel mills producing hot rolled coils: Baosteel , Wuhan Iron and Steel , Masteel, Taihang, Shougang, Ansteel, Taigang , Bagang, Jiugang, Angang, Angang , Panzhihua , Benxi , Tangshan, Handan, Chengde, Jigang, Shagang, Rizhao, Liangang, Chongqing , Shandong , and Xinyi

Material

Q235B、 Q345B、 SPHC、 510L 、 Q345A、Q345E

Related parameters

The allowable deviation of thickness of steel plates and steel strips shall comply with the provisions of Table 2.

Table 2

1.3 The unevenness of the steel plate shall not exceed 12mm. The unit length of unevenness measurement is 1000mm.

1.4 The camber of steel plates and steel strips shall not exceed 4mm per 2 meters.

1.5 The width tolerance of steel plates and steel strips shall comply with the requirements of the following table.

1.6  The overflow edge of the steel coil head and tail should not be greater than 40mm, the overflow edge in the middle and the tower height should not be greater than 30mm.

1.7 The weight of each steel coil should be 5-25 tons.

Product Categories

Hot rolls can be divided into straight rolls and finishing rolls (split rolls, flat rolls and longitudinally cut rolls).

According to their materials and properties, they can be divided into: ordinary carbon structural steel , low alloy steel and alloy steel .

According to their different uses, they can be divided into: cold forming steel, structural steel , automotive structural steel, corrosion-resistant structural steel, mechanical structure steel , steel for welding gas cylinders and pressure vessels , pipeline steel, etc.

use

Due to the excellent properties of hot-rolled steel plate products such as high strength, good toughness, easy processing and forming, and good weldability , they are widely used in manufacturing industries such as ships, automobiles, bridges, construction, machinery, and pressure vessels .

With the increasing maturity of new technologies for controlling hot-rolled dimensional accuracy , plate shape , surface quality , and the continuous emergence of new products, hot-rolled steel plates and strips have been increasingly widely used and have become increasingly competitive in the market.

Steel grade

1. SPHC——The first S stands for Steel, P stands for Plate, H stands for Heat, and C stands for Commercial. As a whole, it means generally used hot-rolled steel plates and strips.

2. SPHD - refers to hot-rolled steel plates and strips for stamping.

3. SPHE——indicates hot rolled steel plates and strips for deep drawing .

4. SPCC - indicates general cold-rolled carbon steel sheets and strips. The third letter C is the abbreviation of Cold. When tensile test is required , add T at the end of the grade to make SPCCT.

5. SPCD —— indicates cold-rolled carbon steel sheets and strips for stamping

6. SPCE - indicates cold-rolled carbon steel sheets and strips for deep drawing. If non-aging properties are required, add N at the end of the grade to make it SPCEN.

The code for cold-rolled carbon steel sheets and strips is : A for annealed state , S for standard tempering, 8 for 1/8 hardness, 4 for 1/4 hardness, 2 for 1/2 hardness, and 1 for hardness. The code for surface processing is : D for matte finish rolling, B for bright finish rolling. For example, SPCC-SD indicates a general cold-rolled carbon sheet with standard tempering and matte finish rolling. Another example is SPCCT-SB, which indicates a cold-rolled carbon sheet with standard tempering and bright processing, and requires guaranteed mechanical properties .

7. The JIS mechanical structure steel grade is represented by: S+carbon content+letter code (C, CK), where the carbon content is represented by the middle value × 100, and the letter C represents carbon and K represents carburizing steel. For example, the carbon content of carbon steel coil S20C is 0.18-0.23%.

Silicon steel sheet grade indication method

(1) Cold-rolled non-oriented silicon steel strip (sheet) Representation method: DW + 100 times the iron loss value (the iron loss per unit weight at a frequency of 50HZ, a sinusoidal magnetic induction peak of 1.5T) + 100 times the thickness value. For example, DW470-50 indicates a cold-rolled non-oriented silicon steel with an iron loss value of 4.7w/kg and a thickness of 0.5mm . The new model is now 50W470.

(2) Cold-rolled oriented silicon steel strip (sheet) Expression method: DQ + iron loss value (100 times the iron loss value per unit weight at a frequency of 50 Hz and a sinusoidal magnetic induction peak of 1.7 T) + 100 times the thickness value. Sometimes G is added after the iron loss value to indicate high magnetic induction.

(3) Hot-rolled silicon steel sheet  Hot-rolled silicon steel sheet is denoted by DR and is divided into low silicon steel ( silicon content ≤ 2.8%) and high silicon steel (silicon content greater than 2.8%) according to the silicon content.

Method of expression: DR + 100 times of iron loss value (iron loss per unit weight when the maximum value of magnetic induction intensity is 1.5T with 50HZ repeated magnetization and sinusoidal change ) + 100 times of thickness value. For example, DR510-50 indicates a hot-rolled silicon steel sheet with an iron loss value of 5.1 and a thickness of 0.5mm. The grade of hot-rolled silicon steel sheet for household appliances is expressed by JDR + iron loss value + thickness value, such as JDR540-50  . Cold- rolled coil is made of hot-rolled steel strip as raw material, which is rolled into steel strip by a coiler after a series of rolling at room temperature. Hot-rolled coil is made of slab as raw material, which is heated to a certain temperature, rolled and cooled to the set temperature by rough rolling and finishing rolling mills, and then rolled into steel strip by a coiler. Compared with hot -rolled steel sheets , cold-rolled steel sheets have better surface quality and higher dimensional accuracy. In addition, after annealing treatment of Q345B[1] , its mechanical properties and process performance are better than those of hot-rolled steel sheets. They are used in many fields that require high precision, especially in the home appliance manufacturing industry and the automotive industry. However, cold-rolled steel sheets are thin, generally less than 4 mm. If the thickness exceeds a certain value, only hot-rolled steel sheets can be used.

Mechanical properties

Note: 1. The tensile test and bending test listed in the table are applicable to longitudinal specimens.

2. The tensile test uses a specimen with L0=50 mm and b=25 mm.

3. The sampling plan for the bending test should be carried out in accordance with the No. 3 specimen of JIS Z 2204, and the test method should be carried out in accordance with JIS Z 2248.

4. Hardness test is carried out in accordance with the provisions of JIS Z 2245

5. The target hardness HRB value is 60±8. The actual value is provided in the warranty, but it is not a requirement for acceptance.

3.3 Surface quality

3.3.1 The surface of the steel plate or strip is not allowed to have defects such as inclusions, cracks, rust, etc. that are harmful to use, and parking spots are not allowed . Defects that do not affect the forming performance are allowed, such as slight scratches that are not felt , light yellow film after pickling, slight pitting , scratches, roller marks and indentations , color difference and slight wrinkles that are not felt, etc.

3.3.2 Since there is no chance to remove defects from the steel strip, it is allowed to be delivered with defects, but the defective part shall not exceed 6% of the total length of the steel coil.

3.3.3  Oiling means that the surface of the steel plate is coated with electrostatic anti-rust oil with certain anti-rust performance . The oiling is divided into light oiling, medium oiling and heavy oiling, which shall be specified by the purchaser in the contract. The supplier shall ensure that the oiled product will be free of rust within 3 months under normal transportation and storage conditions.