AU632187B2

AU632187B2 - An abrasion resistant steel

Info

Publication number: AU632187B2
Application number: AU67720/90A
Authority: AU
Inventors: Kenji Hirabe; Yasunobu Kunisada; Tetsuya Sanpei; Nobuo Shikanai; Kazunori Yako
Original assignee: NKK Corp
Current assignee: JFE Steel Corp
Priority date: 1990-06-06
Filing date: 1990-12-04
Publication date: 1992-12-17
Anticipated expiration: 2010-12-04
Also published as: FI93863B; FI93863C; CA2033222A1; CA2033267A1; AU3111293A; FI906407L; EP0527276A1; EP0527277B1; GB2245282A; JPH0441616A; EP0527276B1; AU1354595A; FI101403B; FI906407A0; CA2033267C; EP0527277A1; FI906406A0; FI101403B1; FI906406L; AU6772090A

Description

Hiroshi sAT~ -,neral Manager patent License Department This form may be completed and filed after the filing of a patent application but the form must not be signed until after It has been completely filled in as indicated by the marginal notes. The place and date of signing must be filled in. Company stamps or seals should not be used.

No legalisation is necessary.

KENNETH JAMES PRINT i I

AUSTRALIA

PATENTS ACT 1952 COMPLETE SPECIFICATION 532187 Form

(ORIGINAL)

FOR OFFICE.USE Short Title: Int. Cl: Application Number: Lodged: Complete Specification-Lodged: Accepted: Lapsed: Published: Priority: Related Art: soft S I t o 0 o 0 0 eo 9 o9 TO BE COMPLETED BY APPLICANT Name of Applicant: Address of Applicant: 6 *0 ac NKK CORPORATION 1-2, 1-CHOME, MARUNOUCHI

CHIYODA-KU

TOKYO

JAPAN

Actual Inventor: 0 4 Address for Service: GRIFFITH HACK CO., 601 St. Kilda Road, Melbourne, Victoria 3004, Australia.

Complete Specification for the invention entitled: AN ABRASION RESISTANT STEEL.

The following statement is a full description of this invention including the best method of performing it known to me:- TITLE OF THE INVENTION AN ABRASION RESISTANT STEEL BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The invention relates to the field of metallurgy and particularly relates to the field of an abrasion resistant steel utilized in the field of construction, civil engineering and mining.

DESCRIPTION OF THE RELATED ART t; t S S Abrasion resistant steels are utilized in the field tS of construction, civil engineerin'g and mining such as in t f, power shovel, bulldozer, hopper and bucket to keep the lives of these machines or their parts. It is well known that the steel having high hardness possesses high abrasion resistance property. For this purpose a high ,it[ alloyed steel treated by quenching has commonly been uti I ized.

Japanese Patent laid open Publication Nos. 142726/19 87, 169359/1988 and 142023/1989 disclose the information about the production of the conventional abrasion resistant steel. In these inventions the Brinell Hardness of the steel is more than 300. The improvements are aimed at the weldability, the toughness and the workability in bending, and the abrasion resistance property is realized by increasing the hardness of the steel.

However the property required for the abrasion -l na*-~Y)

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1 resistant steel has recently become severer and the essential solution to higher abrasion resistance of steel will not be obtained by simply enhancing the hardness of steel. When the hardness of steel is significantly enhanced, the weldability and the workability of steel are deteriorated due to the high alloying and the cost of producing such steels increases significantly.

Accordingly in the practical point of view the significnat increase in the hardness of abrasion resistant steel is facing with a difficulty with respect to the workability of the steel.

SUMMARY OF THE INVENTION 15 It is an object of the invention to provide an abrasion resistant steel.

It is an object of the invention to provide an abrasion resistant steel having an excellent abrasion resistance property without considerably increasing the 20 hardness of steel. According to the invention an abrasion resistant steel is provided with 0.05 to 0.45 wt.% C, 0.1 to 1.0 wt.% Si, 0.1 to 2.0 wt.% Mn, 0.05 to 1.5 wt.% Ti and the balance Fe, wherein the abrasion resistant steel has a ratio of resistance to abrasion in the range of from 6 to 25 12 when measured according to ASGM Standard G65-85.

In addition to the basic elements, at least one element selected from the group consisting of 0.1 to wt.% Cu, 0.1 to 10.0 wt.% Ni, 0.1 to 3.0 wt.% Cr, 0.1 to wt.% Mo and 0.0003 to 0.01 wt.% B may be added to enhance S2 "TUlfiam~i(L SEb=~Vr.?r""n the quenching hardenability of the steel, and at least one element selected from the group consisting of 0.005 to wt.% Nb, 0.01 to 0.5 wt.% V may be added to enhance the precipitation hardenability of the steel.

A more preferable range aiming at the economy of the steel is 0.05 to 0.3 wt.% in Ti content. A more preferable range with respect to thr balance of the stable abrasion resistance and the economy of the steel is 0.3 to 1.0 wt.% in Ti content. A more preferable range for 0 1, stable abrasion resistance is 1.0 to 1.5 wt.% in Ti content.

A more preferable range aiming at the bending workability and the weldability of the steel is 0.05 to 0.2 wt.% in C content. A more preferable range with respect to the balance of the bending workability and the t*t' weldability of the steel and the stable abrasion resistance of the steel is 0.2 to 0.35 wt.% in C content. A more preferable range for stable abrasion resistance of the steel is 0.35to 0.45 wt.% in C content.

BRIEF DESCRIPTION OF THE DRAWING Figure 1 is a graph showing the relationship between the added quantity of titanium and the ratio of resistance to abrasion.

DESCRIPTION OF THE PREFERRED EMBODIMENT The most significant characteristic of the invented steel is effectively utilizing of very hard TiC. In this invention it is not necessary to enhance the hardness -3of the abrasion resistant steel only by transforming the microstructure of the steel to a martensite which is the conventional way to enhance the abrasion resistance of steel.

In the conventional way the purpose of the addition of titanium to steel is to react with the nitrogen so that the nitrogen is stabilized as TiN. As the result boron does not react with nitrogen since there is not enough "oo9,, nitrogen in the steel, and retained in the steel as a o" soluble boron, which enhances the quenching hardenability.The quantity of the addition in this case is o, about 0.02 wt.% of steel. The addition of a large quantity of titanium to steel is limited by the oxidation of the titanium in the steel melting stage, the clogging of titc nozzle and the reaction with the oxidation preventing powder in the casting stage. Therefore the effect of the addition of a large quantity of titanium is not yet known.

The inventors after detailed examination found that the addition of titanium in a large quantity realizes the improvement of steel with respect to the abrasion resistance property.

Figure 1 is a graph showing the relationship between the added quantity of titanium and the ratio of resistance to abrasion. The abscissa denotes the added quantity of titanium and the ordinate denotes the ratio of resistance to abrasion.

-4r, K The ratio of resistance to abrasion is an index V wherein the resistance to abrasion of an abrasion resistant steel is devided by that of a mild steel. The resistance to abrasion is measured according to ASTM Standard G 65-85 wherein an abrasive is introduced between the test specimen and a rotating wheel with a chlorobutyl K rubber tire. The abrasive is a sand composed of 100% silica and of controlled size. The C content of the test specimen is 0.3 wt.% and the specimen is heat treated i by quenching. The Brinell Hardness is below 500.

As shown in Figure 1, the ratio of resistance to abrasion linearly increases with the increase of the added quantity of titanium up to 0.5 The addition of titanium is effective when the added quantity of titanium is 0.05 .i When the added quantity is 1.5 the ratio of ia', resistance to abrasion reaches about 10, which shows the remarkable improvement in the abrasion resistance property.

The followings are the reason why the contents of the -elements of the invented steel is specif.ied.

C is an indispensable element in forming TiC and also enhances the hardness of the matrix of steel.

However when C is increased too much, the weldability and the workability are deteriorated. Therefore the upper limit of C is determined to be 0.45 As for the lower limit of C the minimum quantity of C wherein the effect of TiC is shown is 0.05 wt.%.

A more preferable range aiming at the bending workability and the weldability of the steel is 0.05 to 0.2 wt.% in C content. A more preferable range with respect to the balance of the bending workability and the weldability of the steel and the stable abrasion resistance of the steel is 0.2 to 0.35 wt.% in C content. A more preferable range for the stable abrasion resistance of the steel is 0.35 to 0.45 wt.% in C content.

ooo" 0 Si is an element effective in deoxidation process of So* steel making and a minimum addition of 0.1 wt.% is 00 required for this purpose. Si is also an effective 00 Selement for solution hardening. However when the Si 0041% content exceeds 1.0 the toughness of steel is lowered and the inclusion in steel is increased. Therefore the ooo Si content is determined to be 0.1 to 1.0 wt.%.

Mn is an element effecive in quenching hardenability. At least 0.1 wt.% is required for this 00 purpose. When the Mn content exceeds 2.0 the 000.00 weldability of steel is deteriorated. Therefore the Mn o. content is determined to be 0.1 to 2.0 wt.%.

i. this invention Ti is one of the most important element as is C. The addition of at least 0.05 wt.% of Ti is required to stably form a large quantity of TiC. When the Ti content exceeds 1.5 the steel possesses good abrasion resistance property but high cost is required for the production, also the weldability and the workability of steel are lowered. Therefore the Ti content is -6r_ required to be 0.05 to 1.5 wt.%.

A more preferable range aiming at the economy of the steel is 0.05 to 0.3 wt.% in Ti content. A more preferable range with respect to the balance of the stable abrasion resistance and the economy of the steel is 0.3 to wt.% in Ti content. A more preferable range for stable abrasion resistance of the steel is 1.0 to wt.% in Ti content.

In this invention, in addition to the above basic Selements, at least one element selected from the group consisting of Cu, Ni, Cr, Mo and B may be added to enhance the quenching hardenability and at least one element selected from the group consisting of Nb and V may be added to enhance the precipitation hardening Cu is an element for enhancing the quenching hardenability and effective in controlling the hardness of steel. When the Cu content is below 0.1 the effect is not sufficient. When the Cu content exceeds 2.0 wt.%, the hot workability is lowered and the production cost is increased. Therefore the Cu content is determined to be 0.1 to 2.0 wt.X.

Ni is an element which enhances the quenching hardenability and the low temperature toughness. When the N3 content is below 0.1 the effect is not sufficient. When the Ni content exceeds 10.0 wt.%, the production cost is increased significantly.

Therefore the Ni content is determined to be 0.1 to 10.0 -7-

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wt.%.

Cr is an element which enhances the quenching hardenability. When the Cr content is below 0.1 the effect is not sufficient. When the Cr content exceeds 3.0 the weldability is deteriorated, and the production cost is increased. Therefore the Cr content is determined to be 0.1 to 3.0 wt.%.

SMo is an element which enhances the quenching hardenability. When the Mo content is below 0.1 the effect is not sufficient. When the Mo content exceeds 3.0 the weldability is deteriorated, Sand the production cost is increased. Therefore the Mo content is determined to be 0.1 to 3.0 wt.%.

B is an element which enhances the quenching hardenability by the addition to steel even by a small amount. When the B content is below 0.0003 wt.% the effect is not sufficient. When the B content exceeds 0.01 the weldability is deteriorated, and the quenching hardenability is also deteriorated. Therefore the B content is determined to be 0.0003 to 0.01 wt.%.

Nb is an element effective in the precipitation hardening and can control the hardness of steel according to the purpose of steel. When the Nb content is below 0.005 the effect is not sufficient. When the Nb content exceeds 0.5 the weldability is deteriorated. Therefore the Nb content is determined to be 0.005 to 0.5 wt.%.

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V is an element effective in the precipitation hardening and can control the hardness of steel according to the purpose of steel. When the V content is below 0.01 the effect is not sufficient. When the V content exceeds 0.5 the weldability is deteriorated.

Therefore the V content is determined to be 0.01 to wt.%.

In this invention no specification is required as for the method of working the steel and as for the method of heat treating of the steel. The invention may not be inoperable by heat treatments such as quenching, annealing, aging and stress relief annealing.

EXAMPLE

Table 1 shows the chemical compositions of the samples of the invented and conventional steel.

Samples from A to 0 are made of the invented steel, whereas samples from P to R are made of the steel for comparison. The chemical composition of the samples from P to R varies with respect to Ti and other alloying elements. The chemical compositions of the samples P and Q are within the same range with those of the invented steel except that of Ti. The chemical composition of the sample R is within the same range of the invented steel with respect to Ti, but out of the range with respect to C.

-9- Table 1 C )in

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Ni 4 4 4 4

A

B

C

D

F

G

H

L

0

Q

RI

0.30 0.28 0.29 0 .29 0. 28 0. 31- 0.19 0.14 0.2 2 0.34 0.31 0.29 0. 30 0.31 0.31 30.. 0. 30 0. 03 0.'6 0.37 0 37 0.36 0.36 0.33 0.33 0.34 0.26 0.38 0.

0.36 0. 36 0 .33 0.30 0.30 0 :3 0 0.70 0.73 0. 74 0.71 0.71 0.73 1 .44 1.40 0 .72 1.01 0 .70 0.71 0.71 0.73 0.75 0.96 0. 24 0.35 0. 25 0. 29 0.36 1,02 0. 27 0. 99 0.99 0. 55 1 .0 2 0 63 0. 23 0. 23 0. 23 0. 23.

0.3 0. 21 0. 025 0 .028 0. 022 0.045 0,.04 1 0. 044.

0. 044 0. 045 0. 04-5 0 .09 0.37 0 .98 1 .41 0. 40 1 .08 0.65 0.40 0. 54 0.06 0 .08 0. 19 0 .38 1 .28 0. 02 0.61

N

33 38 36 31 32 22 24 21 4 2 24 23 31 32 37 47 37 0.75 0. 47 1- I I J I I .1 Note: The values are in wt.% except B and N. The values of B and N are in ppm.

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A

Table 2.

44 4 I 44 4 4' 4, 4 4 4 ~l '4 4 4 1*4 44 4 4 4 144 I Ptrocess Ratio of Brinell resistance to H-ardness(HB) A RQ 6.5 474 B 1 RQ 8 .3 393 B RQT (400-C) 6.1 27 7 o 1 DQ 9 .7 335 C 2 DQT (4OO*C) 6.8 245 D RQ 9.3 242 E RQ 8 .6 390 F RQ 9.1 3.21 G RQ 4. 7 302 H DQ 3.4 253 I RQ 10.i 451 3'D 8 .9 417 K RQ 6.4 503' L 1 AR 4.5 293 L 2 DQ 2 507 m -1 AR 4 .7 286 M N-.1 AR 6.1 274 N 2 RQ 11.6 448 o 1 AR 7. 3 246 0- 2 RQ 11.1 275 p RQ 4.9 464 Q-1AR 2. 8 126 Q-2 R Q 5.2 481 R. RQ 1.2 122 4(44 ~lI4 4144 44 44 I I I 44 4~ II 11 Table 2 shows the process of making the samples, the ratio of the resistance to abrasion and the Brinell Hardness of the samples. Samples from A to 0 are made of the invented steel, whereas samples from P to R are made of the steel for comparison.

The abrasion test is carried out according to ASTM G 65-85 as decribed before. The measurement of the abrasion is done by the change of the weight of the sample.

SAs described before the ratio of resistance to St abrasion is the ratio of the weight change of the specimen made of the invented steel versus that of the specimen made of a mild steel.

The processes in the table are classified as follows AR, as rolled; RQ, as quenched after heated to 900 "C following the rolling and air-cooling; RQT, as tempered at the temperature shown in the parenthesis after RQ treatment; DQ, as directly queuched after finish rolled at 880 °C following the heating of the slab at 1150 DQT, as tempered at the temperature shown in the parenthesis 2 following DQ. The thickness of the sample is 1.5 mm. The kind of steel in Table 1 corresponds with those in Table 2.

The steel for comparison P corresponds with the invented steel A, B-1 and D and the Ti content is below the range of the invented steel. Examining the ratio of the resistance bo abrasion, it is found that the ratio is 4.9 in the steel for comparison P, whereas the ratio of the invented steel A is 6.5, that of the steel B-l, 8.3 and that -12r- 1 of the steel D, 9.3. This is to say that the ratio of the invented steel can be enhanced twice as much as that of the steel for comparison which is a conventional abrasion resistant steel. Moreover the hardness of the invented steel is lower than those of the steel for comparison.

This result agrees with the purpose of the invention wherein the invented steel possesses high resistance to abrasion and low hardness.

*o<o The steel for comparison Q corresponds with the Q4 4 invented steel L and N, The ratios of the resistance to abrasion in both L and N are higher than that of Q.

0a The steel for comparison R corresponds with the invented steel B-1. The C content of the steel for comparison R is below the range of the invent,-d steel.

Since the C content of the steel R is so low that the o" ratio of the resistance to abrasion is significantly lower than that of B-l.

-13- -13

Claims

1. An abrasion resistant steel consisting of 0.05 to 0.45 wt.% C, 0.1 to 1.0 wt.% Si, 0.1 to 2.0 wt.% Mn, 0.05 to 1.5 wt.% Ti and the balance Fe, wherein the abrasion resistant steel has a ratio of resistance to abrasion in the range from 6 to 12 when measured according to ASGM Standard G65-85.

2. The abrasion resistant steel of claim 1, wherein Ti content is 0.05 to 0.3 wt.%.

3. The abrasion resistant steel of claim 1, wherein Ti content is 0.3 to 1.0 wt.%.

4. The abrasion resistant steel of claim 1, wherein Ti content is 1.0 to 1.5 wt.%.

5. The abrasion resistant steel of claim 1, wherein C content is 0.05 to 0.2 wt.%.

6. The abrasion resistant steel of claim 1, wherein C content is 0.2 to 0.35 wt.%

7. The abrasion resistant steel of claim 1, wherein C content is 0.35 to 0.45 wt.%.

8. An abrasion resistant steel consisting of 0.05 to 0.45 wt.% C, 0.1 to 1.0 wt.% Si, 0.1 to 2.0 wt.% Mn, 0.05 to 1.5 wt.% Ti, at least one element selected from the group consisting of 0.1 to 2.0 wt.% Cu, 0.1 to 10.0 wt.% Ni, 0.1 to 3.0 wt.% Cr, 0.1 to 3.0 wt.% Mo and 0.0003 to 0.01 wt.% B, and the balance Fe, wherein the abrasion resistant steel has a ratio of resistance to abrasion in the range from 6 to 12 when measured according to ASGM Standard G65-85.

9. The abrasion resistant steel of claim 8, wherein Ti content is 0.05 to 0.3 wt.%. The abrasion resistant steel of claim 8, wherein Ti content is 0.3 to 1.0 wt.%.

11. The abrasion resistant steel of claim 8, V RA wherein Ti content is 1.0 to 1.5 wt.%.

12. The abrasion resistant steel of claim 8, wherein C content i.s 0.05 to 0.2 wt.%.

13. The abrasion resistant steel of claim 8, wherein C content is 0.2 to 0.35 wt.%.

14. The abrasion resistant steel of claim 8, wherein C content is 0.35 to 0.45 wt.%. An abrasion resistant steel consisting of 0.05 to 0.45 wt.% C, 0.1 to 1.0 wt.% Si, 0.1 to 2.0 wt.% Mn, 0.05 to 1.5 wt.% Ti, at least one element selected from the group consiisting of 0.0005 to 0.5 wt.% Nb and 0.01 to wt.% V, and thae balance Fe, wherein the abrasion resistant steel has a ratio of resistance to abrasion in the range from 6 to 12 when measured according to ASGM Standard G65-85. wheein 16. The abrasion resistant steel of claim wheeinTi content is 0.05 to 0.3 wt.%. wheein 17. The abrasion resistant steel of claim wheeinTi content is 0.3 to 1.0 wt.. 20 18. The abrasion resistant steel of claim LI I I wherein Ti content is 1.0 to 1.5 wt.%. 4

19. The abrasion resistant steel. of claim wherein C con~tent is 0.05 to 0.25 wt. The abrasion resistant steel of claim 25 wherein C content is 0.25 to 0.35 wt%.

22. An abrasion resistant steel, consisting 0.05 to 0.45 wt.% C, 0.1 to 1.0 wt.% Si, 0.1 to 2.0 wt.% Mn, 0.05 to 1.5 wt.% Ti, at least one element selected from the group consisting of 0.1 to 2.0 wt.% Cu, 0.1 to 10.0 wt.% Ni, 0.1 to 3.0 wt.% Cr, 0.1 to 3.0 wt.% Mo and 0.0003 to 0.01 wt.% B, at least one element selected from the group consisting of 0.005 to 0.5 wt.% N! and 0.01 to 0.5 wt.% V, V T -WI and the balance Fe, wherein the abrasion resistant steel has a ratio of resistant to abrasion in the range of from 6 to 12 when measured according to ASGM Standard G65-85.

23. The abrasion resistant steel of claim 22, wherein Ti content is 0.05 to 0.3 wt.%.

24. The abrasion resistant steel of claim 22, wherein Ti content is 0.3 to 1.0 wt.%. The abrasion resistant steel of claim 22, wherein Ti content is 1.0 to 1.5 wt.%.

26. The abrasion resistant steel of claim 22, wherein C content is 0.05 to 0.2 wt.%.

27. The abrasion resistant steel of claim 22, wherein C content is 0.2 to 0.35 wt.%. 15 28. The abrasion resistant steel of claim 22, wherein C content is 0.35 to 0.45 wt.%. C C I Ci IC C C Dated this 20th day of October 1992 .1 4. tC i iC C I CC i 4.11C NKK CORPORATION By Its Patent Attorneys GRIFFITH HACK CO Fellows Institute of Patent 25 Attorneys of Australia.