Abrasion-resistant steel plate and method for manufacturing the same

Patent metadata

Field	Value
Publication number	US-2016348208-A1
Application number	US-201515114889-A
Country	US
Kind code	A1
Filing date	Jan 26, 2015
Priority date	Jan 28, 2014
Publication date	Dec 1, 2016
Grant date	—

Abstract

An abrasion resistant steel plate having excellent low-temperature toughness and excellent cracking resistance in a portion which has been heated to a temperature range in which low-temperature temper embrittlement occurs and a method for manufacturing the steel plate. The steel plate includes a microstructure at positions located at ¼ of the thickness and at ¾ of the thickness including a martensite single phase microstructure having an average prior austenaite grain diameter in the range of 20 μm to 60 μm, or a mixed microstructure of martensite and bainite having a proportion of martensite-austenite constituent of less than 5% in terms of area ratio with respect to the whole microstructure.

First claim

1 . An abrasion-resistant steel plate having a surface hardness in the range of 350 to 450 in terms of Brinell hardness (HBW 10/3000), the steel plate having a chemical composition comprising:
C: 0.100% or more and less than 0.175%, by mass %; Si: 0.05% to 1.00%, by mass %; Mn: 0.50% to 1.90%, by mass %; P: less than 0.006%, by mass %; S: 0.005% or less, by mass %; Al: 0.005% to 0.100%, by mass %; Cr: 0.10% to 1.00%, by mass %; Nb: 0.005% to 0.024%, by mass %; Ti: 0.005% to 0.050%, by mass %; B: 0.0003% to 0.0030%, by mass %; N: 0.0010% to 0.0080%, by mass %; and Fe and incidental impurities, wherein the steel plate includes a microstructure at positions located at ¼ of the thickness of the steel plate and at ¾ of the thickness of the steel plate including a martensite single phase microstructure having an average prior austenaite grain diameter in the range of 20 μm to 60 μm, or a mixed microstructure of martensite and bainite having an average prior austenaite grain diameter in the range of 20 μm to 60 μm, and martensite-austenite constituent in bainite being less than 5% in terms of area ratio with respect to the whole microstructure, and the chemical composition satisfies relational expression (1) and relational expression (2):
DIH =33.85×(0.1×C) 0.5 ×(0.7×Si+1)×(3.33×Mn+1)×(0.35×Cu+1)×(0.36×Ni+1)×(2.16×Cr+1)×(3×Mo+1)×(1.75×V+1)≧35  (1),

CES =5.5×C 4/3 +75.5×P+0.90×Mn+0.12×Ni+0.53×Mo≦2.70  (2)

where, in both relational expressions, atomic symbols of the alloying elements denote the contents by mass % of the corresponding elements.

2 . The abrasion-resistant steel plate according to claim 1 , wherein the chemical composition further comprises at least one selected from the group consisting of Mo: 0.05% to 0.80%, by mass %, V: 0.005% to 0.10%, by mass %, Cu: 0.10% to 1.00%, by mass %, and Ni: 0.10% to 2.00%, by mass %.

3 . The abrasion-resistant steel plate according to claim 1 , wherein the chemical composition further comprises at least one selected from the group consisting of Ca: 0.0005% to 0.0040%, by mass %, Mg: 0.0005% to 0.0050%, by mass %, and REM: 0.0005% to 0.0080%, by mass %.

4 . A method for manufacturing an abrasion-resistant steel plate having a surface hardness in the range of 350 to 450 in terms of Brinell hardness (HBW 10/3000), the method comprising:
heating a steel material having a chemical composition to a temperature in the range of 1050° C. to 1200° C., the chemical composition comprising:
C: 0.100% or more and less than 0.175%, by mass %;
Si: 0.05% to 1.00%, by mass %;
Mn: 0.50% to 1.90%, by mass %;
P: less than 0.006%, by mass %;
S: 0.005% or less, by mass %;
Al: 0.005% to 0.100%, by mass %;
Cr: 0.10% to 1.00%, by mass %;
Nb: 0.005% to 0.024%, by mass %;
Ti: 0.005% to 0.050%, by mass %;
B: 0.0003% to 0.0030%, by mass %;
N: 0.0010% to 0.0080%, by mass %; and
Fe and incidental impurities,
the chemical composition satisfying relational expression (1) and relational expression (2):
DIH =33.85×(0.1×C) 0.5 ×(0.7×Si+1)×(3.33×Mn+1)×(0.35×Cu+1)×(0.36×Ni+1)×(2.16×Cr+1)×(3×Mo+1)×(1.75×V+1)≧35  (1),

CES =5.5×C 4/3 +75.5×P+0.90×Mn+0.12×Ni+0.53×Mo≦2.70  (2)

where, in both relational expressions, atomic symbols of the alloying elements denote the contents by mass % of the corresponding elements;
performing hot rolling with a cumulative rolling reduction of 30% or more in a temperature range of 950° C. or higher and a cumulative rolling reduction in the range of 30% to 70% in a temperature range lower than 940° C. to form a steel plate; finishing hot rolling at a surface temperature in the range of (Ar3+80° C.) to (Ar3+180° C.); performing quenching from a temperature of Ar3 or more and cooling to a temperature of 300° C. or lower at a cooling rate of 2° C./s or more at a position located at ½ of the thickness of the steel plate, wherein the steel plate includes a microstructure at positions located at ¼ of the thickness of the steel plate and at ¾ of the thickness of the steel plate including a martensite single phase microstructure having an average prior austenaite grain diameter in the range of 20 μm to 60 μm, or a mixed microstructure of martensite and bainite having an average prior austenaite grain diameter in the range of 20 μm to 60 μm, and martensite-austenite constituent in bainite being less than 5% in terms of area ratio with respect to the whole microstructure.

5 . The abrasion-resistant steel plate according to claim 2 , wherein the chemical composition further comprises at least one selected from the group consisting of Ca: 0.0005% to 0.0040%, by mass %, Mg: 0.0005% to 0.0050%, by mass %, and REM: 0.0005% to 0.0080%, by mass %.

6 . The method for manufacturing an abrasion-resistant steel according to claim 4 , wherein the chemical composition further comprises at least one selected from the group consisting of Mo: 0.05% to 0.80%, by mass %, V: 0.005% to 0.10%, by mass %, Cu: 0.10% to 1.00%, by mass %, and Ni: 0.10% to 2.00%, by mass %.

7 . The method for manufacturing an abrasion-resistant steel according to claim 4 , wherein the chemical composition further comprises at least one selected from the group consisting of Ca: 0.0005% to 0.0040%, by mass %, Mg: 0.0005% to 0.0050%, by mass %, and REM: 0.0005% to 0.0080%, by mass %.

8 . The method for manufacturing an abrasion-resistant steel according to claim 6 , wherein the chemical composition further comprises at least one selected from the group consisting of Ca: 0.0005% to 0.0040%, by mass %, Mg: 0.0005% to 0.0050%, by mass %, and REM: 0.0005% to 0.0080%, by mass %.

Assignees

• Jfe Steel Corp

Inventors

• Yuga Masao
• Miura Shinichi
• Ohmori Akio

Classifications

• C21D8/0226

  Hot rolling · CPC title

• C22C38/50

  with titanium or zirconium · CPC title

• C21D2211/008

  Martensite · CPC title

• C21D2211/001

  Austenite · CPC title

• C22C38/48

  with niobium or tantalum · CPC title