Softening method for high-strength Q and P steel hot roll

Patent metadata

Field	Value
Publication number	US-11981972-B2
Application number	US-201816648781-A
Country	US
Kind code	B2
Filing date	Sep 20, 2018
Priority date	Sep 20, 2017
Publication date	May 14, 2024
Grant date	May 14, 2024

Abstract

There is disclosed a softening method for a high-strength Q & P steel hot-rolled coil, comprising: after heating a Q & P steel ingot, subjecting it to rough rolling, finish rolling, laminar cooling and coiling to obtain a hot-rolled coil; after unloading the coil, covering the coil on-line with an insulating enclosure and moving it into a steel coil warehouse along with a transport chain; after a specified period of insulating time, removing the coil from the insulating enclosure, and cooling it to room temperature in air, wherein the coiling is performed at a temperature of 400-600° C.; said covering on-line with an insulating enclosure means each hot-rolled coil is individually covered with an independent, closed insulating enclosure unit within 60 minutes after unloading; the insulating time of the steel coil in the insulating enclosure is ≥60 minutes. The inventive method replaces the intermediate annealing step in the production process of cold-rolled Q & P steel. The inventive method has low cost and high efficiency, and it is not affected by the surrounding environment.

First claim

What is claimed is:

1. A softening method for a high-strength Q & P steel hot-rolled coil, characterized in:
after heating a Q & P steel ingot, subjecting it to rough rolling, finish rolling, laminar cooling and coiling to obtain a hot-rolled coil;
after unloading the hot-rolled coil, covering the hot-rolled coil individually with an independent, closed insulating enclosure unit within 60 minutes and moving it into a steel coil warehouse along with a transport chain;
after an insulating time of 60 minutes, removing the hot-rolled coil from the insulating enclosure unit, and cooling it to room temperature in air, wherein the coiling is performed at a temperature of 400-600° C., wherein the Q & P steel hot-rolled coil has a yield strength reduction of ≥85 MPa and a tensile strength reduction of ≥150 MPa, while having an elongation of ≥15% in comparison with a method employing a slow cooling of steel coils in stack; and
after treatment with the insulating enclosure unit, the microstructure of the steel coil is mainly bainite+cementite.

2. The softening method for a high-strength Q & P steel hot-rolled coil according to claim 1 , characterized in that the ingot is heated at a temperature of ≥1150° C., and a soaking time is 60 minutes.

3. The softening method for a high-strength Q & P steel hot-rolled coil according to claim 1 , characterized in that the ingot is heated at a temperature of 1200-1300° C., and the soaking time is 1-3 hours.

4. The softening method for a high-strength Q & P steel hot-rolled coil according to claim 1 , characterized in that the rough rolling and finish rolling are performed in a temperature zone for complete austenization, an overall hot rolling reduction rate is ≥90%, and a final rolling temperature is 800-1000° C.

5. The softening method for a high-strength Q & P steel hot-rolled coil according to claim 1 , characterized in that each hot-rolled coil is individually covered with an insulating enclosure within 20 minutes after it is unloaded.

6. The softening method for a high-strength Q & P steel hot-rolled coil according to claim 1 , characterized in that the steel coil is cooled at a cooling rate of ≤15° C./hour in the insulating enclosure.

7. The softening method for a high-strength Q & P steel hot-rolled coil according to claim 1 , characterized in that the insulating time of the steel coil in the insulating enclosure is 1-24 hours.

8. The softening method for a high-strength Q & P steel hot-rolled coil according to claim 1 , characterized in that the coiling is performed at a temperature of 400-523° C.

Assignees

• Baosteel Zhanjiang Iron & Steel Co Ltd
• Baoshan Iron & Steel
• Baosteel Zhanjian Iron & Steel Co Ltd

Inventors

• Gao Xingjian
• Xu Jiachun
• Wang Ye

Classifications

• C21D9/02 Primary

  for springs · CPC title

• C21D8/00

  Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment (hardening articles or materials formed by forging or rolling with no further heating beyond that required for the formation C21D1/02) · CPC title

• C21D1/84 Primary

  Controlled slow cooling (cooling-beds for metal rolling B21B43/00) · CPC title

• B21B1/26

  by hot-rolling {, e.g. Steckel hot mill} · CPC title

• C21D8/0263

  following hot rolling · CPC title