TPT March 2018

AR T I C L E

Shandong Province SiFang Technical Development Co, Ltd

4.4 Comparison of wear resistance and service life in work site Comparison of wear resistance in the same facility and rolling the same material for rolls at home and abroad. Comparison of wear resistance in international advanced heat treatment line straightening mill, see Table 9. Comparison of wear resistance in international advanced φ250MPM unit straightening mill. See Table 10. Comparison of wear resistance in imported φ114 precise rolling pipe unit straightening mill. See Table 11. Comparison of service life in traditional welded pipe unit. See Tables 12 to 15. 5. Selection principle of rolls for welding steel pipe 5.1 Selection principle of rolls for welding steel pipe The general selection principle of roll material is that customers check the cost performance based on how well it copes with meeting the required service conditions. The general performance requirement of roll material selection is difficult and it is important to remember that any material is not perfect, and even good material usually has its special working environment and technical requirements where it will be more effective. The most important thing is that it is suitable for its specific working environment, as it will not be able to do every possible task. The wear resistance of material is not only decided by the roll, but also its relationship with the material it wears against.

The same material will also have different wear resistance depending on the different systems used. The user should always use rolls made from different materials in their best possible working environment for the greatest efficiency. Different mills in different locations have their own working conditions and the material used for the rolls is often different in each case. The same rolling mill, but with a different working rack, for example, being used for finishing, squeezing, sizing and straightening can have a completely different performance depending on the working conditions. In conclusion, the user should take several factors into consideration when selecting roll material. a) High wear resistance and suitable hardness: The wear resistance of material not only depends on its macro hardness, but is also determined by its micro structure – such as carbide – quantity, shape, distribution and its basic toughness. The hardness of material determines its surface resistance ability for metal, but the same hardness might not be as effective with a different material. When used incorrectly a user can easy cause grinding grain spalling or abrasive dust. This is determined by material toughness and carbide type. For the same material, the higher the carbide hardness is and the better the toughness of the material, the higher the wear resistance will be. In terms of roll hardness, the requirement is surface hardness and the same harness inside and outside the roll. The detailed hardness value is determined by using part of the roll and monitoring its response. The wear resistance and hardness of the roll surface have an effect on roll service life and dimension as well as the surface quality of the rolling product. b) Enough strength and toughness: if the roll only has high wear resistance and hardness, but does not have sufficient strength (including fatigue strength) and toughness, it may break the whole roll or it may scale and crack its surface during the process of being used, so this can affect the reliability and security of the roll application.

Number

A

B

C

D

E

Grade

X155CrVMo12-1

D2

SKD11

ZCr20

ZCr15

Stress release and tempering at cast condition

Quenching and tempering

Quenching and tempering

Quenching and tempering

Quenching and tempering

Condition

Table 8: Laboratory wear resistance experiment material number

Roll material, forming method

Rolling quantity with abrasion 1mm in radial direction of the roll

X155CrVMo12-1 forged steel roll

10,000 tons 12,000 tons

ZCr15,ZCr20 casting roll

Table 9: Comparison of wear resistance of thermal straightening

Roll material, forming method X165CrMoV12KU forged steel roll

Rolling quantity with abrasion 1mm in radial direction of the roll

19,000 pieces 13,000 pieces 38,200 pieces

9Cr2Mo forged steel roll ZCr15, ZCr20 casting roll

Table 10: Comparison of wear resistance and cold straightening

Roll material, forming method 9Cr2MoV forged steel roll

Total rolling quantity

82,000 tons 165,000 tons

ZCr20 casting roll

Table 11: Comparison of wear resistance of cold straightening

189

www.read-tpt.com

MARCH 2018