JP7157887B1 - Grinding, stirring, mixing, kneading machine parts - Google Patents

Abstract

The object of the present invention is to improve the impact resistance and impart high corrosion resistance to pulverizing, stirring, mixing and kneading machine members made of the cermet disclosed in Japanese Patent No. 6922110. The mass ratio of each element is Ti: 15 to 40%, Mo: 2 to 29%, Cr: 1 to 15%, C: 2 to 20%, and Co: total of Co and Ni is 30 to 55%. and the raw materials are blended so that the Co / Ni ratio is more than 1, they are mixed to obtain a mixed powder, the mixed powder is press-molded to obtain a pressed body, and the pressed body is sintered. A grinding, stirring, mixing and kneading machine member made of the obtained cermet. This cermet consists of a core phase 2 containing TiCN as a main component, a rim phase 3 covering the core phase and containing (Ti, Mo, Cr) (C, N) as a main component, and a metal phase. 4, and the Mo2C phase and the chromium carbide phase cannot be observed by SEM observation. [Selection drawing] Fig. 1

Description

TECHNICAL FIELD The present invention relates to members for pulverizing, stirring, mixing, and kneading machines made of cermet excellent in impact resistance, wear resistance, and corrosion resistance.

In Patent Document 1, the present inventors disclosed a pulverizing/stirring/mixing/kneading machine member made of cermet with excellent impact resistance and abrasion resistance. That is, the cermet that has magnetism, is lightweight, and has significantly improved abrasion resistance and impact resistance, obtained by the technique of Patent Document 1, can be used for grinding, stirring, mixing, and kneading machine parts that are subject to severe wear for a long time. It has become possible to prolong the life.

Japanese Patent No. 6922110

The inventors of the present invention made prototypes of pulverizing, stirring, mixing, and kneading machine members made of the cermet disclosed in Patent Document 1 and repeated tests, and found that further improvement in impact resistance is desired. In addition, it was found that an improvement in corrosion resistance is also desired depending on the application. That is, high corrosion resistance is required when used for kneading materials containing metal corrosive materials such as positive electrode materials for lithium ion batteries and flame retardants for plastics.

Accordingly, an object of the present invention is to improve the impact resistance and to impart high corrosion resistance to the members of pulverizing, stirring, mixing, and kneading machines made of the cermet disclosed in Patent Document 1.

The present inventors decided to contain Cr in order to solve the above problems, and also considered the balance with other physical properties such as wear resistance and magnetism required for pulverizing, stirring, mixing, and kneading machine parts. Therefore, we reconstructed the composition of cermet for grinding, stirring, mixing, and kneading machine parts.

That is, in the present invention, the mass ratio for each element is
Ti: 15-40%
Mo: 2-29%
Cr: 1-15%
C: 2-20%
Co and Ni total 30-55%
and any of Ti or Ti compounds, Mo or Mo compounds, Cr or Cr compounds, Co or Co compounds, Ni or Ni compounds, and carbon, carbides or carbonitrides such that the Co/Ni ratio is greater than 1 A step of obtaining a mixed powder by using the powder selected as a raw material and mixing them in a wet or dry manner, a step of press-molding the mixed powder at a pressure of 50 to 300 MPa to obtain a pressed body, and a pressed body of 1300 to 1700 °C, vacuum, reduction, inert gas, hydrogen or nitrogen atmosphere, and is mainly composed of Ti(C,N) (including the case where N=0) Three phases: a core phase, a rim phase that exists so as to cover the core phase and is mainly composed of (Ti, Mo, Cr) (C, N) (including the case where N = 0), and a metal phase The above problems have been solved by providing a member for a pulverizer, agitator, mixer, and kneader made of cermet, which has phases and in which the Mo ₂ C phase and the chromium carbide phase cannot be observed by SEM observation.

According to the present invention, it is possible to improve the impact resistance of the crushing, stirring, mixing, and kneading machine members made of the cermet disclosed in Patent Document 1 and to impart high corrosion resistance. It has become possible to extend the life of the
Specific examples of pulverizing, stirring, mixing, and kneading machine parts include screw elements and barrels for twin-screw extruders, crushing pins for pin mill devices, paddles for mixing stirrers, and powder processing device members for bead mills. It can be used preferably.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of a cross-sectional structure of a cermet used for a pulverizing/stirring/mixing/kneading machine member of the present invention; FIG. 2 is a schematic diagram of a cross-sectional structure of a cermet having a phase containing relatively more Mo than a rim phase, which is used for the pulverizing/stirring/mixing/kneading machine member of the present invention. 1 is an SEM observation image of a cermet used for a pulverizing/stirring/mixing/kneading machine member of Example 1. FIG.

The pulverizing/stirring/mixing/kneading member of the present invention can be implemented in the following manner.

First, the mass ratio of each element is
Ti: 15-40%
Mo: 2-29%
Cr: 1-15%
C: 2-20%
Co: 10-50%
Co and Ni total 30-55%
and any of Ti or Ti compounds, Mo or Mo compounds, Cr or Cr compounds, Co or Co compounds, Ni or Ni compounds, and carbon, carbides or carbonitrides such that the Co/Ni ratio is greater than 1 The raw material is the powder selected for
For example, Ti compounds include carbides, nitrides, carbonitrides, composite carbonitrides such as TiC, TiN, TiCN, (Ti, Mo) (C, N), (Ti, W) (C, N) It may be in any form. The same applies to Mo, Cr, Co and Ni. Carbon, carbide or carbonitride can be used as the carbon (C) source.
Then, they are wet- or dry-mixed to obtain a mixed powder, the mixed powder is press-molded at a pressure of 50 to 300 MPa to obtain a pressed body, and the pressed body is heated at 1300 to 1700 ° C. under vacuum, reduction, and non-reduction. By sintering in an atmosphere of either active gas, hydrogen or nitrogen, a pulverizing/stirring/mixing/kneading machine member made of cermet is obtained. This cermet has three phases, a core phase, a rim phase, and a metal phase, and the specific design of each phase will be explained below. In the following explanation, the mass ratio of each element is that of the raw material stage.

(Design of core phase and rim phase)
When C is 2 to 20%, the sinterability is improved and a hard phase consisting of a fine core phase and a rim phase is formed. If the C content is less than 2%, sufficient volumes of the core phase and the rim phase are not generated, resulting in deterioration of wear resistance. On the other hand, when C is added in an amount of more than 20%, a free carbon phase is generated, and the mechanical properties (strength, hardness, impact resistance) are significantly lowered and the corrosion resistance is also lowered.
N may not be added, but when N is added, it can be added arbitrarily in the range of more than 0 and within 5%. Addition of N tends to reduce the thickness of the rim phase, thereby improving wear resistance and impact resistance. Further, by setting the N content to 5% or less, it is possible to suppress the remaining pores in the alloy due to the nitrogen gas generated during sintering, thereby improving the mechanical properties.
Furthermore, it is desirable that C:N=7:3 to 10:0. By setting the C:N ratio within this range, good wettability between the metal phase and the hard phase composed of the core phase and the rim phase is maintained, and the denseness is improved.
Mo is mixed in the range of 2 to 29%. Although the wettability between TiCN forming the core phase and Co and Ni forming the metal phase is poor, the rim phase generated by adding Mo ₂ C or the like allows the formation of a hard phase consisting of a core phase and a rim phase. Wettability can be improved. This increases the sinterability of the material and improves the mechanical properties. Addition of Mo is also effective from the viewpoint of improving corrosion resistance. On the other hand, if more than 29% of Mo is added, the impact resistance is lowered. Cr is mixed in the range of 1 to 15%. If Cr is less than 1%, sufficient corrosion resistance cannot be obtained. On the other hand, when Cr is added by more than 15%, wear resistance and magnetism are lowered.
The sum of Cr and Mo (Cr+Mo) is preferably 3 to 30%. Corrosion resistance improves as the content of (Cr+Mo) increases.
W may not be added, but when W is added, it can be arbitrarily added in a range of more than 0 and less than 10%. Addition of W can further improve wear resistance. This is because the hard phase composed of the core phase and the rim phase is solid-solution strengthened by W atoms, and the hard phase is less likely to break during abrasive wear.
If the total content of Mo and W is 35% or less, alloys of W and Co, Mo and Co, or W, Mo and Co are not formed, and impact resistance is further improved.

(Design of metallic phase)
Co and Ni are 30-55% in total. If the amount of metal is less than this range, the impact resistance will be insufficient. If the amount is large, the abrasion resistance is lowered, and the wear of pulverizing, stirring, mixing, and kneading machine parts becomes severe.
Also, the Co/Ni ratio should be greater than one. By adding a large amount of Co, which has better mechanical properties (hardness and wear resistance) than Ni, the mechanical properties of the members of the pulverizing, stirring, mixing, and kneading machines can be improved. In combination with the effect of improving the corrosion resistance due to the addition of Cr and Mo, it is possible to prolong the life of the pulverizing, stirring, mixing and kneading machine members.
Furthermore, a cermet containing 30% or more of Co and Ni in total has sufficient magnetism required for magnetic separation. Magnetic separation is used for detection of foreign matter in materials due to chipping of parts in grinding, stirring, mixing, and kneading equipment.

The pulverizing/stirring/mixing/kneading member of the present invention can be manufactured by the following manufacturing method as an example.
(Production method)
The following steps (processes) are included in manufacturing the pulverizing/stirring/mixing/kneading machine member of the present invention.
That is, the mass ratio for each element is
Ti: 15-40%
Mo: 2-29%
Cr: 1-15%
C: 2-20%
Co and Ni total 30-55%
and any of Ti or Ti compounds, Mo or Mo compounds, Cr or Cr compounds, Co or Co compounds, Ni or Ni compounds, and carbon, carbides or carbonitrides such that the Co/Ni ratio is greater than 1 The raw material is the powder selected for
a step of wet or dry mixing them to obtain a mixed powder;
A step of press molding the mixed powder at a pressure of 50 to 300 MPa to obtain a pressed body;
A step of sintering the pressed body at 1300 to 1700° C. under an atmosphere of vacuum, reduction, inert gas, hydrogen or nitrogen.
In the case of wet mixing, a volatile solvent such as ethanol is used as the solvent, and the slurry is dried by vacuum static drying or spray drying. At this time, the particle size of the particles forming the core phase and the rim phase after mixing the raw materials (hereinafter referred to as "particle size before sintering") depends on the target value of the average particle size of the hard phase after sintering. Adjust accordingly. For example, when the target value of the average grain size of the hard phase after sintering is less than 3 μm, the grain size before sintering may be 2.0 μm or less, preferably 1.5 μm or less, more preferably 1.5 μm or less. It is preferably 0 μm or less, more preferably 0.6 μm or less. In general, particles grow by sintering, but if the particle size before sintering is 2.0 μm or less, the generation of coarse hard particles can be suppressed, and if it is 1.5 μm or less, The average grain size of the hard phase after sintering can easily be less than 3 μm. If it is 1.0 μm or less, the average grain size of the hard phase after sintering will be smaller, and the wear resistance will be improved. Furthermore, when the thickness is 0.6 μm or less, sintering can be performed at a lower temperature, and wear resistance can be further improved.
On the other hand, when the average particle size of the hard phase after sintering is 3 μm or more, it is sufficient to use a large raw material powder constituting the core phase, or not to pulverize the raw material powder or to shorten the time. , the grain size before sintering should be 2 μm or more.
The raw material mixed powder thus obtained is mixed with a resin component that serves as a molding binder, and granulated. Spray drying may be used for granulation.
The granulated powder is press-molded at 50 to 300 MPa with a die press or a hydrostatic press. After molding, intermediate processing may be performed as necessary.
As for sintering conditions, main sintering is performed in a vacuum or gas atmosphere at 1300 to 1700°C. A degreasing/temporary sintering process may be added before the main sintering, and an intermediate process may be added at each stage after the degreasing and after the temporary sintering, if necessary. The steps of degreasing and preliminary sintering may be performed continuously, and the steps of degreasing and preliminary sintering may also be performed continuously with the main sintering. Debinding and preliminary sintering are performed in a vacuum or gas atmosphere at 600 to 1000°C. Furthermore, hot hydraulic pressing can be performed as needed.
Finally, the final shape is finished by mechanical processing or electrical processing to obtain the desired pulverizing/stirring/mixing/kneading machine member.

(Structure of cermet used for grinding, stirring, mixing, and kneading machine parts)
The structure of the cermet used in the present invention is confirmed by cross-sectional observation by SEM.
The cermet, as schematically shown in its cross-sectional structure 1 in FIG. It exists so as to cover the core phase 2 as a component and the core phase 2, and (Ti, Mo, Cr) (C, N) (including the case where N = 0. That is, when N is not included, (Ti , Mo, Cr)C.) and a metal phase 4. In principle, the cermet does not contain the Mo ₂ C phase and the chromium carbide phase. When the Mo ₂ C phase and the chromium carbide phase are present, they exist in the form of grains with different brightness in the metallic phase other than the core phase and the rim phase in SEM (scanning electron microscope) observation. If it is not possible to make a judgment, analyzes by EPMA (electron probe microanalyzer), EDX (energy dispersive X-ray analysis), and XRD (X-ray diffraction) are performed to comprehensively determine the presence or absence of Mo ₂ C phase and chromium carbide phase. to decide. Even when observed irregularly, the number of particles with a diameter of 1 μm or more is 1 or less, and the number of particles with a diameter of 0.3 μm or more is 5 or less in an observation field of magnification of 10,000. Incidentally, in the present invention, "the Mo ₂ C phase and the chromium carbide phase cannot be observed by SEM observation" means that there is no more than one particle of 1 µm or more in the observation field of view of 10,000 times magnification, and 0.0. A case where the number of particles of 3 μm or more is 5 or less is also included.
With the above configuration, a material with high impact resistance and abrasion resistance can be obtained.

Moreover, the above cermet has the following characteristics.
(core phase)
The core phase is a hard phase mainly composed of Ti(C,N) (including N=0) and has high hardness.
(rim phase)
The rim phase exists so as to cover the core phase and is mainly composed of (Ti _, Mo, Cr) (C, N) (including the case where N=0). As shown in FIG. 2, the rim phase may have two phases, a phase with a relatively large amount of Mo and a phase with a relatively large amount of Ti. In the case of two phases, the hardness of the rim phase is improved, resulting in higher wear resistance.
(Particle size)
The average grain size of the hard phase composed of the core phase and the rim phase is not particularly limited. .
[Number 1]
d _m =(4/π)×(N _L /N _S ) (Formula 1)
N _L = n _L /L (Formula 2)
NS = _ns / _S (Formula 3)
In (Equation 1), _dm is the average particle diameter, π is the circular constant, _NL is the number of particles per unit length hit by an arbitrary straight line on the cross-sectional structure, and _NS is the number of particles within an arbitrary unit area. represents the number of particles contained, where n _L is the number of particles hit by an arbitrary straight line on the cross-sectional structure, L represents the length of an arbitrary straight line on the cross-sectional structure, and (Equation 3 ), n _S represents the number of particles contained in an arbitrary measurement area, and S represents the area of an arbitrary measurement region.

The average particle size of the hard phase consisting of core and rim phases can be less than 3 μm. By setting the average grain size of the hard phase to less than 3 μm, the hardness is improved and the wear resistance is improved. In particular, by setting the average grain size of the hard phase to 1.5 μm or less, the hardness is further improved, and the wear resistance is also further improved.
On the other hand, the average grain size of the hard phase can be 3 μm or more. Fracture toughness is improved by setting the average grain size of the hard phase to 3 μm or more.
Thus, the average particle size of the hard phase may be appropriately determined according to specific uses (required properties). When the average particle size of the hard phase is set to 3 μm or more, the upper limit of the average particle size is not particularly limited and may be determined within the range of common general technical knowledge, for example, 10 μm or less. be able to. When the average grain size of the hard phase after sintering is 3 μm or more and 10 μm or less, for example, the grain size before sintering may be 2 μm or more and 7 μm or less.

(specific gravity)
The pulverization/stirring/mixing/kneading machine member according to the present embodiment has a specific gravity of 9 or less. Conventional pulverizers, agitators, mixers, and kneaders have been designed on the premise that they are equipped with steel materials. It causes load increase. When the specific gravity is 8 or less, it can be handled in the same way as steel materials, and when the specific gravity is 7.5 or less, it becomes lighter than steel materials, and the degree of freedom in device design can be increased.

The cermet having the above characteristics has wear resistance equal to or higher than that of cemented carbide, has a specific gravity equal to that of steel materials, and has magnetism and high impact resistance and corrosion resistance. By applying this material as a member of a pulverizer, agitator, mixer, or kneader, breakage due to contact between members, wear and corrosion of members during use can be suppressed, and a longer service life of members can be achieved.

First, raw material powders shown in Example 1 in Table 1 were pulverized and mixed with an attritor or a ball mill using ethanol as a solvent. The obtained slurry was dried in a vacuum, mixed with paraffin as a binder, and then pressed to produce a pressed body.
This pressed body is preliminarily sintered at 800°C in an atmospheric hydrogen atmosphere, and further sintered at 1400°C in a vacuum atmosphere to obtain a cermet for use in the pulverizing, stirring, mixing, and kneading machine members of the present invention. got
The cermet obtained in Example 1 had an average particle size of 1.13 μm calculated by the above-mentioned Furuman's formula.
The examples and comparative examples after Example 2 were sintered at the lowest temperature within the range of 1300 to 1500° C. at which the highest density was obtained. Other conditions are the same as in Example 1.
Moreover, in Examples 1 to 13 and all comparative examples, the average grain size of the hard phase consisting of the core phase and the rim phase was less than 1.5 μm. On the other hand, in Examples 14 and 15, the average grain size of the hard phase consisting of the core phase and the rim phase was about 5 μm. Comparative Example 1 corresponds to "Example 1" shown in Table 1 of Patent Document 1 above.
Furthermore, when the constituent components of the cermet cross-sectional structure were observed by SEM observation, the existence of Mo ₂ C phase, chromium carbide phase and WC phase could not be confirmed in all the examples. Moreover, in all the examples, a phase with a relatively large amount of Mo component was present in the rim phase.

The elemental composition ratio of the entire cermet structure has a large deviation from the raw material composition, and the coefficient of determination between the raw material composition and the composition ratio of the cermet after sintering is low, so it could not be determined accurately. As explained in Patent Document 1, the reason for this is thought to be the influence of changes in the lattice state due to the formation of a solid solution between the respective constituent elements. That is, as described in Non-Patent Document 1 (Kawabata, Fujimura, Chitoku, "Powder and Powder Metallurgy", Vol. 29, No. 1 (1980), 30-34) cited in Patent Document 1 above, even in past research It is known that the alloy composition of cermet materials is difficult to quantify, and accurate quantification is difficult.
As described above, in the present invention, it is impossible or almost impractical to directly specify the object by its structure or characteristics. exist.

Subsequently, the properties of the produced cermet were evaluated by the following measurement methods.
* Specific gravity: Archimedes method (standard: JIS Z 8807)
*Hardness: Vickers hardness test (standard: JIS Z 2244)
*Abrasion resistance: rubber wheel test (standard: ASTM G65)
*Impact resistance: Charpy impact test with 10R notched test piece
(Standard: JIS Z2242)
* Fracture toughness value: JIS R 1607 (IF method)
*Magnetism: Saturation magnetization measurement *Corrosion resistance: Performed immersion test at room temperature for 24 hours in an acid solution. calculation

Table 3 shows the properties of the cermets in Examples of the present invention and Comparative Examples.
Here, for the evaluation criteria of impact resistance (Charpy impact value) and corrosion resistance, exceeding the cermet "Comparative Example 1" disclosed in Patent Document 1 was taken as a passing level. In terms of wear resistance and magnetism evaluation criteria, a level equal to or higher than cemented carbide (JIS classification: material corresponding to V40) was taken as a passing level.

The impact resistance and corrosion resistance of all the examples exceeded that of the cermet disclosed in Patent Document 1, "Comparative Example 1," showing excellent impact resistance and corrosion resistance. In addition, the specific gravity was suppressed to the target of 9 or less, which was lower than the specific gravity of SKD (7.7). In addition, the wear resistance was equal to or higher than that of cemented carbide (JIS classification: V40 equivalent material).
In addition, in Example 5 in which the amount of W added is 10% or more, the effect of improving the impact resistance is lower than in the other examples. Also, in Examples 3 and 4 in which the amount of W added is 6% or more, the effect of improving the impact resistance is slightly lower than in the other examples. From this, it can be seen that when W is added, the amount added is preferably less than 10%, more preferably less than 6%. As demonstrated in Examples 12 and 13, W does not have to be added to the cermet of the present invention. Furthermore, as demonstrated in Examples 14 and 15, it can be seen that the fracture toughness is improved by setting the average grain size of the hard phase to 3 μm or more.

Comparative Example 1 is the cermet disclosed in Patent Document 1, which is insufficient in impact resistance and corrosion resistance.
In Comparative Example 2, since the added amount of Cr was small, the corrosion resistance was lowered.
In Comparative Example 3, since the amount of Cr added was large, the wear resistance and saturation magnetization were lowered.
In Comparative Example 4, since the amount of Mo added was small, wear resistance and saturation magnetization were lowered.
In Comparative Example 5, since the added amount of Mo was large, the impact resistance was lowered.
In Comparative Example 6, since the Co/Ni ratio was 1 or less, wear resistance and saturation magnetization were lowered.
In Comparative Example 7, since the amount of metal phase (Co+Ni) was large, the wear resistance was lowered.
In Comparative Example 8, since the amount of metal phase (Co+Ni) was small, the impact resistance was lowered.

FIG. 3 shows an SEM observation image of the cermet of Example 1. As shown in FIG. The darkest part is the core phase, the next darkest part is the rim phase, and the lightest part is the metal phase.

1 Cross-sectional structure of cermet 2 Core phase 3 Rim phase 4 Metallic phase 5 Relatively Mo-rich phase

Claims (3)

The mass ratio for each element is
Ti: 15-40%
Mo: 2-29%
Cr: 1-15%
C: 2-20%
Co and Ni total 30-55%
and any of Ti or Ti compounds, Mo or Mo compounds, Cr or Cr compounds, Co or Co compounds, Ni or Ni compounds, and carbon, carbides or carbonitrides such that the Co/Ni ratio is greater than 1 The raw material is the powder selected for
mixing them wet or dry to obtain a mixed powder;
A step of press molding the mixed powder at a pressure of 50 to 300 MPa to obtain a pressed body;
A grinding/stirring/mixing/kneading machine member made of a cermet obtained through a step of sintering a pressed body at 1300 to 1700° C. under an atmosphere of vacuum, reduction, inert gas, hydrogen or nitrogen, ,
A core phase mainly composed of Ti (C, N) (including the case where N = 0) exists so as to cover the periphery of the core phase, and (Ti, Mo, Cr) (C, N) (N = 0.) has a rim phase and a metal phase as the main component,
A grinding/stirring/mixing/kneading member made of cermet in which no Mo ₂ C phase and chromium carbide phase can be observed by SEM observation. A pulverizing, stirring, mixing and kneading machine member made of the cermet according to claim 1, wherein the total mass ratio of Cr and Mo in the raw material is 3 to 30%. The ratio ((Co + Ni)/(Cr + Mo)) of the sum of the mass ratios of Cr and Mo in the raw material (Cr + Mo) to the sum of the mass ratios of Co and Ni in the raw material (Co + Ni) is 0.24 to 1. A pulverizing/stirring/mixing/kneading machine member made of the cermet according to claim 1 or claim 2.

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