TPT March 2018

AR T I C L E

Shandong Province SiFang Technical Development Co, Ltd

Forming 2,3 pass GCr15 forged steel roll Average original hardness HRC 57~59, lower after repairing

Forming 2,3 pass ZCr15, ZCr20 casting roll Average hardness HRC 53~55 from beginning to scrapping

Roll category/rolling pipe specifications

Service life for once

Service life after reparation

Service life for once

Service life after reparation

15-20mm 25-32mm 40-50mm

300 tons 400 tons 500 tons

Lower Lower Lower

910 tons

The same The same The same

1,300 tons 1,650 tons

Table 12: Comparison of service life in traditional welded pipe unit (1)

Squeeze roll 3Cr2W8V forged steel roll

Squeeze roll ZCr25 casting roll

Roll category/rolling pipe specifications

Service life for once

Service life after reparation

Service life for once

Service life after reparation

15-20mm 25-32mm 40-50mm

200 tons 300 tons 400 tons

Lower Lower Lower

700 tons

The same The same The same

1,000 tons 1,300 tons

Table 13: Comparison of service life in traditional welded pipe unit (2)

Forming 2 pass Cr12 forged steel roll Average original hardness HRC 57~59

Forming 2 pass ZCr15, ZCr20 casting roll Average hardness HRC 53~55 from beginning to scrapping

Roll category/rolling Pipe specifications

Service life

Service life

φ76

900-1,100 tons

2200-2300 tons

Table 14: Comparison of service life in traditional welded pipe unit (3)

Squeeze roll 3Cr2W8V forged steel roll

Squeeze roll ZCr25 casting roll

Roll category/rolling Pipe specifications

Service life

Service life

φ76

350-400 tons

1,100-1,200 tons

Table 15: Comparison of service life in traditional welded pipe unit (4)

c) It should have some red hardness, hot strength and heat/ cold resistance, as some rolls are used in special working conditions such as squeeze roll of welded pipe roll, hot sizing roll or welded pipe roll. d) Cold manufacturing and hot manufacturing properties: cold manufacturing means to lathe, grind, mill or drill. Some properties of cold manufacturing are easier for customers to repair. Hot manufacturing means casting, forging and heat treatment. The roll material is the main determining factor in roll performance – and the performance also depends on roll service condition. When selecting the material the user should make sure that the material is well researched and meets the requirements of specific service conditions. For example, the company will have a higher requirement for rolls when the rolling product is made from universal carbon steel, alloy steel, high strength steel and seamless steel. Below is brief information about the roll material and the general selection principle behind each one. When the customer selects material for every batch of rolls it is important to be guided by the following principles: a) Quality of rolling product comes first: it should always have high surface quality, good shape and accuracy, and good material should be chosen for the rolls. Even with small batches, when it is tempting to choose low quality material, it cannot guarantee the surface quality and accuracy of rolling products.

b) Always take thickness, grade level, finished product shape, etc, into consideration. Think about the difficulty of deformation and the power of rolling products and, as always, choose rolls made from good quality material. This is the main precondition of achieving reliable cold forming production reliability. c) When producing rolling products in large or small batches, be that several hundred tons or tens of thousands of tons, always choose rolls of good material for large batch. d) Think about whether rolling speed is high or low. If it is high, then choose rolls of good material.

190

www.read-tpt.com

MARCH 2018