# US 11,078,550 B2 · Method for manufacturing quenched molding, method for manufacturing hot press steel material, and hot press steel material

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 11,078,550 B2
- Document ID: US11078550B2
- Status: Granted
- Kind: B2
- Application number: 16/463,777
- Filed: 2017-11-22
- Published: 2019-11-07
- Granted: 2021-08-03
- Earliest claimed: 2016-11-25
- Assignees: Nippon Steel Corporation
- Applicants: Nippon Steel Corporation
- Inventors: Yoshiaki Nakazawa; Shinichiro Tabata; Kazuo Hikida; Toshiya Suzuki; Atsuo Koga; Koichi Hamada
- Web page: https://patentgrep.com/patent/US11078550B2

## CPC

- C21D 1/18: Hardening (C21D1/02 takes precedence); Quenching with or without subsequent tempering (quenching devices C21D1/62)
- B21D 22/20: Deep-drawing (special deep-drawing arrangements in, or in connection with, presses B21D24/00)
- C21D 8/04: to produce plates or strips for drawing, e.g. for deep-drawing
- C21D 8/0447: {characterised by the heat treatment}
- C21D 9/46: for sheet metals
- C21D 9/48: deep-drawing sheets
- C22C 38/001: {containing N}
- C22C 38/002: {containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60}
- C22C 38/02: containing silicon
- C22C 38/04: containing manganese
- C22C 38/26: with niobium or tantalum
- C22C 38/28: with titanium or zirconium
- C22C 38/32: with boron
- C21D 2211/002: Bainite
- C21D 2211/008: Martensite
- C22C 38/00: Ferrous alloys, e.g. steel alloys (cast-iron alloys C22C37/00)
- C22C 38/38: with more than 1.5% by weight of manganese
- Y02P 10/25: Process efficiency
- C21D: MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass C23F17/00; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials C30B)
- B21D: WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL (working or processing of wire B21F)
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

A method for manufacturing a quenched molding according to the present disclosure is a method including a first heat treatment process of heating a blanked steel material to a temperature higher than its Ac3 transformation point to perform austenite transformation, and then cooling to induce martensite transformation or bainite transformation, and a second heat treatment process of heating the steel material that has undergone the first heat treatment process to a temperature higher than the Ac3 transformation point to perform austenite transformation, and then cooling to induce martensite transformation. After the steel material has been heated to a temperature higher than the Ac3 transformation point in at least one process from out of the first heat treatment process or the second heat treatment process, molding is completed at a temperature higher than an Ar3 transformation point.

## Claims

### Claim 1

A method for manufacturing a quenched molding, the method comprising:
a first processing comprising heating a blanked steel material to a first heat treatment temperature, the first heat treatment temperature being in a range of from an Ac3 transformation point+70° C. to the Ac3 transformation point+170° C., to perform austenite transformation, wherein the Ac3 transformation point is a temperature defined by Equation (1), and then cooling to induce martensite transformation or bainite transformation, wherein the blanked steel material has a chemical composition comprising, in mass %, C: from 0.3% to 0.8%, Si: from 0.001% to 2.0%, Mn: from 0.5% to 3.0%, P: not greater than 0.05%, S: not greater than 0.01%, sol. Al: from 0.001% to 1.0%, N: not greater than 0.01%, and B: not greater than 0.01%, and a remainder comprising Fe and impurities;
a second processing comprising heating the steel material that has undergone the first processing to a second heat treatment temperature, the second heat treatment temperature being in a range of from the Ac3 transformation point+20° C. to the Ac3 transformation point+100° C., to perform austenite transformation, and then cooling to induce martensite transformation, wherein a heating time from reaching said second heat treatment temperature until an end of heating in said second processing is 400 seconds or shorter; and
after the steel material has been heated to a temperature higher than the Ac3 transformation point in at least one of the first processing or the second processing, completing molding at a temperature higher than a Ar3 transformation point,
wherein:
Equation (1):
Ac3(° C.)=910−203×√C (mass %)+44.7×Si (mass %)−30×Mn (mass %)−11×Cr (mass %)+700×S (mass %)+400×Al (mass %)+50×Ti (mass %)
a rate of temperature increase in the first processing, defined as a rate of temperature increase until reaching the first heat treatment temperature, is at least 20° C./second; and
a rate of temperature increase in the second processing, defined as a rate of temperature increase until reaching the second heat treatment temperature, is at least 20° C./second.

### Claim 2 (depends on 1)

The method for manufacturing a quenched molding of claim 1, wherein a heating time from reaching the first heat treatment temperature in the first processing until an end of heating in the first processing is 400 seconds or shorter.

### Claim 3 (depends on 1)

The method for manufacturing a quenched molding of claim 1, wherein steel material processed in the first processing has a volume fraction of a martensite phase and a bainite phase of no greater than 90%.

### Claim 4 (depends on 1)

The method for manufacturing a quenched molding of claim 1, wherein a molding obtained after the second heating and cooling has a martensite structure volume fraction of at least 50%.

### Claim 5 (depends on 1)

The method for manufacturing a quenched molding of claim 1, wherein the cooling of the first processing is performed with the steel material in a clamped state in a mold.

### Claim 6 (depends on 1)

The method for manufacturing a quenched molding of claim 1, wherein the cooling of the second processing step is performed with the steel material in a clamped state in a mold.