A lead-free bimetallic bearing material prepared by arc deposition and its preparation method

Abstract

The present invention discloses a lead-free bimetallic bearing material prepared by arc deposition and a preparation method thereof, which comprises a steel substrate and a copper alloy layer deposited on the surface of the steel substrate. The composition of the copper alloy layer includes: Cu, Sn, Bi, Ni, P and Al. The weight percentages of each component are: 2.0-2.8 wt.% of Sn, 1.5-2.7 wt.% of Bi, 3-5 wt.% of Ni, 0.1-0.16 wt.% of P, 0.1-0.15 wt.% of Al, and the balance is Cu. Using an oxygen-free copper-nickel wire as the electrode for arc ignition in MIG welding and a Sn60Bi40 wire as the bypass wire feeding, alloying elements are added and uniformly mixed in the molten pool to form an arc deposition layer, thus obtaining the material. This material has no defects such as pores and cracks, the Bi phase particles are fine and uniform, and the mechanical and tribological properties are excellent.

Description

Technical Field

[0001] The present invention relates to bearing materials and their use methods, and particularly to a lead-free bimetallic bearing material prepared by arc deposition and its preparation method. Background Art

[0002] A bearing that works under sliding friction is called a sliding bearing. The part of the shaft supported by the bearing is called the journal, and the part that mates with the journal is called the bearing bush. In order to improve the friction properties of the bearing bush surface, the antifriction material layer cast on its inner surface is called the bearing lining. The materials of the bearing bush and the bearing lining are collectively referred to as sliding bearing materials. Generally, it is required that the bearing material has high load-bearing performance, good wear resistance, etc. However, it is difficult for a single material to meet the above requirements at the same time. Therefore, bearing materials are usually composed of two or more layers of materials. The outer layer mainly plays the role of high load-bearing and anti-deformation, and the inner layer close to the journal mainly plays the role of anti-wear and friction reduction.

[0003] Lead bronze is widely used in low-speed and heavy-load sliding friction components and is a Pb-containing self-lubricating material. However, due to the high toxicity of Pb and its compounds, the application of this self-lubricating bearing bush material with both Pb compliance and load-bearing properties is restricted. In recent years, some lead-free bimetallic bearing materials have also been developed, but they cannot replace traditional lead bronze alloys in terms of friction reduction, embedding, and compliance.

[0004] Element Bi has properties similar to those of Pb and is insoluble in copper. The microstructure of bismuth bronze is similar to that of lead bronze. For example, Chinese Patent: CN101474903B discloses a bismuth bronze-steel composite bimetallic bearing material, which is characterized by a layered structure. The base layer is a carbon steel material, and the surface layer is a bismuth bronze alloy. The bismuth bronze alloy is sintered on the surface of the carbon steel material. The chemical composition of the bismuth bronze alloy is calculated by weight percentage as follows: bismuth 1.0 - 12.0%, tin 3.0 - 13.0%, zinc 1.0 - 5.0%, copper 69.5 - 95.0%, and the total content of other impurities does not exceed 0.5%. However, there are defects such as relatively large Bi-phase particles, segregation at grain boundaries, and pores in the alloy layer in the bismuth bronze alloy prepared by powder sintering, which seriously affect the load-bearing performance and friction reduction performance of the bearing material. Summary of the Invention

[0005] Object of the Invention: The object of the present invention is to provide a lead-free bimetallic bearing material prepared by arc deposition.

[0006] Technical solution: The lead-free bimetallic bearing material prepared by arc deposition comprises a steel substrate and a copper alloy layer deposited on the surface of the steel substrate. The composition of the copper alloy layer includes: Cu, Sn, Bi, Ni, P, and Al. The weight percentages of each component are: 2.0 - 2.8 wt.% of Sn, 1.5 - 2.7 wt.% of Bi, 3 - 5 wt.% of Ni, 0.1 - 0.16 wt.% of P, 0.1 - 0.15 wt.% of Al, and the balance is Cu.

[0007] Furthermore, the steel substrate used is low-carbon steel with an aluminum coating on its surface.

[0008] Furthermore, the thickness of the aluminum coating is 20 μm.

[0009] The preparation method of the lead-free bimetallic bearing material prepared by arc deposition includes the following steps:

[0010] Step (1): Load an oxygen-free copper-nickel wire and an Sn60Bi40 welding wire into a CMT six-axis welding robot and an external adjustable wire feeding machine respectively.

[0011] Step (2): Clean the surface of the aluminum-coated low-carbon steel plate, and perform treatments such as degreasing and drying.

[0012] Step (3): Deposit a copper alloy layer on the steel plate surface through a single heat source dual wire feeding arc deposition system to prepare the bimetallic bearing material.

[0013] Furthermore, the process parameters for arc deposition in Step (3) are: current 70 A - 90 A, voltage 9.5 - 12.5 V, argon gas flow rate 9 - 15 L / min, swing amplitude 8 - 13 mm, additive manufacturing speed 6 - 10 cm / min, swing frequency 1 - 2 Hz, external wire feeding speed 2.7 - 27 mm / s, and the angle range between the external wire feeding gun head and the welding gun is 30° - 90°.

[0014] In the present invention, an oxygen-free copper-nickel wire is used as the electrode for arc ignition in MIG welding, and an Sn60Bi40 wire is used as the bypass wire feeding. Alloying elements are added and mixed evenly in the molten pool to form an arc deposition layer, thereby preparing a solid-liquid composite bimetallic bearing material. The heat input of the substrate, combined with the effect of Ni and Al elements in suppressing crack generation, can eliminate the crack problem.

[0015] Among them, an oxygen-free copper-nickel welding wire with a diameter of 1.2 mm is placed in a CMT six-axis welding robot, and a Sn60Bi40 welding wire with a diameter of 1.0 mm is placed in an externally placed wire feeding machine with adjustable speed; the wire feeding speed of the externally placed bypass wire feeding machine is divided into 0-9 gears, corresponding to wire feeding speeds of 2.7-27 mm / s; the wire feeding port of the externally placed wire feeder is connected to the welding gun head of the CMT six-axis welding robot through a deformable pipe; the angle range between the gun head of the externally placed wire feeder and the welding gun is 30° to 90°.

[0016] Further, in step (3), the parameters of the CMT six-axis welding robot are: current 70 A to 90 A, voltage 9.5 to 12.5 V, argon gas flow rate 9 to 15 L / min, swing amplitude 8 to 13 mm, additive speed 6 to 10 cm / min, swing frequency 1 to 2 Hz;

[0017] Further, in step (3), the angle between the gun head of the welding gun and the steel plate is 45° to 90°.

[0018] Further, the main elements of the finally prepared copper layer alloy are Cu, Sn, Bi, P and Al, and the weight percentages of each component are: 2.0 to 2.8 wt.% of Sn, 1.5 to 2.7 wt.% of Bi, 3 to 5 wt.% of Ni, 0.1 to 0.16 wt.% of P, 0.1 to 0.15 wt.% of Al, and the rest is Cu; further, the thickness of the copper layer alloy is 0.8 to 1.2 mm;

[0019] Further, in the finally prepared bimetallic bearing material, the steel plate used is a low-carbon steel with aluminized surface, and the thickness is 2.0 to 3.0 mm;

[0020] The inventive principle of the present invention: Research shows that when the mass fraction of Bi content in the copper alloy structure exceeds 5%, the Bi phase will segregate and grow at the grain boundaries of the copper alloy, cutting the matrix. At the same time, Bi and Sn elements are also harmful elements that cause cracks in the steel substrate during the bimetallic liquid-solid composite process, and their content must be controlled. However, insufficient Sn content will result in insufficient mechanical properties of the copper alloy. Ni and Cu can form an infinite solid solution, and the addition of Ni can improve the strength, hardness, corrosion resistance, and fatigue resistance of the copper alloy. A small amount of P element can improve the fluidity of the liquid copper alloy, which is helpful for better composite of the liquid copper alloy and the steel substrate. Al element is not only a beneficial element to prevent the liquid copper alloy from causing cracks in the steel plate but also can combine with oxygen element to form alumina, eliminating the porosity problem in the alloy layer. During the process of arc deposition liquid-solid bimetallic composite, in addition to the harmful elements in the liquid metal, the thermal effect of the arc itself is also the reason for the cracks in the steel substrate. By side-axis wire feeding, the heat input to the steel substrate during the arc deposition process can be reduced to a certain extent. Coupled with the crack-inhibiting effect of Ni and Al elements, the crack problem can be eliminated. Therefore, the present invention can prepare a lead-free bimetallic bearing material without defects such as pores and cracks, with fine and uniform Bi phase particles and excellent mechanical and tribological properties.

[0021] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0022] The lead-free bimetallic bearing material of the present invention has no defects such as pores and cracks, with fine and uniform Bi phase particles and excellent mechanical and tribological properties. It solves the problems of coarse Bi phase particles and segregation at the grain boundaries during the powder sintering of bismuth bronze. The present invention greatly improves the defects and deficiencies of the existing bismuth bronze alloy, and its comprehensive performance is comparable to that of traditional lead bronze. Description of the drawings

[0023] Figure 1 It is a schematic diagram of the arc deposition double wire feeding for preparing the lead-free bimetallic bearing material designed by the present invention;

[0024] Figure 2 It is the macroscopic morphology and cross-sectional metallographic structure diagram of the sample prepared by the present invention. Detailed implementation manners

[0025] Example 1:

[0026] Implementation purpose: To prepare a lead-free bismuth-containing bimetallic composite material with a total thickness of 3.3 - 3.7 mm, a length of 210 mm, a width of 25 mm, and a copper alloy layer thickness of 0.8 - 1.2 mm, and the wire feeding speed of the external adjustable wire feeding machine is at the 3rd gear.

[0027] Implementation steps:

[0028] (1) Load the copper-nickel alloy welding wire and Sn60Bi40 welding wire into the CMT six-axis welding robot and the external adjustable wire feeder respectively. Adjust the wire feeding speed of the external wire feeder to 3 gears.

[0029] (2) Use aluminized low-carbon steel plates with a thickness of 2 - 3 mm, a length of 220 mm, and a width of 70 mm. Clean the oil stains on the surface and perform drying treatment.

[0030] (3) After clamping and fixing the steel plate, deposit a copper alloy layer by arc deposition through a single heat source and double wire feeding system. The angle between the welding torch tip and the steel plate is 45°. The wire feeding speed of the external adjustable wire feeder is 3 gears. The angle between the copper-nickel welding wire and the Sn60Bi40 welding wire is 45°. The parameters of the CMT six-axis welding robot are: current 70A - 90A, voltage 9 - 12V, swing amplitude 8 - 13 mm, additive manufacturing speed 6 - 10 cm / min, swing frequency 1 - 2 Hz2.

[0031] (4) Use high-purity argon as the shielding gas, and the argon flow rate is 9 - 15 L / min to prevent the oxidation of the copper alloy layer during the arc deposition process.

[0032] After testing, the composition of the copper alloy layer of the bimetallic bearing material prepared in this case is 2.4 wt.% Sn, 1.5 wt.% Bi, 3.2 wt.% Ni, 0.14 wt.% P, 0.12 wt.% Al, and the rest is Cu. The thickness is 0.8 - 1.2 mm, the structure is uniform, and it meets the subsequent processing requirements; the tensile strength of the copper-steel bimetal is 299 Mpa, and the bonding strength of the bimetal is 257 Mpa; under a load of 10 N, the pin-on-disc tribological performance is tested for 10 min, and the average friction coefficient is 0.35, while the average friction coefficient of the lead bronze alloy with the same content under the same test conditions is 0.36.

[0033] Example 2:

[0034] Implementation purpose: Prepare a lead-free bismuth-containing bimetallic composite material with a total thickness of 3.3 - 3.7 mm, a length of 210 mm, a width of 25 mm, and a copper alloy layer thickness of 0.8 - 1.2 mm. The wire feeding speed of the external adjustable wire feeder is 6 gears.

[0035] Implementation steps:

[0036] (1) Load the oxygen-free copper-nickel alloy welding wire and Sn60Bi40 welding wire into the CMT six-axis welding robot and the external adjustable wire feeder respectively. Adjust the wire feeding speed of the external wire feeder to 6 gears.

[0037] (2) Use aluminized low-carbon steel plates with a thickness of 2 - 3 mm, a length of 220 mm, and a width of 70 mm. Clean the oil stains on the surface and perform drying treatment.

[0038] (3) After clamping and fixing the steel plate, an arc deposition copper alloy layer is carried out through a single heat source and double wire feeding arc deposition system. The angle between the welding torch tip and the steel plate is 45°. The wire feeding speed of the external adjustable wire feeding machine is at 6 gears. The angle between the copper-nickel alloy wire and the Sn60Bi40 wire is 45°. The parameters of the CMT six-axis welding robot are: current 70A - 90A, voltage 9.5 - 12.5V, swing amplitude 8 - 13mm, additive manufacturing speed 6 - 10cm / min, swing frequency 1 - 2Hz:

[0039] (4) High-purity argon is used as the shielding gas, and the argon gas flow rate is 9 - 15L / min to prevent the oxidation of the copper alloy layer during the arc deposition process.

[0040] After testing, the composition of the copper alloy layer of the bimetallic bearing material prepared in this case is 2.8wt.% Sn, 1.8wt.% Bi, 3.1wt.% Ni, 0.13wt.% P, 0.14wt.% Al, and the rest is Cu. The thickness is 0.8 - 1.2mm, and the structure is uniform, meeting the subsequent processing requirements; the tensile strength of the copper / steel bimetal is 246Mpa, and the bonding strength of the bimetal is 200Mpa; under a load of 10N, a reciprocating tribological performance test is carried out for 10min, and the average friction coefficient is 0.32.

Claims

1. A lead-free bimetallic bearing material deposited by arc, comprising a steel substrate and a copper alloy layer deposited on the surface of the steel substrate, characterized in that, the composition of the copper alloy layer includes: Cu, Sn, Bi, Ni, P and Al, and the weight percentages of each component are: 2.0 - 2.8 wt.% of Sn, 1.5 - 2.7 wt.% of Bi, 3 - 5 wt.% of Ni, 0.1 - 0.16 wt.% of P, 0.1 - 0.15 wt.% of Al, and the balance is Cu.

2. The lead-free bimetallic bearing material deposited by arc according to claim 1, characterized in that, the steel substrate used is low-carbon steel with an aluminum coating on the surface.

3. The lead-free bimetallic bearing material deposited by arc according to claim 2, characterized in that, the thickness of the aluminum coating is 20 μm.

4. The preparation method of the lead-free bimetallic bearing material deposited by arc according to claim 1, characterized in that, it includes the following steps: Step (1), respectively load an oxygen-free copper-nickel wire and a Sn60Bi40 welding wire into a CMT six-axis welding robot and an external adjustable wire feeding machine; Step (2), clean the surface of the aluminized low-carbon steel plate, and perform degreasing and drying treatments; Step (3), deposit a copper alloy layer on the steel plate surface through a single heat source double wire feeding arc deposition system to prepare a bimetallic bearing material.

5. The preparation method of the lead-free bimetallic bearing material deposited by arc according to claim 4, characterized in that, the process parameters of the arc deposition in Step (3) are: current 70A - 90A, voltage 9.5 - 12.5V, argon gas flow rate 9 - 15L / min, swing amplitude 8 - 13mm, additive manufacturing speed 6 - 10cm / min, swing frequency 1 - 2Hz, the external wire feeding speed is 3 - 6 gears, and the angle range between the external wire feeding gun head and the welding gun is 30° - 90°.

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