WO2020041925A1 - Lead-free superhard self-lubricating copper alloy and manufacturing method therefor - Google Patents

Abstract

Disclosed are a lead-free superhard self-lubricating copper alloy and manufacturing method therefor. The mass fractions of elements in the copper alloy are: 52.0%-85.0% of copper, 4.0%-9.0% of manganese, 1%-3% of aluminum, 1%-3% of iron, 0.2%-0.8% of silicon, 0.2-0.6% of nickel, and 1.36%-4.07% of sulfur; in addition to copper, iron, nickel, and zinc, the sum of the contents of one or more metals having an affinity to sulfur less than the affinity of manganese to sulfur is less than or equal to 15.0%; and the balance being zinc and inevitable impurities, the content of lead in the impurities is less than or equal to 0.05%. The lead-free superhard self-lubricating copper alloy has excellent wear resistance and friction reduction and anti-lock abilities, excellent process performances such as machining and cold and hot deformation performances, and excellent use performances such as high hardness.

Description

Lead-free superhard self-lubricating copper alloy and manufacturing method thereof Technical field

The invention relates to a lead-free superhard self-lubricating copper alloy and a manufacturing method thereof.

Background technique

When an object and another object move along the tangential direction of the contact surface or have a tendency of relative motion, there is a force between the contact surfaces of the two objects that hinders their relative movement. This force is called friction. This phenomenon or characteristic between the contact surfaces is called "friction". It is estimated that about 1 / 2-1 / 3 of the world's energy is consumed in friction in various forms. And the wear caused by friction is the main reason for the failure of machinery and equipment. About 80% of the parts are damaged due to various forms of wear. Friction is an irreversible process. As a result, there must be energy loss and loss or migration of friction surface materials, that is, wear. Wear will cause surface damage and material loss. Since friction is inevitable and wear is inevitable, it cannot be eliminated, and people can only do everything possible to reduce friction and thereby reduce wear. Although there are many factors that affect wear, experience has shown that the higher the hardness of metal materials, the more resistant they are to wear. Therefore, anti-wear metal materials are mostly high-hard materials such as high-chromium cast iron and even hard alloys. In order to improve the wear resistance of the workpiece, that is, to increase its service life during friction work, it is generally necessary to consider the use of higher hardness metal materials. Friction couples generally work together with two counterparts. If both mating parts are made of hard or soft materials, it is easy for both mating parts to fail and cause the friction couple to fail. A pair of excellent friction pairs are both a hard counterpart and a soft counterpart, and the hardness of the two is best matched through optimization. In addition, the soft counterpart should be relatively easy to replace, so as to achieve the lowest cost and the best technical and economic value of the friction couple. Because the friction pair generates relative motion during work, the work is performed under the effect of force and converted into heat, which causes the friction pair to heat up. In order to achieve the best service life of the friction pair, the following factors are important: the hardness matching of the two counterparts, the lubrication of the moving contact surface, and the timely release of friction heat. Sliding bearings, especially those with high requirements on the accuracy of movement, use copper-based bearings. This is because copper alloys have excellent heat conduction and heat dissipation capabilities, which will not cause the temperature of the friction pair to be too high due to heat not being able to be guided away in time, thereby reducing friction. The increased strength of the pair causes the mechanism to fail prematurely. In the machine tool manufacturing industry, due to the extensive use of heat-treated steel for shafts, its high hardness and wear resistance are very strong. The hardness of the copper-based bearing of the heat-treated steel is generally much lower than that of the heat-treated steel shaft. In order to improve the life, the hardness of the copper-based bearing should be increased as much as possible, that is, the super-hard copper-based bearing is matched with the heat-treated steel shaft. Especially in the mold industry, high precision is required. The main point of the design of the dual copper sleeve is to use a higher hardness copper alloy to improve the wear resistance and thus the service life. Copper and copper alloys are relatively soft non-ferrous metal materials, and their hardness is difficult to increase. Higher hardness copper alloys are the goal that materials researchers are diligently seeking. The thermal expansion coefficient of copper is significantly higher than that of steel. If a copper-based bearing produces frictional heat to reduce the inner diameter of the bearing, the copper-based bearing will seize and lock the steel shaft, so in order to prevent this from happening The higher the self-lubricating and antifriction ability of copper-based bearings, the better.

In order to increase the service life of the friction pair, good lubrication is essential because it is an important means of reducing friction. Liquid film has very good lubricating effect and is the first means to reduce friction, such as adding lubricating oil to the movement mechanism. Oil-containing self-lubricating bearings have a large number of pores and are filled with a large amount of lubricating oil. The lubrication effect is very good and has been widely used. It is also because of the oily nature that there must be a large number of pores in the self-lubricating bearing to store oil, resulting in its low strength, hardness, and toughness, which can only be used in light load and low speed scenarios. Aiming at the conditions of medium and high speed and heavy load, especially the scenes that require high accuracy of motion, oil-containing bearings are far below the requirements for use. Due to the fluidity of the liquid, it is easy to spill the friction pair and contaminate the system. In many cases, such as food machinery, medical machinery, electronic machinery, and vacuum and dust-free environments, the use is limited. On the other hand, when the lubrication fluid is inconvenient to add or occasionally has poor lubrication even with the lubrication fluid, the life of the friction pair is strongly reduced. These situations require the use of a solid phase antifriction agent to effectively improve the friction reduction ability of the friction pair. When there is no liquid film lubrication, solid phase friction reduction or self-lubrication is the only means to reduce wear, increase the service life of the mechanism, and improve efficiency.

Lead brass has the characteristics of good self-lubrication, hot and cold workability, and excellent cutting performance. It was once recognized by the world as an important basic metal material and widely used in machinery manufacturing and other fields. Due to the widespread use of lead brass, there are a large number of discarded lead brass parts, of which only a small number are recycled and many small pieces are discarded as garbage. The waste lead brass comes into contact with the soil, and the lead contained in it will enter the soil under the long-term effects of rain and the atmosphere, thereby contaminating the soil and water sources. When waste lead brass is incinerated as garbage, lead vapor is emitted into the atmosphere, causing great harm to the human body, so its application is increasingly restricted by laws and regulations. In addition, lead brass has low hardness and low self-lubricating ability. No matter its anti-wear ability or self-lubricating and anti-friction ability, it is not ideal, far from meeting the requirements of friction pairs.

As a traditional bearing material, tin bronze has moderate strength and hardness, a certain self-lubricating ability, and strong machining ability. It is widely and long-term used in the machinery industry. However, it must be pointed out that its self-lubricating ability is low and it cannot meet the requirements of high self-lubricating ability. The tin bronze is not high in hardness, its wear resistance is average, and it cannot meet the application scenarios of medium and high speed and heavy load. Self-lubricating high-strength brass is drilled in the bearing and inlaid with solid-phase lubrication particles such as graphite or molybdenum disulfide, and has good self-lubricating ability. Its hardness is up to HB220, good toughness and anti-wear ability. Strong, can basically meet the application scenarios of medium and high speed and heavy load. However, self-lubricating high-strength brass must be drilled when the solid-phase lubricating phase is inlaid, and the distribution of the holes is non-uniform, which causes non-uniform damage to the high-strength brass bearing and seriously reduces the high-strength brass bearing. The consistency of strength and hardness makes it appear uneven wear. Especially under the conditions of medium and high speed and heavy load, it is prone to abnormal wear failure. On the other hand, due to the uneven distribution of pores, the solid phase particles are also unevenly distributed, which in turn causes uneven friction reduction capabilities. Although self-lubricating high-strength brass is an excellent anti-friction and wear-resistant copper alloy, it is not an ideal anti-friction and wear-resistant copper alloy.

Summary of the Invention

The technical problem solved by the present invention is that the market strongly requires a new type of copper alloy to overcome the shortcomings of the friction-reducing and wear-resistant copper alloy described above. This requires the development of a dense, oil-free and lead-free superhard self-lubricating anti-lock copper alloy with uniform solid-phase lubrication particle distribution and uniform matrix properties to fully meet the high-speed, medium- and heavy-load application scenarios with high accuracy. The present invention has been developed in consideration of this need.

The technical solution of the present invention is to provide a lead-free superhard self-lubricating copper alloy. The mass fraction of each element in the copper alloy is:

Copper 52.0% -85.0%; manganese 4.0% -9.0%; aluminum 1% -3%; iron 1% -3%; silicon 0.2% -0.8%; nickel 0.2-0.6%; sulfur 1.36% -4.07%;

Except copper, iron, nickel, zinc, one or more of metals having an affinity for sulfur that is less than the affinity for manganese and sulfur, and the sum of the contents is ≤15.0%;

The balance is zinc and inevitable impurities, and the lead in the impurities is ≤0.05%.

Preferably, the metal having an affinity for sulfur that is less than the affinity for manganese and sulfur is cobalt, tin, tungsten, molybdenum, niobium, antimony, and bismuth.

Preferably, the mass fraction of each element in the copper alloy is: copper 54.0% -72.0%; manganese 4.5% -8.0%; aluminum 1.2% -2.8%; iron 1.2% -2.8%; silicon 0.3% -0.8%; nickel 0.2 % -0.5%; Sulfur 1.50% -3.50%; Except copper, iron, nickel, zinc, one or more of metals with an affinity for sulfur less than that of manganese and sulfur, the sum of the contents is ≤15.0%; the balance is zinc and Inevitable impurities. Lead in impurities is ≤0.05%.

Preferably, the mass fraction of each element in the copper alloy is: copper 56.0% -68.0%; manganese 5.0% -7.0%; aluminum 1.4% -2.6%; iron 1.4% -2.6%; silicon 0.3% -0.8%; nickel 0.3 % -0.5%; sulfur 1.70% -3.00%; in addition to copper, iron, nickel, zinc, one or more of metals with an affinity for sulfur less than that of manganese and sulfur, the sum of the contents is ≤15.0%; the balance is zinc and Inevitable impurities. Lead in impurities is ≤0.05%.

Preferably, the mass fraction of each element in the copper alloy is: copper 58.0% -65.0%; manganese 5.0% -7.0%; aluminum 1.6% -2.4%; iron 1.6% -2.4%; silicon 0.3% -0.7%; nickel 0.3 % -0.5%; Sulfur 1.90% -2.80%; Except copper, iron, nickel, zinc, one or more metals with an affinity for sulfur less than that of manganese and sulfur, the sum of the content is 1.0% -15.0%; the balance For zinc and unavoidable impurities, the lead in the impurities is ≤0.05%.

Preferably, the mass fraction of each element in the copper alloy is: copper 59.0% -62.0%; manganese 5.0% -7.0%; aluminum 1.7% -2.3%; iron 1.7% -2.3%; silicon 0.3% -0.7%; nickel 0.3 % -0.5%; sulfur 2.10% -2.60%; one or more of metals other than copper, iron, nickel, zinc having a sulfur affinity lower than that of manganese and sulfur, the sum of the content is 1.0% -15.0%; The amount is zinc and unavoidable impurities, and the lead in the impurities is ≤0.05%.

The invention also provides the manufacturing method of the copper alloy, which includes the following steps:

(1) Melt copper, nickel, copper-iron master alloy, manganese, silicon, zinc, and aluminum in sequence. After the alloying elements are homogenized, the copper alloy raw material powder is made by the atomization method;

(2) Compounding copper alloy raw material powder with metal sulfide, and then adding 0.5% -1.5% of forming agent, mixing for 0.5-8h, so that the various powders are uniformly mixed; the affinity of the metal and sulfur in the metal sulfide is less than that of manganese Affinity with sulfur;

(3) pressing the uniformly mixed powder into a shape and then sintering, the sintering process is: starting from room temperature to a sintering temperature of 650-870 ° C, heating for 1-5h, holding for 30-300min, and the sintering atmosphere is a reducing atmosphere or an inert atmosphere;

(4) The sintered copper alloy is heated to 300-800 ° C, and then heat-repressed with a pressure of 300-600 MPa after holding for 1-3 hours; and then re-fired, the re-fired process is: heating from room temperature to sintering temperature 800-870 ℃, heating for 1-16h, holding temperature for 30-300min, reburning atmosphere is reducing or inert atmosphere;

(5) The hot-deformed copper alloy is thermally deformed, and the temperature of the thermal deformation is 650-870 degrees.

Preferably, the copper alloy raw material powder is prepared by a gas atomization method or a water atomization method.

Preferably, the metal sulfide is a solid metal sulfide.

Preferably, the solid metal sulfide is selected from the sulfides of eleven metals of iron, cobalt, nickel, tin, tungsten, molybdenum, niobium, copper, zinc, antimony, and bismuth.

Preferably, the sulfides of the eleven metals are copper sulfide, cuprous sulfide, zinc sulfide, tin sulfide, nickel sulfide, iron sulfide, ferrous disulfide, ferrous sulfide, tungsten sulfide, cobalt sulfide, and disulfide. Molybdenum, molybdenum trisulfide, antimony tetrasulfide, antimony pentasulfide, antimony trisulfide, bismuth trisulfide, niobium disulfide, and niobium trisulfide.

Preferably, the solid metal sulfide is copper sulfide, zinc sulfide, and iron sulfide.

Preferably, the thermal deformation is hot forging or hot extrusion.

Manganese has a significant solid solution strengthening effect on brass, and its strengthening attenuation effect is not obvious as the quantity increases. The manganese content in the present invention is controlled between 4.0% and 9.0%, which has a good effect on improving the hardness of brass. Aluminum is a strong strengthening element of brass, which can significantly improve the hardness of brass. In the present invention, aluminum is controlled between 1% and 3%; iron plays a role in refining grains in brass, and it can also suppress the recrystallization. The grains grow, and the iron content in the present invention is controlled between 1% and 3%, which also has a better effect on improving the hardness of brass. Both silicon and nickel have a solid solution strengthening effect on brass. In the present invention, the silicon content is controlled between 0.2% and 0.8%, and the nickel content is controlled between 0.2% and 0.6%. The small multivariate strengthening effect is very obvious and the hardness of the alloy is significantly improved. . Other elements such as cobalt, tin, tungsten, molybdenum, niobium, antimony, and bismuth also strengthen brass. The invented brass has very high hardness, which is the result of the combined action of manganese, aluminum, iron and all strengthening elements such as silicon and silicon.

In the present invention, a method of simultaneously adding manganese and metal sulfide to a copper alloy is used. During the sintering process, since the activity of manganese is higher than that of the metal sulfide added, the sulfide reacts with the manganese and generates sulfide in situ Manganese or a mixture of manganese sulfide and other sulfides. The in-situ reaction product, manganese sulfide, has a layered structure, and its structural characteristics are similar to graphite, but it also has soft and slippery properties. The presence of manganese sulfide in the copper alloy is equivalent to the presence of soft particles with lubricating effects in the copper alloy, which produces a self-lubricating effect similar to graphite. The in-situ generated manganese sulfide and copper alloy grains have good bonding, the interface is coherent or semi-coherent, and the bonding strength is high. The combination of graphite particles and copper alloy grains in graphite self-lubricating copper alloys does not have the effect of manganese sulfide particles. The interface often has impurities and its bonding strength is very low. These factors cause its low hardness and deformability. difference. The invented superhard self-lubricating copper alloy not only has good lubricating function, but also has higher hardness and better cold and hot deformation ability than graphite self-lubricating copper alloy. On the other hand, due to the high interface strength of the manganese sulfide generated in situ, the amount added can be increased without reducing the cold and hot deformation ability of superhard self-lubricating copper. Because the graphite particles and the copper alloy grains are a simple mechanical meshing, the cold and hot deformation ability of the copper alloy will be significantly reduced, so its limited amount of addition makes its self-lubricating ability limited.

The invention has the advantages that the lead-free super-hard self-lubricating copper alloy has excellent anti-friction, anti-friction and anti-locking capabilities, excellent process performance such as cutting processing, hot and cold deformation, and excellent use performance such as high hardness. The UMT-3 friction test machine in the United States has found that the friction coefficient of the alloy is small and the amount of wear is extremely small under the conditions of 180r / min, -50N, and 30min dry friction. Strong anti-seizure ability, suitable for wear-resistant wear reduction such as copper sleeve for machine tool manufacturing industry, guide sleeve for mold matching and wear plate. The porosity is low, the relative density is higher than 99.7%, and it is dense and oil-free (such as oil immersion may not be required when manufacturing bearings), which is especially suitable for scenarios where oil film lubrication is not available. The constituent elements do not contain lead, cadmium, mercury, arsenic and other harmful elements, and the production process is pollution-free and environmentally friendly.

detailed description

Example 1:

The mass fraction of each element in the copper alloy raw material powder is: copper 58.0%, manganese 5.0%, aluminum 2.6%, iron 2.2%, silicon 0.8%, nickel 0.5%, the balance is zinc and unavoidable impurities. The mass fractions of various powders are as follows: The sulfide powder is a mixture of copper sulfide powder and zinc sulfide powder, the content of which is 1.0% and 5.0%, the content of the addition of a paraffin powder of the forming agent is 0.5%, and the balance is the above-mentioned copper alloy raw materials. powder. The powder mixing time is 4.0h. After the mixing is finished, it is pressed. After pressing, it is put into a sintering furnace for sintering. The sintering process is: heating from room temperature to sintering temperature, heating time 5.0h, fully removing the forming agent, and sintering temperature 680. ℃, holding time 100min, sintering atmosphere is inert atmosphere. The sintered brass rod is re-pressed at a pressure of 300 ° C and 600 MPa, and then re-sintered. The re-sintering process is: heating from room temperature to 820 ° C, heating time 3.0h, holding time 120min, and sintering atmosphere is inert atmosphere. . The refired brass was hot-extruded at 800 ° C. Samples of the tensile strength, hardness, density, friction test samples, and simulated working samples assembled with the shaft were taken from the extruded rod. The experimental results found that compared with 100% of the theoretical dense density (there are generally holes in powder metallurgy products, which cannot reach full density), the relative density is 99.7%, the tensile strength of the alloy is 428.0MPa, and the yield strength is 276.5MPa, The Brinell hardness is HB216.7, the friction coefficient is 0.151, and the amount of wear is 329.9μg. The simulation of the shaft and bearing assembly is completely normal, and there is no seizure.

Example 2-33 The compositional element mass fraction of the copper alloy raw material powder in all the examples of Example 2-33 is shown in Table 1, and the mass fraction of various powders when mixed is shown in Table 2, which corresponds to the process of manufacturing the copper alloy in the example. The parameters are shown in Table 3, and the properties of the copper alloy in the corresponding examples are shown in Table 4.

Table 1 Mass fraction of each element in the copper alloy raw material powder in all examples

Table 2 Mass fractions of various powders in all examples when mixed

Table 3 Manufacturing process parameters of copper alloys in all examples

Table 4 Properties of copper alloys in all examples

Claims (13)

1. A lead-free superhard self-lubricating copper alloy, characterized in that the mass fraction of each element in the copper alloy is:

   Copper 52.0% -85.0%;

   Manganese 4.0% -9.0%;

   1% -3% aluminum;

   Iron 1% -3%;

   Silicon 0.2% -0.8%;

   Nickel 0.2-0.6%;

   Sulfur 1.36% -4.07%;

   Except copper, iron, nickel, zinc, one or more of metals having an affinity for sulfur that is less than the affinity for manganese and sulfur, and the sum of the contents is ≤15.0%;

   The balance is zinc and inevitable impurities, and the lead in the impurities is ≤0.05%.
2. The copper alloy according to claim 1, wherein the metal having an affinity for sulfur that is less than the affinity for manganese and sulfur is cobalt, tin, tungsten, molybdenum, niobium, antimony, and bismuth.
3. The copper alloy according to claim 1 or 2, wherein the mass fraction of each element in the copper alloy is: copper 54.0% -72.0%; manganese 4.5% -8.0%; aluminum 1.2% -2.8%; iron 1.2% -2.8%; silicon 0.3% -0.8%; nickel 0.2% -0.5%; sulfur 1.50% -3.50%; other than copper, iron, nickel, zinc, the affinity of sulfur is less than that of manganese and sulfur , The sum of the contents is ≤15.0%; the balance is zinc and unavoidable impurities, and the lead in the impurities is ≤0.05%.
4. The copper alloy according to claim 1 or 2, characterized in that the mass fraction of each element in the copper alloy is: copper 56.0% -68.0%; manganese 5.0% -7.0%; aluminum 1.4% -2.6%; iron 1.4% -2.6%; silicon 0.3% -0.8%; nickel 0.3% -0.5%; sulfur 1.70% -3.00%; one or more of metals other than copper, iron, nickel, and zinc having an affinity for sulfur that is less than the affinity for manganese and sulfur , The sum of the contents is ≤15.0%; the balance is zinc and unavoidable impurities, and the lead in the impurities is ≤0.05%.
5. The copper alloy according to claim 1 or 2, wherein the mass fraction of each element in the copper alloy is: copper 58.0% -65.0%; manganese 5.0% -7.0%; aluminum 1.6% -2.4%; iron 1.6% -2.4%; silicon 0.3% -0.7%; nickel 0.3% -0.5%; sulfur 1.90% -2.80%; in addition to copper, iron, nickel, zinc, the affinity of sulfur is less than that of manganese and sulfur , The sum of the content is 1.0% -15.0%; the balance is zinc and unavoidable impurities, and the lead in the impurities is ≤0.05%.
6. The copper alloy according to claim 1 or 2, wherein the mass fraction of each element in the copper alloy is: copper 59.0% -62.0%; manganese 5.0% -7.0%; aluminum 1.7% -2.3%; iron 1.7% -2.3%; silicon 0.3% -0.7%; nickel 0.3% -0.5%; sulfur 2.10% -2.60%; except copper, iron, nickel, zinc, one or more of metals having an affinity for sulfur that is less than the affinity for manganese and sulfur Species, the sum of the content is 1.0% -15.0%; the balance is zinc and unavoidable impurities, and the lead in the impurities is ≤0.05%.
7. A method for manufacturing a copper alloy according to any one of claims 1-6, comprising the following steps:

   (1) Melt copper, nickel, copper-iron master alloy, manganese, silicon, zinc, and aluminum in sequence. After the alloying elements are homogenized, the copper alloy raw material powder is made by the atomization method;

   (2) Compounding copper alloy raw material powder with metal sulfide, and then adding 0.5% -1.5% of forming agent, mixing for 0.5-8h, so that the various powders are mixed uniformly; the affinity of metal and sulfur in the metal sulfide is less than that of manganese Affinity with sulfur;

   (3) pressing the uniformly mixed powder into a shape and then sintering, the sintering process is: starting from room temperature to a sintering temperature of 650-870 ° C, heating for 1-5h, holding for 30-300min, and the sintering atmosphere is a reducing atmosphere or an inert atmosphere;

   (4) The sintered copper alloy is heated to 300-800 ° C, and then heat-repressed with a pressure of 300-600 MPa after holding for 1-3 hours; and then re-fired, the re-fired process is: heating from room temperature to sintering temperature 800-870 ℃, heating for 1-16h, holding temperature for 30-300min, reburning atmosphere is reducing or inert atmosphere;

   (5) The hot-deformed copper alloy is thermally deformed, and the temperature of the thermal deformation is 650-870 degrees.
8. The manufacturing method according to claim 7, wherein the copper alloy raw material powder is prepared by a gas atomization method or a water atomization method.
9. The method according to claim 7, wherein the metal sulfide is a solid metal sulfide.
10. The method of claim 9, wherein the solid metal sulfide is selected from the group consisting of eleven metals including iron, cobalt, nickel, tin, tungsten, molybdenum, niobium, copper, zinc, antimony, and bismuth. Thing.
11. The manufacturing method according to claim 10, wherein the sulfides of the eleven metals are copper sulfide, cuprous sulfide, zinc sulfide, tin sulfide, nickel sulfide, iron sulfide, ferrous disulfide, and sulfide Ferrous, tungsten sulfide, cobalt sulfide, molybdenum disulfide, molybdenum trisulfide, antimony tetrasulfide, antimony pentasulfide, antimony trisulfide, bismuth trisulfide, niobium disulfide, and niobium trisulfide.
12. The manufacturing method according to claim 9, wherein the solid metal sulfide is copper sulfide, zinc sulfide, and iron sulfide.
13. The manufacturing method according to claim 7, wherein the thermal deformation is hot forging or hot extrusion.