TPT January 2013

Article

4.4 Comparing mechanics property sampled from product See table 3. 4.5 Comparing wear resistance in the field: The result is compared using the same equipment and rolled same steel pipe Comparing wear resistance on straightening mill of world’s advanced heat treatment production line, see table 4. The compare wear resistance on straightening mill of world’s advanced Ф250MPM mills, see table 5. 4.6 Comparing wear resistance testing sampled from product in the laboratory See table 6 5 Summary Persisting in taking the road of “speciality, precision, characteristic and new” and “continuous innovation”, persisting in taking the researching direction of “the problems of customers and the problems in the field are our researching

SDSF new material is first selected for straightening steel pipe roll at home and also has full approval in the way of selecting material for large scale HFW/ERW welding pipe roll and cold roll formed steel roll at home and abroad. The chemical composition system of SDSF material is different from between the chemical composition of forging steel roll and that of high chromium alloy roll for plate and strip steel rolling. 4.2 Microstructure The carbide of SDSF material is mainly M 7 C 3 , its microhardness is up to 1800Hm. The microstructure appeared as no continuous strip state, block state, particle state and chrysanthemum state, and the content of carbides about 20 per cent. According to service condition of various roll the matrix is selected as austenite, bainite, martensite, and mixing matrix of austenite, bainite and martensite etc. The macrohardness is up to HRC 50-65. The matrix of D2, X155CrVMo121 and SKD11 is martensite and the content of M 7 C 3 carbide is about 15 per cent. 4.3 Comparing hardness and quenching degree sampled from product See table 2.

Table 2 : The compared hardness and quenching degree of new roll of SDSF with that of high grade similar roll in the world

Hardness average value distanced 30mm from surface [HRC]

Hardness average value distanced 60mm from surface [HRC]

Hardness average value distanced 120mm from surface [HRC]

Average value of surface hardness HRC

Brand

State

Quenching, tempering Quenching, tempering Quenching, tempering

D2

59.5

59.6

59.9

59.8

X155CrVMo121

58.2

58.8

57.9

57

SKD11

57.7

57.3

57.1

54.6

SDSF High chromium alloy roll

Tempering for eliminating stress

58.8

58.4

58.6

58

SDSF High chromium alloy roll

Quenching, tempering

60.1

59.9

59.5

59.3

Table 3 : The compared mechanics property of SDSF new roll with that of high grade similar roll in the world

Impact toughness J/cm 2

Brand

State

Sampled direction Tensile strength MPa

D2

Quenching, tempering

radial

733

3.1

X155CrVMo121

Quenching, tempering

radial

711

3

SKD11

Quenching, tempering

radial

750

3.5

SDSF High chromium alloy roll SDSF High chromium alloy roll

Eliminating stress in casting

radial

500

13.5

Quenching, tempering

radial

540

7.5

102

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January 2013