# US 10,370,735 B2 · Heat treated steel product having high strength and excellent chemical conversion coating ability and method of production of same

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- Number: US 10,370,735 B2
- Document ID: US10370735B2
- Status: Granted
- Kind: B2
- Application number: 15/517,720
- Filed: 2015-10-05
- Published: 2017-10-12
- Granted: 2019-08-06
- Earliest claimed: 2014-10-08
- Assignees: Nippon Steel Corporation
- Applicants: Nippon Steel & Sumitomo Metal Corporation
- Inventors: Hideki Matsuda; Koji Akioka; Kazuo Uematsu
- Web page: https://patentgrep.com/patent/US10370735B2

## CPC

- C21D 9/085: {Cooling or quenching}
- B21B 1/22: for rolling {plates, strips,} bands or sheets of indefinite length (B21B1/42 takes precedence)
- B21D 7/16: Auxiliary equipment, e.g. for heating or cooling of bends
- C21D 1/18: Hardening (C21D1/02 takes precedence); Quenching with or without subsequent tempering (quenching devices C21D1/62)
- C21D 1/74: Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
- C22C 38/00: Ferrous alloys, e.g. steel alloys (cast-iron alloys C22C37/00)
- 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 38/06: containing aluminium
- C22C 38/26: with niobium or tantalum
- C22C 38/28: with titanium or zirconium
- C22C 38/32: with boron
- B21B 2001/225: {by hot-rolling}
- C21D 2211/008: Martensite
- C21D 2241/00: Treatments in a special environment
- C23C 22/12: containing zinc cations
- 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)
- B21B: ROLLING OF METAL (auxiliary operations used in connection with metal-working operations covered in B21, see B21C; bending by rolling B21D; manufacture of particular objects, e.g. screws, wheels, rings, barrels, balls, by rolling B21H; pressure welding by means of a rolling mill B23K20/04)
- 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)
- C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04)

## Abstract

A steel product bent by heating to 600° C. or more, specifically a heat treated steel product having high strength and excellent chemical conversion coating ability which has scale with FeO content of 90% or more, having a thickness of 1 μm or less on the surface.

## Claims

### Claim 1

Heat A heat treated steel product comprising a scale with FeO content of 90% or more, having a thickness of 1 μm or less on a surface,
wherein a maximum value and a minimum value of a thickness of the scale are within ±10% of an average value of the thickness.

### Claim 2 (depends on 1)

The heat treated steel product according to claim 1, wherein the steel has a structure consisting of martensite, or martensite and tempered martensite.

### Claim 3 (depends on 1)

The heat treated steel product according to claim 1, wherein the steel product is a hollow member having a closed horizontal cross-sectional shape.

### Claim 4 (depends on 2)

The heat treated steel product according to claim 2, wherein the steel product is a hollow member having a closed horizontal cross-sectional shape.