Steel for high-strength bolt, and high-strength bolt

Patent metadata

Field	Value
Publication number	US-10913993-B2
Application number	US-201515506506-A
Country	US
Kind code	B2
Filing date	Aug 7, 2015
Priority date	Aug 29, 2014
Publication date	Feb 9, 2021
Grant date	Feb 9, 2021

Abstract

A steel for a high-strength bolt that includes from 0.50 mass % to 0.65 mass % carbon, from 1.5 mass % to 2.5 mass % silicon, 1.0 mass % or more chromium, 0.4 mass % or less manganese, greater than 1.5 mass % molybdenum, 0.03 mass % or less phosphorus and sulfur combined, and balance iron and inevitable impurities.

First claim

The invention claimed is:

1. A high-strength bolt containing: from 0.50 mass % to 0.65 mass % carbon, from 1.5 mass % to 2.5 mass % silicon, 1.0 mass % or more chromium, 0.4 mass % or less manganese, greater than 1.5 mass % molybdenum, 0.03 mass % or less phosphorus and sulfur combined, and balance iron and inevitable impurities, wherein a microstructure of the bolt comprises an intergranular cementite that is spheroidized and dispersed, and wherein the bolt has a tensile strength of 1500 MPa or more.

2. The high-strength bolt according to claim 1 , comprising an iron phosphate coating and/or a chromium plate coating on a surface.

3. The high-strength bolt according to claim 1 , containing 1.6 mass % or less chromium.

4. The high-strength bolt according to claim 1 , containing 1.4 mass % or less chromium.

5. The high-strength bolt according to claim 1 , containing greater than 0 mass % manganese.

6. The high-strength bolt according to claim 1 , containing 0.2 mass % or more manganese.

7. The high-strength bolt according to claim 1 , containing 2.2 mass % or less molybdenum.

8. The high-strength bolt according to claim 1 , containing 1.65 mass % or less molybdenum.

9. The high-strength bolt according to claim 1 , containing 0.02 mass % or less phosphorus and sulfur combined.

10. The high-strength bolt according to claim 1 , further comprising an iron phosphate coating on a surface.

11. The high-strength bolt according to claim 10 , further comprising a chromium plate coating on the surface.

12. The high-strength bolt according to claim 1 , containing from 1.5 mass % to 2.2 mass % silicon, from 1.0 mass % to 1.4 mass % chromium, from 0.2 mass % to 0.4 mass % manganese, from 1.51 mass % to 2.2 mass % molybdenum.

Assignees

• Nissan Motor

Inventors

• Hamada Takahiro
• Nakamura Tsuyoshi
• Kimura Kosuke

Classifications

• F16B35/00

  Screw-bolts; Stay-bolts; Screw-threaded studs; Screws; Set screws ({F16B33/008 takes precedence; joining sheets or plates using screws with two separate threads F16B5/0275; using screws with adjustment sleeves F16B5/0283}; thread cutting screws F16B25/00) · 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

• C22C38/00

  Ferrous alloys, e.g. steel alloys (cast-iron alloys C22C37/00) · CPC title

• C21D9/0093

  for screws; for bolts · CPC title

• C22C38/04

  containing manganese · CPC title