Center crack control process of large-scale 42CrMo round steel with size of 70mm or more

A central crack and large-scale technology, which is applied in the field of central crack control of large-scale 42CrMo round steel above 70mm, can solve the problem of not combining rolling welding and material cooling systematic process plan, and not comprehensively considering rolling welding and material cooling. Reasons for cooling and other issues to achieve the effect of eliminating center cracks and improving center cracks

Active Publication Date: 2020-03-24
HANDAN IRON & STEEL GROUP +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0005] At present, most of the methods to improve the central crack are to study the central crack of the slab unilaterally, without combining the rolling welding and material cooling systemic process plan, and not considering the influence of the rolling compression ratio on the central crack of the slab for the size of the specifications.
For example, the patent application with the application number CN201710405042 discloses "a supercritical high-pressure boiler pipe steel and its control method for the central crack of the continuous casting slab". Reasons for alloy and material cooling

Method used

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  • Center crack control process of large-scale 42CrMo round steel with size of 70mm or more
  • Center crack control process of large-scale 42CrMo round steel with size of 70mm or more
  • Center crack control process of large-scale 42CrMo round steel with size of 70mm or more

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Experimental program
Comparison scheme
Effect test

Embodiment 1

[0056] Production of Φ90mm 42CrMo round steel, continuous casting slab narrow composition control, C: 0.43wt%, Si: 0.21wt%, Mn: 0.64wt%, Cr: 1.01wt%, Mo: 0.19wt%, P: 0.016wt% , S: 0.008wt%; converter high-drawing carbon, end point C: 0.11%, P: 0.014%; LF refining white slag operation, white slag making time 15min, Als content in steel 0.0150%, S content 0.007%; RH vacuum debonding Gas, the vacuum time is kept at 27Pa for 10 minutes, the hydrogen content of molten steel is 2.0ppm, and the soft blowing time is 20 minutes.

[0057] Adopt 200×200mm 2 Cross section continuous casting machine, crystallizer electromagnetic stirring, terminal electromagnetic stirring current 300A, 6HZ, secondary cooling adopts weak cooling cooling mode, water distribution ratio is 0.50L / kg, casting speed is controlled at 1.1m / min, molten steel superheat is controlled △T= At 26°C, the low magnification rating of the casting slab in this furnace is 1.5 for central porosity, 1.5 for central segregation,...

Embodiment 2

[0060] Embodiment 2: The process for improving the central crack of 42CrMo round steel with a specification of 70 mm or more is as follows.

[0061] Produce 42CrMo round steel with a specification of 70mm. Continuous casting slab narrow composition control, C: 0.41%, Si: 0.20%, Mn: 0.65%, Cr: 1.03%, Mo: 0.19%, P: 0.011%, S: 0.003%. Converter high-drawing carbon, endpoint C: 0.08%, P: 0.015%. LF refining white slag operation, white slag production time 16min, Als content in steel 0.030%, S content 0.004%. RH vacuum degassing, the vacuum is kept at 25Pa for 15 minutes, the hydrogen content of molten steel is 1.5ppm, and the soft blowing time is 15 minutes.

[0062] Adopt 200×200mm 2 Cross section continuous casting machine, crystallizer electromagnetic stirring, terminal electromagnetic stirring current 300A, 6HZ, secondary cooling adopts weak cooling cooling mode, water distribution ratio is 0.52L / kg, casting speed is controlled at 1.1m / min, superheat of molten steel is cont...

Embodiment 3

[0065] Embodiment 3: The process for improving the center crack of 42CrMo round steel with a size of more than 70 mm is specifically described as follows.

[0066] Produce Φ80mm 42CrMo round steel. Narrow composition control, C: 0.40%, Si: 0.21%, Mn: 0.73%, Cr: 1.00%, Mo: 0.19%, P: 0.015%, S: 0.006%. Converter high-drawing carbon, endpoint C: 0.08%, P: 0.014%. LF refining white slag operation, white slag production time 25min, Als content in steel 0.028%, S content 0.007%. RH vacuum degassing, the vacuum time is kept at 23Pa for 12min, the hydrogen content of molten steel is 1.2ppm, and the soft blowing time is 18min.

[0067] Adopt 200×200mm 2 Cross section continuous casting machine, crystallizer electromagnetic stirring, terminal electromagnetic stirring current 300A, 6HZ, secondary cooling adopts weak cooling mode, water distribution ratio is 0.55L / kg, casting speed is controlled at 1.1m / min, superheat of molten steel is controlled △T= 30°C. The low power and process ...

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Abstract

The invention relates to a center crack control process of large-scale 42CrMo round steel with a size of 70mm or more, including converter smelting, LF+RH double refining, continuous casting, castingblank classification, rolling and round steel slow cooling. The continuous casting step uses low degree of superheat pouring, constant-speed control, and a secondary cooling water ratio of 0.50 to 0.55L/kg. The casting blank classification comprises: according to a casting blank low magnification rating result and a casting blank continuous casting process parameter, divides casting blanks into I-level casting blanks and II-level casting blank. Specifically: the I-level casting blank has a low magnification rating result of center porosity <= 2.0, central segregation <= 2.0, shrinkage cavity <= 1.0, and a continuous casting process parameter of self open and degree of superheat [delta]T <= 30 degrees centigrade. The II-level casting blank has a low magnification rating result of center porosity <= 3.0, central segregation <= 3.0, shrinkage cavity <= 1.5, and a continuous casting process parameter of self open or not, an open pouring time no more than 8 minutes and the molten steel cladburning no more than once, and degree of superheat [delta]T <= 40 degrees centigrade. The rolling uses I-level casting blank rolling. The center crack control process can eliminates the center crackof large-scale 42CrMo round steel with a size of more than 70mm.

Description

technical field [0001] The invention belongs to the technical field of iron and steel metallurgical rolling, and in particular relates to a process for controlling cracks in the center of large-sized 42CrMo round steel with a size of more than 70 mm. Background technique [0002] 42CrMo round steel belongs to the series of high-strength alloy structural steel, with superior performance and wide application. It is mainly used in the production of high-end applications such as auto parts and high-strength fasteners. The 42CrMo round steel used for automobile forgings is generally more than 70mm Large-scale round steel, such as crankshafts, transmission shafts, etc.; automotive forgings have strict requirements on the internal quality of round steel, and central cracks are not allowed. There are two reasons: firstly, automobile forgings such as crankshafts or transmission shafts are safety parts, and they are subjected to cyclic stresses such as bending, torsion, vibration, ten...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B21B1/46B22D11/16B22D11/18C22C38/02C22C38/04C22C38/22C21C7/06C21C7/064C21C7/10
CPCB21B1/463B22D11/16B22D11/18C21C7/06C21C7/064C21C7/10C22C38/02C22C38/04C22C38/22
Inventor 李仕超李金波范全保李昂王强徐学良靳国兵
Owner HANDAN IRON & STEEL GROUP
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