Double-layer centrifugally cast rolls with working layer of nickel-chromium cast iron. Chemical composition, microstructure and properties.

     The microstructure of metal working layer of rolls consists of a grid of eutectic cementite forming ledeburitic colonies of small graphite inclusions with compact and spherical shape and martensitic-bainitic metal matrix with needle structure. This structure allows to obtain an excellent quality of the roll surface and rolled stock, and is characterized by high hardness and wear resistance due to significant volume fraction of carbide phase, wherein the spherical graphite inclusions improve the mechanical properties of the working layer of rolls and provide sufficient fracture strength and lubrication during their operation.
The core material is traditionally made of ductile cast iron with nodular graphite and pearlite-ferrite matrix.

     Field of application:
        - The industry standard for finishing stands F5-F7
        - Rolling mills Steckel
        - Temper-rolled mill and tin rolling mills for medium numbers.

Microstructure of chromium-nickel cast iron with increasing x100 and x500 times.

нетравленая, х100
non-etched, х100 etched, х100 etched, х500

    

 

      Microstructure of core of chromium-nickel rolls

non-etched, х100 etched, х100

 

Table 1. Chemical compound of metal of working layer of chromium-nickel rolls.     

Execution

Chemical compound, %

С

Si

Mn

P

S

Cr

Ni

Mo

V

W

no more

ЛПХНМдц-73 (76)

2,9-3,5

0,5-1,1

0,5-1,0

0,1

0,04

1,2-2,0

4,0-4,6

0,2-0,6

0,1-0,2

0,1-0,4

 

Table 2. Technological and physical-mechanical properties.

Roll execution Working layer depths, mm Hardness, HS

Bending strength,

МPа

Coefficient of elasticity, GPa Impact strength, Joule/cm2 Heat conductivity, W/m*К Heat capacity, Joule /kg*К Coefficient of linear extension (20?1000С)

ЛПХНМдц-73(76)

40-60

73 - 86

320-450

18-20

2,7-3,0

35-40

540-560

12-13

* Hardness decrease to working layer depths no more 5 %

 

Table 3. Chemical compound of metal core.

Name of the material

Chemical compound, %

С

Si

Mn

P

S

Ni

Cu

Mg

no more

Сердцевина валка ВЧ

3,0 - 3,4

1,6 - 2,4

0,5 - 1,0

0,1

0,02

0,5-1,5

до 0,2

0,03-0,06

 

Table 4. Physical-mechanical properties of metal core.

Type of cast iron Hardness, HS

Bending strength,

МPа

Coefficient of elasticity, GPa Impact strength, Joule/cm2 Heat conductivity, W/m*К Heat capacity, Joule /kg*К Coefficient of linear extension (20?1000С)106/°С
High-strength cast iron

35 - 45

350 - 480

16 - 19

4,2 - 4,6

45 - 50

550 - 580

11 - 12

 

 

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08 December 2019

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