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Production method of hot-rolled round steel for annealing-free low-hardness spring

A production method and low-hardness technology, applied in the direction of metal rolling, etc., can solve the problems of extended production cycle and production process, too fast cooling rate, unable to meet the demand, etc., and achieve the effect of shortening the production cycle and reducing the annealing process

Inactive Publication Date: 2021-02-02
SHIJIAZHUANG IRON & STEEL
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Due to the limitation of shearing and blanking, downstream customers put forward new requirements for delivery hardness ≤321HBW, but the normal production of φ13~φ20mm spring steel has a hardness of 350HBW due to excessive cooling rate, which cannot meet the demand
In order to improve the hardness of the steel, subsequent annealing treatment is required, which not only increases the cost but also leads to the extension of the production cycle and production process

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0020] Embodiment 1: 55Cr3 steel grade, φ 13mm specification exempts the production method of annealing low-hardness spring hot-rolled round steel as follows:

[0021] (1) Converter smelting molten steel, refining and adjusting composition, and then continuous casting into 150mm 2 Billet, its composition by weight percentage is: C0.54%, Si 0.30%, Mn 0.90%, Cr 0.90%, B 0.0004%;

[0022] (2) Billets are slowly cooled for 72 hours;

[0023] (3) The slab is heated slowly, the temperature in the preheating section is 680°C, the tapping temperature is 975°C, and the heating time is 78 minutes; after the slab is released from the furnace, high-pressure water is used to descale and remove the scale, and the descaling pressure is 17.5MPa;

[0024] (4) After 6 passes of rough rolling, 6 passes of intermediate rolling, water cooling, 6 passes of finish rolling, water cooling, 2 passes of reducing and sizing rolling to φ13mm, the temperature of entering and finishing rolling is 862°C; fi...

Embodiment 2

[0028] Embodiment 2: steel grade 55Cr3, specification Φ 17mm exempts the production method of annealing low-hardness spring hot-rolled round steel as follows:

[0029] (1) Smelting molten steel, refining and continuous casting into 150mm 2 Billet, its composition by weight percentage is: C 0.53%, Si 0.32%, Mn 0.91%, Cr 0.89%, B 0.0003%, P 0.010%, S 0.008%;

[0030] (2) Billets are slowly cooled for 78 hours;

[0031] (3) The slab is heated slowly, the temperature in the preheating section is 690°C, and the tapping temperature is 900°C; the heating time is 72 minutes; after the slab is released from the furnace, high-pressure water is used to descale and remove the scale, and the descaling pressure is 18MPa;

[0032] (4) After 6 passes of rough rolling, 6 passes of intermediate rolling, water cooling, 4 passes of finish rolling, water cooling, and 2 passes of reducing and sizing rolling, the φ17mm finished product is produced; the temperature of entering and finishing rolling ...

Embodiment 3

[0036] Embodiment 3: steel grade 55Cr3, the production method of the hot-rolled round steel for exempting annealing low-hardness spring from specification φ 20mm is as follows:

[0037] (1) Smelting molten steel, refining and continuous casting into 150mm 2 Billet, its composition by weight percentage is: C 0.52%, Si 0.32%, Mn 0.92%, Cr 0.89%, B 0.0004%, P 0.010%, S 0.009%;

[0038] (2) Billets are slowly cooled for 76 hours;

[0039] (3) The slab is heated slowly, the temperature in the preheating section is 687°C, and the tapping temperature is 920°C; the heating time is 74min; after the slab is released from the furnace, high-pressure water is used to descale and remove the scale, and the descaling pressure is 17MPa;

[0040] (4) After 6 passes of rough rolling, 6 passes of intermediate rolling, water cooling, 6 passes of finish rolling, water cooling, and rolling into φ20mm finished products; the temperature of entering and finishing rolling is 900°C; the final rolling sp...

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Abstract

The invention discloses a production method of hot-rolled round steel for an annealing-free low-hardness spring. The production method comprises the following steps of (1) smelting molten steel in a converter, conducting refining and component adjusting, conducting continuous casting to form a square billet, and controlling component B of the casting billet to be less than 0.0005%; (2) slowly cooling the casting billet for more than or equal to 72 hours; (3) slowly heating the steel billet, and descaling with high-pressure water; (3) conducting rough rolling, intermediate rolling, finish rolling and reducing and sizing rolling, wherein the finish rolling temperature is controlled to be 860-900 DEG C; and (4) preheating a cooling bed to ensure that the temperature of movable and static racks is greater than 140 DEG C, slowly cooling by adopting a heat preservation cover with the phase-change cooling rate of less than 2 DEG C / s and the tapping temperature of less than 550 DEG C, and cooling steel to 180-250 DEG C to be sheared; and (5) enabling the sheared steel to be subjected to stack cooling at the wind sheltering position with the stack cooling time of longer than or equal to 16h. The production method can be used for producing the spring steel with the phi of 13-20 mm and the hardness of less than 300 HBW, the processes of annealing and reducing the hardness are reduced, and the characteristics of low cost, energy conservation and environmental protection are achieved.

Description

technical field [0001] The invention relates to a method for producing hot-rolled round steel for annealing-free low-hardness springs, belonging to the field of steel rolling. Background technique [0002] Spring steel is an important material for the manufacture of basic parts of mechanical equipment, mainly used in aerospace, automobiles, railway vehicles, track fasteners, agricultural vehicles and many other fields. With downstream customers' demand for economical and high-performance spring steel, there is an urgent need to improve the strength and service life of spring steel, and hardenability is a very important indicator. Among them, Si-Cr and Cr-V spring steels have high strength and toughness and good hardenability, but they bring new challenges to the hardness value of hot-rolled materials. Due to the limitation of shearing and blanking, the downstream customers put forward new requirements for the delivery hardness ≤321HBW, but the normal production of φ13~φ20mm...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/02C22C38/04C22C38/32C21D8/06B21B1/46
CPCC22C38/02C22C38/04C22C38/32C21D8/065B21B1/463
Inventor 刘毅李俊慧周玉朋赵争喜于波阎同丽陈红卫李杰徐建霞
Owner SHIJIAZHUANG IRON & STEEL