Bimetal sliding bearing and additive preparation method thereof

Abstract

The invention discloses a bimetallic sliding bearing and an additive preparation method thereof. The preparation method comprises the following steps: surfacing a welding wire A and a welding wire B on the surface of a steel substrate in a double-wire welding alternate arcing manner; during alternate arcing, the welding wire A is melted firstly, then the welding wire B is melted, the welding wire A and the welding wire B are arranged in an inclined and crossed mode, and the center lines of the two welding wires are focused on the same point of the surface of the steel base body; the welding wire A comprises any one of a pure tin wire, a tin-nickel alloy wire and a nickel-tin plated welding wire; and the welding wire B comprises a pure copper wire or a copper alloy wire. Two molten pools are mixed by controlling double-wire components, wire feeding angles and welding parameters, so that in-situ synthesis of high-tin bronze is realized, and the problem that the high-tin bronze welding wire is difficult to prepare is solved; an iron-tin phase formed by the tin-melting welding wire firstly can effectively prevent liquid copper from permeating into a carbon steel substrate, and permeation cracks can be reduced or avoided; and a variable polarity technology is introduced, so that the heat input of a matrix is greatly reduced, the propagation of permeation cracks is inhibited, and the bonding strength of heterogeneous additive materials is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing, and more particularly, to a bimetallic sliding bearing and an additive manufacturing method thereof. Background Art

[0002] Under the background of the "dual carbon" strategy, wind turbines are developing towards larger size and offshore. However, traditional rolling bearings face problems such as insufficient load-bearing capacity and high failure rate, and it has become an inevitable trend to replace rolling with sliding in bearings. Bimetallic sliding bearings are more suitable for the working conditions of high load and large impact of wind power equipment due to their advantages of high load-bearing capacity, low cost, and less maintenance. High-tin bronze alloy, with a relatively high tin content, high strength, small friction coefficient, and self-lubricating effect, is an ideal material for sliding bearings. At present, methods such as powder sintering, laser cladding, and composite casting and rolling are often used to prepare copper / steel bimetallic sliding bearings. However, the bearings prepared by such methods have problems such as low density, poor bonding strength, small specific pressure, many defects, and low preparation efficiency.

[0003] As an advanced near-net shaping technology, arc additive manufacturing is the key technology for manufacturing bimetallic bearings and can solve many deficiencies of the above processes. In the process of arc additive manufacturing, welding wires are usually required. However, when the Sn content in high-tin bronze is greater than 10%, brittle intermetallic compounds, such as Cu6Sn5 phase, are easily generated during solidification, which will significantly reduce the toughness and ductility of the material, and it is easy to crack during cold rolling or wire drawing, resulting in high processing difficulty and cost of alloy wires. In addition, during the arc additive manufacturing process of tin bronze, liquid copper is likely to penetrate into the carbon steel matrix, forming penetration cracks, causing a decrease in bonding strength and the problem of liquid-phase penetration embrittlement, which restricts the wide promotion of copper / steel bimetals in sliding bearings.

[0004] CN 119144953A discloses a method for preparing a composite coating of a bimetallic sliding bearing. First, nickel-based alloy powder is additively manufactured onto the surface of a steel matrix by laser cladding to suppress the generation of crack defects through a gradient transition of the bottom layer and improve the bonding strength between interfaces. Then, the cladding layer is polished smooth, and copper alloy powder is cladded onto the nickel-based alloy surface to obtain a sliding bearing with a composite coating. However, the method of using a deposited transition layer as a primer has a cumbersome process and low preparation efficiency.

[0005] In view of this, the present invention is specifically proposed. Summary of the Invention

[0006] The first object of the present invention is to provide an additive manufacturing method for a bimetallic sliding bearing. The method uses the alternating arc starting method of twin-wire welding for surfacing, controls the wire composition and wire feeding angle to mix the two molten pools, realizes the in-situ synthesis of high-tin bronze, and solves the problem of difficult preparation of high-tin bronze welding wires. At the same time, by controlling the arc starting sequence, the tin wire is melted first and then the copper wire, and the FeSn2 intermetallic compound formed first can effectively block the infiltration of liquid copper into the carbon steel substrate, reducing or avoiding the generation of penetration cracks. By introducing the variable polarity technology, the polarity of a single wire is continuously switched, and the polarities between the two wires are always opposite, effectively reducing the heat input to the substrate, suppressing the generation of penetration cracks, and improving the bonding strength.

[0007] The second object of the present invention is to provide a bimetallic sliding bearing prepared by using the above-mentioned additive manufacturing method for a bimetallic sliding bearing.

[0008] In order to achieve the above objects of the present invention, the following technical solutions are specifically adopted:

[0009] An additive manufacturing method for a bimetallic sliding bearing includes the following steps:

[0010] Using the alternating arc starting method of twin-wire welding, the A wire and the B wire are surfacing welded onto the surface of the steel substrate; when alternating arc starting, the A wire is melted first and then the B wire, and the A wire and the B wire are arranged in an inclined cross pattern, so that the center lines of the two wires focus on the same point on the surface of the steel substrate; wherein, the A wire includes any one of pure tin wire, tin-nickel alloy wire, and nickel-plated tin welding wire; the B wire includes pure copper wire or copper alloy wire.

[0011] Preferably, the alternating current variable polarity CMT welding process is used for the surfacing welding, the welding of the A wire and the B wire is carried out by two welding machines respectively, and the polarities of the two welding machines are opposite.

[0012] Preferably, the phase difference of the welding frequencies of the A wire and the B wire is 180 degrees.

[0013] Preferably, the copper alloy wire includes any one of copper-nickel alloy wire, copper-tin alloy wire, and copper-tin-nickel alloy wire, and the Sn content in the copper alloy wire is 0-5wt%.

[0014] Preferably, the copper alloy wire is copper-nickel alloy wire or copper-tin-nickel alloy wire, and by mass percentage, it includes 0-5% of Sn, 1.5%-2.5% of Ni, and the balance of copper.

[0015] Preferably, the included angle between the A wire and the B wire is 5-30 degrees.

[0016] Preferably, the wire diameter of the A wire is 0.5-0.8mm, and the wire feeding speed is 5-10m / min.

[0017] Preferably, the wire diameter of the B wire is 1.4 - 1.8 mm, and the wire feeding speed is 5 - 10 m / min.

[0018] Preferably, the welding current of the A wire is 50 - 70 A, and the welding voltage is 5 - 7 V.

[0019] Preferably, the welding current of the B wire is 150 - 170 A, and the welding voltage is 15 - 17 V.

[0020] Preferably, before the surfacing, it further includes the steps of cleaning and drying the surface of the steel substrate.

[0021] Preferably, the welding equipment used in the additive manufacturing method includes two welding machines, two independent wire feeding systems, and two welding tips. The two welding machines are respectively connected to the two wire feeding systems and the two welding tips. The two wire feeding systems and the two welding tips are arranged in the same welding torch, and the center lines of the two welding tips are distributed in an inclined cross pattern. The welding torch includes a gas nozzle.

[0022] A bimetallic sliding bearing is prepared by using the additive manufacturing method of the bimetallic sliding bearing according to any one of the foregoing embodiments.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] The present invention uses the method of alternating arc starting with double - wire welding to surfacing the tin wire and copper wire on the surface of the steel substrate. The two wires are arranged at a certain angle, and the center lines focus on the same point on the surface of the steel substrate to achieve uniform mixing of the front and rear two molten pools, and in - situ form a high - tin bronze coating, solving the problem of difficult processing of high - tin bronze wire. At the same time, the arc starting sequence is controlled, first melting the A wire and then melting the B wire. The FeSn2 intermetallic compound formed first on the surface of the steel substrate can effectively block the infiltration of liquid copper into the steel substrate, reduce or avoid the generation of penetration cracks, and improve the bonding strength. The present invention adopts the AC variable - polarity CMT welding process, reduces the welding heat input to the substrate, avoids the expansion of penetration cracks, and further improves the bonding strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0026] Figure 1 It is a schematic diagram of the arrangement of the two wires during the double - wire welding process of the present invention;

[0027] Figure 2 Schematic diagram of the welding voltage-time curve for the twin-wire welding of the present invention;

[0028] Figure 3 Schematic diagrams of the metallographic structures of the comparative example and the examples; among them, (a) is the metallographic structure diagram of Comparative Example 1, (b) is the metallographic structure diagram of Example 2, and (c) is the metallographic structure diagram of Example 1. Detailed implementation manners

[0029] The technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific implementation manners. However, those skilled in the art will understand that the following described embodiments are some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention. For those conditions not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0030] The first aspect of the present invention provides a method for additive manufacturing of a bimetallic sliding bearing, including the following steps:

[0031] Using the method of alternating arc starting for twin-wire welding, the A wire and the B wire are surfacing welded onto the surface of the steel substrate; when alternating arc starting, the A wire is melted first and then the B wire, and the A wire and the B wire are arranged in an inclined cross pattern, so that the center lines of the two wires focus on the same point on the surface of the steel substrate; among them, the A wire includes any one of pure tin wire, tin-nickel alloy wire, and nickel-plated tin wire; the B wire includes pure copper wire or copper alloy wire.

[0032] As wind turbines move towards 20 MW and above 30 MW, higher requirements are put forward for the load-bearing capacity, antifriction property, and fatigue resistance of sliding bearings. High-tin bronze (such as CuSn12Ni2, CuSn16) combines high load-bearing capacity and antifriction characteristics and is an ideal shaft lining material for wind turbine gearboxes. However, brittle second phases are likely to be generated between grains, making it extremely difficult for it to undergo plastic deformation. For example, when the Sn content in high-tin bronze is greater than 10%, brittle intermetallic compounds are likely to be generated during solidification, such as the Cu6Sn5 phase, which will significantly reduce the toughness and ductility of the material and is prone to cracking during cold rolling or wire drawing, resulting in high processing difficulty and cost of high-tin bronze wire and restricting its application. And when tin bronze is subjected to arc additive manufacturing, liquid copper is likely to penetrate into the steel substrate, forming penetration cracks, resulting in a reduction in joint strength.

[0033] To solve the above problems, the present invention adopts double-wire molten pool hybrid welding to achieve in-situ synthesis of components. By arranging the tin wire (A wire) and the copper wire (B wire) at a certain angle, their centerlines are focused on the same point on the surface of the steel substrate, and arc starting is alternated for surfacing to achieve uniform mixing of the front and rear molten pools (as Figure 1 shown), and a high-tin bronze coating is formed in-situ, solving the problem of difficult processing of high-tin bronze welding wires. By controlling the arc starting sequence, first melt the tin wire to form a thin layer of iron-tin phase on the substrate surface first, and then melt the copper wire. Under the action of the arc force and heat input, the front and rear molten pools are mixed. The previously formed iron-tin phase can effectively block the infiltration of liquid copper into the carbon steel substrate and generate cracks, solving the problem of embrittlement caused by copper liquid phase infiltration, improving the bonding strength, and the prepared sliding bearing can meet the application requirements of high-power wind turbines.

[0034] In the present invention, if the two welding wires are arranged in parallel, molten pool mixing cannot be achieved, and the formed coating is not a high-tin bronze coating with uniform composition, but an alternating arrangement of two alloys, unable to achieve the purpose of in-situ synthesis of high-tin bronze alloy. Moreover, the copper alloy part is also directly surfacing welded to the surface of the steel substrate, and liquid-phase copper will still penetrate into the steel substrate to generate penetration cracks; only when the two welding wires are arranged in an inclined and crossed manner and their centerlines are focused on the same point on the surface of the steel substrate can molten pool mixing be achieved. And during surfacing, only when wire A acts first and wire B acts later can the generation of penetration cracks be reduced or avoided. Therefore, the arrangement method and arc starting sequence of wire A and wire B are the key factors affecting the performance of the bearing.

[0035] In some specific embodiments of the present invention, an alternating polarity CMT welding process is adopted for surfacing. Among them, the welding of wire A and wire B is carried out by two welding machines respectively, and the polarities of the two welding machines are opposite. As Figure 2 shown, the present invention adopts an alternating polarity welding process. In the short-circuit stage of CMT welding, by using the characteristic that the current is almost 0 at the moment of short circuit, through system control, the polarity switching of the positive and negative poles is realized. By periodically switching the current polarity, precise control of heat input is achieved. For example, when the welding wire is the negative pole and the workpiece is the positive pole, the electrons generated after the arc ionization will act on the substrate under the action of voltage, and the heat is concentrated on the surface of the workpiece, which is beneficial to increasing the penetration depth; when the welding wire is the positive pole and the workpiece is the negative pole, the arc energy is concentrated on the welding wire, reducing the heat input to the base material and improving the melting efficiency; in the present invention, the two welding machines always maintain opposite polarities and complete the polarity exchange of the positive and negative poles at the moment of short circuit; the present invention adopts an alternating polarity technology, and both wires achieve the alternating change of the positive and negative poles within the short-circuit cycle, reducing the heat accumulation of the carbon steel substrate, further blocking the expansion of penetration cracks, improving the bonding strength, and improving the load-bearing capacity of the sliding bearing.

[0036] In some specific embodiments of the present invention, the welding frequency phase difference between welding wire A and welding wire B is 180 degrees. When the pulse current frequency phase difference between the two welding wires in double-wire welding is 180 degrees, it means that the current waveforms of the two differ by half a cycle on the time axis, that is, they are in an "anti-phase" state. For example, welding wire A melts the welding wire and forms a molten droplet at the pulse peak stage, and welding wire B is in the base current stage at the same time, and the welding wire is retracted to prepare for the next transition. In this state, the molten droplet transition, energy release and other processes of the two arcs are performed alternately to avoid the simultaneous generation of high heat or current superposition. The two welding machines of the present invention are digitally controlled to make the welding frequency phase difference of 180 degrees, and a stable welding process is achieved by staggering the current peaks.

[0037] In some specific embodiments of the present invention, the copper alloy wire used includes any one of copper-nickel alloy wire, copper-tin alloy wire, and copper-tin-nickel alloy wire. The Sn content in the copper alloy wire is 0-5wt%. For example, it can be any point value among 0, 1%, 2%, 3%, 4%, and 5%, or a range value composed of any two point values; the copper alloy may contain a small amount of Sn, but a Sn content higher than 10% will form a brittle phase, resulting in increased brittleness of the wire and increased processing difficulty. Therefore, the Sn content in the copper alloy wire needs to be reasonably controlled.

[0038] In some specific embodiments of the present invention, the copper alloy wire is a copper-nickel alloy wire or a copper-tin-nickel alloy wire, which, by mass percentage, includes 0-5% Sn, 1.5%-2.5% Ni and the remainder copper. For example, the mass percentage of Sn can be any point value among 0, 1%, 3%, 5%, or a range value consisting of any two point values; the mass percentage of Ni can be any point value among 1.5%, 1.8%, 2%, 2.2%, 2.5%, or a range value consisting of any two point values.

[0039] In some specific embodiments of the present invention, the angle between the center lines of welding wire A and welding wire B is 5-30 degrees, for example, it can be any point value among 5 degrees, 10 degrees, 15 degrees, 20 degrees, 25 degrees, 30 degrees or a range value consisting of any two point values. During welding, the distance between the workpiece and the conductive nozzle is usually 16-25 mm. The angle of the two welding wires is set between 5-30 degrees. When the distance between the steel substrate to be welded and the conductive nozzle is appropriate, the center lines of the two welding wires can intersect at the same point on the steel substrate to be welded, so as to achieve molten pool mixing.

[0040] In some specific embodiments of the present invention, the wire diameter of wire A is 0.5 - 0.8 mm. For example, it can be any point value among 0.5 mm, 0.55 mm, 0.6 mm, 0.65 mm, 0.7 mm, 0.75 mm, 0.8 mm or a range value composed of any two point values; the wire feeding speed is 5 - 10 m / min. For example, it can be any point value among 5 m / min, 6 m / min, 7 m / min, 8 m / min, 9 m / min, 10 m / min or a range value composed of any two point values.

[0041] In some specific embodiments of the present invention, the wire diameter of wire B is 1.4 - 1.8 mm. For example, it can be any point value among 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm or a range value composed of any two point values; the wire feeding speed is 5 - 10 m / min. For example, it can be any point value among 5 m / min, 6 m / min, 7 m / min, 8 m / min, 9 m / min, 10 m / min or a range value composed of any two point values.

[0042] By adjusting the composition, wire diameter and wire feeding speed of wire A and wire B, the composition of the in-situ formed high-tin bronze alloy coating is further regulated.

[0043] In some specific embodiments of the present invention, the welding current of wire A is 50 - 70 A. For example, it can be any point value among 50 A, 55 A, 60 A, 65 A, 70 A or a range value composed of any two point values; the welding voltage is 5 - 7 V. For example, it can be any point value among 5 V, 5.5 V, 6 V, 6.5 V, 7 V or a range value composed of any two point values.

[0044] In some specific embodiments of the present invention, the welding current of wire B is 150 - 170 A. For example, it can be any point value among 150 A, 155 A, 160 A, 165 A, 170 A or a range value composed of any two point values; the welding voltage is 15 - 17 V. For example, it can be any point value among 15 V, 15.5 V, 16 V, 16.5 V, 17 V or a range value composed of any two point values.

[0045] First, the low-melting-point tin wire is surfacing welded to the surface of the steel substrate with low current parameters, and the first formed FeSn2 intermetallic compound can effectively block the infiltration of liquid copper; then the copper wire is surfacing welded with high current parameters. Under the action of the arc force and heat input, the front and rear molten pools are mixed to prepare a high-tin bronze coating. This method can achieve uniform mixing of the front and rear molten pools through double-wire welding, avoiding the penetration of liquid copper into the carbon steel substrate and generating cracks. The introduction of the phase difference and variable polarity technology of the double wires can prevent crack propagation and at the same time solve the technical problem of difficult preparation of high-tin bronze.

[0046] In some specific embodiments of the present invention, before surfacing welding, it further includes the steps of cleaning and drying the surface of the steel substrate, aiming to remove oil and rust on the surface of the steel substrate.

[0047] In some specific embodiments of the present invention, the welding equipment used in the additive manufacturing method includes two welding machines, two independent wire feeding systems, and two welding tips. The two welding machines are respectively connected to the two wire feeding systems and the two welding tips. The two wire feeding systems and the two welding tips are arranged in the same welding torch, and the center lines of the two welding tips are distributed in an inclined cross pattern. The welding torch used includes a gas nozzle. During operation, the A wire and the B wire are respectively fed into the two welding tips through the two wire feeding systems. The welding is carried out by the two welding machines respectively, with alternate arc starting. The A wire acts first, and then the B wire acts to achieve molten pool mixing. The first-formed iron-tin phase can prevent the liquid-phase copper from penetrating into the steel substrate, reducing or avoiding the generation of penetration cracks.

[0048] In some specific embodiments of the present invention, the included angle between the center lines of the two welding tips is 5 - 30 degrees, aiming to make the center lines of the two wires focus on the same point on the surface of the steel substrate to be welded, and at the same time ensure that the distance between the welding tip and the surface of the steel substrate to be welded is appropriate.

[0049] The second aspect of the present invention provides a bimetallic sliding bearing, which is prepared by using the additive manufacturing method of the bimetallic sliding bearing described in any one of the foregoing embodiments; it includes a steel substrate and a high-tin bronze alloy coating on the surface of the steel substrate. As an example, by mass percentage, the composition of the high-tin bronze alloy coating includes 10% - 16% of Sn, 0 - 3% of Ni, and the balance of copper. The bimetallic sliding bearing provided by the present invention has few cracks, small crack sizes (<10 μm), high bonding strength (not less than 390 MPa), and large load-bearing capacity.

[0050] The following combines specific application examples to make a detailed description of some embodiments of the present invention. The raw material substances used in the examples can be obtained through commercial purchase without special instructions.

[0051] Example 1

[0052] The surface of the low-carbon steel substrate is polished and cleaned, and degreasing, rust removal, and drying treatments are carried out;

[0053] A pure tin wire is used as the A wire, with a wire diameter of 0.5 mm;

[0054] A copper alloy wire is used as the B wire. By mass percentage, the composition is 2.0% of Ni, 5.0% of Sn, and the balance of copper, with a wire diameter of 1.6 mm;

[0055] The A welding wire and the B welding wire are respectively fed by two wire feeding devices. The welding parameters of the A welding wire are: CMT welding mode, wire feeding speed of 7 m / min, welding current of 60 A, and welding voltage of 6 V; the welding parameters of the B welding wire are: CMT welding mode, wire feeding speed of 7 m / min, welding current of 160 A, and welding voltage of 16 V. The CMT additive manufacturing technology with alternating current variable polarity is adopted. The two welding machines always maintain opposite polarities and complete the positive and negative polarity exchange at the moment of short circuit, reducing the heat input during welding. The welding frequencies of the two welding machines have a phase difference of 180 degrees, and the center lines of the two welding nozzles are arranged at an angle of 15°. They act alternately. During the surfacing process, the A welding wire acts first, and then the B welding wire acts (that is, the A welding wire is melted first and then the B welding wire), realizing the uniform mixing of the molten pool and in-situ forming a CuSn12Ni2 high-tin bronze coating.

[0056] Example 2

[0057] Example 2 is similar to Example 1, with the only difference being that when surfacing with the A welding wire and the B welding wire, the non-variable polarity CMT technology is used for additive manufacturing. The polarities of the two welding machines are the same, both with the welding wire as the negative pole and the carbon steel substrate as the positive pole. The other conditions are the same as those in Example 1.

[0058] Comparative Example 1

[0059] The surface of the low-carbon steel substrate is polished and cleaned, and degreasing, rust removal, and drying treatments are carried out.

[0060] The A welding wire and the B welding wire used are the same as those in Example 1.

[0061] During welding, the A welding wire and the B welding wire are respectively fed by two wire feeding devices. The welding parameters of the A welding wire are: CMT welding mode, wire feeding speed of 7 m / min, welding current of 60 A, and welding voltage of 6 V; the welding parameters of the wire B are: CMT welding mode, wire feeding speed of 7 m / min, welding current of 160 A, and welding voltage of 16 V. The welding frequencies of the two welding machines have a phase difference of 180 degrees, and the two welding nozzles are arranged in parallel, and the distance between the center lines of the two welding nozzles is 10 mm. They act alternately to realize the side-by-side arrangement of the A welding wire and the B welding wire. The non-variable polarity CMT technology is used for additive manufacturing, and the polarities of the two welding machines are the same, both with the welding wire as the negative pole and the carbon steel substrate as the positive pole.

[0062] Comparative Example 2

[0063] Comparative Example 2 is similar to Example 1, with the only difference being that when surfacing by alternately starting the arc, the B welding wire is melted first and then the A welding wire. The other conditions are the same as those in Example 1.

[0064] Test Example

[0065] The bonding strength between the high tin bronze coating and the carbon steel substrate in each embodiment and each comparative example was tested according to ISO 4386-2-2012-2 "Bearing metal layer thickness greater than or equal to 2 mm bond destructive test", and the size of the penetration crack was observed through the metallographic image. The test results are shown in Table 1.

[0066] Table 1

[0067] Crack size Bonding strength Example 1 < 10μm 420 MPa Example 2 10 - 30μm 390 MPa Comparative Example 1 > 50μm 120 MPa Comparative Example 2 > 40μm 340 MPa

[0068] It can be seen from the data in Table 1 that when welding in the manner of Comparative Example 1, the two conductive nozzles are arranged in parallel and act alternately to achieve the parallel arrangement of welding wire A and welding wire B. In this case, the two molten pools cannot be fused, and the penetration cracks of the copper alloy cannot be avoided. Therefore, the crack size is relatively large, above 50 μm. In the bonding strength test, due to the low strength of the babbitt alloy and the carbon steel matrix, the overall bonding strength of the bushing is low, about 120 MPa.

[0069] When welding in the manner of Example 1, the center lines of the two conductive nozzles are arranged at an angle of 15° and act alternately. During the surfacing process, the A welding wire acts first, and then the B welding wire acts, so as to achieve uniform mixing of the molten pool and form a high-tin bronze CuSn12Ni2 coating in situ. The FeSn phase formed first blocks the expansion of liquid copper to the carbon steel matrix, and the variable polarity technology reduces the heat input of the carbon steel matrix, further inhibiting the expansion of the penetration crack. Therefore, the size of its penetration crack is small, all <10μm, and the bonding strength is about 420MPa.

[0070] The difference between Example 2 and Example 1 is that the polarity change technology is not used, the heat input of the matrix is higher, and the penetration crack is more likely to expand along the carbon steel grain boundary under high temperature. Therefore, the crack size is about 30 μm and the bonding strength is about 390 MPa.

[0071] The difference between Comparative Example 2 and Example 1 is that the welding wire B is first added, and the liquid copper directly reacts with the carbon steel matrix. Although the in-situ synthesis of high-tin bronze can be achieved, penetration cracks cannot be avoided. The crack size is about 40 μm, and the bonding strength is about 340 MPa.

[0072] Figure 3Metallographic structure diagrams of the coatings in Examples 1-2 and Comparative Example 1, where (a) is the metallographic structure diagram of Comparative Example 1. Since welding wire A and welding wire B are arranged side by side in parallel, both double welding wires directly act on the carbon steel substrate. When tin bronze directly acts on the carbon steel substrate, liquid copper infiltrates into the interior of the carbon steel substrate, forming penetration cracks. Under the action of positive electrode heat accumulation, the penetration cracks further expand, and their crack size is relatively large, more than 50 μm. (b) is the metallographic structure diagram of Example 2. Since welding wire A acts on the surface of the carbon steel substrate first, forming a FeSn phase with the carbon steel substrate, blocking the infiltration of liquid copper into the substrate. However, due to excessive heat input to the substrate, the expansion of penetration cracks is caused, and the crack size is about 20 μm. (c) is the metallographic structure diagram of Example 1. Since welding wire A acts on the surface of the carbon steel substrate first, forming a FeSn phase with the carbon steel substrate, blocking the infiltration of liquid copper into the substrate. At the same time, the variable polarity technology is adopted to reduce the heat accumulation of the carbon steel substrate, and its cracks are controlled, and the crack size is below 10 μm.

[0073] Although the present invention has been illustrated and described with reference to specific embodiments, it should be appreciated that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Those of ordinary skill in the art should understand that: without departing from the spirit and scope of the present invention, the technical solutions described in the foregoing embodiments may be modified, or some or all of the technical features may be equivalently replaced; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. An additive manufacturing method for a bimetallic sliding bearing, characterized in that, It includes the following steps: The A welding wire and the B welding wire are surfacing welded onto the surface of the steel substrate in an alternating arc starting manner of double-wire welding; when alternating arc starting, the A welding wire is melted first and then the B welding wire, and the A welding wire and the B welding wire are arranged in an inclined cross pattern, so that the center lines of the two welding wires focus on the same point on the surface of the steel substrate; wherein, the A welding wire includes any one of pure tin wire, tin-nickel alloy wire, and nickel-plated tin welding wire; the B welding wire includes pure copper wire or copper alloy wire.

2. The additive manufacturing method of the bimetallic sliding bearing according to claim 1, characterized in that, The surfacing welding is carried out by using an alternating current variable polarity CMT welding process. The welding of the A welding wire and the B welding wire is carried out by two welding machines respectively, and the polarities of the two welding machines are opposite.

3. The additive manufacturing method of the bimetallic sliding bearing according to claim 1, characterized in that, The phase difference of the welding frequencies of the A welding wire and the B welding wire is 180 degrees.

4. The additive manufacturing method of the bimetallic sliding bearing according to claim 1, characterized in that, The copper alloy wire includes any one of copper-nickel alloy wire, copper-tin alloy wire, and copper-tin-nickel alloy wire, and the Sn content in the copper alloy wire is 0-5wt%.

5. The additive manufacturing method of the bimetallic sliding bearing according to claim 4, characterized in that, The copper alloy wire is copper-nickel alloy wire or copper-tin-nickel alloy wire, and by mass percentage, it includes 0-5% of Sn, 1.5%-2.5% of Ni, and the balance of copper.

6. The additive manufacturing method of the bimetallic sliding bearing according to claim 1, characterized in that, The included angle between the A welding wire and the B welding wire is 5-30 degrees.

7. The additive manufacturing method of the bimetallic sliding bearing according to claim 1, characterized in that, It satisfies at least one of the following characteristics: (1) The wire diameter of the A welding wire is 0.5-0.8mm, and the wire feeding speed is 5-10m / min; (2) The wire diameter of the B welding wire is 1.4-1.8mm, and the wire feeding speed is 5-10m / min; (3) The welding current of the A welding wire is 50-70A, and the welding voltage is 5-7V; (4) The welding current of the B welding wire is 150-170A, and the welding voltage is 15-17V.

8. The additive manufacturing method of the bimetallic sliding bearing according to claim 1, characterized in that Before the surfacing welding, it also includes the steps of cleaning and drying the surface of the steel substrate.

9. The additive manufacturing method of the bimetallic sliding bearing according to claim 1, characterized in that, The welding equipment used in the additive manufacturing method includes two welding machines, two independent wire feeding systems, and two welding tips. The two welding machines are respectively connected to the two wire feeding systems and the two welding tips. The two wire feeding systems and the two welding tips are arranged in the same welding torch, and the center lines of the two welding tips are distributed in an inclined cross pattern. The welding torch includes a gas nozzle.

10. A bimetallic sliding bearing, characterized in that, It is prepared by using the additive manufacturing method of the bimetallic sliding bearing according to any one of claims 1-9.

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