TPT March 2018

AR T I C L E

Shandong Province SiFang Technical Development Co, Ltd

Chemical component (mass fraction,%)

Grade

C

Si

Mn

P

S

Cr

Ni

W

Mo

V

Cu

GCr15

0.95-1.05 0.15-0.35 0.25-0.45 ≤0.025 ≤0.025 1.40-1.65 0.85-0.95 0.25-0.45 0.20-0.35 ≤0.025 ≤0.025 1.70-2.10 0.85-0.95 0.25-0.45 0.20-0.35 ≤0.025 ≤0.025 1.70-2.10 2.00-2.30 1.75-2.25 0.60-1.00 ≤0.030 ≤0.030 11.50-13.00

≤0.30

— ≤0.10 — 0.20-0.40

— ≤0.25 — ≤0.025

9Cr2Mo 9Cr2MoV

≤0.025 ≤0.025

— 0.20-0.30 0.10-0.20 ≤0.025

Cr12

—

—

—

— —

3Cr2W8V Cr12MoV

0.30-0.40 ≤0.40 1.45-1.70 ≤0.40

≤0.40 ≤0.030 ≤0.030 2.20-2.70 ≤0.40 ≤0.030 ≤0.030 11.00-12.50 ≤0.60 ≤0.030 ≤0.030 11.00-13.00

— 7.50-9.00

— 0.20-0.50

— — — — — — —

— —

— 0.40-0.60 0.15-0.30 — 0.70-1.20 0.50-1.10 — 1.10-1.75 0.80-1.20 — 0.50-3.00 ≤1.00 — 0.50-2.50 ≤1.00 — 0.50-2.00 ≤1.00

Cr12Mo1V1 1.40-1.60 ≤0.60

4Cr5MoSiV1 0.32-0.45 0.80-1.20 0.20-0.50 ≤0.030 ≤0.030 4.75-5.50 1.40-1.80

ZCr15 ZCr20 ZCr25

1.80-2.80 ≤1.20 1.80-2.80 ≤1.20 1.80-2.80 ≤1.20

≤1.20 ≤0.030 ≤0.025 12.00-16.00 0.50-3.50 ≤1.20 ≤0.030 ≤0.025 16.00-22.00 0.50-3.50 ≤1.20 ≤0.030 ≤0.025 22.00-28.00 0.50-3.50

Cr12MoV: Co≤1.00%; GCr15: Ni+Cu≤0.50% ZCr15, ZCr20, ZCr25: Nb+Ti≤1.00% Table 1: Chemical component of roll

Sampling direction

Tensile strength (MPa)

Impact toughness (J/cm 2 )

Hardness (HRC)

Along forging direction

1,039-1,321

9-17

58-59.5

Perpendicular to forging direction 2.1-4.0 Table 2: Different mechanical properties of welded pipe rolls made from materials of X155CrVMo121, D2, SKD11 683-771

3.1.3 Forged steel 3Cr2W8V This is used for hot work die steel. It has good thermal conductivity, good red hardness, heat strength and tempering stability. But toughness, plasticity and wear resistance is poor and hardenability is medium. Commonly used in high temperature and high stress environments, which do not impact the mould. Used in welding extrusion roll but it is expensive and performance is not ideal. The service life is only about 4Cr5MoSiV1.

pieces. A single finished roll could be heavier than ten tons or lighter than 10kg per piece. Welded tube is required at a certain thickness to maintain the same performance after repair and to ensure a long service life. 2.2 Standard selection of materials The new standard selects eight kinds of materials for forging roll and three kinds of materials for casting roll for users to use. Both have a common level of forging roll and advanced level forging Cr12Mo1V1, Cr12MoV roll. China’s aim is to meet the international advanced level of casting ZCr15, ZCr20 and ZCr25 roll. The grade and chemical composition of the roll are shown in Table 1. 3. Analysis of the roll grade recommended in the standard 3.1 Forging roll 3.1.1 Forged steel GCr15 and forged steel 9Cr2Mo, 9Cr2MoV These materials all have similar chemical composition, low alloy content – mainly M 3 C type carbide – 800Hv hardness, less quantity and wear resistance and are inexpensive and easy to purchase. It is a mature processing technology and can be used to produce small rolls. 3.1.2 Forged steel Cr12 This has a high quench degree, hardenability and abrasion resistance. It is easy to form carbide with uneven distribution, reticular carbide and carbide segregation increased significantly. Uneven carbide is difficult to use, so heat treatment methods can improve the mechanical properties of anisotropy significantly. It is suitable for the manufacture of small impact loads with high wear requirements and small parts.

Rolls made by SDSF for SMS group

186

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MARCH 2018