JPH10102185A - Production of member with high toughness and high temperature wear resistance and thick steel plate therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a thick steel plate having excellent high temp. wear resistance, etc., by providing a steel composition consisting of specific weight percentages of C, Si, Mn, Cr, Mo, Nb, and V and the balance Fe. SOLUTION: A steel, having a composition consisting of, by weight, 0.2-0.4% C, 1.0-2.0% Si, <=0.5% Mn, 2.0-5.0% Cr, 1.0-2.0% Mo, 0.01-0.2% Nb, 0.02-0.12% V, and the balance Fe with inevitable impurities, is used. During use, a compound precipitate of Cr, Mo, and V, in which V is used as necleus, is formed. Further, one or more kinds among <=10% Ni, 0.01-0.2% Ti, and 0.0005-0.005% B are incorporated. Moreover, the steel is hot-rolled at <=900 deg.C at <=50% cumulative draft based on finishing plate thickness, hardened at 880-950 deg.C, and tempered at 200-550 deg.C. By this method, the thick steel plate, combining excellent workability, breakage resistance, quenching crack resistance, etc., with toughness, can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-toughness high-temperature wear-resistant member used for crushing industrial waste and wear parts of a crusher and a method for producing a thick steel plate thereof.

[0002]

2. Description of the Related Art In recent years, as the amount of industrial waste discharged has increased, recycling of the waste has been strongly demanded in consideration of global environmental problems. In order to promote resource recycling, it is very important to efficiently and economically crush and grind various industrial wastes.

[0003] Various wear-resistant members are used in crushers and pulverizers according to their uses, but most of them are consumables. Due to frictional heat and environmental temperature, such a member may have a surface in use of about 400 ° C. to about 600 ° C. In such a case, the member is particularly worn out and has a short service life, so that its durability is low. Improvement and cost reduction are also major issues for reducing industrial waste disposal costs.

The materials used for such applications include 60
In addition to high-temperature abrasion resistance up to about 0 ° C, toughness is required from the viewpoint of workability and breakage resistance, and high productivity and low cost are required.

As a material having excellent high-temperature wear resistance, there is a high chromium cast steel, but its use is limited because of its low toughness. Some low-alloy cast materials are considered to have relatively good toughness (for example, JP-A-52-86916, JP-A-54-118320, JP-A-1-219145, etc.). This increases the production cost. Japanese Patent Application Laid-Open No. 59-10706 discloses a steel material produced by hot rolling, which is considered to have excellent high-temperature wear resistance and toughness.
6 and others. In these steel materials, the content of C and Si, which increase the hardness of the base material, is considerably increased as a hot-rolled material in order to enhance the high-temperature wear resistance, and Cr, Mo, and V, which further improve the high-temperature hardness, are used. Are often added. All of these are elements that reduce toughness, and therefore, satisfactory toughness has not yet been obtained in terms of workability and breakage resistance. Further, in the case of such relatively high materials such as C, Si, and V, particularly in the case of thick materials, so-called quenching cracks often occur in steel sheets during quenching heat treatment, which is a cause of impairing productivity. It is necessary to increase the toughness in order to avoid this burning crack. That is, there has not been a member and a thick steel plate having both high-temperature abrasion resistance and sufficient toughness satisfying workability, breakage resistance, and fire cracking resistance.

[0006]

SUMMARY OF THE INVENTION A member having both excellent high-temperature wear resistance and sufficient toughness to satisfy workability, breakage resistance, and cracking resistance, and a thick steel plate (plate thickness 9)
SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for inexpensively producing (mm or more, especially 50 mm or more) by rolling.

[0007]

The inventors of the present invention have conducted various studies on the effects of alloying elements and manufacturing methods on high-temperature wear resistance and toughness, and have found that they contain appropriate amounts of Si, Nb, Cr, Mo, V, and the like. A member having both excellent high-temperature wear resistance and sufficient toughness to satisfy workability, breakage resistance, sintering crack resistance, and the like, and a method of inexpensively manufacturing a thick steel plate by controlled rolling and appropriate heat treatment. Was able to develop. The constitution of the present invention is as follows: (1) By weight%, C: 0.2 to 0.4%, Si: 1.0%
-2.0%, Mn: 0.5% or less, Cr: 2.0-5.
0%, Mo: 1.0-2.0%, Nb: 0.01-0.
2%, V: 0.02 to 0.12%, a wear-resistant member composed of a thick steel plate having a composition of residual Fe and unavoidable impurities, wherein Cr and M having V as a core during use.
A high-toughness high-temperature wear-resistant member formed with a composite precipitate of o and V.

(2) C: 0.2-0.4% by weight,
Si: 1.0 to 2.0%, Mn: 0.5% or less, Cr:
2.0-5.0%, Mo: 1.0-2.0%, Nb:
0.01-0.2%, V: 0.02-0.2%,
Further, Ni: 10% or less, Ti: 0.01 to 0.2%,
B: One or two of 0.0005 to 0.005%
A wear-resistant member made of a thick steel plate containing at least one or more species and having a balance of Fe and unavoidable impurities, and having high toughness in which a composite precipitate of Cr, Mo, and V having V as a nucleus is formed during use. High temperature wear resistant member.

(3) C: 0.2 to 0.4% by weight,
Si: 1.0 to 2.0%, Mn: 0.5% or less, Cr:
2.0-5.0%, Mo: 1. ~ 2.0%, Nb: 0.
A steel slab or a cast slab having a composition of 0.01 to 0.2% and V: 0.02 to 0.2%, the balance being Fe and unavoidable impurities is heated, and the thickness of the finished plate is reduced to 900 ° C. or less. On the other hand, hot rolling is performed to ensure a cumulative draft of at least 50% to obtain a thick steel plate, which is heated to a temperature in the range of 880 ° C to 950 ° C and quenched, and then subjected to a tempering heat treatment at 200 ° C to 550 ° C. A method for producing a thick steel plate for a high toughness high-temperature wear-resistant member.

(4) C: 0.2-0.4% by weight,
Si: 1.0 to 2.0%, Mn: 0.5% or less, Cr:
2. To 5.0%, Mo: 1.0 to 2.0%, Nb: 0.
01-0.2%, V: 0.2-0.2%, Ni: 10% or less, Ti: 0.01-0.2%, B:
A steel slab or a cast slab containing one or more of 0.0005% to 0.005% and having a balance of Fe and unavoidable impurities is heated, and the thickness of the finished plate is reduced to 900 ° C or less. On the other hand, hot rolling is performed to secure a cumulative draft of 50% or more to obtain a thick steel plate.
After quenching by heating to the range of 0 ° C, 200 ° C to 550 ° C
A method for producing a thick steel plate for a high-toughness high-temperature wear-resistant member, characterized by performing a tempering heat treatment at a temperature.

[0011] Even in steels in which high-temperature wear resistance is a problem, it is ductility and toughness at room temperature that affect workability, burn-out resistance, and breakage resistance, and the influence of toughness is particularly large. C,
Mn and the like are effective in high-temperature wear resistance because they improve high-temperature hardness by increasing hardenability, but these elements significantly increase room-temperature hardness more than high-temperature hardness, so that toughness at normal temperature The drop is also large. As for C, the content is preferably at least 0.4% or less in order to obtain sufficient ductility and toughness satisfying the workability, the squeeze cracking resistance, and the breakage resistance. As for the breakage resistance, it is necessary to improve the toughness, and at the same time, it is important to minimize the inclusions that cause the fracture, and MnS is particularly harmful. Therefore, it is preferable to reduce Mn to at least 0.5% or less. Since Cr, Mo, and V have the effect of increasing the high-temperature hardness by precipitation strengthening and increasing the high-temperature wear resistance, they are more advantageous in toughness than hardenability improving elements such as C and Mn. However, when these are added in a large amount, they also have the disadvantage of reducing toughness.

The present inventor has studied the relationship between high-temperature wear resistance and toughness of various component systems and manufacturing processes. As a result, the synergistic action of Cr, M
It has been found that the high-temperature wear resistance can be significantly improved while the contents of o and V are kept to a minimum. With this effect,
It is not necessary to increase the hardness of the member before use in increasing the wear resistance at high temperatures. Therefore, the addition of hardenability improving elements such as C and Mn can be suppressed, so that the toughness can be greatly improved. As a result, workability, quenching cracking resistance, and breakage resistance can also be significantly improved.

Utilization of Cr, Mo, and V composite materials using V as a core When using members, appropriate amounts of Cr, Mo, and V are added, and the quenching temperature and the tempering temperature are specified.
C with V as the core during use of the member at about 0 ° C to 600 ° C)
It forms a fine composite of r, Mo, and V, which is more stable at high temperatures for a long time as it is fine compared to other single deposits, and significantly enhances wear resistance at high temperatures. The present inventor thinks. In order to obtain fine composite precipitates, it is necessary to sufficiently dissolve V, Cr, and Mo before use, and thus the quenching temperature and the tempering temperature are specified. If the quenching temperature is too low, coarse precipitates after rolling remain, tend to agglomerate and coarse, and lack stability at high temperatures, making it difficult to obtain sufficient high-temperature wear resistance. On the other hand, if the quenching temperature is too high, the effect of the following controlled rolling of Nb is lost, so that a composite precipitate of Cr, Mo and V with V as a core having excellent long-term stability cannot be obtained. The tempering heat treatment not only adjusts the hardness and toughness at room temperature, but also forms a precipitation nucleus that can form the above-mentioned composite precipitate during use at a high temperature. In other words, if the tempering temperature is relatively high (600 ° C. or higher), the fine composite precipitates described above may not be obtained. It is preferable not to fix Cr, Mo, and V as precipitates.

Ensuring precipitation sites capable of extracting the composite precipitates and improving long-term stability A proper amount of Nb is added, and austenite grains are refined by appropriate controlled rolling, and the martensite or bainite structure after quenching is obtained. Is increased to secure the grain boundary precipitation site of the composite precipitate. In addition, by adding an appropriate amount of Si, embrittlement during use at high temperatures is prevented, and the long-term stability of the precipitate is improved.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

First, the reasons for limiting the steel composition of the present invention will be described.

C: C is important for increasing the normal temperature and high temperature hardness of steel and increasing the high temperature wear resistance. In the present invention, the C content is suppressed to a low level by the effect of improving the high-temperature wear resistance of the composite precipitate of Cr and Mo and V.
If it is less than 2%, high temperature wear resistance cannot be maintained. Also, 0.
When the content exceeds 4%, ductility and toughness decrease, and workability, squeeze crack resistance, and breakage resistance decrease.
Limited to 0.2-0.4%.

Si: Si has the effect of increasing the hardness at room temperature and high temperature and increasing the tempering softening resistance. In the steel of the present invention, tempering heat treatment after quenching is performed to improve toughness. However, when Si is low, the toughness may be lowered due to temper embrittlement. Further, there is a case where a composite precipitate of Cr, Mo, and V which is stable at a high temperature for a long time is difficult to precipitate. Therefore, in order to provide sufficient temper softening resistance, Si is added in an amount of 1.0% or more. However, when the content exceeds 2.0%, Si itself lowers the toughness of the matrix and becomes harmful to the toughness.
To 2.0%.

Mn: Mn improves hardenability, but does not increase the effect of high-temperature hardness. On the other hand, when added in a large amount, Mn reduces toughness and forms MnS, which is extremely poor in breaking resistance. Since it is harmful, it is better to reduce it, and the upper limit is set to 0.5%.

Cr: Cr has a large effect of improving high-temperature wear resistance and is one of the important elements in the present invention. To achieve this effect, 2.0% or more must be added.
Even if added in excess of 0%, it does not form a solid solution at the time of quenching and reheating, so that the effect is saturated and becomes harmful rather than toughness. Therefore, the Cr content is set to 2.0 to 5.0%. .

Mo: Mo is also an important element having a large effect of improving the high-temperature wear resistance. This is one of the effects
% Or more is required, and if it exceeds 2%, it is detrimental to toughness. Therefore, the amount of Mo added is set to 1 to 2%.

Nb: Nb promotes the effect of controlled rolling by suppressing the coarsening of austenite grains and increasing the recrystallization temperature during heating before rolling, contributes to the refinement of crystal grains, improves toughness and serves as a precipitation site. Is an essential element for utilizing Cr, Mo, and V composite precipitates having V as a nucleus. In order to exhibit this effect, 0.01% or more must be added. However,
If added in excess of 0.2%, coarse Nb precipitates are formed and the toughness is reduced. Therefore, the Nb content is 0.01 to
0.2%.

V: V is an essential element in the present invention for forming a composite precipitate with Cr and Mo which is stable at a high temperature.
In order to exhibit this effect, at least 0.02% or more must be added. However, even if it is added in excess of 0.2%, it does not form a solid solution at the time of quenching and reheating, so that an effective fine composite precipitate is formed. Since it does not form, the high-temperature wear resistance does not improve much further, but rather forms coarse precipitates and significantly reduces the toughness. (Experiments on the relationship between the amount of V added and the high-temperature wear resistance and toughness in FIGS. 1 and 2) It is clear from the results). Therefore, the V content is set to 0.02 to 0.2%.

The above are the basic components of steel according to the present invention. In the present invention, one or more of Ni, Ti and B can be added in addition to the above components.

Ni: Ni does not contribute much to high-temperature wear resistance, but is effective for improving toughness. However, if an excessively large amount is added, austenite is generated and the wear resistance is reduced, so the upper limit in the case of adding Ni is set to 10%. The lower limit is not particularly limited, but 1% or more is preferably added to improve toughness.

Ti: Ti is effective in refining crystal grains. For this effect, it is necessary to add 0.01% or more, but if added in excess of 0.2%, toughness is reduced. , Ti content is desirably 0.01 to 0.2%.

B: B enhances hardenability to increase hardness,
It also contributes to improving high temperature wear resistance. To achieve the effect, 0.0005% or more is required, but if it is 0.005% or more, toughness is reduced. Therefore, the content of B is 0.1.
It is desirable to set it to 0005 to 0.005%.

As unavoidable impurities other than the above components,
Since P, S, N, and O are harmful elements that lower the toughness, the smaller the amount, the better. Preferably, P:
0.005% or less, S: 0.003% or less, N: 0.0
1% or less, O: 0.003% or less.

Next, the manufacturing method will be described.

First, a slab or a slab having the above-mentioned steel composition is heated, and at a temperature of 900 ° C. or less, 50% or less of the finished plate thickness.
% Hot rolling is performed to ensure a cumulative draft of at least%. The purpose is to refine the austenite grains. If the rolling finish temperature is higher than 900 ° C or the cumulative rolling reduction at 900 ° C or less is insufficient, the grain refinement is insufficient, and in addition to the decrease in toughness, the high-temperature wear resistance is also reduced due to the decrease in the grain boundaries as precipitation sites. descend.

Next, the hot-rolled steel is heated at 880 ° C. to 950 ° C.
Heat to the range of quenching. In order to exhibit the effect of the composite precipitation in the present invention, Cr, Mo,
A heating temperature of at least 880 ° C. or more is necessary to sufficiently dissolve V. However, if the temperature is 950 ° C. or higher, austenite becomes coarse again and it becomes difficult to form grain boundary precipitates. Therefore, the reheating quenching temperature is limited to 880 ° C. to 950 ° C.

The quenched steel is then subjected to a tempering heat treatment at 200 ° C. or higher. The purpose is to improve toughness, and for that purpose the tempering temperature needs to be 200 ° C. or higher. If a certain degree of room temperature hardness is required depending on the purpose of use, it is desirable to perform tempering at a low temperature of 200 ° C to 350 ° C.

[0033]

EXAMPLES Steel slabs obtained by smelting steel having the composition shown in Table 1 were manufactured into steel plates having a thickness of 15 mm to 140 mm based on the respective manufacturing conditions of the present invention and the comparative method shown in Table 2. .

Regarding these, the toughness of the base material, the hardness at room temperature and high temperature, the wear resistance at high temperature, and the Cr and M
The presence or absence of composite precipitates of o and V was investigated. The toughness is-
It was evaluated by the absorbed energy value of the Charpy impact test at 40 ° C. (J1S Z22014 test piece, sampling position of the test piece in the thickness direction: １ ／ t, the test piece sampling direction was perpendicular to the thickness direction). The hardness is measured by the Vickers hardness test method (J1
SZ2244), the hardness at room temperature was measured at 25 ° C, and the hardness at high temperature was measured at 500 ° C. The high-temperature abrasion resistance was measured by performing a shot grain type abrasion test in a furnace at an ambient temperature of 500 ° C. on the same-shaped test specimen, measuring the abrasion loss after a fixed time, and simultaneously measuring a standard test specimen (room temperature Vickers). Hardness 5
The evaluation was made based on the ratio of the wear loss of No. 39 (general wear-resistant steel) to the wear loss (standard test piece wear loss / test material wear loss). The higher the index, the higher the high temperature wear resistance. The presence or absence of a composite precipitate of Cr, Mo, and V having V as a nucleus was observed by an electron microscope.

In the table, the underlined numerical values indicate those having insufficient component values, temperature conditions and characteristics outside the present invention.

In the examples of the present invention (1-A to 11-J in Table 2), both toughness and high-temperature wear resistance are at high levels. On the other hand, in the comparative steels deviating from the chemical composition range limited by the present invention, despite the production method being the method of the present invention, Example 12-K has a low C content, and thus Example 15-N
Is low in Cr content, and Example 17-P is low in Mo content.
Each has low high temperature wear resistance. Example 16-O is Mo.
Since the amount is high, Example 19-R has low toughness due to the high V amount. Furthermore, Example 13-L has a low Si content, Example 14-M has a high Mn content, and Example 18-Q has a low Nb content, so that both toughness and high-temperature wear resistance are low. Even in the case of the steel of the present invention, in the comparative method deviating from the production method of the present invention, Example 2 was used.
Since 0-B has a high rolling start temperature, Example 21-B has a low cumulative reduction ratio, and Example 22-B has a low quenching reheating temperature, and thus has low toughness and high-temperature wear resistance, respectively.
In addition, Example 23-B has low toughness because tempering is not performed.

[0037]

[Table 1]

[0038]

[Table 2]

[0039]

According to the chemical composition range and the manufacturing method of the present invention, a thick steel plate having excellent high-temperature wear resistance and sufficient toughness to satisfy workability, breakage resistance, and squeezing crack resistance, and the thickness thereof. A high temperature wear-resistant member made of a steel plate is obtained.

[Brief description of the drawings]

FIG. 1 shows C: 0.35%, Si: 1.5%, Mn: 0.1%.
3%, Cr: 3%, Mo: 1.5%, Nb: 0.05%
FIG. 4 is a graph showing the relationship between the amount of V added and high-temperature wear resistance of steel to which V is added.

FIG. 2: C: 0.35%, Si: 1.5%, Mn: 0.
3%, Cr: 3%, Mo: 1.5%, Nb: 0.05%
FIG. 4 is a diagram showing the relationship between the amount of V added and the toughness of steel to which V is added.

Claims (4)

[Claims] 1. C .: 0.2 to 0.4% by weight, S
i: 1.0 to 2.0%, Mn: 0.5% or less, Cr:
2.0-5.0%, Mo: 1.0-2.0%, Nb:
A wear-resistant member made of a thick steel plate having a composition of 0.01 to 0.2%, V: 0.02 to 0.12%, and a balance of Fe and unavoidable impurities. A high-toughness high-temperature wear-resistant member formed with a composite precipitate of Cr, Mo, and V as a nucleus. 2. C: 0.2 to 0.4% by weight, S
i: 1.0 to 2.0%, Mn: 0.5% or less, Cr:
2.0-5.0%, Mo: 1.0-2.0%, Nb:
0.01-0.2%, V: 0.02-0.2%,
Further, Ni: 10% or less, Ti: 0.01 to 0.2%,
B: One or two of 0.0005 to 0.005%
A wear-resistant member made of a thick steel plate containing at least one or more species and having a balance of Fe and unavoidable impurities, and having high toughness in which a composite precipitate of Cr, Mo, and V having V as a nucleus is formed during use. High temperature wear resistant member. 3. C: 0.2 to 0.4% by weight, S
i: 1.0 to 2.0%, Mn: 0.5% or less, Cr:
2.0-5.0%, Mo: 1.0-2.0%, Nb:
0.01-0.2%, V: 0.02-0.2%,
A steel plate or a slab having a composition consisting of the balance of Fe and unavoidable impurities is heated and subjected to hot rolling at a temperature of 900 ° C. or less to ensure a cumulative draft of 50% or more with respect to the finished plate thickness. A method for producing a thick steel plate for a high-toughness high-temperature wear-resistant member, wherein the steel plate is heated and quenched in the range of 880 ° C to 950 ° C, and then subjected to a tempering heat treatment at 200 ° C to 550 ° C. 4. C: 0.2 to 0.4% by weight, S
i: 1.0 to 2.0%, Mn: 0.5% or less, Cr:
2.0-5.0%, Mo: 1.0-2.0%, Nb:
0.01-0.2%, V: 0.02-0.2%,
Further, Ni: 10% or less, Ti: 0.01 to 0.2%,
B: One or two of 0.0005 to 0.005%
Hot rolling that heats a steel slab or slab having a composition consisting of Fe and unavoidable impurities, containing at least one seed, and ensuring a cumulative draft of 50% or more with respect to the finished plate thickness at a temperature of 900 ° C or less. To make a thick steel plate,
After quenching by heating to the range of 950 ° C.,
A method for producing a thick steel plate for a high-toughness high-temperature wear-resistant member, comprising performing a tempering heat treatment at 0 ° C.