JPH07173571A - High workability wear resistant steel and production thereof - Google Patents

Abstract

PURPOSE:To produce a wear resistant steel soft at the time of working and hardened at the time of wear use and showing wear resistance and provide a method for producing the same. CONSTITUTION:This wear resistant steel has a compsn. contg., as fundamental components, 0.10 to O.50% C, 0.60 to 2.5O% Si, 0.05 to 2.0%, Mn, 0.03 to 0.1% Al, 0.0003 to 0.005$ B, <=0.006% N, <=0.02% P and <=0.02% S, contg., at need, Cu, Ni, Cr, Mo, V, Wb and Ti and contg. 5 to 20% retained austenite, and the method for producing the wear resistant steel in which a steel having a compsn. contg. the same fundamental components and the same selective components according to necessary is heated to >=1000 deg.C, is thereafter rolled at the Ar3 point or above and is next cooled from the Ar3 point or above at >=3 deg.C/sec cooling rate, and after that, the cooling is stopped at 300 to 550 deg.C, and air-cooling is executed is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention has a good workability, which is used for industrial machines and construction machines. The present invention relates to wear steel and a method for manufacturing the same.

[0002]

2. Description of the Related Art Generally, wear-resistant steel is used in industrial machines and construction machines where it collides with and contacts earth and sand and rocks, and has a great effect on extending the life of the machine. In this case, the basis for enhancing the wear resistance is to increase the hardness of the worn portion. In the conventional method, steel having a chemical composition in which the amount of C and the amount of alloy added are adjusted is hardened, or quenched and tempered to obtain sufficient hardness as a hardened martensite structure over the entire plate thickness and wear resistance. The sex is enhanced.

For example, in Japanese Unexamined Patent Publication No. 60-243250, a method of producing a high hardness and wear resistant steel having excellent weldability by quenching a steel having a specified ratio of components and a PH value for evaluating weldability is specified. Is proposed. In the traditional way,
In this way, it is general to make the entire plate thickness high hardness by quenching.

[0004]

However, if steel having a chemical composition in which the amount of C and the amount of alloy added are adjusted to be hardened and martensite has a high hardness over the entire plate thickness, the steel plate is processed into a desired shape. Becomes very difficult. There is a strong demand for the development of wear-resistant steel that has high wear resistance and can be easily processed at will.

[0005]

As a result of various studies to solve this problem, the inventors of the present invention have found that a method of utilizing only the hardened martensite structure applied to conventional wear-resistant steel is used. Change, soften to some extent before use,
The present invention has invented a steel sheet which can be easily processed into a desired shape and has a property of being hardened when used and having wear resistance, and a method for producing the steel sheet. That is, the required hardness is finally obtained, and
By combining the chemical composition that appropriately retains austenite and the heating, rolling, and cooling methods, a quenched-automatic tempered structure containing retained austenite is formed before steel sheet processing. It has been found that when this steel is used under wear conditions, retained austenite transforms to high-C martensite, and only the wear part has high hardness, and wear resistance can be improved.

The present invention is constructed on the basis of the above findings, and the gist thereof is as follows. (1) C: 0.10 to 0.50% by weight, Si: 0.60 to 2.50
%, Mn: 0.05 to 2.0%, Al: 0.03 to 0.
1%, B: 0.0003 to 0.005%, N: 0.00
6% or less, P: 0.02% or less, S: 0.02% or less as a basic component, the balance consisting of Fe and unavoidable impurities, and containing 5 to 20% of retained austenite, good workability Abrasion resistant steel.

(2) Further, Cu: 2% or less, Ni: 2
% Or less, Cr: 2% or less, Mo: 1% or less, V: 0.1
% Of the strength-improving element group, or one or more kinds of the strength-improving element group. (3) Good workability according to the above item 1, further comprising one or two of a low temperature toughness improving element group consisting of Nb: 0.1% or less and Ti: 0.1% or less. Wear steel.

(4) Further, Cu: 2% or less, Ni: 2
% Or less, Cr: 2% or less, Mo: 1% or less, V: 0.1
% Or less, and one or two or more of the group of strength improving elements, and Nb: 0.1% or less and Ti: one or two of the low temperature toughness improving element groups of 0.1% or less. Good workability wear-resistant steel according to item 1 above, which is characterized by including. (5) C: 0.10 to 0.50% by weight, Si: 0.60 to 2.50
%, Mn: 0.05 to 2.0%, Al: 0.03 to 0.
1%, B: 0.0003 to 0.005%, N: 0.00
Steel containing 6% or less, P: 0.02% or less, S: 0.02% or less as a basic component and the balance of Fe and unavoidable impurities is heated to 1000 ° C. or more and then rolled at Ar ₃ point or more, Then, after cooling from the Ar ₃ point or more at a cooling rate of 3 ° C./sec or more, the cooling is stopped at 300 to 550 ° C.,
Remaining austenite characterized by air cooling to 5 to 2
A method for producing a wear-resistant steel with good workability containing 0%.

(6) Further, Cu: 2% or less, Ni: 2
% Or less, Cr: 2% or less, Mo: 1% or less, V: 0.1
% Or less of the strength-improving element group, and a method for producing a good workable wear-resistant steel containing 5 to 20% of retained austenite according to the above item 5. (7) The retained austenite according to the above item 5, further containing one or two elements of a low temperature toughness improving element group consisting of Nb: 0.1% or less and Ti: 0.1% or less. A method for manufacturing a wear-resistant steel having good workability, containing -20%.

(8) Further, Cu: 2% or less, Ni: 2
% Or less, Cr: 2% or less, Mo: 1% or less, V: 0.1
% Or less, and one or two or more of the group of strength improving elements, and Nb: 0.1% or less and Ti: one or two of the low temperature toughness improving element groups of 0.1% or less. The residual austenite according to the above item 5 is contained in 5
A method for manufacturing a wear-resistant steel having good workability, containing -20%.

[0011]

The present invention will be described in detail below. First, the reason for limiting the steel composition as described above will be described. C is necessary to secure the hardness of the steel sheet, and its content is 0.10%.
If less than 0.5, the required hardness cannot be obtained, while on the other hand, 0.5
If it exceeds 0%, cracking susceptibility due to cooling increases, so the content is limited to 0.10 to 0.50%.

Si is particularly important for stabilizing austenite and allowing a large amount of retained austenite to exist, but if it is less than 0.60%, its effect is small. Also,
If it exceeds 2.50%, the decrease in toughness will increase, so
It is limited to 0.60 to 2.50%. Mn is required to be 0.05% or more in order to fix S, improve hardenability, and secure hardness and toughness, but if it is contained in excess of 2.0%, toughness is lowered, so 0 .05 to 2.0%
Limited to

[0013] Al is necessary to achieve fine graining and to obtain B which is effective for hardenability, and in order to exert the effect, 0.03% or more is necessary, but it exceeds 0.1%. The addition causes an increase in alumina inclusions and impairs the cleanliness and toughness of the steel sheet, so the upper limit is 0.1%. B is an essential element for improving the hardenability of steel, and 0.0003
% Or more is necessary, but addition of more than 0.005% is
Since the amount of system inclusions is increased and the toughness is impaired, 0.0003-
It is limited to 0.005%.

N is combined with Al, Nb and Ti to form a nitride, which is effective for making the austenite grains finer. However, if it exceeds 0.006%, the amount of solid solution N increases and the weld zone Since the toughness is reduced, the upper limit is 0.006%. Both P and S have the effect of improving the toughness by lowering them, but both elements have an effect of improving the toughness.
It is necessary to set it to 02% or less.

In the present invention, in addition to the above essential basic components, one or two of the following elements may be selected depending on the required properties of steel.
One or more species can be selectively contained. Cu, Ni,
Cr, Mo and V have an equal effect of enhancing the hardenability of steel and improving the strength. If necessary, one or more of them may be contained, but Cu: 2% and N, respectively.
i: 2%, Cr: 2%, Mo: under 1% and V: 0.1%
Even if it is contained in excess, the upper limit of each component is set as described above, because it becomes expensive unnecessarily.

Further, Nb and Ti have an equal effect of improving the low temperature toughness of steel by grain refining, and if necessary, one or two of them may be contained.
If the content exceeds 0.1% and Ti: 0.1%, the weldability is impaired, so the upper limit of each component is set as described above. Further, in the steel of the present invention, it is necessary to secure a certain amount of retained austenite in order to secure martensite during wear. When the residual austenite is less than 5%, the amount of martensite obtained by the subsequent abrasion is small and the required increase in hardness cannot be obtained. Further, if there is retained austenite in excess of 20%, the toughness is greatly reduced, so the range is 5 to 20%.

Next, the heat treatment method for the steel of the present invention will be described.
In addition to the above steel components, the heat treatment method must be appropriate in order to obtain good properties as a wear resistant steel. Here, the reason for limiting the heat treatment conditions will be described. First, heating the slab requires heating to 1000 ° C. or higher in order to form a solid solution with alloying elements and precipitation elements.
The lower limit is ℃. Further, since heating above 1300 ° C is practically impossible, 1300 ° C or lower is desirable.

In the rolling after heating, in order to secure the hardenability, the temperature immediately before cooling after that is set as the austenite one-phase region,
Ar ₃ or more rolling is required. Further, the rolling temperature corresponds to the heating temperature, and it is practically difficult to roll at a high temperature exceeding 1200 ° C., so 1200 ° C. or less is desirable. The cooling start temperature after rolling is set to the lower limit of the Ar ₃ point in order to sufficiently quench and cool the austenite one-phase region. Also, the cooling rate is 3 ° C in order to perform sufficient quenching.
/ Sec is the lower limit. If the cooling rate is too high, it becomes difficult to stop the next cooling, so 100 ° C./sec or less is desirable.

Next, when cooling is stopped, it is necessary to appropriately retain the retained austenite and secure an appropriate amount of the retained austenite for causing the austenite → martensite transformation at the time of wear. Low temperature transformation occurs and less retained austenite. On the other hand, if the temperature exceeds 550 ° C, the retained austenite will decrease due to the high temperature transformation. Therefore 300 ~
Limited to 550 ° C.

[0020]

EXAMPLES Slabs having the composition of components shown in Table 1 were produced, and these were subjected to rolling and heat treatment under the conditions shown in Table 2. Then, a test piece was cut out from the obtained steel sheet, and the mechanical properties and the amount of retained austenite were evaluated, and the results are shown in Table 3.

As is clear from the results shown in Table 3, the steel sheet under the conditions specified in the present invention has a significantly hardened surface hardness after use, that is, after wear, and has good bendability and toughness. Test numbers 13, 14 and 15 are examples of comparative steels. Test No. 13 has Si and B out of the specified ranges among the basic components of the present invention, has low wear hardness and low toughness. Test Nos. 14 and 15 are examples of wear resistant steel produced by conventional methods. In this case, the hardness is high, but the retained austenite is small, and the hardness does not increase after abrasion. And bendability is poor.

Next, even if the composition is the same as that of the steel of the present invention, good performance cannot be obtained if the manufacturing method deviates from the definition of the present invention. For example, test numbers 16 and 18 have rolling end temperatures of less than Ar ₃ points, but have a lower hardness before wear and a lower surface hardness after wear than test numbers 1 and 4. Test Nos. 17, 21 and 22 are cases in which the cooling stop temperature is below the lower limit and out of the upper limit, but in each case, the residual austenite before wear is small, and the hardness increase amount after wear is small as compared with the examples of the present invention. I understand. Test No. 19 is when the cooling rate is lower than the specified value, and Test No. 20 is when the heating temperature is lower than the specified temperature. However, compared to Test Nos. 6 and 9, the hardness before abrasion is low. Also, the surface hardness after abrasion is low.

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

[Table 3]

[0026]

As described above, according to the present invention, it is possible to provide a wear-resistant steel having good workability and high wear resistance during wear, and industrially useful effects are exhibited.

Claims (8)

[Claims] 1. C: 0.10 to 0.50% by weight%, Si: 0.60 to 2.50%, Mn: 0.05 to 2.0%, Al: 0.03 to 0.1 %, B: 0.0003 to 0.005%, N: 0.006% or less, P: 0.02% or less, S: 0.02% or less as a basic component, and the balance consisting of Fe and inevitable impurities, Good workability wear-resistant steel characterized by containing 5 to 20% of retained austenite. 2. One or more of a group of strength improving elements consisting of Cu: 2% or less, Ni: 2% or less, Cr: 2% or less, Mo: 1% or less, V: 0.1% or less. Good workability wear-resistant steel according to claim 1, characterized in that it contains two or more kinds. 3. Further, Nb: 0.1% or less, Ti:
The good workability wear-resistant steel according to claim 1, wherein the good workability wear-resistant steel is characterized by containing one or two kinds of a low temperature toughness improving element group consisting of 0.1% or less. 4. Further, one or more of a strength improving element group consisting of Cu: 2% or less, Ni: 2% or less, Cr: 2% or less, Mo: 1% or less, V: 0.1% or less. The good workability according to claim 1, wherein the good workability includes two or more kinds and one or two kinds of a low temperature toughness improving element group consisting of Nb: 0.1% or less and Ti: 0.1% or less. Abrasion resistant steel. 5. By weight%, C: 0.10 to 0.50%, Si: 0.60 to 2.50%, Mn: 0.05 to 2.0%, Al: 0.03 to 0.1. %, B: 0.0003 to 0.005%, N: 0.006% or less, P: 0.02% or less, S: 0.02% or less as a basic component, and the balance Fe and unavoidable impurities Was heated to 1000 ° C. or higher, rolled at Ar ₃ point or higher, then cooled at a cooling rate of 3 ° C./sec or higher from Ar ₃ point or higher, and then cooled at 300 to 550 ° C.,
Remaining austenite characterized by air cooling to 5 to 2
A method for producing a wear-resistant steel with good workability containing 0%. 6. One or more of a strength improving element group consisting of Cu: 2% or less, Ni: 2% or less, Cr: 2% or less, Mo: 1% or less, V: 0.1% or less. The method for producing a good workable wear resistant steel containing 5 to 20% of retained austenite according to claim 5, wherein the method comprises at least two kinds. 7. Further, Nb: 0.1% or less, Ti:
The method for producing a good workable wear-resistant steel containing 5 to 20% of retained austenite according to claim 5, which contains one or two kinds of a low temperature toughness improving element group consisting of 0.1% or less. 8. One or more of a strength improving element group consisting of Cu: 2% or less, Ni: 2% or less, Cr: 2% or less, Mo: 1% or less, V: 0.1% or less. The retained austenite according to claim 5, which contains one or two kinds of a low temperature toughness improving element group consisting of two or more kinds and Nb: 0.1% or less and Ti: 0.1% or less. 5-
A method for producing wear-resistant steel with good workability containing 20%.