Ultrahigh-speed laser cladding coating preparation method of oversized oil cylinder piston rod

Abstract

The invention discloses a preparation method of an ultra-high-speed laser cladding coating of an ultra-large oil cylinder piston rod, which is characterized by comprising the following steps in sequence: (1) machining before cladding: clamping the piston rod on a turning and grinding integrated bed, supporting a rod body by using a roller bracket, and carrying out segmented rough turning and finish turning on an outer circle by taking the roller bracket as an interval; (2) ultra-high-speed laser cladding: replacing an ultra-high-speed laser cladding head for a tool rest, carrying out ultra-high-speed laser cladding in sections by taking a roller bracket as an interval, and seamlessly overlapping multiple sections of cladding layers; and (3) finish machining after cladding: starting a grinding tool rest, replacing a bearing bush bracket, grinding a coating layer in a segmented manner to the final finished product size, and polishing an outer round through body. By means of the method, the coating with the uniform thickness can be obtained on the surface of the oversized part, and a series of problems such as long process flow, insufficient follow-up machining allowance, stress cracking, powder rebounding and splashing and powder blocking of a cladding head are effectively solved.

Description

Technical Field

[0001] The invention relates to the technical field of surface engineering, and in particular to a method for preparing an ultra-high-speed laser cladding coating of an ultra-large oil cylinder piston rod. Background Art

[0002] Ultra-large hydraulic cylinders are key core components in offshore equipment, construction machinery and other fields. Especially under high-salt and high-humidity marine working conditions, the cylinder piston rod is in a corrosive environment for a long time, and the surface is frequently subjected to reciprocating friction, which places extremely high demands on wear resistance and corrosion resistance. The performance of the surface coating directly determines the service life and reliability of the cylinder.

[0003] The traditional coating preparation process has certain limitations: the electroplating process produces pollution, the coating is easy to peel off, and it is difficult to build an extra-large electroplating pool, which cannot be used for the preparation of surface coatings for extra-large cylinder piston rods; the thermal spraying process coating has pores, weak corrosion resistance, and is prone to peeling and cracking, and the cost is high; traditional laser cladding technology has low working efficiency, and excessive heat input will cause problems such as reduced local corrosion resistance of the coating and deformation of the substrate.

[0004] Ultra-high-speed laser cladding technology has the advantages of high efficiency, low cost, small heat-affected zone, and low coating dilution rate. It is particularly suitable for the preparation of surface coatings on rotating parts. However, the technology is currently limited to the application of small and medium-sized parts, such as coal machine hydraulic supports and oil plunger pumps. Oversized parts will also cause key problems such as precision tolerances, stress cracking, and long-term working stability. Summary of the invention

[0005] The present invention provides a method for preparing ultra-high-speed laser cladding coatings for an ultra-large oil cylinder piston rod, which effectively solves the following problems: a. The dimensional tolerance of large-sized parts is large. If the coating thickness is uneven, the coating is prone to wear through, bottom exposure, or lack of light during subsequent machining; b. The rod body is long and needs to be overlapped in sections for multiple times. The laser heat accumulation is large, and cracks are prone to occur if the control is improper; c. The cladding time is long, and the cladding head has the risk of powder blockage and ablation.

[0006] The present invention is achieved through the following technical solutions:

[0007] The present invention provides a method for preparing an ultra-high-speed laser cladding coating of an ultra-large oil cylinder piston rod, which is characterized by comprising the following sequential steps:

[0008] (1) Machining before cladding:

[0009] a) Clamp the piston rod on the turning and grinding machine, with one end clamped by a four-jaw chuck and the other end tightened by a top, and the rod body supported by multiple roller brackets arranged at intervals of 3 to 5 meters;

[0010] b) Adopt a segmented machining strategy. First, perform rough turning between the support areas of the roller brackets to make the surface roughness Ra of the outer circle ≤ 12.5 μm;

[0011] c) After moving the roller brackets to the machined area, perform supplementary turning on the original support areas;

[0012] d) Repeat the above segmented machining process for finish turning, and finally make the surface roughness Ra of the entire outer circle ≤ 3.2 μm;

[0013] (2) Ultra-high-speed laser cladding:

[0014] a) Install an ultra-high-speed laser cladding head, and adjust the position of the nozzle so that the perpendicular distance L from the powder convergence point to the outer circle tangent of the workpiece is 10 - 15 mm, and the perpendicular distance H from the outer circle radial normal is H = sinθ·(L + R), where R is the outer circle radius and θ = 5° - 12°;

[0015] b) Perform degreasing and dust removal treatment on the surface;

[0016] c) Use a high-frequency induction preheating device to preheat the starting position of the cladding, and control the surface temperature of the workpiece ≥ 100°C;

[0017] d) Adopt a segmented cladding process to perform ultra-high-speed laser cladding between the support areas of the roller brackets. The process parameters include: laser power 4 - 6 kW, spot diameter 2.5 - 3.8 mm, and the linear speed of workpiece rotation 12 - 20 m / min;

[0018] e) Perform segmented finish turning on the cladding layer, and machine a 30 - 40° transition chamfer at the end of the cladding layer;

[0019] f) After moving the roller brackets, perform supplementary cladding on the original support areas, and achieve seamless lap joint of the new and old cladding layers through power gradient control;

[0020] (3) Finish machining after cladding:

[0021] a) Adopt a grinding process to remove the coating allowance at the support parts in regions;

[0022] b) Perform overall polishing treatment to obtain a finished product with a surface hardness of 580 - 650 HV and a corrosion resistance reaching the 9th level of 4200 h neutral salt spray.

[0023] Furthermore, the diameter of the piston rod of the oversized oil cylinder is ≥ 0.5 m, and the length is ≥ 10 m.

[0024] Furthermore, in step 1.1, the turning and grinding integrated machine tool includes a turning tool rest and a grinding tool rest, the chuck is a four-jaw chuck, and the roller brackets are spaced 3 - 5 m apart.

[0025] Further, the width of the spacing area is greater than the width of the roller bracket roller and the width of the bearing bush of the bearing bush bracket.

[0026] Further, the perpendicular distance L from the working position to the outer circle tangent is 10 - 15 mm, and the perpendicular distance H from the working position to the outer circle radial normal is H = sinθ·(L + R), where R is the outer circle radius and θ is 5° - 12°.

[0027] Further, the preheating method is high-frequency induction preheating, the width of the heating coil is 200 - 400 mm, the distance between the coil and the workpiece surface is 8 - 12 mm, and the workpiece rotates clockwise during the preheating process.

[0028] Further, the process parameters of the ultra-high speed laser cladding are as follows: the laser spot diameter is 2.5 - 3.8 mm, the laser power is 4 - 6 kW, the rotational linear velocity of the workpiece outer diameter is 12 - 20 m / min, the moving speed of the spot along the workpiece axis is 0.8 - 1.2 mm / r, the powder-carrying argon gas flow rate is 5 - 10 L / min, the protective argon gas flow rate is 8 - 12 L / min, the powder spot convergence diameter is 1.5 - 2.0 mm, and the powder feeding rate is 50 - 60 g / min.

[0029] Further, the powder composition used for the ultra-high speed laser cladding is as follows: Cr: 18.0 - 20.0%, Ni: 0.5 - 2.0%, Mn: 0.1 - 0.3%, Mo: 0.4 - 1.0%, Nb: 0.1 - 0.3%, C: ≤0.2%, B: 0.8 - 1.0%, Si: 0.8 - 1.0%, and the balance is Fe; the particle size range is: D10 ≤ 15 μm, D50 ≤ 45 μm, D90 ≤ 70 μm; the Hall fluidity ≤ 15 s / 50 g.

[0030] Further, during the overlapping process, the time for the laser power to increase from 0 to the set value at the starting light output position is 500 - 1000 ms, and the increasing method is linear increase.

[0031] Further, the surface hardness of the final coating product is 580 - 650 HV, and the corrosion resistance is at the 9 - level of neutral salt spray for 4200 h.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] a), The present invention integrates multiple processes such as rough turning, finish turning, laser cladding, grinding, and polishing on one machine tool. The entire process only needs to be clamped once, shortening the production cycle, avoiding the machining errors caused by repeated clamping, reducing the subsequent machining allowance, and effectively reducing the risks of coating wear-through, exposure, and non-illumination.

[0034] b), The ultra-high speed laser cladding process adopted by the present invention has high efficiency, small subsequent machining allowance for the coating, saves more materials, the surface of the coating is flatter than the traditional process, and can be directly ground subsequently, reducing one turning process, and the comprehensive cost is lower.

[0035] c), The piston rod of the super-large oil cylinder has a large diameter and a long stroke, and the continuous non-stop working time of laser cladding is long. The present invention offsets the working position by a certain angle and distance and conforms to the rotation direction of the workpiece, so that the powder rebounds and splashes laterally, avoiding the phenomenon of powder sticking and powder blocking in the powder feeding head of ultra-high speed laser cladding.

[0036] d), The present invention adopts a high-frequency induction preheating method, and keeps the workpiece rotating during the preheating process, so that the workpiece is heated evenly, avoiding bending deformation caused by uneven heating and affecting the subsequent machining allowance.

[0037] e), Segment cladding inevitably requires multiple cladding layer lap joints. Different from directly cladding on the substrate, the lap starting position is on the surface of the coating, with a higher hardness, and the rapid laser energy impact is likely to generate micro-cracks in the coating. The present invention first ensures the preheating temperature during the lap joint process, and secondly adopts a slow linear increase method of laser power, avoiding energy impact and effectively reducing the cracking risk. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is a schematic diagram of the piston rod clamped on a turning and grinding integrated machine;

[0039] Figure 2 is a schematic diagram of the working position of the ultra-high speed laser cladding head;

[0040] Figure 3 is a schematic diagram of the finish turning chamfer of the coating;

[0041] Figure 4 is a schematic diagram of the coating lap joint;

[0042] Figure 5 is the coating thickness at different positions.

[0043] Reference numerals: 1, headstock; 2, bed body; 3, chuck; 4, turning tool rest; 5, piston rod; 6, roller bracket; 7, grinding tool rest; 8, tailstock; 9, working position of the cladding head; 10, coating; 11, finish turning chamfer of the coating; 12, coating lap joint area. DETAILED DESCRIPTION OF THE INVENTION

[0044] In order to more clearly illustrate the technical solutions and features of the present invention, the present invention will be described in detail below with reference to the drawings and specific embodiments.

[0045] A method for preparing a super-high-speed laser cladding coating on a piston rod of an oversized oil cylinder. Taking a marine oil cylinder piston rod with a diameter of Φ1.12×20m as an example, the final thickness requirement of the surface coating is 0.6mm, and the following steps are carried out:

[0046] (1): Machining before cladding

[0047] a) As Figure 1 shown, clamp the piston rod blank on a turning and grinding integrated machine. Clamp one end in a four-jaw chuck and tighten the other end with a center. Support the rod body with 4 roller brackets, and the center distance between the roller brackets is 4 - 5m;

[0048] b) Install a rough turning tool bit on the turning tool rest. Segmentally rough turn the outer diameter to Φ1119.0mm with the roller brackets as the intervals, and the surface roughness Ra ≤ 12.5μm; the width of the roller of the roller bracket is 500mm, and the width of the interval area is 800mm;

[0049] c) Move the 4 roller brackets 1000mm towards the chuck direction respectively, and rough turn the outer diameter of the original bracket interval area to Φ1119.0mm, with the surface roughness Ra ≤ 12.5μm;

[0050] d) Replace the turning tool bit on the tool rest with a finishing tool bit. Segmentally finish turn the outer diameter to Φ1118.8mm with the roller brackets as the intervals, and the surface roughness Ra ≤ 3.2μm; the width of the interval area is 800mm;

[0051] e) Move the 4 roller brackets 1000mm towards the tailstock direction respectively, and finish turn the outer diameter of the original bracket interval area to Φ1118.8mm, with the surface roughness Ra ≤ 3.2μm.

[0052] (2): Super-high-speed laser cladding

[0053] a) Replace the turning tool bit on the tool rest with a super-high-speed laser cladding head. As Figure 2 shown, adjust the working position of the powder convergence point of the nozzle so that the perpendicular distance from it to the outer circle tangent is 15mm, the perpendicular distance from it to the outer circle radial normal is 100mm, and the included angle θ between the connection line of the convergence point and the outer circle center and the outer circle radial normal is 10°;

[0054] b) Degrease and dust-remove the surface of the piston rod with alcohol;

[0055] c) Preheat the starting position of the cladding to above 100℃ by high-frequency induction preheating. The width of the heating coil is 400mm, and the distance between the coil and the workpiece surface is 10mm. Keep the workpiece rotating clockwise during the preheating process;

[0056] d) Set the parameters of the ultra-high speed laser cladding process as follows: laser spot diameter 3.5 mm, laser power 5.8 kW, rotational linear velocity of the workpiece outer diameter 15 m / min, moving speed of the spot along the workpiece axis 1.0 mm / r, powder-carrying argon gas flow rate 6 L / min, protective argon gas flow rate 10 L / min, powder spot convergence diameter 2.0 mm, powder feeding rate 55 g / min.

[0057] The powder used for ultra-high speed laser cladding has the following composition: Cr: 18.0 - 20.0%, Ni: 0.5 - 2.0%, Mn: 0.1 - 0.3%, Mo: 0.4 - 1.0%, Nb: 0.1 - 0.3%, C: ≤0.2%, B: 0.8 - 1.0%, Si: 0.8 - 1.0%, with the balance being Fe; particle size range: D10 ≤ 15 μm, D50 ≤ 45 μm, D90 ≤ 70 μm; Hall flowability ≤ 15 s / 50 g.

[0058] With the roller brackets as intervals, perform ultra-high speed laser cladding in segments, with a coating thickness of 1.0 mm;

[0059] e) Replace the finishing tool bit on the tool rest, and finish turning the outer diameter to Φ1120.3 mm in the left area (chuck direction) of the roller brackets, with a surface roughness Ra ≤ 3.2 μm and an area width of 800 mm;

[0060] f) As shown in Figure 3 finish turning a 30° chamfer on the coatings at both ends of the interval area of the roller brackets;

[0061] g) Move the roller brackets to the finish turning area, replace the tool rest with an ultra-high speed laser cladding head, and repeat steps a) - c);

[0062] h) Repeat step d) to perform ultra-high speed laser cladding on the original interval area of the roller brackets, with seamless lap joint with the original cladding layer, as shown in Figure 4 ;

[0063] The time for the laser power to increase from 0 to 5.8 kW at the starting light output position is 1000 ms, and the increasing method is linear increase;

[0064] (3) Machining after cladding

[0065] a) Start the grinding tool rest and grind the coatings except for the roller bracket area to the final finished size of Φ1120.0(-0.098, -0.203) mm;

[0066] b) Remove the roller brackets and replace them with bearing bush brackets, and grind the coatings in the original roller bracket area to the final finished size;

[0067] c) Polish the entire outer diameter of the piston rod.

[0068] Taking the chuck end as the origin, sampling blocks are cut every 2m, and the coating thickness is measured under metallography. The results are as Figure 5 shown. The coating thickness ranges from 0.58 to 0.63mm, and the average thickness is 0.61mm. The Vickers hardness of the coating is tested to be 588 - 655HV according to GB / T4340.4 - 2009. The corrosion resistance of the coating reaches the 9th level of neutral salt spray for 4200h when tested according to GB / T2423.17 - 2008.

[0069] As mentioned above, it is only the preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing ultra-high-speed laser cladding coating for an ultra-large oil cylinder piston rod, characterized in that The following steps are involved: (1) Machining before cladding: a) Clamp the piston rod on the turning and grinding machine, with one end clamped by a four-jaw chuck and the other end tightened by a top, and the rod body supported by multiple roller brackets arranged at intervals of 3 to 5 meters; b) Using a segmented processing strategy, firstly perform rough turning between the roller bracket support areas to make the outer surface roughness Ra ≤ 12.5μm; c) After moving the roller bracket to the processed area, perform additional machining on the original support area; d) Repeat the above segmented processing to perform fine turning, and finally make the surface roughness of the entire outer circle Ra ≤ 3.2 μm; (2) Ultra-high-speed laser cladding: a) Install the ultra-high-speed laser cladding head and adjust the nozzle position so that the powder convergence point is at a vertical distance L = 10-15 mm from the tangent line of the outer circle of the workpiece and a vertical distance H = sinθ·(L+R) from the radial normal line of the outer circle, where R is the radius of the outer circle and θ = 5°-12°; b) Remove oil and dust from the surface; c) Use a high-frequency induction preheating device to preheat the starting position of the cladding to control the surface temperature of the workpiece to ≥100°C; d) Using segmented cladding process, ultra-high-speed laser cladding is performed between the roller bracket support areas. The process parameters include: laser power 4-6kW, spot diameter 2.5-3.8mm, workpiece rotation linear speed 12-20m / min; e) The cladding layer is finely machined in sections, and a 30-40° transition chamfer is processed at the end of the cladding layer; f) After moving the roller bracket, the original support area is subjected to supplementary cladding processing, and the new and old cladding layers are seamlessly overlapped by power gradient control; (3) Finishing after cladding: a) Use grinding process to remove the coating residue in the support area in different areas; b) Perform overall polishing to obtain a finished product with a surface hardness of 580-650 HV and corrosion resistance reaching 4200h neutral salt spray level 9.

2. The method for preparing ultra-high speed laser cladding coating for an ultra-large oil cylinder piston rod according to claim 1 is characterized in that: The piston rod of the super-large oil cylinder has a diameter of ≥0.5m and a length of ≥10m.

3. The method for preparing ultra-high speed laser cladding coating for an ultra-large oil cylinder piston rod according to claim 1 is characterized in that: The turning and grinding machine comprises a turning tool holder and a grinding tool holder, the chuck is a four-jaw chuck, and the roller brackets are spaced 3 to 5 meters apart.

4. The method for preparing ultra-high speed laser cladding coating for an ultra-large oil cylinder piston rod according to claim 1 is characterized in that: The width of the spacing area is greater than the roller width of the roller bracket and the bearing width of the bearing bracket.

5. The method for preparing ultra-high speed laser cladding coating for an ultra-large oil cylinder piston rod according to claim 1 is characterized in that: The working position is at a vertical distance L=10-15 mm from the tangent line of the outer circle, and at a vertical distance H=sinθ·(L+R) from the radial normal line of the outer circle, wherein R is the radius of the outer circle, and θ is 5°-12°.

6. The method for preparing ultra-high speed laser cladding coating for an ultra-large oil cylinder piston rod according to claim 1 is characterized in that: The preheating method is high-frequency induction preheating, the width of the heating coil is 200-400 mm, the distance between the coil and the workpiece surface is 8-12 mm, and the workpiece is kept rotating clockwise during the preheating process.

7. The method for preparing ultra-high speed laser cladding coating for an ultra-large oil cylinder piston rod according to claim 1 is characterized in that: The ultra-high-speed laser cladding process parameters are: laser spot diameter 2.5-3.8 mm, laser power 4-6 kW, workpiece outer diameter rotation linear speed 12-20 m / min, spot axial movement speed along the workpiece 0.8-1.2 mm / r, powder-carrying argon gas flow rate 5-10 L / min, protective argon gas flow rate 8-12 L / min, powder spot convergence diameter 1.5-2.0 mm, and powder feeding rate 50-60 g / min.

8. The method for preparing ultra-high speed laser cladding coating for an ultra-large oil cylinder piston rod according to claim 1 is characterized in that: The powder composition used for ultra-high-speed laser cladding is: Cr: 18.0-20.0%, Ni: 0.5-2.0%, Mn: 0.1-0.3%, Mo: 0.4-1.0%, Nb: 0.1-0.3%, C: ≤0.2%, B: 0.8-1.0%, Si: 0.8-1.0%, and the balance is Fe; particle size range: D10≤15μm, D50≤45μm, D90≤70μm; Hall fluidity≤15s / 50g.

9. The method for preparing ultra-high speed laser cladding coating for an ultra-large oil cylinder piston rod according to claim 1, characterized in that: During the overlapping process, the time for the laser power at the initial light emitting position to increase from 0 to the set value is 500-1000ms, and the increasing method is linear increasing.

10. The method for preparing ultra-high speed laser cladding coating for an ultra-large oil cylinder piston rod according to claim 1, characterized in that: The final coating product has a surface hardness of 580-650 HV and a corrosion resistance of 4200h neutral salt spray level 9.

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