Carbon-containing steel material and method for producing same

Patent metadata

Field	Value
Publication number	US-10793935-B2
Application number	US-201515539559-A
Country	US
Kind code	B2
Filing date	Dec 17, 2015
Priority date	Dec 24, 2014
Publication date	Oct 6, 2020
Grant date	Oct 6, 2020

Abstract

An object of the present invention is to provide a clock screw having a deep interference film blue color that contributes to decorativeness while also having superior scratch resistance and corrosion resistance, and a method for producing the same. The means for solving provided by the present invention consists of: a clock screw comprising a screw base material made of steel containing carbon at 0.5% by weight to 1.0% by weight, an oxide layer of the steel on the screw base material having a thickness of 60 nm to 80 nm, and a fluorine coating film on the oxide layer; and, a method for producing the clock screw comprising: a step for preparing the screw base material, a step for forming the oxide layer by heating the screw base material for 30 minutes or longer at a temperature of 300° C. or lower in an air atmosphere, and a step for forming the fluorine coating film on the oxide layer.

First claim

The invention claimed is:

1. A carbon-containing steel material, comprising: a base material made of steel containing carbon at 0.5% by weight to 1.0% by weight, an oxide layer of the steel on the base material having a thickness of 60 nm to 80 nm, which brings about deep interference film blue color, and a fluorine coating film on the oxide layer, wherein the oxide layer has 10 or fewer pinholes having a diameter of 0.3 μm or more per a surface area having a dimension of 50 μm ×50 μm square.

2. The carbon-containing steel material according to claim 1 , wherein the thickness of the fluorine coating film is 2 nm to 6 nm.

3. The carbon-containing steel material according to claim 1 , wherein the surface hardness of the base material is Hv 500 to Hv 700.

4. A method for producing the carbon-containing steel material according to claim 1 , comprising:
a step for preparing the base material,
a step for heating the base material for 30 minutes or longer at a temperature of 300° C. or lower in an air atmosphere, to form the oxide layer, and
a step for forming the fluorine coating film on the oxide layer.

5. The production method according to claim 4 , wherein the heating time is 6 hours or less.

6. The production method according to claim 4 , further comprising a step for quenching and tempering the base material prior to the heating step.

7. The production method according to claim 4 , wherein, in the heating step, 1000 or more of the base materials are heated simultaneously.

Assignees

• Citizen Watch Co Ltd

Inventors

• Yamazaki Haruko
• Hirai Yoshiro

Classifications

• C23C8/14

  Oxidising of ferrous surfaces · CPC title

• F16B33/06

  Surface treatment of parts furnished with screw-thread, e.g. for preventing seizure {or fretting (corrosion preventing means F16B33/008; settable coatings for locking threaded members F16B39/225; deformable coatings for locking threaded members F16B39/34)} · CPC title

• B05D7/24

  for applying particular liquids or other fluent materials · CPC title

• C23C8/80

  After-treatment · CPC title

• B05D7/14

  to metal, e.g. car bodies (involving a chemical reaction between the metal and the coating C23) · CPC title