JP2001049381A - Wear resistant alloy cast iron material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make more wear resistance and a certain-grade toughnes compatible, with each other in a wear resistant material of high Cr cast iron. SOLUTION: This material consists of high Cr cast iron essentially consisting of, by weight, 3.8 to 4.5% C, 10.0 to 20.0% Cr, 3.0 to 4.5% Mo, 3.0 to 4.0% W and 3.0 to 5.0% Nb. The material is provided with high hardness of C69 Rockwell hardness or >=100 Shore hardness, and the C% and Cr% consumed by the carbide forming action of W and Nb always shift within the hypoeutectic range on the low C side than the Fe-Cr-C carbide eutectic line, thus the formation of carbide having higher hardness and the maintenance of toughness are made compatible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wear-resistant alloy cast iron, in particular, a crusher roller, a kneader blade, various liners,
The present invention relates to a member such as a chute that mainly faces abrasion wear of a device.

[0002]

2. Description of the Related Art Since ancient times, construction equipment, ceramics, crushed stone, mining, electric power, dredging, and other equipment and industrial machinery have been exposed to remarkable contact with raw materials and materials to be handled and abrasion of members to be rubbed. In addition to the target strength, wear resistance is an important condition, and various wear-resistant materials have been developed and used properly according to applications.

Abrasion-resistant materials have to be replaced because they wear out and retreat after a certain period of use and cannot achieve a predetermined work efficiency. Therefore, high wear resistance for crushing and pulverizing a larger amount of raw materials to withstand use for a longer period of time and a material capable of satisfying a predetermined mechanical strength as a structural member are required. It was used extensively within.

[0004] Table 1 shows well-known ASTM: A532 / A53.
This is an excerpt of the chemical composition of the high chromium cast iron specified in 2M. Class I is the so-called Ni-Hard.
The materials, Class II and III are high Cr materials, and add Ni and Mo mainly with Cr to C value in the range of hypoeutectic to precipitate high hardness carbides and disperse them in the matrix. The basic principle is to form a dense and strong wear-resistant structure.

[0005]

[Table 1]

However, since the wear-resistant material also plays a role as a member constituting the machine and the device, the mechanical strength,
In particular, from the viewpoint of toughness, the structure and components must be selected to satisfy both requirements of wear resistance and toughness. By manipulating the content ratio of C and Cr, it is possible to crystallize an appropriate amount of high-hardness carbide, which is effective for improving wear resistance, but as the ratio of carbide increases, mechanical strength is guaranteed due to a decrease in toughness. It becomes impossible, and conversely, if the amount ratio of carbide is reduced, the wear resistance is reduced. For this reason, a material having a target composition of a hypoeutectic slightly lower than the eutectic point defined by the C: Cr ratio and having a higher base hardness by hardening and quenching heat treatment is generally used.

FIG. 6 is a graph showing the above-mentioned A to Fe--Cr--C phase diagram.
It is the figure which added the composition of C and Cr of each STM in a superimposed manner, and all are lower C side than the eutectic line which separates the boundary of γ phase to M ₇ C ₃ or M ₃ C carbide precipitation, that is, the hypoeutectic range. , Indicating that the component is a component that takes into account some mechanical strength and impact resistance.

However, as one of recent measures for reducing operating costs and maintenance costs, there is a strong demand for wear resistance exceeding the level of the prior art. Mainly, members that operate under abrasion wear conditions have mechanical strength. Is not a critical factor, high chromium cast iron having a hypereutectic composition has also been used. For example, C: 3.0 to 4.0% by weight.
0%, Cr: 20.0-30.0%, Mo: 3.0% are applied, and wear-resistant materials whose ultimate hardness reaches a high value of about 65 (Shore hardness Hs90) in Rockwell C hardness (HRC) are used. Have been. However, there is still an endless demand for a reduction in operating costs, and there is a trend that the industry strongly demands the development of higher wear-resistant members.

[0009]

THE INVENTION Problems to be Solved] To improve wear resistance of (hereinafter abbreviated as HmV) mass added to the micro-Vickers hardness of C and Cr than the prior art of M ₇ C ₃ type reaching 1800 The method of precipitating excessive Cr carbide is straightforward.

However, Cr carbide of M ₇ C ₃ is so brittle that excessive crystallization causes problems such as casting cracks in manufacturing members. Further, when a large amount of C and Cr is added and enters the hypereutectic range, the mechanical strength is greatly reduced, and thus the risk of cracking increases even when used under abrasion wear conditions. Therefore, there is a limit to the improvement in wear resistance of the conventional alloy cast iron material in which a large amount of Cr carbide is crystallized.

For example, in the prior art of Japanese Patent Application Laid-Open No. 5-214483, weight% C: 3.0 to 7.0 is used as a main component.
%, Cr: 15.0 to 35.0%, Mo: 3.0 to 10
0%, W: 3.0 to 10.0%, V: 0.5 to 2.0
% Lump-resistant mineral wear material was proposed. The conventional high Cr cast iron lump-resistant mineral wear member breaks and falls off carbides due to collisions with lump minerals.The low strength of the base makes it impossible to hold carbides. The purpose is to achieve.

However, when the range specified by C-Cr% of the prior art is added to the above-mentioned FIG. 6 (hatched portion in the figure), most of the range belongs to the range of the hypereutectic composition. Even if strength and hardness can be expected to improve as expected, there is room for concern whether cracks, ruptures and peeling can be sufficiently achieved when an impact is encountered, so that the working conditions must be carefully restricted.

On the other hand, there is a prior art in which the base holding the carbide is in a hypoeutectic range where the mechanical strength is maintained at a certain level, and only the wear resistance of the wear surface is locally improved by special casting means. JP-A-5-253665 discloses that the main component is
2.5 to 3.7%, Cr: 14 to 18%, M
o: 1-4%, V: 0.5-1%, Nb: 0.3-1.
In the hypoeutectic component of 0% and the balance of Fe, only the portion particularly requiring abrasion resistance is rapidly cooled to obtain HRC67.
It claims to have formed the above wear surface. As a method of quenching, the mold surface forming the wear surface is molded with steel grains,
The mold (cooling method) is used.

In this method, the base component is made to have a hypoeutectic composition, and it is intended to strengthen only a necessary wear surface while maintaining mechanical properties that can resist a fracture crack. However, it is difficult to use special molds locally unless the factory has a complete system for recycling sand foundry.
As for the chilling system, preparations for all sizes and shapes of various members are extremely complicated and inefficient.

In order to solve the above-mentioned problems, the present invention improves the wear resistance of the wear surface by adding a component element which forms carbide having higher hardness than conventional Cr carbide,
The purpose is to shift the base composition to the hypoeutectic range by the consumption of carbon accompanying the carbide forming action of the added element, and to further improve the base hardness by the optimal heat treatment to achieve an outstanding level of wear resistance. And

[0016]

According to the present invention, a wear-resistant alloy cast iron material according to the present invention comprises C: 3.8 to 4.5%, Si: 1.0% or less,
Mn: 1.5% or less, Cr: 10.0 to 20.0%, M
o: 3.0 to 4.5%, W: 3.0 to 4.0%, Nb:
3.0 to 5.0% (all in weight%) and the unavoidable impurity element and the balance is substantially composed of high Cr cast iron of Fe. After being heated and maintained at an optimal heat treatment temperature, a quenching treatment is performed. And a high hardness of Rockwell hardness C (HRC) of 69 or Shore hardness (Hs) of 100 or more, and Fe-Cr in the relationship between C weight% and Cr weight% corrected by the carbide forming action of W and Nb. The above problem was solved by being always included in the hypoeutectic range lower on the C side than the -C based carbide eutectic line.

Under the above basic conditions, the correction of C% of the carbide forming action is C%-[W% × (C atomic weight / W atomic weight) + Nb% × (C
Atomic weight / Nb atomic weight)] is a preferred embodiment.

In the Fe--Cr--C phase diagram of FIG.
When adding the C and Cr composition ranges of the STM standard, they are included in the hypoeutectic range. However, the primary carbides grow coarsely and significantly reduce toughness. High-Cr cast iron belonging to
It was also a reality that the risk of breakage and cracking was constantly faced. In the present invention, Nb and W carbide forming elements are added to the Fe—Cr—C system to form Cr carbide (HmV: up to 1800).
Even higher hardness WC, NbC (HmV: 2400
3000) by dispersing and precipitating to significantly improve the wear resistance of the carbide itself, and also by consuming carbon with the formation of carbide and shifting the composition from the hypereutectic to the hypoeutectic range to improve the mechanical strength. It is characterized by.

The C consumption can be calculated from the atomic weights of C, Nb and W. That is, the consumption amount per 1% by weight of W is 12 / 183.90 = 0.065%, and the consumption amount of C per 1% by weight of Nb is 12 / 92.91 = 0.129.
%, Which means that this consumed amount has been subtracted from the reference composition. Therefore, in the hypereutectic composition to which a large amount of Fe-Cr-C-based C is added, a large amount of C is consumed by adding a large amount of W and Nb, and the transition to the eutectic or hypoeutectic composition contributes to the improvement of mechanical strength. I do.

Nb is 3.0 to 4.5% by weight in high Cr cast iron
As shown in the metal micrograph of FIG. 2 (400 magnification), petal eutectic MC (carbide mainly composed of Nb) was crystallized, and when W was added in an amount of 3.0 to 4.0% by weight,
A fish-bone-like primary crystal (a carbide mainly composed of W) is formed. N
The hardness of bC is HmV2400, WC, W ₂ C, (Fe,
W) comprising a 2400~3000HmV in W carbides such as ₆ C, this is the difference is evident Come to comparison with metal microscope photograph of the high Cr cast iron of the prior art of FIG. 3 in the same conditions, later performed As shown in the examples, it has been proved that the presence or absence of the primary carbides of W and Nb is a cause that significantly controls the measured value of HRC.

The component limitation of the present invention will be described individually. All units are% by weight. C: 3.8% to 4.5% If C is less than 3.8%, the amount of carbides to be crystallized is small and the wear resistance is insufficient. If it is 4.5% or more, the mechanical strength is poor, and the risk of casting cracks and cracks during use increases. Si: 1.0% or less Added mainly for the purpose of deoxidizing molten metal.
If it exceeds 0.005%, troostite is formed to deteriorate wear resistance, and it is not preferable in terms of toughness. Mn: 1.0% or less The molten metal has a deoxidizing effect, but if it exceeds 1.5%, retained austenite increases and causes a decrease in hardness. Cr: 10.0 to 20.0% Cr is a main element that forms a hard carbide by forming a solid solution in a part of the matrix, improving the quenchability, and combining with C. But one
If it is less than 0%, the amount of carbides formed is small, so that the wear resistance is inferior. If it exceeds 20%, casting cracks increase and stable production becomes difficult. Mo: 3.0 to 4.5% Mo is necessary for improving the hardenability at the time of heat treatment and for suppressing the formation of troostite in a thick-walled product having a slow cooling rate. Also, some Mo forms a hard carbide in the matrix, which is effective in improving the hardness of the matrix. W: 3.0 to 4.0% W is a main element of the material of the present invention that combines with C to form a high-hardness M ₆ C-type carbide and improves wear resistance. 3.0%
If it is less than 4%, the effect is small, and if it exceeds 4%, the toughness is poor. Therefore, the content is limited to 3.0 to 4.0%. Nb: 3.0 to 5.0% Nb is a main element of the material of the present invention that combines C to form a high-hardness MC-type carbide. Almost no solid solution in the base, C
Does not form double carbides with r and Fe. If it is less than 3%, Nb carbide is hardly crystallized, and if it is more than 5.0%, it becomes difficult to dissolve, and further addition is unnecessary.

The heat treatment will be described.
If the temperature is less than 123 ° K, the amount of M ₂₃ C ₆ type carbide generated in the matrix structure is small. If the temperature exceeds 1273 ° K, the amount of retained austenite increases, the hardness decreases, and the wear resistance decreases. Therefore, the quenching temperature is 1123 to 1273 ° K
And Under the above conditions, the wear-resistant alloy cast iron of the present invention becomes a material having a hardness of HRC69 (Hs100) or more and having excellent wear resistance, and a material which does not crack during production and use.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention (sample No. 1,
2) and the comparative example (No. 3) and the conventional example (No. 3).
The effect of the present invention was demonstrated by arranging 4) for each component, hardness and wear resistance. As a method of the verification test, the test material was unified with a Y block of 30T, melted in the air by a high-frequency melting furnace, cast into block brick, and the Y block was 1123-
After heating and holding at 1273 ° K, air cooling quenching was performed.
Table 2 shows the chemical components of the test materials. Further, the amount of C consumed during the formation of the carbide is calculated from the component% (wt%) of W and Nb, and the corrected C weight% is subtracted from the original C weight%.
Is also described.

[0024]

[Table 2]

FIG. 1 shows the same Fe—Cr—C phase diagram as FIG. 1 to No. C-Cr
Are plotted, and the intersection of the corrected C weight% -Cr weight% of each sample is plotted as
It is a relationship diagram indicated by 'and connecting the transitions due to correction with arrows. As shown in FIG. 1, N
o. 2 was shifted from the initial point to ',' after the correction, and almost entered the eutectic line or the hypoeutectic range, whereas the comparative example, including the corrected ', remained in the hypereutectic range. , In that sense the mechanical strength for the operating conditions,
Or there is a clear difference that the impact resistance concerns have not been improved.

As a fact supporting this concern, Comparative Example N
o. In No. 3, cracks were observed by Y-block casting appearance inspection, and it is clear that a large amount of C, Cr, and Nb can enhance wear resistance and improve hardness, but decrease toughness in the hypereutectic range. Also clearly indicate that it contains fears that cannot be practically tolerated.

In practice, the sample No. 1 or No. 2 is F
On the e-Cr-C phase diagram, Cr belongs to hypereutectic in the relation of Cr-C, and Cr calculated by the carbide forming action of W and Nb.
From the corrected C%, components near the transition to the hypoeutectic range can be recommended as a highly preferred embodiment in which the balance between wear resistance and toughness is well maintained.

Next, No. 1 to No. 30T made from 4
After heat treatment of 1123, 1173, and 1223 ° K on the Y block, a hardness test piece was collected and subjected to a Rockwell hardness test and a Micro Vickers hardness test. The test was performed. Table 3
Shows the test results. The value of the pressure abrasion test indicates the pressure abrasion resistance ratio of the invented material based on the conventional material. In the embodiment of the present invention, No. 1, No. No. 2 is No. 2 of the conventional material. Compared to No. 4, both Rockwell hardness and Micro Vickers hardness were improved, and the abrasion resistance was about 1.6 times higher. FIG. 4 shows the relationship between the Rockwell hardness and micro Vickers hardness and the wear resistance under pressure. From FIG. 4, it can be seen that the increase in hardness improves the wear resistance under pressure.

[0029]

[Table 3]

[0030] In the sample of the present invention, the highest hardness was obtained. No. 2 and No. 2 which is a conventional material. No. 4 was applied to a spiral flow mixer blade for kneading asphalt to compare the abrasion resistance. The product is a flat plate having a weight of about 8 kg, a wall thickness of 30 mm, a length of 200 mm and a width of 140 mm, which is arranged on a rotating arm of a mixer, and is rotated spirally to knead asphalt including crushed stone, sand, coal tar and the like. The wear amount of the product after 9 months of the actual operation period was measured, and the wear resistance ratio of the example of the present invention is shown in Table 4 and FIG. As is clear from FIG. 5, in the actual operation, the abrasion resistance is improved 2.1 times in the example of the present invention as compared with the conventional material.

[0031]

[Table 4]

[0032]

As described above, the present invention maintains the toughness substantially the same as the hypoeutectic range where the toughness is not lost, while the inherent improvement in wear resistance falls within the well-established hypereutectic range. Thus, an ideal wear-resistant member having both the effect of forming extremely hard W and Nb carbides and the base strength in a relatively stable hypoeutectic range and dispersing and precipitating fine Cr carbides is produced. Has the effect of providing. Needless to say, high C
The action itself of increasing the hardness of carbide by further adding a carbide-forming element to the cast iron is known, and many prior arts have been reported, but as in the present invention, the equilibrium relationship between wear resistance and toughness is determined. The prior art that has reached the principle of high versatility specified from the state diagram is infinite, and the contribution to the technical field is remarkably remarkable when concrete guidelines are specified.

[Brief description of the drawings]

FIG. 1 is a graph showing the effects of the present invention and the prior art.
It is a state diagram of a Cr-C system.

FIGS. 2A and 2B are a metallographic micrograph (A) and a schematic diagram (B) illustrating a precipitation composition of an example of the present invention.

FIG. 3 is a metallographic micrograph of a conventional technique.

FIG. 4 is a graph showing the relationship between the Rockwell C hardness (HRC) and the micro Vickers hardness (HmV) and the wear resistance under pressure.

FIG. 5 shows an embodiment of the present invention (No. 2) and a prior art material (N).
o. 4) It is a relation diagram of the amount of wear in the field test.

FIG. 6 shows Fe—Cr—C showing the composition range of the prior art.
It is a system phase diagram.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Seiji Nose 1-12-19 Kitahorie, Nishi-ku, Osaka City Inside Kurimoto Iron Works Co., Ltd. (72) Yoshiaki Shingu 1-1-12-19 Kitahorie, Nishi-ku, Osaka City Inside Kurimoto Ironworks Co., Ltd.

Claims (2)

[Claims] 1. C: 3.8 to 4.5%, Si: 1.0%
Mn: 1.5% or less, Cr: 10.0 to 20.0
%, Mo: 3.0 to 4.5%, W: 3.0 to 4.0%,
Nb: 3.0 to 5.0% (all by weight) and unavoidable impurity elements, and the balance is substantially made of high Cr cast iron of Fe. After being heated and maintained at an optimal heat treatment temperature, quenching treatment is performed. To provide a high hardness of Rockwell hardness C (HRC) of 69 or Shore hardness (Hs) of 100 or more, and Fe- in the relation of C weight% and Cr weight% corrected by the carbide forming action of W and Nb. A wear-resistant alloy cast iron material, which is always included in a hypoeutectic range on a lower C side than a Cr-C based carbide eutectic line. 2. The method according to claim 1, wherein the correction of C% by the carbide forming action is performed by weight%, and C% − [W% × (C atomic weight / W atomic weight) + Nb% × (C
Atomic weight / Nb atomic weight)].