TPT May 2014

Article

Shandong Province SiFang Technical Development Co, Ltd

Chemical Composition (Mass fraction%)

Country

Material

Use

C

Si

Mn

Cr

Ni

Mo

V

Co

1.40~ 1.60 0.32~ 0.42 1.40~ 1.60 0.32~ 0.42

0.30~ 0.50 0.80~ 1.00

0.30~ 0.50

11.0~ 13.0

0.70~ 1.20 1.10~ 1.75 0.80~ 1.20 1.00~ 1.50 0.60~ 0.80 1.20~ 1.50

Forming roll, Sizing roll

D2

-

(0.8)

(0.6)

America

0.60~ 1.00 0.20~ 0.50 0.80~ 1.20 0.90~ 1.10 0.90~ 1.10

W:1.0~ 2.4

H13

≤0.40 4.50~ 5.50

-

Extrusion roll

Forming roll, Sizing roll

SKD-11

<0.40 ≤0.60 11.0~ 13.0

-

-

Japan

0.80~ 1.20 0.10~ 0.40 0.90~ 1.20

SKD-61

≤0.50 4.50~ 5.50

-

-

Extrusion roll

0.15~ 0.45 0.30~ 0.50

11.0~ 12.0 4.80~ 5.50

Forming roll, Sizing roll

X155CrVMo121 1.50~ 1.60

-

-

Germany

0.37~ 0.43

W:0.4~ 0.6

X40CrMoV5-1

-

Extrusion roll

Table 3: The chemical composition of American, German, Japanese rolls for welding steel pipe and cold roll formed steel

If this material is used for making large size rolls the quenching degree and wear resistance are very poor except the above problems. The wear resistance of GCr15 material is even not as good as alloy casting iron. Comparing the forming roll and sizing roll made of GCr15 material with made of bainite ductile iron and pearlitic ductile iron the wear resistance of GCr15 is also lower than alloy casting iron even if both have the same macrostructure hardness. 3.2. Cr12 forging roll Cr12 steel belongs in cold working die steel with high carbon and high chromium content, its carbon and chromium content are higher than GCr15, so the wear resistance is also higher than GCr15. Due to increasing net carbide and carbide segregation and existing anisotropy in mechanical property the steel easily produces cracking and dropping in the unstable production condition and it is not used widely. 3.3. Cr12MoV forging roll Cr12MoV steel belongs also in cold working die steel with high carbon and high chromium content. Pointing to fault of Cr12, through decreasing carbon content from 2.00-2.30% to 1.45-1.70% and increasing Mo and V content, the property is enhanced greatly. The steel has not only high hardness and wear resistance, but also increasing comprehensive properties including quenching degree and stability, etc. The property of the steel produced by our country can be good compared with America’s D2, Germany’s X155CrVMo121 and Japan’s SKD11. Because of having high price and difficult production, the steel is not used widely. 3.4. 9Cr2, 9Cr2Mo, 9Cr2MoV forging roll 9Cr2, 9CrMo, 9Cr2MoV steel belongs in alloy tool steel for cold rolling roll, and it is the same with GCr15 in chemical composition and using property. 9Cr2Mo steel is added into Mo element based on 9Cr2 and 9CrMoV is added into V element based on 9Cr2Mo, and those added elements have great benefit to refine crystal, increase quenching degree and wear resistance of steel and they are widely used in producing cold working rolls in recent years.

3.5. 3Cr2W8V, 42CrMo forging roll 3Cr2W8V belongs in hot working die steel with higher tungsten. For ensuring high toughness and excellent thermal conductivity, the steel contains lower carbon and for possessing excellent red hardness, heating strength and tempering stability, the steel contains higher tungsten. Its hardness and wear resistance are not better than GCr15, and its quenched hardness can be up to HRC47-52, so it is mainly used to produce extrusion roll which is speedily chilling and heating resistance near by heating source. The steel has high alloy element content and high price but its property is not ideal compared with the same grade heat working die steel. The steel contains 8% tungsten, but the property is equal to that containing 5% tungsten. Due to lower chromium content the attacking and corrosion resistance ability by oxidation and hot rolled piece in high temperature are marked lower than hot working die steel with high chromium content. The cross section area of the steel has great influence on its toughness and the toughness can decrease by 50% to increase its diameter from 70mm to 150mm. On the whole, the properties of the steel are not better than H13 (4Cr5MoSiV1). 42CrMo steel belongs in alloy structure steel. It can ensure high toughness and excellent heat conductivity of steel under lower carbon content. It contains certain Cr and Mo elements and possesses good quenching degree, impact toughness and certain red hardness, so it can make extrusion rolls. The roll made of this steel has poor wear resistance, lower red hardness and it can be used in rolling small batch steel product. 3.6. Imported roll The imported roll includes America’s D2, H13; Germany’s X155CrVMo121, X40CrMoV5-1; and Japan’s SKD11 and SKD61. The chemical composition is shown in table 3. The C and Cr in D2, X155CrVMo121 and SKD11 are corresponding with that of Cr12MoV, and its Mo and V element content are higher than Cr12MoV specially adding cobalt, actually it is corresponding with Cr12MoV1. The property of H13, X40CrMoV5-1 and SKD61 is better than 3Cr2W8V.

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May 2014