The material selection of Welded pipe roll
Eric（浩） T.
BD Manager | Specialzing rolls, rings and DM me for if you have any trouble to find related spare parts in the steel industry
Ⅰ.Squeeze roller material selection
1. Selection of squeeze upper roller material
The squeeze upper roll has the worst working condition in the whole rolling line, it has to withstand high temperatures and large pressure. At present, the roller is mainly made of hot work die steel, and there are two commonly used materials, one is 3Cr2W8V, which is common in China, and the other one is the material 4C5 MoSiV1 (equivalent to USH13, Japan SKD61).
Comparing the two materials, 4Cr5 MoSiV1 is better than 3Cr2W8V. Because the former has high hardness and good thermal cracking resistance.
4Cr5 MoSiV1 quenching can reach HRC50-54, while 3Cr2W8V can only reach HRC47-52 , Thus, the capacity of 4Cr5 MoSiV1 roller is 15-20 % higher than the 3Cr2W8V.
2. Material selection of squeeze side roll and lower roll
Although the rolls at the above positions are also installed on the squeeze frame machine, their material can be selected according to precision forming rolls. Since it immediately touches the weld seam, coupled with water cooling, the temperature of the roll generally does not exceed 150 ° C.
Ⅱ. Selection of other roll materials (including rough forming, fine forming, sizing, polishing, pulling out, etc.)
1. GCr15
GCr15 is a typical bearing steel, which is commonly used in China. Due to its mature technology, cheap price, and good performance, it has been widely used by welded pipe manufacturers and roll manufacturers. However, because of its low alloy content and poor quenching permeability, it is only suitable for rolls below Φ 165 units, If it is used to produce medium and large rolls, the formation of flaky soft spots will reduce the life of the roll and affects the appearance quality of the steel pipe.
Technical performance: quenching hardness HRC5862, hardened layer depth 10mm.
2. 9C2Mo
The material of 9Cr2Mo is a relatively common forged steel cold rolling steel in China. Compared with GCr15, the C is increased and Mo is added, which improves the hardenability and hardenability of the material, and the quenched layer is 2-3mm deeper than GCr15, and the lamellar soft spots in the pass have been greatly improved, and the wear resistance has also increased by 15%.
Therefore, it is more suitable for making medium-sized rolls for Φ 508-165 units.
Technical performance: quenching hardness HRC5862, hardened layer depth 13mm.
3. 86 CrMoV7
86 CrMoV7 is used to make welded pipe rolls in recent years. It belongs to the steel for forged steel cold rolls.
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There is a tendency to gradually replace the 9Cr2Mo material in the production of cold rolls. Due to the increased Cr content in the composition and the added V element, the hardenability, hardenability, and wear resistance have been further improved. The depth of the hardened layer is 5mm deeper than GCr15, and the wear resistance is also increased by 30%. Therefore, it is more suitable for making large rolls and rough-forming rolls for Φ660-508 units
4. Cr12MoV
Cr12MoV is a commonly used cold die steel in China, and its chemical composition is similar to that of American D2, Japanese SKD11, and GermanX155 CrMoV12.1. Due to the increase of C, Cr, and V content, it has good hardenability and hardenability.
The quenching depth can reach 20mm, and the wear resistance can reach more than 2 times that of GCr15.
However, due to its poor forge ability and strong deformation resistance, it can only be used to make small rolls for many years. (The weight of the blank is less than 1 ton).
At present, several ERW production lines imported from abroad are required to be made of Cr12MoV.
?However, in my opinion, 86CMoV7 is perfectly applied in ERW production. The order quantity of steel pipes is generally as little as tens of tons and as many as tens of thousands of tons.
Rolls of the same specification cannot be put on the rolling mill several times in a year. Because 86CMoV7 and other materials already have qualified wear resistance.
Usually, a set of rolls can be used for 5 to 10 years, or even longer. Equipped with multiple sets of Cr12MoV rollers will take up a large number of funds for the enterprise, so it is suggested that steel pipe manufacturers should choose carefully.
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