Controlled rolling and controlled cooling method for medium-carbon CrMo steel wire rod capable of being directly subjected to drawing machining in hot rolling state

A technology of controlled rolling and controlled cooling and steel wire rod, which is applied to the rolling and cooling of medium carbon CrMo steel wire rod, the production process of medium carbon CrMo steel wire rod, and the elimination of martensite and bainite of medium carbon CrMo steel wire rod. In the field of controlled rolling and controlled cooling of the body structure, it can solve the problems such as the holding time, the minimum cooling rate cannot meet the complete transformation, the hot-rolled wire rod cannot be directly drawn, and the steel strengthening and toughening are affected, so as to optimize the spinning temperature and reduce energy. Consume, reduce stability effect

Active Publication Date: 2020-07-03
ZENITH STEEL GROUP CORP +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] 2. Affect the tempering process of steel
[0005] 3. Affect the strengthening and toughening of steel
Under such process conditions, the holding time and the minimum cooling rate of the Stelmo controlled cooling line cannot meet the complete transformation of the medium carbon CrMo steel in the controlled cooling line, and there is still a certain proportion of supercooled austenite when the wire rod leaves the controlled cooling line. The microstructure of hot-rolled wire rod is usually a mixed structure of ferrite, pearlite, bainite and martensite. This kind of hot-rolled wire rod It cannot be directly drawn and processed, and advanced spheroidizing annealing is required
The other is the scheme of conventional rolling combined with air cooling and then slow cooling after rolling. This scheme can make the hot-rolled wire rod obtain the microstructure mainly composed of pearlite and bainite, but due to the poor plasticity of bainite Due to the limitation of the hot-rolled wire rod during the drawing process, there will be problems such as drawing fracture and transverse cracks on the surface after drawing, and it is still difficult to meet the needs of drawing without annealing

Method used

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  • Controlled rolling and controlled cooling method for medium-carbon CrMo steel wire rod capable of being directly subjected to drawing machining in hot rolling state
  • Controlled rolling and controlled cooling method for medium-carbon CrMo steel wire rod capable of being directly subjected to drawing machining in hot rolling state
  • Controlled rolling and controlled cooling method for medium-carbon CrMo steel wire rod capable of being directly subjected to drawing machining in hot rolling state

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0052] 1. Billet heating:

[0053] Billet composition C: 0.35%, Si: 0.19%, Mn: 0.65%, P: 0.013%, S: 0.012%, Cr: 0.98%, Ni: 0.07%, Cu: 0.08%, Mo: 0.20%, Al: 0.023 %.

[0054] Heat the continuous casting billet with a section of 160mm*160mm at a temperature of 1020-1060°C for 2.0 hours.

[0055] 2. Controlled rolling

[0056] The starting temperature of rough rolling is 930~960℃, the rolled piece enters the finishing rolling unit for rolling, the rolling temperature of the finishing rolling unit is 721~740℃, and the rolled piece rolled by the finishing rolling unit enters the mini unit to be rolled into finished wire rod specification Φ8 .0mm, the rolling temperature of the mini unit is 722-739°C, and the final rolling temperature is 772-789°C.

[0057] 3. Silk spinning

[0058] After the final rolling, the wire rod is formed into coils through the laying machine, and the laying temperature is 730-750°C.

[0059] 4. Control cooling

[0060] After spinning into coils, the c...

Embodiment 2

[0063] 1. Billet heating:

[0064] Billet composition C: 0.38%, Si: 0.28%, Mn: 0.85%, P: 0.015%, S: 0.016%, Cr: 1.11%, Ni: 0.09%, Cu: 0.04%, Mo: 0.30%, Al: 0.030 %.

[0065] Heat the continuous casting billet with a section of 160mm*160mm at a temperature of 1040-1100°C for 1.6 hours.

[0066] 2. Controlled rolling

[0067] The starting temperature of rough rolling is 950~990℃, and the rolled piece enters the finishing rolling unit for rolling, and the rolling temperature of the finishing rolling unit is 728~746℃. .0mm, the rolling temperature of the mini unit is 725-741°C, and the final rolling temperature is 782-798°C.

[0068] 3. Silk spinning

[0069] After the final rolling, the wire rod is formed into coils through the laying machine, and the laying temperature is 730-750°C.

[0070] 4. Control cooling

[0071] After spinning into loops, the cooling is controlled on the Stelmo cooling control line. All heat preservation covers on the control cooling line are closed...

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Abstract

The invention belongs to the technical field of rolling, and relates to a controlled rolling and controlled cooling method for a medium-carbon CrMo steel wire rod capable of being directly subjected to drawing machining in a hot rolling state. The method comprises the steps that a steel billet is heated at the temperature not higher than 1,100 DEG C for 1.5-2 hours; a finish rolling unit and a mini unit conduct rolling at the ultralow temperature not higher than 750 DEG C; the spinning temperature adopts the ultralow temperature not higher than 750 DEG C; and the cooling speed of the steel wire rod on a Stelmor controlled cooling line is not higher than 0.12 DEG C/s. According to the technology, separation of a proeutectoid structure is effectively promoted, it is guaranteed that undercooled austenite is completely converted on the Stelmor controlled cooling line, and conversion of bainite and martensite is effectively prevented; and meanwhile, the gain size of ferrite is not smaller than that of a 12-grade fine grain structure, the medium-carbon CrMo steel wire rod has the good drawing performance in the hot rolling state, cold drawing with the reduction rate not lower than 30% can be conducted at a time, and the one-time spheroidizing annealing cost is reduced for downstream users.

Description

technical field [0001] The invention belongs to the technical field of rolling, and relates to a rolling and cooling method of a medium-carbon CrMo steel wire rod, in particular to a production process of a medium-carbon CrMo steel wire rod that can be directly drawn in a hot-rolled state. It further relates to a controlled rolling and controlled cooling method for eliminating the martensite and bainite structures of the medium carbon CrMo steel wire rod. Background technique [0002] Alloy structural steel refers to steel that is used as mechanical parts and various engineering components and contains one or several certain alloying elements. Common alloying elements include Cr, Mo, Mn, V, B, Si, Ti, Ni, Cu et al. Due to the appropriate hardenability of alloy structural steel, after appropriate metal heat treatment, the microstructure is uniform sorbite, bainite or very fine pearlite, so it has high tensile strength and yield ratio , higher toughness and fatigue strength,...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/02C22C38/04C22C38/22C22C38/20C22C38/44C22C38/42C22C38/06C21D8/06B21B37/74
CPCB21B37/74C21D8/065C21D2211/005C21D2211/009C22C38/02C22C38/04C22C38/06C22C38/20C22C38/22C22C38/42C22C38/44
Inventor 苏振伟张盛华周淼屠兴圹高协清左锦中
Owner ZENITH STEEL GROUP CORP
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