FI101403B - Wear-resistant steel - Google Patents

Description

101403

This invention relates to wear-resistant steel used in the construction, civil and civil engineering and mining industries.

Wear-resistant steels are used in the construction, civil engineering and mining industries, such as machine shovels, earthmoving buffers, dredgers and grapples, to extend the life of these machines and their parts. It is well known that steel with high hardness also has good abrasion resistance property. Highly alloyed steel, which has been treated by hardening, has been commonly used for this purpose.

JP Patent Publication Nos. 15 142726/1987, 169359/1988 and 142023/1989, which have become public, describe the production of conventional wear-resistant steel. In these inventions, the Brinell hardness of the steel is more than 300. The improvements are aimed at weldability, toughness and machinability in bending, and the wear resistance property to-20 is realized by increasing the hardness of the steel.

However, the performance requirements for wear-resistant steel have recently become more stringent and the essential solution for steel with better wear resistance is simply not achieved. 25 by increasing the hardness of the steel. When the hardness of the steel is significantly increased, the weldability and machinability of the steel deteriorate due to the strong alloying, and the manufacturing cost of such steels increases significantly. Thus, from a practical point of view, a significant increase in the hardness of wear-resistant steel faces difficulties with regard to the machinability of the steel.

It is an object of the present invention to provide a wear-resistant steel.

It is an object of the present invention to provide a wear-resistant steel having excellent wear resistance properties without significantly increasing the hardness of the steel.

The invention relates to wear-resistant steel, which is characterized in that it contains the following components: 5 C 0.05 to 0.2% by weight,

Si 0.1 to 1.0% by weight,

Mn 0.1 to 2.0% by weight,

Ti 0.3 to 1.0% by weight, wherein it contains one or more quencher-10 moieties selected from the group consisting of copper, nickel, chromium, molybdenum and boron, in weight ratios:

Cu 0.1 - 2.0% by weight

Ni 0.1 to 10.0% by weight

Cr 0.1 to 3.0% by weight 15 Mo 0.1 to 3.0% by weight B 0.0003 to 0.01% by weight; and optionally one or more precipitation hardening ingredients selected from the group consisting of niobium and vanadium in weight ratios: 20 Nb 0.005 to 0.5% by weight V 0.01 to 0.5% by weight.

Figure 1 is a graph showing the relationship between the amount of titanium added and the relative wear duration.

The most significant feature of the steel of this invention, 25, is the efficient utilization of very hard TiC. In the present invention, it is not necessary to improve the hardness of the wear-resistant steel simply by converting the steel microstructure to martensitic, which is a conventional way to improve the wear resistance of the steel.

In the conventional manner, the addition of titanium to the steel is intended to react it with nitrogen so that the nitrogen is stabilized to TiN. As a result, boron does not react with nitrogen because there is not enough nitrogen in the steel, and it remains soluble in the steel as boron-35, which improves the immersion hardenability. The addition amount is 101403 3 in this case about 0.02% by weight of the steel. The addition of a large amount of titanium to the steel is limited by the oxidation of titanium in the steel smelting step, the clogging of the nozzle, and the reaction with the antioxidant powder in the casting step. Therefore, the effect of adding a large amount of titanium is not yet known.

After a detailed study, it has been found that the addition of a large amount of titanium causes an improvement in the wear resistance property of the steel.

Fig. 1 is a graph showing the relationship between the amount of titanium added and the relative wear life. The abscissa shows the amount of titanium added and the ordinate shows the relative wear time.

Relative wear life is a factor where the wear life of wear-15 steel is divided by the wear life of carbon steel. The wear resistance is measured according to ASTM G 65-85, in which an abrasive is fed between a test piece and a rotating wheel with a chlorobutyl rubber ring. The abrasive is sand composed of 100% silica with a controlled size. The C content of the test piece is 0.3% by weight and the sample is heat-treated by cooling with water. The Brinell hardness is less than 500. As shown in Figure 1, the relative wear resistance increases linearly with increasing amount of titanium up to 0.5% by weight up to 25% by weight. The addition of titanium is effective when the amount of titanium added is 0.05% by weight. When the added amount is 1.5% by weight, the relative wear resistance reaches a value of about 10, which indicates a significant improvement in the wear resistance property.

The following is the reason for determining the elemental contents of the steel according to the invention.

C is an essential element in the formation of TiC and also improves the hardness of the steel matrix. However, when the amount of C increases too much, the weldability and machinability deteriorate. With respect to the lower limit of C, the minimum amount of C at which the effect of TiC is observed is 0.05% by weight.

The range aimed at the bendability and weldability of the steel is 0.05-0.2 5% by weight for the C content.

Si is an element which is effective in the deoxygenation process of steelmaking and for this purpose an addition of at least 0.1% by weight is required. Si is also an effective element in solution hardening. However, when the Si content 10 exceeds 1.0% by weight, the toughness of the steel deteriorates and the inclusions in the steel increase. Therefore, the Si content has been determined to be 0.1 to 1.0% by weight.

Mn is an effective element in immersion hardening. At least 0.1% by weight is required for this purpose. When the Mn-pi-15 content exceeds 2.0% by weight, the weldability of the steel deteriorates. Therefore, the Mn content has been determined to be 0.1 to 2.0% by weight.

In the present invention, Ti is one of the most important elements as well as C. The range for the stable wear life and economy of the steel is 0.3 to 1.0% by weight for the Ti content.

In the present invention, in addition to the basic elements described above, at least one element selected from the group consisting of Cu, Ni, Cr, Mo and B is added to improve the sudden hardenability, wherein one or more elements selected from the group consisting of Nb and V, can be added to improve the precipitation hardenability.

Cu is an element that improves the sudden hardenability 30 and is effective in adjusting the hardness of steel. When the Cu content is less than 0.1% by weight, the effect is not sufficient. When the Cu content exceeds 2.0% by weight, the hot workability deteriorates and the production cost increases. Therefore, the Cu content has been determined to be 0.1 to 2.0% by weight.

101403 5

Ni is an element that improves sudden hardenability and low temperature toughness. When the Ni content is less than 0.1% by weight, the effect is not sufficient. When the Ni content exceeds 10.0% by weight, the production cost increases significantly. Therefore, the Ni content has been determined to be 0.1-10.0% by weight.

Cr is an element that improves sudden hardenability. When the Cr content is less than 0.1% by weight, the effect is not sufficient. When the Cr content exceeds 3.0% by weight, the weldability deteriorates and the production costs increase. Therefore, the Cr content has been determined to be 0.1 to 3.0% by weight.

Mo is an element that improves sudden hardenability. When the Mo content is less than 0.1% by weight, the effect is not sufficient. When the Mo content exceeds 3.0% by weight, the inertia deteriorates and the production costs increase. Therefore, the Mo content has been determined to be 0.1 to 3.0% by weight.

B is an element which improves the immersion hardenability 20 even in small amounts when added to steel. When the B content is less than 0.0003% by weight, the effect is not sufficient. When the B content exceeds 0.01% by weight, the weldability deteriorates and also the sudden hardenability deteriorates. Therefore, the B content is defined to be 0.0003 to 0.01% by weight.

. 25 Nb is an element which is effective in precipitation hardening and can adjust the hardness of steel according to the purpose of the steel. When the Nb content is less than 0.005% by weight, the effect is not sufficient. When the Nb content exceeds 0.5% by weight, the weldability deteriorates. Therefore, a content of 30 Nb has been determined to be 0.005 to 0.5% by weight.

V is an element which is effective in precipitation hardening and can adjust the hardness of steel according to the purpose of the steel. When the V content is less than 0.01% by weight, the effect is not sufficient. When the V content is more than 0.5 6 101403% by weight, the weldability deteriorates. Therefore, the V content has been determined to be 0.01 to 0.5% by weight.

The present invention does not require any specification as regards the method of machining the steel or the method of heat treatment of the steel. Heat treatments such as quenching, emission, aging, and stress release heat treatment cannot render this invention inoperative.

Example

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

table 1

C Si Hn Cu Hi Cr Ho Hb V Tl B N

A 0.30 0.36 0.70 - - - - - - 0.09 - 33 B 0.23 0.37 0.73 - .... - o, 37 - 30 C 0.29 0.37 0 .74 - ----- o .98 - 36 D 0.29 0.36 0.71 - '- - - 1.41 - 30 E 0.28 0.36 0-71 0.24 0.29 - 0.40 - 31 20 rr 1> 1 F 0, 31 0.33 0.73 - - 1} 02 0.23 - - 1.08 10 32 G 0, 19 0.33 1.44 - - 0, .27 - 0, 65 9 22 H 0.14 0.34 1.40 - - 0.025 - 0.40 - 24 I 0.32 0, 34 0.72 - - 0.045 0.41 - 21 25 J 0, 34 0, 26 1, 01 0.35 0.55 - - 0.028 0.041 0, 54 - 42 K 0.31 0.38 0.71 - - 0.99 0.23 0.022 0.044 0.06 8 24 L 0.29 0.38 0.70 - - 0.99 0.23 - 0.044 0.08 9 23 M 0, 30 0.36 0.7 1 0, 25 - 0.55 0, 23 - 0, 045 0, 19. 8 30 N 0.31 0.36 0.71 - - 1.02 0.23 - 0.045 0.38 8 31 30 O 0.31 0.33 0.73 - 0.36 0.63 0.34 - - 1.28 - 32 P 0.30 0.30 0.75 - ---- - 0.22 - 37 Q 0.30 0.30 0.96 - - 1.03 0.21 - 0.045 0.01 11 47 R 0, 03 0 ^ 30 0.75 - - - - 0.47 - 37

Note: Values are by weight except for B and N, which are in ppm 35 7 1 O 1 4 ϋ 3

Table 2

Relative Brinell- 5 Process wear hardness (HB) ~ A RQ "6.5 474 B - 1 RQ 8.3 393" b - 2 ...... RQT (4 Ö Ö * C j ...... ........ 6 * / 1 ..................... 27 7 .........

C - 1 DQ 9.7 iTi C - "2 ........ DQT (4 q6 * C j .............. 6, 8 ...... .................. 24 5 ...........

D RQ__9 ^ 3__24 2 E__RQ__BjJJ__390 F ~ RQ 9,1__3.21 15 G__RQ__4 ^ 7__302 H DQ 3; 4 253 I__RQ__1_0jJ__451 J DQ 8? 9__417 K RQ 6.4 503 20 --- 1 --— L - 1 AR 4,5 293 L - 2 '............ DQ .......... ...... ......... 8 t 2,507 M - 1 AR 4.7 286 "M - 2 ............ DQ ...... .................... 9, 'ϊ__454 25 N - 1 Å 6.1 274 N- 2 RQ ............. ......... Π, 6 44 8 0-1 AR 7, 3 24 6 0-2 ............... RQ ........ ................ li.1 1 ....................... 27 5 --- / - P RQ 4; 9 464 30 Q - 1 ÄR 2,8 3 ~ 26. · - ··· —............... rq .......... ................ 5.2 "" 481 R RQ__IjJ .__ 122 101403 8

Table 2 shows the sample preparation process, the relative wear durability of the samples and the Brinell hardness.

The wear test has been performed according to ASTM G 65-85 as described above. Wear measurement is performed on the weight change of the sample.

As discussed above, the relative wear resistance is the ratio of the weight change of the steel specimen of the present invention to the carbon steel specimen.

10 The processes shown in the table are classified as follows: AR-rolled; RQ-cooled in water after heating to 900 ° C after rolling and air cooling; RQT rejuvenated at the temperature indicated in parentheses after RQ treatment; DQ-directly cooled in water after finishing rolled at 880 ° C after heating the slab to 1150 ° C; DQT rejuvenated at the temperature indicated in parentheses after DQ treatment. The thickness of the sample is 15 mm. The steel grade in Table 1 corresponds to the grade in Table 2.

Claims (6)

101403 1. Wear-resistant steel, characterized in that it contains the following components: Abrasion-resistant steel according to Claim 1, characterized in that the one or more abrupt hardening components are boron in an amount of 0.0003 to 0.01% by weight. Abrasion-resistant steel according to Claim 1, characterized in that the one or more abrupt hardening components are copper in an amount of 0.1 to 2.0% by weight. Abrasion-resistant steel according to Claim 1, characterized in that the one or more abrupt hardening components are nickel in an amount of 0.1 to 10.0% by weight. 101403 Abrasion-resistant steel according to Claim 1, characterized in that the one or more abrupt hardening components are chromium in an amount of 0.1 to 3.0% by weight. 5 C 0.05 to 0.2% by weight, Si 0.1 to 1.0% by weight, Mn 0.1 to 2.0% by weight, Ti 0.3 to 1.0% by weight, whereby it contains one or more parts of the quenching agent-10 selected from the group consisting of copper, nickel, chromium, molybdenum and boron, in weight ratios: Cu 0.1 to 2.0% by weight Ni 0.1 to 10.0% by weight Cr 0 , 1 to 3.0% by weight 15 Mo 0.1 to 3.0% by weight B 0.0003 to 0.01% by weight; and optionally one or more precipitation hardening ingredients selected from the group consisting of niobium and vanadium in weight ratios: 20 Nb 0.005 to 0.5% by weight V 0.01 to 0.5% by weight, the rest being Fe and possible impurities. Abrasion-resistant steel according to Claim 1, characterized in that the one or more abrupt hardening components are molybdenum in an amount of 0.1 to 3.0% by weight. 10 i 4 U 3