Steel with high hardness and excellent toughness

Patent metadata

Field	Value
Publication number	US-2020080180-A1
Application number	US-201816467225-A
Country	US
Kind code	A1
Filing date	Aug 8, 2018
Priority date	Aug 18, 2017
Publication date	Mar 12, 2020
Grant date	—

Abstract

A steel with high hardness and excellent toughness contains, in mass %, 0.40-1.00% C, 0.10-2.00% Si, 0.10-1.00% Mn, 0.030% or less P, 0.030% or less S, 1.10-3.20% Cr, 0.010-0.10% Al, and 0.15-0.50% V, and further contains at least one or two of 2.50% or less Ni and 1.00% or less Mo, with an amount of (C+V) being 0.60% or more in mass %, with the balance consisting of Fe and unavoidable impurities. The steel has a microstructure which is a martensitic structure with finely dispersed Fe-based ε carbides, with its prior austenite grain size being 20 μm or less.

First claim

1 . A steel with high hardness and excellent toughness, containing, in mass %, 0.40-1.00% C, 0.10-2.00% Si, 0.10-1.00% Mn, 0.030% or less P, 0.030% or less S, 1.10-3.20% Cr, 0.010-0.10% Al, and 0.15-0.50% V, and further containing at least one of 2.50% or less Ni and 1.00% or less Mo, with an amount of (C+V) being 0.60% or more in mass %, with the balance consisting of Fe and unavoidable impurities, the steel having a microstructure which is a martensitic structure with finely dispersed Fe-based a carbides and with a prior austenite grain size of 20 μm or less.

2 . The steel with high hardness and excellent toughness according to claim 1 , having the chemical components and the microstructure of claim 1 , wherein the martensitic structure tempered at a low temperature of 130° C. to 250° C. has V-containing fine carbides with a diameter of 0.50 μm or less precipitated dispersively therein, and an amount of the precipitated V-containing fine carbides constitutes 0.10-0.90 vol % of a total martensite volume.

3 . The steel with high hardness and excellent toughness according to claim 1 , having the chemical components and the microstructure of claim 1 , wherein in the microstructure, an amount of precipitated cementite in the martensitic structure tempered at a low temperature of 130° C. to 250° C. constitutes 0.50 vol % or less of a total martensite volume.

4 . The steel with high hardness and excellent toughness according to claim 2 , having the chemical components and the microstructure of claim 1 and the microstructure of claim 2 , wherein an amount of precipitated cementite in the martensitic structure tempered at a low temperature of 130° C. to 250° C. constitutes 0.50 vol % or less of the total martensite volume.

Assignees

• Univ Osaka
• Komatsu Mfg Co Ltd

Inventors

• Minamino Yoritoshi
• Hagihara Koji
• Yamamoto Koji
• Ikurumi Shohei
• Hiratsuka Yusuke
• Fujimatsu Takeshi
• Sugimoto Toshiyuki

Classifications

• C21D6/00

  Heat treatment of ferrous alloys · CPC title

• C21D6/005

  containing Mn · CPC title

• C22C38/002

  containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60 · CPC title

• C21D2211/004

  Dispersions; Precipitations · CPC title

• C21D6/004

  containing Cr and Ni · CPC title