2020-02-27
Mill rolls are essential in the metal working industry. They are manufactured to an optimum hardness to resist wear and prevent marking. Forged steel roll is a type of rolling mill rolls. The roll has a microstructure which allows the surface finish to be resistant to thermal shock and a hardness depth prevent from rehardening in subsequent applications.
Firstly, we give some basic knowledge about the forged steel roll including the definition, types, feature, chemical composition, etc.
What Are Forged Steel Roll
Forge steel roll provides a mill roller solution for rolling mill. It is one of the most wear parts during the rolling process. It is mainly made of forged steel. It is forged in hydraulic presses for high toughness and pureness, widely used in cold rolling mill, steckel mills and continuous hot strip mills. As different rolling mills have specific requirements and various rolling conditions, different alloy elements can be added into the steel for higher performance of the roll. The roll covers forged steel work roll or intermediate roll, forged steel back up roll.
Forged Steel Roll
Definition
The forged steel rolls are made from steel ingots by forging, which can solve metallurgical defects such as loose and shrinkage holes in the ingot, and crush the coarse cast structure to obtain superior quality roll with high resistance.
The production process includes smelting, ingot casting, forging, post-forging heat treatment, rough processing, final heat treatment and finishing.
Feature
High Toughness
Surface Hardness Uniformity
Fatigue Resistance
High Hardness And Durability
Application
It is mainly used as strip rolling mill working roll and backup roll and is a high speed roll (HSS roll) for tandem and reversing cold reduction mills.
Chemical Composition
| Roll name | C | Si | Mn | Cr | Mo | V |
| 42CrMo | 0.38~0.45 | 0.17~0.37 | 0.50~0.80 | 0.90~1.20 | 0.15~0.25 | / |
| 3%Cr | 0.3~0.55 | 0.2~0.5 | 0.2~1.0 | 2.5~3.5 | 0.2~0.6 | 0.05~0.2 |
| 5%Cr | 0.3~0.55 | 0.2~0.5 | 0.2~1.0 | 4.5~5.5 | 0.2~0.6 | 0.05~0.2 |
| 9Cr2Mo | 0.85~0.95 | 0.25~0.45 | 0.2~0.35 | 1.7~2.1 | 0.2~0.4 | / |
Physical Properties
| Roll name | Roll-body hardness HSD | Tensile strength Mpa |
| 42CrMo | 30~42 | 1080 |
| 3%Cr | 56~69 | 1100~1470 |
| 5%Cr | 60~75 | 1200~1500 |
| 9Cr2Mo | 65~105 | 1100~1400 |
Forged Steel Back Up Roll
Definition
The forged back up roll is a mill roll that supports the work roll and intermediate roll for the purpose of avoiding deflection of the work roll and affecting on the yield and quality of the plate and strip rolling mill. This is the key function of back up roll to ensure the operation of the whole rolling mill. The common materials are 9Cr2Mo, 86CrMoV7, 70Cr3Mo with 0.80% to 0.95% carbon content 2% Cr content. The diameter of roll body ranges from 350mm-1600mm.
Feature
High Rigidity
The back up roll requires high rigidity to ensure the smallest deformation for supporting work roll.
Good Fatigue Resistance And High Peeling Resistance
The backup roll always need to support work roll or intermediate roll. Overloadig cause the subcutaneous miccrocrack propagation and roll body peeling off. So the excellent fatigue resistance is necessary.
High Surface Hardness With Good Hardness Uniformity
Outstanding surface hardness ensures the exceptional wear resistance and can reduce the formation of concave roll shape.
Excellent Yield Strength And High Toughness
To guarantee the long service life, the deep hardened layer of roll body, good strength and toughness of roll neck and roll body and strong anti-accidents are required.
Application
Forged steel back up roll is applicable for 4-Hi mill, 6-Hi mill, and other some small mill
Chemical Composition
| Roll Grade | C | Si | Mn | Cr | Mo | V |
| SB H 62 F | 0.52-0.62 | 0.2-0.5 | 0.3-0.7 | 3.0-3.3 | 0.3-0.6 | 0.1-0.3 |
| SB H 64 F | 0.52-0.62 | 0.2-0.5 | 0.3-0.7 | 3.0-3.3 | 0.3-0.6 | 0.1-0.3 |
| SB Mo H 64 F | 0.55-0.65 | 0.2-0.5 | 0.3-0.7 | 3.0-3.3 | 0.6~1.0 | 0.1-0.3 |
| SB Mo H 66 F | 0.55-0.65 | 0.2-0.5 | 0.3-0.7 | 3.0-3.3 | 0.6~1.0 | 0.1-0.3 |
| SB Cr H 66 F | 0.45-0.55 | 0.2-0.5 | 0.3-0.7 | 5.0-5.3 | 0.3-0.6 | 0.1-0.3 |
| SB Cr H 68 F | 0.45-0.55 | 0.2-0.5 | 0.3-0.7 | 5.0-5.3 | 0.3-0.6 | 0.1-0.3 |
| SB Cr Mo H 70 F | 0.5-0.6 | 0.2-0.5 | 0.3-0.7 | 5.0-5.3 | 0.6~1.0 | 0.1-0.3 |
| SB Cr Mo H 72 F | 0.5-0.6 | 0.2-0.5 | 0.3-0.7 | 5.0-5.3 | 0.6~1.0 | 0.1-0.3 |
Physical Properties
| Roll name | Roll-body hardness HSD | Tensile strength Mpa |
| U.T.S (N/mm)2 | 1300-1800 | 700-1300 |
| Yield Strength (N/mm)2 | 1200-1500 | 630-1050 |
| Bending Strength (N/mm)2 | 2500-3000 | 1000-1500 |
| Elongation % | 6-12 | 12-22 |
| U.T.S (N/mm)2 | 1300-1800 | 700-1300 |
Forged Steel Work Roll
Definition
The forged steel work roll is solid-forged roll made of alloyed steel, close to eutectoid and hypereutectoid steel. It has a good combination with hardened surface which creates a strengthened working layer, heat check and tough core resistance to breakage. Heat treatment reduces and equalizes residual internal stress.
Feature
High Hardness
The high hardness and great depth of hardness are needed for cold reduction mills.
Increased Heat Resistance
With the strong heat resistance, the roll can be capable of retain high hardness with the roll under continuous and constant heating rate
No Metallurgical Flaws
High Resistance
It is also can ideal hardness and high resistance to spalling, surface flaws, cracks, scaling,etc.
No Microstructure Flaws
The surface microstructure consists of fine grain martensite and finely dispersed chromium carbides.
Application
Tandem mills
Reversing cold rolling mills
Temper mills
Chemical Composition
| Standard | Falcon | |
| C | 0.72% | 0.84% |
| Mn | 0.45% | 0.45% |
| Si | 0.45% | 0.40% |
| Cr | 3.25% | 4.00% |
| Mo | 0.10% | 0.50% |
| V | 0.06% | 0.06% |
Physical Properties
| Property | Anneal (525 Equotip Ld) | Normalize/Temper (600 Equotip Ld) |
| Tensile Strength (ksi) | 90 | 140 |
| Yield Strength (ksi) | 52 | 80 |
| Elongation (%) | 34 | 15 |
| Reduction of Area (%) | 65 | 30 |
Forged Steel Rolls Used In Rolling Mills
Hot Rolling Mill
The forged steel rolls can be used for hot plate mill and these rolls have the features of rich in alignment, high toughness and strong wear ability. They are made of forges steel blanks and can withstand the special heat treatment for excellent hardness.
Cold Rolling Mill
The back up roll and work roll can be used for cold rolling mill. The forged rolls are produced by steel-making, refining and forging. A homogenous highly dispersed structure provides mechanical properties of the internal layer for complicated heat treatment. It becomes easier for exceptional performance by using the forged rolls which are applied in cold rolling mill.
Forged steel roll is an important mill roll with its outstanding working performance. It can be used as work roll, back up roll and intermediate roll with its high hardness, superior yield strength and high resistance to spalling, fatigue, scaling, etc.
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https://www.hrbtinvo.com/products/detail/forging-steel-roll.html
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