ABSTRACT
Rolling is the most important through-processing technology of metallic materials. The roll is an important part of the equipment in the process of rolling mill. Different types of rolls are used in different rolling processes. GB/T1503-1991 specifies one of the characteristics of rolls, that is, cast steel rolls. This standard specifies the classification, technical requirements and inspection rules of cast steel rolls.
Keywords: cast steel roll; GB/T1503-1991; classification; technical requirements; inspection rules
1. Introduction
Rolls are important tools used in the process of rolling mill. Different types of rolls are used for different rolling processes. Cast steel rolls are widely used in rolling mills for flat rolling, profile rolling, cross-section rolling, forging, calendering and other related processes.
GB/T1503-1991 specifies the safety performance of cast steel rolls, including the requirements for classification, technical requirements, inspection rules, packaging, transport and storage. The standard provides necessary technical specifications for manufacturers, sellers and users of cast steel rolls.
2. Classification of Cast Steel Rolls
According to the material, presence of sulfide inclusion and temperature of dynamic state, cast steel rolls are divided into four categories, namely A, B, C and D. Geometric sizes and dynamic strength grades of each type of rolls shall be determined accordingly.
2.1 Category A
This type of roll is made of carbon structural steel or low-alloy structural steel, with Quasi-eutectic or non-eutectic structure and no sulphides. The thermal stability grade range is Grade 2-Grade 12.
2.2 Category B
This type of roll contains low content of sulphides, but no long string-shaped or disconnected sulphide networks. In dynamic state, the temperature is above Grade A, Grade 12-Grade 25.
2.3 Category C
This type of roll contains long string-shaped sulphide networks or ball-shaped sulphide networks which are easily dispersed. In dynamic state, the temperature is Grade 15-Grade 25.
2.4 Category D
This type of roll contains many disconnected sulphides. In dynamic state, the temperature is Grade 25-Grade 40.
3. Technical Requirements of Cast Steel Rolls
3.1 Rolling force
The rolling force of cast steel rolls shall be greater than or equal to the applicable values specified in Table 1.
Table 1 Rolling force of cast steel rolls
Grade of roll Dynamic state Cutting force (KN/cm) A Grade 2-Grade 6 Not less than 3 A Grade 8-Grade 12 Not less than 4 B Grade 12-Grade 25 Not less than 5 C Grade 15-Grade 25 Not less than 6 D Grade 25-Grade 40 Not less than 8
3.2 Hardness
The surface hardness of the roll shall not be lower than the applicable values specified in Table 2.
Table 2 Surface hardness of cast steel rolls
Grade of roll Dynamic state Hardness (HSD) A Grade 2-Grade 6 Not less than 55 A Grade 8-Grade 12 Not less than 52 B Grade 12-Grade 25 Not less than 50 C Grade 15-Grade 25 Not less than 48 D Grade 25-Grade 40 Not less than 46
3.3 Size
The size and shape of cast steel rolls shall meet the requirements specified in Table 3.
Table 3 Size and shape of cast steel rolls
Grade of roll Geometric size A Grade 2-Grade 12 Diameter 500mm-1400mm B Grade 12-Grade 25 Diameter 400mm-1400mm C Grade 15-Grade 25 Diameter 300mm-1000mm D Grade 25-Grade 40 Diameter 300mm-700mm
3.4 Wear
The wear area of the roll shall not exceed the requirements specified in Table 4.
Table 4 Wear of cast steel rolls
Grade of roll Wear area (mm2/cm) A Grade 2-Grade 6 Not more than 0.2 A Grade 8-Grade 12 Not more than 0.3 B Grade 12-Grade 25 Not more than 0.4 C Grade 15-Grade 25 Not more than 0.5 D Grade 25-Grade 40 Not more than 0.6
4. Inspection Rules of Cast Steel Rolls
The inspection of cast steel rolls shall include the following aspects:
4.1 Visual inspection
Inspect the appearance of the rolls for cracks, pits, blooms, oxides and other defects.
4.2 Metallographic examination
Inspect the microstructure of the roll for eutectic, nil eutectic, sulphide inclusions, scale and other defects.
4.3 Hardness test
Check the surface hardness of the roll with Rockwell or other suitable hardness tester.
4.4 Rolling force test
Check the rolling force of the roll with a rolling force measuring instrument.
4.5 Wear test
Measure the wear area of the roll after rolling for a certain time.
4.6 Size inspection
Inspect the size and shape of the roll using the appropriate measuring tools.
5. Conclusion
GB/T1503-1991 specifies the safety performance of cast steel rolls, including the requirements for classification, technical requirements, inspection rules, packaging, transport and storage. It provides necessary technical specifications for manufacturers, sellers and users of cast steel rolls. The classification, technical requirements and inspection rules of cast steel rolls specified by the standard are helpful to guarantee the performance of cast steel rolls.
