CN118007028B

CN118007028B - A high-density non-magnetic compressor balance block and its preparation method

Info

Publication number: CN118007028B
Application number: CN202410268337.4A
Authority: CN
Inventors: 李刚
Original assignee: Individual
Current assignee: Individual
Priority date: 2024-03-10
Filing date: 2024-03-10
Publication date: 2026-01-30
Anticipated expiration: 2044-03-10
Also published as: CN118007028A

Abstract

The invention relates to a high-density non-magnetic compressor balance block and a preparation method thereof, wherein the high-density non-magnetic compressor balance block is prepared by a sintering process, and comprises the following components of 0.3-0.8% of C, 13-18% of Mn, 4-6% of Pb and the balance of Fe, the density of the high-density non-magnetic compressor balance block is more than 7.8g/cm ³ ³, and the magnetic induction intensity is below 0.05 mT.

Description

High-density non-magnetic compressor balance weight and preparation method thereof

Technical Field

The invention relates to a high-density non-magnetic compressor balance block and a preparation method thereof, the high-density non-magnetic compressor balance weight has high density and non-magnetism, is beneficial to reducing the volume of the balance weight and realizes the miniaturization of the compressor.

Background

In refrigeration equipment compressors, a counterweight is a common component. Because the effect of the centrifugal force of the crankshaft of the compressor in the rotation process can lead to unbalance of the compressor in the working process, in order to adjust dynamic balance in the rotation process of the crankshaft, a counterweight part (i.e. a counterweight) is required to be arranged on the crankshaft, thus vibration and noise in the working process of the compressor can be greatly reduced, the crankshaft can be prevented from working under the condition of stress unbalance, and the service life of the crankshaft is prolonged.

The balance weight is made of nonmagnetic materials, so that the interference of the balance weight to the magnetic field of the motor can be avoided. Previously, the balance weight was typically copper because of its high density, which is advantageous for compressor miniaturization, but copper is relatively expensive. Later, inexpensive high manganese steel is gradually used as a material of the balance weight instead of copper, and the high manganese steel is austenitic single-phase steel and has a non-magnetic characteristic. The method for preparing the balance weight by using the high manganese steel can be carried out in two modes of smelting and casting and powder metallurgy, the material density of the smelting and casting method is higher and can reach more than 7.7g/cm ³, but the preparation process is relatively complex, the energy consumption is high, the pollution is large, one-step forming cannot be realized, the subsequent processing is relatively complex, the powder metallurgy method can directly form the balance weight material in one step, the working procedure is relatively simple, the preparation process is energy-saving and environment-friendly, but the material density is lower than that of the smelting and casting method, and the compressor is not beneficial to miniaturization.

Therefore, the invention provides the high-density non-magnetic balance block prepared by the powder metallurgy process.

Disclosure of Invention

The present invention is directed to solving the technical problems of the prior art as pointed out in the foregoing background. The invention provides a high-density non-magnetic balance block, which is prepared by a powder metallurgy (sintering) method, has high density and non-magnetic characteristics, is beneficial to reducing the volume of the balance block, realizes the miniaturization of a compressor, has uniform density distribution, and can reduce vibration and noise in the working process of the compressor.

The technical problems of the invention are solved and corresponding technical effects are obtained through the following technical scheme.

The invention provides a high-density non-magnetic compressor balance block which is characterized by being prepared by a sintering process and comprising the following components of 0.3-0.8% of C, 13-18% of Mn, 4-6% of Pb and the balance of Fe, wherein the density of the high-density non-magnetic compressor balance block is more than 7.8g/cm ³, and the magnetic induction intensity is less than 0.05 mT.

The high-density nonmagnetic compressor balance block provided by the invention has a room-temperature austenite single-phase structure, so that the high-density nonmagnetic compressor balance block has nonmagnetic characteristics, and is suitable for being used as a compressor balance block material.

The density of the high-density non-magnetic compressor balance weight is more than 7.8g/cm ³, preferably more than 7.9g/cm ³, especially when the Pb content is close to the upper limit of 6 percent and the Mn addition amount is close to the lower limit of 13 percent, the density of the high-density non-magnetic compressor balance weight can be more than 7.95g/cm ³, and the volume of the compressor balance weight is reduced on the premise of the same mass, thereby being beneficial to the miniaturization of the compressor.

C and Mn are elements for ensuring that the compressor balance block of the invention has a room temperature austenite structure, and can both improve the hardenability and the room temperature stability of austenite, and ensure that a room temperature austenite single-phase structure is obtained, thereby ensuring that the compressor balance block of the invention has a non-magnetic characteristic, and C and Mn are important elements for ensuring the mechanical property of the compressor balance block of the invention. In the invention, the addition amount of C is controlled to be 0.3-0.8%, and the addition amount of Mn is controlled to be 13-18%. On the premise of ensuring room temperature austenite to be stable, the lower the addition amount of C and Mn is, the better the addition amount of C and Mn is, and the lower the addition amount of C and Mn is, so that the density of the balance weight of the compressor is improved.

Pb is one of the important improvements of the present invention to the conventional high manganese steel composition. Pb has a high density characteristic, its density reaches 11.34g/cm ³, and its melting point is very low, about 327.5 ℃and boiling point about 1750 ℃. In the conventional technical idea, pb is generally considered as an impurity element except in some special steels (such as free-cutting steels), resulting in deterioration of the steel properties and thus being limited to be added. However, in practical work, it is found that the balance weight plays a role in the working process, the requirement on performance is mainly nonmagnetic, and the requirement on mechanical performance is very low, from this point, the inventor breaks through the conventional cognitive limitation, and the great attempt Pb is taken as an additive of the balance weight steel material at the expense of certain mechanical performance of the steel material, and the balance weight density which is important for the miniaturization of the compressor is improved by replacing the improvement of the density of the high manganese steel, namely discarding a part of mechanical performance which is not important for the balance weight.

The Pb addition has the advantages that firstly, the Pb element density is very high, the proper Pb addition is beneficial to improving the density of the material of the balance weight, so that the miniaturization of the compressor is realized, secondly, the Pb element has very low melting point, the Pb element is melted in the sintering temperature range (about 1100 ℃) of the high manganese steel, the melted Pb forms liquid phase in the sintering process, the diffusion of other powder is facilitated, the connection and growth of a sintering neck can be promoted, and pores are well filled, so that the density of the balance weight is improved.

That is, the high manganese steel added with a certain amount of Pb according to the present invention must be manufactured by sintering because the conventional high manganese steel has a melting temperature close to the boiling point of Pb, pb is easily volatilized and Pb is toxic, and the sintering temperature is far lower than the boiling point of Pb, and thus, the weight of the present invention must be manufactured by a powder metallurgy process in terms of both the yield of Pb element and the manufacturing environment.

In the present invention, in order to ensure that the compressor balance weight has a high density and that the mechanical strength is still within an acceptable range, pb is added in an amount of 4 to 6%. The addition amount of Pb is too high, the mechanical property is too great to damage, the working reliability of the compressor is affected, the addition amount of Pb is too low, and the effect of improving the density is not obvious enough.

By controlling the addition amount of C, mn and Pb, the compressor balance weight has the density of at least 7.8g/cm ³, the magnetic induction intensity is below 0.05mT, the tensile strength at room temperature is above 380MPa, the yield strength is above 300MPa, the elongation is above 4.5%, and the density of the compressor balance weight is improved on the basis of considering the mechanical property and the magnetic property of the compressor balance weight, so that the compressor balance weight is beneficial to miniaturization of the compressor.

The high-density non-magnetic compressor balance block is prepared by a powder metallurgy process and comprises the steps of 1) preparing C, mn, pb, fe raw material powder according to components, 2) placing the raw materials in a planetary ball mill, performing low-energy ball milling to obtain mixed powder, 3) compacting the mixed powder, and 4) sintering the compacted compact to obtain the high-density non-magnetic compressor balance block.

C. the Mn, pb and Fe raw material powder is preferably simple substance raw material powder, and the particle size of each simple substance raw material powder is controlled to be 20-50 mu m.

The method has the advantages that the density of the balance weight of the non-magnetic compressor is improved, the uniform density distribution is obtained, vibration and noise in the working process of the compressor can be effectively avoided, and the service lives of the balance weight and the compressor are prolonged.

The Pb element added specially is softer, so that the ball milling process parameters are required to be strictly controlled in the process of preparing the mixed powder, so that cold welding of Pb element powder and other raw material powder is avoided. Because Pb is soft, therefore, once cold welding of Pb and other element powder occurs, pb will be wrapped on the surface of other element powder, and as ball milling proceeds, the cold welding effect will be multiplied like 'snowball', finally resulting in agglomeration of mixed powder, on one hand, the cold welding and agglomeration will lead to unbalance of Pb distribution in mixed powder, on the other hand, since unbalance of Pb distribution will lead to unbalance of Pb in the material in the sintering process for improving the density, and finally affect uniformity of density distribution of the compressor balance weight, resulting in unbalance of the compressor balance weight in the working process of the compressor.

Thus, the compressor balance weight preparation of the present invention must employ low energy ball milling during the compounding stage and requires a wet milling process for the addition of process control agents, which may be deionized water, absolute ethanol, and the like. And, the addition amount of the wet milling process control agent is not less than 45% of the total weight of the raw material powder, if the addition amount of the process control agent is too small, the mixture after ball milling is agglomerated, and the density distribution of the balance weight of the compressor is affected. In addition, the ball milling of the raw material components is low-energy ball milling, the high-energy ball milling energy is excessively introduced, a large amount of cold welding phenomenon can occur, and agglomeration cannot be avoided, so that the compressor balance weight containing the heightened Pb is subjected to material mixing in a low-energy ball milling mode, the ball milling rotating speed is controlled to be 20-40r/min, and the ball milling time is controlled to be 2-5h. The problems of cold welding and agglomeration of powder can be caused by too high ball milling rotating speed and too long ball milling time.

After wet grinding, the mixed powder is dried, pressed into a blank under 800-1500MPa, sintered at 1050-1250 ℃ for 1.5-3.0h.

The compressor balance block prepared by the method has the density of at least 7.8g/cm ³, the magnetic induction intensity of less than 0.05mT, the density distribution is uniform, and the density difference of different parts is not more than 0.05g/cm ³. Although Pb is added to deteriorate the performance, the room temperature mechanical performance still meets the requirements of the tensile strength reaching more than 380MPa, the yield strength reaching more than 300MPa and the elongation rate reaching more than 4.5 percent, and can completely meet the mechanical performance requirements of the balance weight of the compressor.

The invention also provides a preparation process of the high-density nonmagnetic balance block, which specifically comprises the steps of 1) preparing C, mn, pb, fe raw material powder according to the components, 2) placing the raw materials in a planetary ball mill, performing low-energy ball milling to obtain mixed powder, 3) compacting the mixed powder, and 4) sintering the compacted compact to obtain the high-density nonmagnetic compressor balance block. The low-energy ball milling is wet milling, the addition amount of a wet milling process control agent is not less than 45% of the total weight of raw material powder, such as 55%, 65%, 75% and the like, the ball milling speed of the low-energy ball milling is 20-40r/min, the ball milling time is 2-5h, and the ball-material ratio is preferably controlled to be 1-8:1. And drying the mixed powder after wet grinding, and then performing compaction molding, wherein the compaction molding pressure is 800-1500MPa, sintering is performed after compaction, the sintering temperature is controlled at 1050-1250 ℃, and the sintering time is 1.5-3.0h.

As has been described above, the technical solution of the present invention has the following technical improvements.

According to the practical use condition of the compressor balance block, the inventor comprehensively balances the density and mechanical properties of steel, intentionally adds a certain amount of Pb on the basis of the traditional high manganese steel balance block, and breaks through the traditional cognitive confinement of Pb as impurities. The balance weight density, which is critical for compressor miniaturization, is increased at the expense of certain mechanical properties of the steel material, in exchange for an increase in the density of the high manganese steel, i.e., by discarding a portion of the mechanical properties that are not important for the balance weight. The Pb element has very high density, and proper Pb addition is favorable for improving the density of the material of the balance weight, so that the compressor is miniaturized, the melting point of the Pb element is very low, the Pb element is molten in the sintering temperature range (about 1100 ℃) of the high manganese steel, the molten Pb forms a liquid phase in the sintering process, the diffusion of other powder is favorable, the connection and growth of a sintering neck can be promoted, pores are well filled, and the density of the balance weight is improved. The invention is suitable for adding Pb element, specially adopts low-energy ball milling wet milling to prepare mixed powder, controls the rotation speed and time of ball milling and the addition amount of a process control agent, avoids cold welding of soft Pb other element powder and prevents agglomeration, thereby ensuring that a balance block of a compressor has uniform density distribution, and ensuring that the compressor works stably, has low noise and small vibration.

The compressor balance block has the density of at least 7.8g/cm ³, the magnetic induction intensity of less than 0.05mT, the density distribution is uniform, and the density difference of different parts is not more than 0.05g/cm ³. Although Pb is added to deteriorate the performance, the room temperature mechanical performance still meets the requirements of the tensile strength reaching more than 380MPa, the yield strength reaching more than 300MPa and the elongation rate reaching more than 4.5 percent, and can completely meet the mechanical performance requirements of the balance weight of the compressor.

Detailed Description

In order for those of ordinary skill in the art to fully understand the technical solutions and advantageous effects of the present invention, the present invention will be further described with reference to specific embodiments.

Test example one.

The method comprises the steps of 1) preparing C, mn, pb, fe raw material simple substance powder according to the components, controlling the particle size of the powder to be 20-50 mu m, 2) placing the raw material into a planetary ball mill, adding absolute ethyl alcohol which is 50% of the total weight of the raw material powder into a ball milling tank as a process control agent, adopting ZrO ₂ grinding balls with the diameter of 5mm, wherein the weight ratio of the ZrO ₂ grinding balls to the total weight of the raw material powder is 2:1, ball milling for 3h under the condition of 30r/min, 3) obtaining mixed powder after ball milling, drying the powder at 110 ℃, then compacting the dried mixed powder at the pressure of 1000MPa, and 4) sintering the compacted powder at 1130 ℃ for 2.5h to obtain a sample with the diameter of 30cm and the height of 15 cm.

The density of the sample was measured, the magnetic induction of the sample was measured using a Gaussian meter, the specific measurement results are shown in Table 1, and the tensile strength, yield strength and elongation of the sample were measured according to national standard GB/T228.1-2021, and the specific measurement results are shown in Table 2.

Table 1 the composition (Fe balance), density, and magnetic induction of each compressor balance weight.

Table 2 mechanical properties of each compressor balance weight.

As can be seen from Table 1, the magnetic induction intensity of all samples is below 0.05mT, and the nonmagnetic requirement of the invention can be met. However, the density is that the sample (sample No. 1-8) with Pb content within the required range of the invention satisfies the density requirement of the invention, the Pb content of sample No. 11 is highest, which also has the highest density, the Pb content of sample No. 9 is low, the Pb is not added to sample No. 10, 12, the Pb content is reduced or Pb is not added, on the one hand, the density is reduced from the composition of the raw materials, on the other hand, the too low Pb content or Pb not added causes insufficient liquid phase in the sintering process, the powder diffusion is not facilitated, the connection and growth effect of the sintering neck are poor, the pores cannot be effectively filled, and the density requirement of the invention cannot be satisfied by the samples of sample No. 9, 10 and 12.

It is clear from Table 2 that the samples (sample Nos. 1 to 8) having Pb contents within the range required by the present invention have mechanical properties satisfying the requirements of the present invention, that the samples (sample Nos. 9, 10, 12) having a low Pb content or no Pb addition have better mechanical properties, but such mechanical properties are far too much excessive for the weight material to be effective in practical use of the compressor and cannot manifest the value of the high mechanical properties of the weight of the compressor, and that the Pb content of sample No. 11 is too high to be effective in satisfying the requirements of the present invention.

Taken together, it was confirmed that sample numbers 1 to 8 satisfying the composition requirements of the present invention can satisfy the invention requirements in terms of density, magnetic characteristics, mechanical properties, and sample numbers 9 to 11 not satisfying the invention requirements cannot satisfy the invention requirements in terms of density or mechanical properties.

Test example two.

According to the proportion of C0.45%, mn 15.7%, pb 5.0% and Fe as the rest, preparing raw material powder, wherein the raw material powder is selected as simple substance powder, and the grain diameter is controlled to be 20-50 μm. The raw materials were placed in a planetary ball mill, absolute ethanol was used as a process control agent in the scheme of using the process control agent, 4mm diameter ZrO ₂ grinding balls were used, the ratio of the weight of ZrO ₂ grinding balls to the total weight of the raw material powder was 2:1, and the amount of the process control agent, the ball milling rotational speed, and the ball milling time were as shown in table 3. And (3) drying the powder at 100 ℃ after ball milling is finished to obtain mixed powder, compacting the dried mixed powder under 1050MPa for molding, and sintering the compacted powder at 1200 ℃ for 2 hours to obtain a compressor balance block sample with the length of 30cm, the width of 20cm and the thickness of 10 cm.

The obtained sample is measured for the overall density of the sample and is marked as rho ₀, then 6 cubic sample blocks with the side length of 4cm are cut at random different positions of the sample, the measured densities are respectively marked as rho ₁、ρ₂、ρ₂、ρ₄、ρ₅、ρ₆, and the maximum difference between rho ₁、ρ₂、ρ₂、ρ₄、ρ₅、ρ₆ is marked as Deltarho _max. The results of the measurements are recorded in Table 4 in g/cm ³.

Table 3 the ball milling process parameters for each compressor balance weight.

The density of each sample in Table 4 is given in g/cm ³.

The process control agent such as sample 1302 is added in a smaller amount, and although the overall density is still 7.8g/cm ³ or more in the present invention, it is still somewhat lower than sample 1301, and the density difference at different positions is up to 0.29g/cm ³. The analysis is because the addition amount of the process control agent is small, the phenomenon of cold welding and agglomeration of Pb powder occurs more or less, pb is unevenly distributed in the mixed powder, pb is locally concentrated in a part of the mixed powder, and is poor in a part of the mixed powder, so that a sufficient liquid phase cannot be obtained in the part of the mixed powder in the sintering process, the powder diffusion condition is poor, the sintering neck connection and growth effect of the powder are insufficient, the filling of pores is insufficient, the overall density tends to be lowered, and the density uniformity of the sample is poor due to the cold welding and agglomeration of Pb, which is caused to be concentrated in the part of the mixed powder.

Likewise, sample numbers 1303, 1304, 1307 are also caused by too high ball milling rotational speed and too long ball milling time, or the phenomenon that more ball milling energy is transferred to mixed powder material due to no process control agent is added, pb cold welding or agglomeration occurs, and as a result, the overall density of the material is reduced differently, the density uniformity of the sample is poor, the requirements of the invention cannot be met, and the reason for the occurrence of the phenomenon is the same as that of the sample number 1302.

Sample numbers 1305, 1306 are too low in ball milling speed or too short in ball milling time, which results in that Pb cannot be uniformly distributed, pb in the sintered blank is concentrated in a part of the region and is poor in the part of the region, so that a sufficient liquid phase cannot be obtained in the part of the region in the sintering process, powder diffusion conditions are poor, powder sintering necks are connected and grow up, filling of pores is insufficient, the overall density tends to be reduced, and the density uniformity of the sample is poor due to uneven distribution of Pb.

Sample number 1301 has proper process control agent dosage, ball milling rotating speed and ball milling time, and finally, the overall density of the material is higher and reaches more than 7.8g/cm ³, the density distribution uniformity is good, the density difference value of different parts is not higher than 0.05g/cm ³, and the overall density and the density distribution uniformity can meet the requirements of the invention.

From the above, it is believed that by controlling the addition amount of the process control agent in the ball milling process, the ball milling rotation speed and the ball milling time to a reasonable interval range, a compressor balance weight material having a high density and a uniform density distribution can be obtained.

Claims

1. The high-density non-magnetic compressor balance block is characterized by being prepared by a sintering process, and comprises the following components of 0.3-0.8% of C, 13-18% of Mn, 4-6% of Pb and the balance of Fe, wherein the density of the high-density non-magnetic compressor balance block is more than 7.8g/cm ³, and the magnetic induction intensity is less than 0.05 mT;

The high-density non-magnetic compressor balance block is prepared by the following process:

1) Preparing C, mn, pb, fe raw material powder according to the components;

2) Placing the raw materials into a planetary ball mill, and performing low-energy ball milling to obtain mixed powder;

3) Compacting the mixed powder into a compact;

4) Sintering the pressed compact to obtain a high-density non-magnetic compressor balance block;

The low-energy ball milling is wet milling, the addition amount of the control agent in the wet milling process is not less than 45% of the total weight of the raw material powder, the ball milling rotating speed of the low-energy ball milling is 20-40r/min, and the ball milling time is 2-5h.

2. The high-density non-magnetic compressor weight of claim 1, wherein the high-density non-magnetic compressor weight has a room temperature austenite single phase structure.

3. The high-density non-magnetic compressor balance weight according to claim 1, wherein the pressing pressure of the pressed compact is 800-1500MPa, the sintering temperature is controlled at 1050-1250 ℃, and the sintering time is 1.5-3.0h.

4. The method for preparing the high-density non-magnetic compressor balance block as claimed in claim 1, wherein the method comprises the following steps:

1) Preparing C, mn, pb, fe raw material powder according to the components;

3) Compacting the mixed powder into a compact;

the low-energy ball milling is wet milling, the addition amount of a control agent in the wet milling process is not less than 45% of the total weight of the raw material powder, the ball milling rotating speed of the low-energy ball milling is 20-40r/min, and the ball milling time is 2-5h.

5. The method for manufacturing a high-density non-magnetic compressor balance weight according to claim 4, wherein the wet milling is followed by drying of the mixed powder and then compacting.