Method for making an abrasion resistant steel plate and plate obtained

• US 20060162826A1
• Filed: 11/13/2003
• Published: 07/27/2006
• Est. Priority Date: 11/19/2002
• Status: Active Grant

• Current Assignee: Industeel France S.A. (ArcelorMittal SA)
• Original Assignee: Industeel France S.A. (ArcelorMittal SA)
• Inventors: Beguinot, Jean, Brisson, Jean-Georges
• Granted Patent: US 7,713,362 B2
• Time in Patent Office: Days
• US Class Current: 148/664
• CPC Class Codes: C21D 1/19 by interrupted quenching
• CPC Class Codes: C21D 2211/001 Austenite
• CPC Class Codes: C21D 2211/002 Bainite
• CPC Class Codes: C21D 2211/008 Martensite
• CPC Class Codes: C21D 9/46 for sheet metals
• CPC Class Codes: C22C 38/02 containing silicon
• CPC Class Codes: C22C 38/44 with molybdenum or tungsten
• CPC Class Codes: C22C 38/50 with titanium or zirconium
• CPC Class Codes: C22C 38/58 with more than 1.5% by weight of manganese

Abstract

The invention concerns a method for making an abrasion resistant steel plate having a chemical composition comprising, by weight: 0.24%≦C≦0.35%; 0%—Si—2%; 0%—Al≦2%; 0.5%≦Si+Al≦2%; 0%≦Mn≦2.5% 0%≦Ni≦5 %; 0%≦Cr≦<5% 0%≦Mo≦1%; 0%≦W≦2%; 0.1%≦Mo+W/2≦1%; 0%≦B≦0.02%; 0%≦Ti≦1.1%; 0%≦Zr≦2.2%; 0.35%≦Ti+Zr/2≦1.1%; 0%≦S<0.15%; N<0,03%, optionally 0% to 1,5% of copper; optionally at least one element selected among Nb, Ta and V in contents such that Nb/2+Ta/4+V≦0.5%; optionally at least one element selected among Te, Ca, Bi, Pb in contents not more than 0.1%; the rest being iron and impurities resulting from the preparation, moreover the chemical composition satisfying the following relationships: 0.095%≦C*=C−Ti/4−Zr/8+7×N/8 and 1.05×Mn+0.54×Ni+0.50×Cr+0.3×(Mo+W/2)¹¹²+K>1.8, with K=0.5 if B≦0.0005% and K=0 if B<0.0005%. The method consists in subjecting the plate to a hardening, in rolling heat or after austenitization in a furnace; cooling the plate at a cooling speed higher than 0.5° C./s between a temperature higher than AC₃ and a temperature ranging between T=800−270×C*−90×Mn−37×Ni−70×Cr−83×(Mo+W/2) and T-50° C.; then cooling the plate at a core cooling speed Vr<1150xep⁻¹⁷ between temperature T and 100° C. (ep=plate temperature expressed in mm); cooling the plate down to room temperature and, optionally planishing. The invention also concerns the resulting plate.

Claims

1. Method for producing a workpiece or a plate of steel which is resistant to abrasion and whose chemical composition comprises, by weight:

0.24%≦

C<

0.35%
0%≦

Si≦

2%
0%≦

Al≦

2%
0.5%≦

Si+Al≦

2%
0%≦

Mn≦

2.5%
0%≦

Ni≦

5%
0%≦

Cr≦

5%
0%≦

Mo≦

1%
0%≦

W≦

2%
0.1%≦

Mo+W/2≦

1%
0%≦

B≦

0.02%
0%≦

Ti≦

1.1%
0%≦

Zr≦

2.2%
0.35%<

Ti+Zr/2≦

1.1%
0%≦

S≦

0.15%
N<

0.03%

optionally from 0% to 1.5% of copper,

optionally at least one element selected from Nb, Ta and V at contents such that Nb/2+Ta/4+V≦

0.5%,

optionally at least one element selected from Se, Te, Ca, Bi, Pb at contents which are less than or equal to 0.1%, the balance being iron and impurities resulting from the production operation, the chemical composition further complying with the following relationships;

C*=C−

Ti/4−

Zr/8+7×

N/8≧

0.095%
and;


1.05×

Mn+0.54×

Ni+0.50×

Cr+0.3×

(Mo+W/2)^1/2+K>

1.8

with;

K=0.5 if B≧

0.0005% and K=0 if B<

0.0005%.

according to which the plate is subjected to a thermal quenching processing operation which is carried out in the heat for forming in the hot state and, for example, rolling heat, or after austenitization by reheating in a furnace, in order to carry out the quenching;

the workpiece or the plate is cooled at a mean cooling rate greater than 0.5°

C./s between a temperature greater than AC₃ and a temperature of from approximately T=800−

270×

C*−

90×

Mn−

37×

Ni−

70×

Cr−

83×

(Mo+W/2), to T-50°

C.,

the workpiece or the plate is then cooled at a mean core cooling rate Vr<

1150×

ep<sup>−

1.7</sup> and greater than 0.1°

C./s between the temperature T and 100°

C., ep being the thickness of the plate expressed in mm,

the workpiece or the plate is cooled as far as ambient temperature and optionally planishing is carried out.

2. Method according to claim 1, characterized in that:

1.05×

Mn+0.54×

Ni+0.50×

Cr+0.3×

(Mo+W/2)^1/2+K>

2.

3. Method according to claim 1, characterized in that

Ti+Zr/2≧

0.4%.

4. Method according to claim 1, characterized in that:

C*≧

0.12%.

5. Method according to claim 1, characterized in that:

Si+Al≧

0.7%.

6. Method according to claim 1, characterized in that tempering is further carried out at a temperature which is less than or equal to 350°

C.

7. Method according to claim 1, characterized in that, in order to add titanium to the steel, the liquid steel is placed in contact with a slag containing titanium and the titanium of the slag is caused to diffuse slowly in the liquid steel.

8. Workpiece, and in particular a plate, of steel which is resistant to abrasion and whose chemical composition comprises, by weight:

0.24%≦

C<

0.35%
0%≦

Si≦

2%
0%≦

Al≦

2%
0.5%≦

Si+Al≦

2%
0%≦

Mn≦

2.5%
0%≦

Ni≦

5%
0%≦

Cr≦

5%
0%≦

Mo≦

1%
0%≦

W≦

2%
0.1%≦

Mo+W/2≦

1%
0%≦

B≦

0.02%
0%≦

Ti≦

1.1%
0%≦

Zr≦

2.2%
0.35%<

Ti+Zr/≦

1.1%
0%≦

S≦

0.15%
N<

0.03%

optionally from 0% to 1.5% of copper,

optionally at least one element selected from Nb, Ta and V at contents such that Nb/2+Ta/4+V≦

0.5%,

optionally at least one element selected from Se, Te, Ca, Bi, Pb at contents which are less than or equal to 0.1%,

the balance being iron and impurities resulting from the production operation, the chemical composition further complying with the following relationships;

C−

Ti/4−

Zr/8+7×

N/8≦

0.095%
and;


1.05×

Mn+0.54×

Ni+0.50×

Cr+0.3×

(Mo+W/2)^1/2+K>

1.8

with;

K=0.5 if B≧

0.0005% and K=0 if B<

0.0005%,

the steel having a martensitic or martensitic/bainitic structure, the structure containing from 5% to 20% of retained austenite and carbides.

9. Workpiece according to claim 8, characterized in that:

1.05×

Mn+0.54×

Ni+0.50×

Cr+0.3×

(Mo+W/2)^1/2+K>

2.

10. Workpiece according to claim 8, characterized in that:

Ti+Zr/2≧

0.4%.

11. Workpiece according to claim 8, characterized in that:

C*≧

0.12%.

12. Workpiece according to claim 8, characterized in that:

Si+Al≧

0.7%

13. Workpiece according to claim 8, characterized in that it is a plate having a thickness of from 2 mm to 150 mm.