JPH02185946A - Alloyed cast iron material for compression crusher screw - Google Patents

Abstract

PURPOSE:To obtain a screw material excellent in wear resistance and toughness as a screw material for a compression crusher for chaff by carrying out casting by the use of alloyed cast iron with a specific composition as a raw material and subjecting the resulting casting to quench-and-temper treatment under respectively specified temp. conditions. CONSTITUTION:As a screw material used at the time of pulverizing a hard material with low specific gravity, such as chaff, by means of a compression crucher having a structure in which a screw is turned in a cylinder, a molten alloyed cast iron which has a composition containing, by weight, 2.5-3.8% C, 0.3-2.0% Si, 0.3-1.0% Mn, 3.5-6.5% Cr, 0.5-9.5% Mo, 0.5-8.0% W, 5-15% V, <0.2% P, and <0.1% S or further containing <0.5% Ti or <=3% Ni, Co, etc., or, together with the above Ni and Co, <5% Nb is tapped from a furnace at >=1580 deg.C and cast, and the resulting casting is quenched at 800-1100 deg.C and tempered at 200-600 deg.C. At this time, at the time of adding Ti, V, Nb, etc., to the molten metal, the surface of the molten metal is regulated to an inert-gas atmosphere and the above Ti, V, Nb, etc., are added in the form of master alloys, such as Fe-Ti, Fe-V, Fe-Nb, etc., to the molten metal of 1550 deg.C, by which the oxidational losses of Ti, V, Nb, etc., can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an alloy cast iron material suitable as a screw material used in a compressor for crushing, for example, rice husk.

[Conventional technology]

Rice husks are generated during the harvesting of brown rice, but their specific gravity is extremely low, making them difficult to collect, and because they themselves are a strong combination of silica, cellulose, and lignin, it takes a lot of equipment and power to completely pulverize them. It costs too much,
Currently, it is not being used effectively.

Recently, a method of compressing and crushing rice husks has been put into practical use in order to effectively utilize the rice husks, and a compression crusher has been used as a means for this purpose. This has a structure in which a screw rotates within a cylinder, and the rice husks introduced between the cylinder and the screw are compressed and crushed while moving forward due to the rotation of the screw. In this way, the screw of the compression crusher is used for compressing and
During the crushing operation, the temperature rises to approximately 600°C, and the material is subjected to strong stress and severe friction. Therefore, the screw is required to have high mechanical strength (such as toughness) and high wear resistance. For this reason, conventionally, the screw material for a single rice husk compression crusher was 5KDII or 5KDII or 5KDII.
Mold steel such as KD61 is used. In addition, using these mold steels as base materials, CV, D (T i
Surface hardening treatments such as chemical adhesion of C), self-fluxing alloy spraying, or WC spraying are also used.

[Problem to be solved by the invention]

However, in the case of mold steel that is not subjected to surface hardening treatment, the screw blades wear out in an extremely short period of time, making it unusable. In addition, when mold steel is subjected to surface hardening treatment such as CVD, self-fusing alloy spraying, or WC spraying, each surface hardened layer is only 1 m thick at maximum, so it takes about 5 hours to surface. The hardened layer will peel off. Furthermore, there is a problem in that local wear is significant, and for this reason, these screw materials are insufficient from a practical point of view.

In order to solve the above-mentioned problems, the present applicant has already applied for an alloy cast iron material suitable for use as a compressor crusher screw (see Japanese Patent Application Laid-open No. 63-28843). The above-mentioned proposal has made it possible to solve the problems existing in the prior art, and to produce a compressor crusher screener having extremely high wear resistance without surface treatment. However, since the alloy cast iron material proposed above is a high-alloy cast iron, it is extremely difficult to maintain a high level of product quality by requiring careful attention and advanced technology in each of the 5 melting, casting, and heat treatment steps. Yes 2 Often causes cavities and other defects. Furthermore, in recent years, the specifications required for this type of material have become increasingly strict, and in this respect it cannot be denied that there is room for some improvement in the alloy cast iron material that is the improvement proposal mentioned above.

The object of the present invention is to solve the problems of the above-mentioned prior art and to provide a further improved alloy cast iron for use in a compressor crusher screw.

[Means to solve the problem]

In order to achieve the above object, in the first invention, the chemical component is 02.5 to 3.8% by weight.

510.3-2.0%, Mn0.3-1.0%, Cr3
．． 5-6.5%, Mo0.5-9.0%, W0.5-8
．． 0%.

■5.0-15.0%, P0.294 or less, 30.1%
below.

The remainder essentially consists of Fe, and the molten metal is heated to 1550°C or higher during melting in a melting furnace, the surface of the molten metal is coated with an inert gas, the Fe-V alloy is added, and the molten metal is heated to 1580°C or higher.
We adopted the technical means of tapping the metal by raising the temperature above ℃, heating it after casting to 800 to 1100 ℃ for quenching, and tempering it at 200 to 600 ℃ to achieve a hardness of HS 70 or higher1. did.

Next, in the second invention, the chemical components are C2,
5-3.8%, Si0.3-2.0%, Mn0.3-1
．． 0%, Cr3.5-6.5%, Mo0.5-9.0%
.

W 0.5-8.0%, V5.0-15.0%, P0.
2% or less, 50.1% or less, TI 0.5% or less, the remainder substantially consists of Fe, and 155
The surface of the molten metal is heated to 0°C or above and coated with an inert gas, Fe-V alloy and Fe-Ti alloy are added, and the molten metal is heated to 1580°C or above, tapped and cast.
It is heated to 00~1100℃ and hardened.

Hardness is increased to 8370 or higher by tempering at 200 to 600°C. A technical method was adopted.

Furthermore, in the third invention, the chemical components have a weight ratio of C2,
5-3.8%, Si0.3-2.0%, Mn0.3-1
．． 0%, Cr3.5-6.5%, Mo0.5-9.
0% WO15-8.0%, V5.0-15.0%, P0
．． 2% or less, S0.1% or less, Ni and/or Co
3.0% or less, the remainder substantially consisting of Fe, and the molten metal is heated to 1550°C or higher during melting in a melting furnace, the surface of the molten metal is coated with an inert gas, and an Fe-V alloy is added to the molten metal. Raise the temperature to 1580℃ or higher to 111? Easy to cast, heated to 1k s00~1100℃ and quenched, 2
The hardness is increased to 8 by tempering at 00~600℃.
Make it 370 or more. A technical method was adopted.

Furthermore, in the fourth invention, the chemical component is C by weight ratio.
2.5-3.8%, SI0.3-2.0%, Mn0.3
~1.0%, Cr3.5~6.5%, Mo0.5~
9°0%, W0. S~8. θ%, V5.0-15.0%
, PO 12% or less, 30.1% or less, Nb 5.0%
Below, Ni and/or Co is 3.0% or less, the balance is substantially Fe, and 155% is used during melting in the melting furnace.
The surface of the molten metal is heated to 0°C or higher, coated with an inert gas, Fe-V alloy and Fe-Nb alloy are added, the molten metal is heated to 1580°C or higher and tapped, and after casting it is heated to 800°C.
Quenched by heating to 1100℃, 200-600℃
The hardness is made to be HS 70 or higher by tempering. This technical method was adopted.

Next, the reasons for limiting the alloy components in the present invention will be described.

C: 2.5 to 3.8% (weight ratio, hereinafter referred to as the following) C is an element that crystallizes carbides and increases the hardness of the material.
When it is less than 5%, the amount of carbides crystallized is small and the wear resistance is not sufficient, and when it exceeds 3.8%, it is not preferable because it deteriorates the toughness during use. The preferred range is 2.8-3.6%.

Si: 0.3-2.0% St is added mainly for the purpose of deoxidizing the molten metal, but 0.3%
If it is less than 2.0%, the effect will be small, and if it exceeds 2.0%, the effect will be saturated and the toughness of the material will decrease. Therefore, it should be 0.3 to 2.0%, but the preferable range is 0.5%.
~1.5%.

Mn: 0.3 to 1.0% Mn is effective in hardening the material and improving wear resistance, and at the same time has a deoxidizing effect. If it is less than 0.3%, the effect will be small, and if it is more than 1.0%, retained austenite will increase and hardening will not occur. Therefore, its content is 0.3-1.0%
shall be. The preferred range is 0.4-0.9%.

Cr: 3.5 to 6.5% Cr content of 3.5 to 6.5% is required to maintain a predetermined hardness and wear resistance. However, if it exceeds 6.5%, Cr carbides will crystallize, making it unsuitable in terms of toughness. The preferred range is 4.0-5.5%.

Mo: 0.5 to 9.0% MO is necessary to harden the material and form a hard carbide containing Mo. However, if it is less than 0.5%, the effect is small, and if it exceeds 9.0%, MbC carbide will precipitate. This MaC carbide has lower hardness than Vanadium J carbide, and when it becomes a mixed structure with vanadium carbide, the bulk vanadium carbide loses its shape, reducing toughness and promoting wear. For this reason, the content of Mo is set to 0.5 to 9.0%.

The preferred range is 1.0-8.0%.

W F 0.5-8.0% W is an essential component for maintaining high temperature hardness, but 10.
If it is less than 5%, the effect will be small, and if it exceeds 8.0%, M, C or M&C will tend to precipitate and the wear resistance will not be sufficient, so it is necessary to keep it below that. Also 8,
If it exceeds 0%, the shape of the lumpy, uniform vanadium carbide will collapse, resulting in increased wear. Therefore, the W content is 0
．． 5 to 8.0%. The preferred range is 1.0 to 7.0
%.

V: 5.0~15.0% ■ is 5.0~l 2.5~3.8 when in the range of 5.0%
% of C and a balanced structure in which only one grain of vanadium carbide is uniformly and finely dispersed and crystallized. For this reason, V needs to be in the range of 5.0 to 15.0%. The preferred range is 8.0-12.0%.

Ti: 0.5% or less Ti is effective in refining carbides.

If it is in excess, the effect will be saturated, so the amount should be 0.5% or less.

Ni and/or Co: 3.0% or less Ni improves hardenability and increases hardness, and Co ensures hardness at high temperatures and is effective in improving wear resistance, but if 1 is in excess Since the effect is saturated, it is set to 3.0% or less.

Nb: 5.0% or less Nb forms carbides and improves wear resistance, and at the same time has the effect of crystallizing lumpy carbides finely and uniformly as in ①, but if it exceeds 5.0% This is disadvantageous because it makes dissolution difficult.

In the invention of the present application, elements such as V and T1Nb are added to the molten metal as Fe-V, Fe-Ti, and Fe-Nb, respectively, but in order to ensure the dissolution and dispersion of these ferroalloys, It is preferable to maintain the melting temperature of the molten metal in the melting furnace at 1550°C or higher.

In addition, when heating to the above temperature, it is preferable to cover the surface of the molten metal with, for example, argon gas or other inert gas to prevent oxidation of the molten metal. If such a coating is missing, the molten metal will oxidize, resulting in so-called slag.

This is inconvenient because it gets mixed into the product during casting and causes casting defects.

Furthermore, after the composition adjustment of the molten metal is completed, the molten metal is
Casting is performed by raising the temperature to 580'C or higher, and by raising the temperature in this way, it is possible to remove the oxide film generated on the surface of the molten metal. If the temperature is lower than this, the removal of the oxide film will be incomplete.

This is inconvenient because it gets mixed into the molten metal during casting and causes casting defects.

Next, the alloy cast iron material of the invention of the present application has residual austenite in the as-cast state, and has poor wear resistance when used as a screw in a compression crusher as it is. For this purpose, a hardening treatment is performed by air cooling from 800 to 1100°C, and further a tempering treatment is performed at least once at 200 to 600°C.

If the quenching temperature is less than 800° C., the melting of the alloy into the matrix will be insufficient and the quenching will not be effective. The higher the upper limit temperature for quenching, the better, but if it is higher than 1150°C, melting will begin to occur, so for safety reasons, it is set at 1100°C. Further, when the tempering temperature is less than 200°C, transformation of austenite to martensite or bainite is not sufficient. Moreover, when the temperature rises above 600° C., the matrix structure softens.The alloy of the present invention has a large amount of alloy, making it difficult to decompose retained austenite. Therefore, the tempering temperature is 200~6
It is desirable to carry out the test at least once at 00°C.

Although the hardness of the alloy cast iron material can be increased by the above-described treatment, if the hardness is less than HS 70, it is disadvantageous because the wear resistance is insufficient for use in the screw of a compression crusher.

[Function] With the above configuration, the hard carbide is uniformly dispersed in the matrix, and has the toughness to withstand the strong stress generated during use and has wear resistance. In addition, there is no need for any special surface treatment, and it can be made into a screw material for a compression crusher using simple casting and heat treatment techniques.

The metal is tapped and cast into a screw mold. In addition, in order to prevent oxidation of the molten metal in the melting furnace, the above-mentioned argon gas is continuously blown into the melting furnace. After casting, the mold is dismantled, sand is removed, sprues and other parts are removed, and the mold is heated to 1050°C and quenched by air cooling.

Further, tempering treatment is performed at 550° C. The atmosphere in the heating furnace in the above-mentioned quenching and tempering treatment is maintained at a non-oxidizing atmosphere using, for example, argon gas.

The hardnesses listed in Table 1 are values measured on the copper surface of the screw, and all are 8370 or higher.

〔Example〕

Raw materials are blended to have the chemical components shown in Table 1, melted in a high-frequency melting furnace, heated to 1550°C or higher, and argon gas is blown to coat the surface of the molten metal to prevent oxidation. Next, Fe-V alloy and FeTi alloy or Fe-Nb alloy are added and melted to have the contents shown in Table 1, and the molten metal is heated to 1580 to 1650'C.
After increasing the temperature to
Wear test specimens of 0 m x 10 fins were collected and subjected to wear tests.

Table 2 shows the amount of wear in this wear test. In the wear test, a SiC disk with a grain size number of 400 was rotated at 35 rpm, and the wear test piece was weighed with 13.3 g.
Pressing was performed for 3 minutes at a pressing pressure of /-1. Further, the positives in Table 2 correspond to the circles in Table 1 above. 5K
D-11 is a comparative material.

Table 2 As is clear from Table 2, the wear amount of the alloy cast iron materials of the present invention is 115 to 1/1 of that of the comparative material 5KII-41.
6 and 1, which indicates that the wear resistance is 5 to 6 times higher.

Next, the figure is a photograph showing the metal structure of the alloy cast iron material in the example of the present invention, and is for stone 7 in Table 1 above. In the figure, the white granular portions are vanadium carbide, and it is recognized that they are uniformly distributed throughout the structure. The presence of such uniformly distributed hard vanadium carbides is presumed to be the reason for the excellent wear resistance shown in Table 2 above. Furthermore, SEM observation conducted separately revealed that fine secondary carbide precipitates were also present inside the base. Furthermore, by quenching and tempering heat treatment, the base also becomes acicular martensite and bainite.
[It has transformed into a weave, and the overall hardness has reached HS84. These structural elements and hardness appear as the differences in performance shown in Table 2.

〔Effect of the invention〕

As detailed above, the alloy cast iron material of the present invention has a &[I weave in which granular fine vanadium carbide is uniformly dispersed,
It has extremely high wear resistance. Therefore, C
There is no need for surface treatment such as VD or WC spraying. Alloy cast iron materials having such high wear resistance are extremely useful as screw materials used for compressing and crushing rice husks and the like.

Claims (4)

[Claims] (1) Chemical components are C2.5-3.8% by weight, Si0
．． 3-2.0%, Mn0.3-1.0%, Cr3.5-
6.5%, Mo0.5-9.0%, W0.5-8.0%
, V5.0-15.0%, P0.2% or less, S0.1%
Hereinafter, the remainder essentially consists of Fe, and the molten metal is heated to 1,550°C or higher during melting in a melting furnace, the surface of the molten metal is coated with an inert gas, and an Fe-V alloy is added.
The temperature is raised to 580℃ or higher, and the temperature is 800 to 110℃ after casting.
An alloy cast iron material for a compression crusher screw, characterized in that the hardness is made HS70 or higher by heating to 0°C, quenching, and tempering at 200 to 600°C. (2) Chemical components are C2.5-3.8% by weight, Si0
．． 3-2.0%, Mn0.3-1.0%, Cr3.5-
6.5%, Mo0.5-9.0%, W0.5-8.0%
, V5.0-15.0%, P0.2% or less, S0.1%
Hereinafter, the Fe-V alloy and Fe-Ti are made by using 0.5% or less of Ti and the remainder being substantially Fe, and heating the molten metal to 1550°C or higher during melting in a melting furnace and coating the molten metal surface with an inert gas. Add the alloy, raise the temperature of the molten metal to 1580℃ or higher, tap it, heat it to 800-1100℃ after casting, quench it, and temper it at 200-600℃ to increase the hardness to HS70 or higher. Alloy cast iron material for compressor crusher screws. (3) Chemical components are C2.5-3.8% by weight, Si0
．． 3-2.0%, Mn0.3-1.0%, Cr3.5-
6.5%, Mo0.5-9.0%, W0.5-8.0%
, V5.0-15.0%, P0.2% or less, S0.1%
Hereinafter, Ni and/or Co is 3.0% or less, the balance is substantially Fe, and 1550% is used during melting in a melting furnace.
The molten metal is heated above ℃, the surface of the molten metal is coated with inert gas, Fe-V alloy is added, the molten metal is heated to 1580℃ or above and tapped, and after casting it is heated to 800-1100℃ for quenching. An alloy cast iron material for a compression crusher screw, characterized in that the hardness is made HS70 or higher by tempering at 200 to 600°C. (4) Chemical components are C2.5-3.8% by weight, Si0
．． 3-2.0%, Mn0.3-1.0%, Cr3.5-
6.5%, Mo0.5-9.0%, W0.5-8.0%
, V5.0-15.0%, P0.2% or less, S0.1%
Below, Nb5.0% or less, Ni and/or Co3.
Fe-V alloy and Fe-Nb alloy are added by heating the metal to 1550°C or higher during melting in a melting furnace and coating the molten metal surface with an inert gas. The molten metal is heated to 1,580°C or higher, tapped, and after casting is heated to 800-1,100°C for quenching, and then tempered at 200-600°C to achieve a hardness of HS70 or higher. Alloy cast iron material for compression crusher screws.