JPH108210A - Wear resistant high manganese cast steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a high Mn cast steel excellent in wear resistance by preparing a high Mn cast steel in which the concn. of P as an impurity element is prescribed and contg. specified ratios of C, Si, Mn, Cr and Mo. SOLUTION: This high Mn cast steel having a compsn. contg., by weight, 1.3 to 1.7% C, 0.3 to 1.0% Si, 10 to 35% Mn, >=5% Cr, and >=2% Mo, in which the concn. of P as an impurity element is regulated to <=0.01% and also [%C].[%P]<=0.015 is satisfied, and the balance Fe with inevitable impurities is prepd. If required, either or both of Ti and Al may furthermore be incorporated according to necessary, and moreover, one or>=two kinds among V, Nb, B, Ta and Zr may moreover be incorporated by 0.01 to 3.0% in total. In this way, the high Mn cast steel having excellent wear resistance can be obtd., which can be used for a wear resistant member to be applied with heavy impact.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high Mn cast steel having excellent wear resistance, which is used for a liner material of a crusher such as a cone crusher or a jaw crusher for crushing rock, which is used for crushing rocks. It is about.

[0002]

2. Description of the Related Art High-Mn cast steel is a material originally having good work hardening characteristics and toughness, and utilizing such characteristics, abrasion-resistant members which have hitherto been subjected to heavy impact, for example, cones for crushing rocks It has been widely used as a liner material for crushers such as crushers and jaw crushers. However, in recent years,
With regard to crushers and the like, in particular, crushers for industrial wastes and rocks have been required to have improved processing capacity, and crushers and the like have been increased in size and crushing ratio has been increased. Along with this, the wear conditions of wear-resistant members used in crushers and the like tend to become more severe in the future, and high-M
The development of n steel is urgent.

There have been various attempts to improve the wear resistance of high Mn cast steel. For example, JP-B-57-17937, JP-B-63-8181, JP-B-1-14303, JP-A-62-139855, and JP-A-1-142958 disclose a high Mn of JIS standard.
An example of an alloy in which the wear resistance is improved by increasing the C concentration from the steel composition is described.

[0004]

However, when a liner material for a crusher having a large thickness is actually manufactured and used with the alloy materials described in the above-mentioned publications, the ductility is significantly reduced more than expected. The means of "increase in C concentration", which should enhance abrasion, cannot be immediately adopted, and has been achieved up to the present. The present inventors have also focused on the fact that the wear resistance can be significantly improved by increasing the C concentration. On the other hand, focusing on the above-described phenomenon of reduced ductility and examining the cause of the reduced ductility, the inventors found that “C Based on the belief that the means of `` enhancing the concentration '' could be truly an effective means for improving wear resistance, experiments were started with the aim of clarifying the cause of such a decrease in ductility,
The following findings were obtained.

[0005] Normally, high Mn cast steel is currently used because it is melted by blending scrap, and because ferromanganese, which is the raw material for melting, contains several 1/10% of P. High Mn cast steel contains about 0.02 to 0.07% of P, and this P segregates between dendrite arms during smelting, particularly at the crystal grain boundaries, and becomes large in the solution temperature range during the subsequent water toughening treatment. It was found that a eutectic compound of Fe-CP as shown in FIG. 1 was formed, and this was the cause of lowering ductility. Next, the present inventors have proposed such Fe-CP
In order to avoid the formation of the eutectic compound, the solution temperature during the water toughening treatment was set to be equal to or lower than the formation temperature of the eutectic compound, and this time, the carbide (M ₃ C) was not completely dissolved.
It was also found that the presence of this carbide also reduced ductility. Therefore, the present inventors anticipate that the P concentration, which is one of the factors for forming the eutectic compound of Fe-CP, has a large effect, and consider the P concentration itself and the correlation between the P concentration and the C concentration. We arrived at the idea that there should be a clue to how to determine the effects of relationships on ductility.

The present invention has been made under such circumstances, and an object thereof is to improve the wear resistance of a high Mn cast steel and provide a wear-resistant member having a longer life.

[0007]

Means for Solving the Problems Among the present invention which has achieved the above object, the invention according to claim 1 is characterized in that:
3 to 1.7%, Si: 0.3 to 1.0%, Mn 10 to 3
5%, Cr: 5% or less, Mo: 2% or less, P concentration as an impurity element is 0.01% or less, and [% C]. [% P]
≦ 0.015, the balance being Fe and unavoidable impurities. The invention according to claim 2 provides Ti, A in addition to the above constituent elements.
1 is a wear-resistant high Mn cast steel containing one or both of 0.01 and 0.6%, and the invention according to claim 3 further includes V, Nb, B, Ta, and Zr. It is a wear-resistant high Mn cast steel containing one or two or more kinds in total of 0.01 to 3.0%.

The present invention has been made based on completely new findings as described in detail below. That is, conventionally, P is an impurity element, and although it is said that a smaller amount is preferable, as described in JP-B-2-15623 and the Iron and Steel Handbook (1962) P1456,
It has been considered that ductility can be ensured unless the P concentration exceeds 0.07% in high Mn cast steel. For this reason, almost no attempt has been made to greatly reduce the P concentration until the manufacturing cost is increased. In particular, no attempt has been made at all to attempt to exert a certain technical effect in relation to ductility and abrasion resistance by suppressing the P concentration to a range lower than 0.01% as in the present invention. Was.

There have been a few research reports on the effect of P concentration on mechanical properties. For example, Trans Int Conf Struct Mech React Technol, 11t
h, G2 (1991) P93 ~ 98, Izv Vyssh Uchebn Zaved ChernMet
all, 3 (1989) P109-113, Litejnoe Proizvod, 11 (1988) P8
~ 9. However, even in these descriptions, only the range where the P concentration is 0.02% or more is mentioned. Then, the present inventors set the P concentration to 0.02%.
Further experimental studies have been conducted to clarify the effect of P concentration on ductility, including the following ranges. As a result, P
By making the concentration 0.01% or less and satisfying the conditions and further keeping the P concentration (relative concentration) relative to the C concentration within a certain range, the ductility is dramatically improved, and the wear resistance is improved. It has been found that excellent high Mn cast steel can be realized, and the present invention has been completed.

That is, the concentration of P as an impurity is set to 0.01%.
By setting [% C] · [% P] ≦ 0.015, high ductility can be ensured even when the C concentration is 1.3% or more with respect to the liner material having a thickness of more than 100 mm. , C concentration can be increased from 1.0 to 1.3% of the current high Mn cast steel to a maximum of 1.7%, and the wear resistance has been drastically improved. Therefore, first, the reasons for limiting the component range of the high Mn cast steel of the present invention will be described.

(A) C: 1.3 to 1.7% When the C concentration is less than 1.3%, only the wear resistance equivalent to that of the conventional high Mn steel material is obtained, while the C concentration is 1.7%. When the P content exceeds 0.01%, the ductility and toughness are reduced even when the P concentration is suppressed to 0.01%, and cracks occur during the production or use of the wear-resistant member.
Therefore, the C concentration was limited to the range of 1.3 to 1.7%.

(B) Si: 0.3% to 1.0% In order to deoxidize the molten metal at the time of melting and ensure fluidity, it is necessary to add 0.3% or more of Si, but more than 1%. When,
Precipitation of carbides at crystal grain boundaries is promoted, and toughness is reduced.

(C) Mn: 10 to 35% Mn is an element necessary for obtaining an austenite structure, and increases the solid solubility limit of C to suppress carbide precipitation in the cooling process of the water toughness treatment. Contributes to improved ductility. For this purpose, it is necessary to add Mn at 10% or more.
If it exceeds 5%, the amount of carbide precipitation in an as-cast state increases, which causes cracking during casting.

(D) Cr: 5% or less Cr is an effective element for improving work hardening characteristics.
If it exceeds 5%, carbide precipitation during casting and in the cooling process of the water toughness treatment becomes remarkable, and the ductility decreases. Therefore, 5%
Add as necessary within the following range.

(E) Mo: 2% or less Mo has the effect of suppressing the precipitation of carbides in the cooling process of the water toughness treatment and improving the ductility. However, if added over 2%, the effect is lost.

(F) The P concentration as an impurity element is 0.01
% Or less and [% C] · [% P] ≦ 0.015 The concentration of the impurity P is 0.01% or less and [% C]
・ By setting [% P] ≦ 0.015, the wall thickness becomes 1
For a liner material exceeding 00 mm, the C concentration is 1.3.
% Or more, high ductility can be ensured, and the C concentration can be increased from 1.0 to 1.3% of the current high Mn cast steel to a maximum of 1.7%, and the wear resistance is dramatically improved. Can be done. On the other hand, under conditions where the P concentration exceeds 0.01% or [% C] · [% P] exceeds 0.15,
The formation of the Fe-CP eutectic compound is promoted, and the ductility is reduced.

The high Mn cast steel of the present invention comprises C, Si, Mn,
Cr and Mo as basic components, P concentration as an impurity element is 0.01% or less, and [% C]. [% P] ≦ 0.015
And the balance is composed of Fe and unavoidable impurities, but if necessary, Ti, Al, V, Nb, B, Ta,
A predetermined amount of the element of Zr may be contained. The reasons for limiting the component ranges when these elements are contained are as follows.

Ti, Al: 0.1 or more in either one or both.
Addition of 01 to 0.6% Ti and Al is effective for forming oxides or nitrides in the molten metal and refining crystal grains. Ti, Al
When one or both of the addition amounts are 0.01 or more, there is an effect, and when it exceeds 0.6%, coarse inclusions are formed, so that ductility and toughness decrease. In addition, in dissolving in the air, Al is added as a deoxidizing material. Further, similarly to Mo, the addition of Ti has an effect of suppressing carbide precipitation during the cooling process of the water toughness treatment.

V, Nb, B, Ta, Zr: 0.01 to 3.0% in total of one or more of these V, Nb, B, Ta, Zr are work hardening characteristics due to precipitation of carbides. Contributes to the improvement of
The effect is obtained at an addition amount of 1% or more, and when the addition amount exceeds 3.0%, ductility and toughness are reduced.

Incidentally, in order to obtain the high Mn cast steel according to the present invention, the P concentration (about 0.02 to 0.07%) in the currently used high Mn cast steel is reduced, that is, P is removed. Although it is necessary, the specific methods mainly include the following three methods (1) to (3). (1) oxidative de P using Ba0 system and Na ₄ Si0 ₄ based flux during refining. (2) At the time of refining, P is reduced and removed using a CaC ₂ -CaF ₂ flux. (3) Mn without using ferromanganese as a melting raw material
Mn is added to molten steel containing no. In particular, in order to reduce the P concentration to 0.01% or less, it is essential to reduce the use of ferromanganese as much as possible.

[0021]

EXAMPLE A high Mn cast steel having the chemical composition shown in Table 1 was melted using a high-frequency induction heating melting furnace.

[0022]

[Table 1]

In the ingot-shaped sand mold shown in FIG. 2, the thickness of the ingot was set to about 100 mm assuming an actual liner material. The casting temperature is 100 ± 5 ° C from the liquidus temperature of each composition.
High temperature. Melted ingot is 1100 ° C × 6h
Was subjected to a water toughness treatment of cooling with water after the solution treatment. After the water toughness treatment, ductility was evaluated by a tensile test, and work hardening characteristics were evaluated by a compression test. In each case, the test piece was taken from the center with respect to the thickness of the ingot (about 100 mm), and the test piece was performed under the following test conditions (FIG. 2).
reference). (1) Tensile test: A test piece of JIS No. A type A was 10 ⁻³ / s
And the ductility was evaluated from the elongation at break. (2) Compression test: A test piece of 8φ × 12 hmm was subjected to 10 ⁻³ /
The rate of work hardening was evaluated from the deformation resistance at a strain of 50% at a strain rate of s.

Since high-Mn steel is a material that exhibits excellent wear resistance due to work hardening, as shown in FIG. 3, the work-hardening amount and the wear life of the actual machine liner are reduced. Since it is known that a good correlation can be obtained, by examining the degree of work hardening, it is possible to know the quality of properties such as wear resistance and wear life. The test results are shown in Table 2, and the relationship between P concentration and elongation (ductility) is shown in FIG. In addition, the number N with asterisks attached to the right shoulder
o. Is an example satisfying the requirements of the present invention, the evaluation is
Those having an elongation of> 20% and a work hardening amount of> 350 kgf / mm ² were judged as acceptable (O).

[0025]

[Table 2]

According to Tables 1 and 2, the lower the P concentration, the more the elongation (ductility) and the amount of work hardening (abrasion resistance) tend to be improved. It can be seen that the elongation is significantly improved (Example N
o. 2 ^* , 3 ^* , 4 ^* , 6 ^* , 7 ^* , 8 ^* , 9 ^* , 13
^* , 14 ^* , 15 ^* , 17 ^* , 18 ^* ). When the C concentration is high, it is particularly necessary to lower the P concentration (Comparative Example N
o. 19) Conversely, when the C concentration is low, the ductility is good even when the P concentration is high, but the work hardening amount is small and there is a problem in the wear life (Comparative Example No. 1). Also, when the elongation is about 10% or less, cracks occur with high strain in the compression test,
The amount of work hardening is significantly reduced (Comparative Examples No. 10, 1
1, 12, 16, 19, 20). From the above results, the P concentration was 0.01% or less and [% C]. [% P] ≦ 0.01.
By setting it to 5, it can be understood that it is possible to improve the amount of work hardening and remarkably improve wear resistance while securing necessary ductility even when the thickness of the ingot is 100 mm or more.

Further, addition of Ti and Mo is effective for improving ductility (Examples No. 7 ^* , 13 ^* , 14 ^* ).
In order to improve the amount of work hardening, Ti and carbide forming elements (V, N
b, Ta, B) is effective (Example No. 1).
7 ^* , 15 ^* ). This improvement in the amount of work hardening is mainly due to the effect of refining crystal grains. However, when the carbide-forming element exceeds 3%, a large amount of carbide precipitates to lower ductility (Comparative Example No. 16).

[0028]

As described above, according to the first aspect of the present invention, C: 1.3 to 1.7% by weight, S:
i: 0.3 to 1.0%, Mn: 10 to 35%, Cr: 5
%, Mo: 2% or less, P concentration as an impurity element is 0.01% or less, and [% C]. [% P] ≦ 0.015
Wherein the balance is Fe and unavoidable impurities. In particular, when the P concentration is 0.0
By being 1% or less and [% C] · [% P] ≦ 0.015, ductility is improved, and the thickness is about 100 mm.
Alternatively, the work hardening characteristics can be improved by increasing the C concentration to 1.3% or more for even higher members, and high Mn
It has become possible to dramatically improve the wear life of the steel wear-resistant liner material.

According to a second aspect of the present invention, one or both of Ti and Al are added to the structure of the first aspect of the invention in an amount of 0.01 to 0.6%. In addition to the effects of the described invention, high Mn which is more excellent in ductility
Cast steel can be provided. Further, the invention according to claim 3 has a configuration in which V, Nb, B,
One or more of Ta and Zr are used in total of 0.01 to
3.0% is added, and in addition to the effect of the invention described in claim 2, a high Mn cast steel excellent in work hardening characteristics (wear resistance) can be provided.

[Brief description of the drawings]

FIG. 1 is a micrograph showing a Fe-CP eutectic compound formed at a crystal grain boundary of a working high Mn steel after a water toughness treatment.

FIG. 2 is a diagram showing the relationship between the shape and thickness of an ingot used in Examples and the positions at which a tensile test piece and a compression test piece are sampled.

FIG. 3 is a diagram showing the relationship between the amount of work hardening and the life of the actual cone crusher liner material.

FIG. 4 is a diagram showing a relationship between P concentration and elongation (ductility).

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Koji Minagawa 2-3-1, Shinhama, Araimachi, Takasago-shi, Hyogo Inside Kobe Steel, Ltd. Takasago Mfg. Co., Ltd. 1 Yonago Steel Corporation (72) Inventor Toshinao Nakai 88-1 Fuminmachi, Yonago City, Tottori Prefecture 1 Yonago Steel Corporation

Claims (3)

[Claims] C. 1.3 to 1.7% by weight of C, Si:
0.3 to 1.0%, Mn: 10 to 35%, Cr: 5% or less, Mo: 2% or less, P concentration as an impurity element is 0.0
1% or less and [% C] · [% P] ≦ 0.015,
A wear-resistant high Mn cast steel characterized in that the balance is Fe and inevitable impurities. 2. The wear-resistant high Mn cast steel according to claim 1, further comprising 0.01 to 0.6% of one or both of Ti and Al. 3. The high wear resistance Mn according to claim 2, further comprising one or more of V, Nb, B, Ta, and Zr in a total amount of 0.01 to 3.0%. Cast steel.