A spray welding remelting device and spray welding remelting method for an elongated solid core roller

Abstract

The present application relates to the technical field of steel metallurgical part machining, in particular to a spray welding remelting device and method for an elongated solid core roller, which is developed from the material characteristics of the base material and the alloy layer material, and is implemented through process design and related auxiliary devices, successfully realizes the preparation of a high-hardness nickel-based alloy coating on the surface of the elongated solid core roller without cracking, effectively solves the bending problem of the elongated roller after high-temperature remelting of the coating, and the coating is uniform, dense and wear-resistant.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of steel metallurgical part machining, in particular to a spraying and remelting device and spraying and remelting method for an elongated solid core roller. BACKGROUND

[0002] The pin shaft is a key component of a steel hot rolling line, has a design specification of Φ280*2800 (roller surface length)*3385 (total length) mm, is made of 34CrNiMo forge piece, has a whole solid core structure, and the surface Φ280*2800 part of the shaft is designed with a single side 1.5 mm thick nickel-based alloy spraying layer. The product belongs to an elongated solid core roller.

[0003] The nickel-based alloy spraying is a conventional technology applied to a medium and low carbon structural steel base metal, and the coating preparation process is mature and not easy to crack. However, since the base metal 34CrNiMo of the pin shaft is a medium carbon alloy structural steel, the nickel-based alloy layer spraying wettability is poor, the mutual solubility and weldability are poor, the thermal expansion coefficients of the alloy layer and the 34CrNiMo base metal are quite different, the coating preparation is difficult, and the process control is not easy to crack. In addition, the spraying of the elongated shaft is a high temperature treatment and is also easy to bend.

[0004] In view of the above defects, the present application is finally obtained through long-term research and practice. SUMMARY

[0005] The present application aims to solve the problems of poor wettability and poor mutual solubility and weldability of the nickel-based alloy layer spraying of the medium carbon alloy structural steel, the quite different thermal expansion coefficients of the alloy layer and the 34CrNiMo base metal, the difficult coating preparation, and the easy cracking of the process control, and provides a spraying and remelting device and spraying and remelting method for an elongated solid core roller.

[0006] An elongated solid core roller remelting device, comprising a remelting machine tool, a movable electromagnetic induction mechanism and a heat preservation mechanism, the heat preservation mechanism is arranged on the remelting machine tool, the elongated solid core roller is arranged on the heat preservation mechanism, and the movable electromagnetic induction mechanism is arranged above the elongated solid core roller to perform remelting on the elongated solid core roller.

[0007] The heat preservation mechanism comprises a heat preservation base, a resistance band, a temperature measuring thermocouple and a heat preservation mechanism control cabinet, the heat preservation base is arranged on the remelting machine tool, the heat preservation base is a cuboid, the upper half is open, U-shaped holes are arranged on the two side end faces of the heat preservation base, the elongated solid core roller is arranged on the U-shaped holes, the resistance band is arranged on the inner wall length direction of the heat preservation base, the temperature measuring thermocouple is arranged in the heat preservation base, the heat preservation mechanism control cabinet is connected with the temperature measuring thermocouple and the heat preservation base, and the temperature of the heat preservation base is adjusted.

[0008] The movable electromagnetic induction mechanism comprises a movable electromagnetic induction coil, an induction coil cooling water tank and an induction coil control cabinet, the movable electromagnetic induction coil is arranged on the elongated solid core roller, and the induction coil cooling water tank and the induction coil control cabinet are connected.

[0009] The heat preservation mechanism is provided with auxiliary supporting wheels at two ends, the auxiliary supporting wheels are arranged on the remelting machine tool, and the two ends of the elongated solid core roller are supported.

[0010] The application further discloses a method for spray welding and remelting an elongated solid core roller.

[0011] S1, roller body manufacturing and processing: after quenching and tempering of the roller body, the roller surface is processed to the size before surfacing, the edge of the roller surface is rounded, and the remaining shaft head position is reserved for processing after coating preparation;

[0012] S2, a low-carbon low-alloy steel welding layer is prepared on the roller surface of the elongated solid core roller by using the submerged arc surfacing method, which is used for transition of the subsequent high-hardness nickel-based alloy layer spray welding, the roller is supported and rotated for surfacing to prevent bending, annealing is carried out after welding to eliminate stress, then the roller surface is machined to be flat, the thickness of the surfacing layer is reserved to be 2mm on one side, and the roller surface size is controlled to the size before spray welding;

[0013] S3, first preheating: the elongated roller is preheated in a trolley type heating furnace, three points are supported in the middle of the shaft head and the roller body on both sides of the elongated roller to prevent bending, the heating furnace is heated to 250 DEG C, and the furnace is discharged after 2h of heat preservation, and the oil and moisture on the roller surface are cleaned;

[0014] S4, sand blasting: the elongated roller is sandblasted and roughened;

[0015] S5, cleaning: the roller surface of the elongated roller after sandblasting is cleaned;

[0016] S6, second preheating: the cleaned elongated roller is clamped on a powder spraying machine tool, the roller body is rotated, and the roller surface is reciprocally baked and heated by using a flame spraying gun, the temperature is 260-280 DEG C, temperature conditions are provided for deposition of the flame sprayed powder, the roller surface temperature is about 290-320 DEG C after powder spraying, and the shaft head and the roller body core temperature is about 100-120 DEG C;

[0017] S7, flame powder spraying: the roller is rotated on the powder spraying machine tool, and the roller surface is sprayed with powder by using the flame spraying gun;

[0018] S8, three preheating: The trolley heating furnace is preheated to 320℃. The powder-coated rollers are preheated in the trolley heating furnace. The rollers are supported at three points on both sides of the slender roller head and in the middle of the roller body to prevent bending. First, they are kept at 320℃ for 1.5h to ensure that the roller head and the core of the roller body are heated to the same temperature. Then, they are heated to 660℃ in the furnace. The heating rate is controlled at 60℃ / h. After reaching the temperature, they are kept for 6-8h. The roller surface temperature is tested after exiting the furnace and is ≥650℃, so that the solid roller body is thoroughly heated inside and out.

[0019] S9, Pre-remelting: The heat preservation base is pre-installed on the machine tool. The preheated rollers are clamped onto the remelting machine tool. When placing them, the roller surface of the workpiece is within the length of the furnace cavity of the heat preservation device. An auxiliary support roller device is placed on the chuck side and the tailstock side of the machine tool. The shaft head of the chuck clamps one side. The tailstock ejector pin is slightly attached to the ejector pin hole of the workpiece without being tightly pressed. The auxiliary support roller can provide load-bearing assistance and effectively prevent the bending deformation of the slender roller after high temperature treatment. The roller rotates and the moving induction coil is pre-remelted back and forth on the roller surface until the coating on the roller surface is dark red and unmelted. During the process, the power supply of the heat preservation device is turned on simultaneously to start heating and raise its displayed temperature to 620-640℃.

[0020] S10, Remelting: Increase the coil power to start remelting. Remelting is carried out by rotating the roller and stepping the induction coil, starting from one end face. The induction coil is energized to form an eddy current magnetic field to heat the coating on the roller surface. When the coating temperature reaches 1080-1130℃, the coating becomes a bright molten mirror surface. Then the coil moves forward step by step. After the coil moves away, the already melted coating will gradually cool, solidify and crystallize to form a dense coating. This process is repeated until the entire roller surface coating is remelted. During the remelting process, the heating power of the heat preservation device is adjusted to ensure that the workpiece is in an atmosphere of 630℃.

[0021] S11, slow cooling in the furnace: Preheat the trolley-type heating furnace to 630℃ in advance. After the coating on the entire roller surface is remelted, the workpiece is immediately put into the furnace and multiple supports are provided to prevent bending. First, keep it at 630℃ for 2 hours to release stress. Then, start slow cooling. The cooling rate must be controlled at 10-12℃ / h. After the furnace temperature cools down to ≤30℃, measure the surface temperature of the workpiece. The surface temperature of the workpiece must also be kept at ≤30℃ before it can be taken out of the furnace for subsequent processing.

[0022] S12, Machining: Machin the coated part of the workpiece roller surface to a size of Φ280mm, and machine the remaining parts to the drawing.

[0023] In step S1, the roller surface dimension before welding is Φ273mm.

[0024] In step S2, the roller surface dimension before spray welding is Φ277mm.

[0025] In step S3, the temperature of the roller surface after preheating is ≥200℃.

[0026] In step S3, the surface roughness of the slender solid roller after sandblasting is Ra10-12μm.

[0027] In step S6, the number of powder spraying passes is 7 to 9, and the diameter of the roller surface increases to Φ282.8 to Φ283.2 mm after powder spraying.

[0028] In step S8, the power of the induction coil during pre-remelting is 50kW, and the roller surface temperature is 830℃ when the coating on the roller surface is in a dark red, unmelted state.

[0029] The power of the induction coil during remelting in step S9 is 105kW.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows: Starting from the characteristics of the base material and alloy layer material, the present invention develops a spray welding and remelting process method for slender solid rollers through process design and related equipment implementation. It successfully achieves the coating preparation on the surface of slender solid rollers without cracking, and effectively solves the bending problem after high-temperature remelting of the coating. The coating obtained by this method is thicker and more uniform and dense than the conventional coating, and has good wear resistance in actual use. Attached Figure Description

[0031] Figure 1 A schematic diagram of a spray welding and remelting device for slender solid rollers;

[0032] Figure 2 Cracking of the coating prepared by conventional process (a) and no cracking of the coating prepared by the process of this application (b).

[0033] The numbers in the image represent:

[0034] 1-Remelting machine tool; 2-Slender solid roller; 3-Movable induction coil; 4-Insulated base; 5-Induction coil control cabinet; 6-Induction coil cooling water tank; 7-Coating; 8-Auxiliary support roller; 9-Insulation device control cabinet; 10-Temperature measuring thermocouple. Detailed Implementation

[0035] The above-mentioned and other technical features and advantages of the present invention will be described in more detail below with reference to the accompanying drawings.

[0036] This embodiment provides a spray welding and remelting device for a slender solid roller, including a remelting machine tool 1, a movable electromagnetic induction mechanism 3, and a heat preservation mechanism. The heat preservation mechanism is disposed on the remelting machine tool 1, the slender solid roller 2 is disposed on the heat preservation mechanism, and the movable electromagnetic induction mechanism is disposed above the slender solid roller 2 to remelt the slender solid roller 2.

[0037] The insulation mechanism includes an insulation base 4, a resistance band, a temperature measuring thermocouple 10, and an insulation mechanism control cabinet 9. The insulation base 4 is mounted on the remelting machine tool 1. The insulation base 4 is rectangular with an open upper part. U-shaped holes are provided on both end faces of the insulation base 4. The slender solid roller 2 is mounted on the U-shaped holes. The resistance band is located along the length of the inner wall of the insulation base. The temperature measuring thermocouple 10 is located inside the insulation base 4. The insulation mechanism control cabinet is connected to the temperature measuring thermocouple 10 and the insulation base 4 to adjust the temperature of the insulation base 4.

[0038] The movable electromagnetic induction mechanism includes a movable electromagnetic induction coil 3, an induction coil cooling water tank 6, and an induction coil control cabinet 5. The movable electromagnetic induction coil 3 is mounted on the slender solid roller 2, and the induction coil cooling water tank 6 and the induction coil control cabinet 5 are connected.

[0039] In this embodiment, the customized induction coil is made by winding a rectangular copper tube with a central opening (cooling water flows through the connecting pipe to the water tank). The inner diameter of the coil is Φ320mm. The coil is kept equidistant from the workpiece roller surface by 20mm to ensure that the coating powder material on the roller surface is heated evenly.

[0040] The heat preservation mechanism is provided with auxiliary support rollers 8 at both ends. The auxiliary support rollers 8 are mounted on the remelting machine tool 1 to support both ends of the slender solid roller 2.

[0041] This embodiment provides a spray welding and remelting method for slender solid rollers. A nickel-based alloy coating is prepared by spray welding on the surface of a slender solid roller with a diameter of Φ280*2816 / 3385mm. The steps are as follows:

[0042] 1. Roller body manufacturing and processing: The roller body is made of 34CrNiMo solid forging. After quenching and tempering, the roller surface is machined to the size Φ273mm before welding. The remaining shaft head stops will be machined after the coating is prepared.

[0043] 2. First, a low-carbon, low-alloy steel layer is prepared on the surface of the slender solid roller using submerged arc welding to serve as a transition for subsequent high-hardness nickel-based alloy spray welding. The transition layer composition is C 0.1-0.15%, Cr 0.8-1.2%, Mn 1.2-1.4%, Ni 0.7-1.0%, Si 0.5-0.8%, and Fe (the remainder). During the welding process, rollers are used to support the rotation of the weld to prevent bending. After welding, stress is relieved by annealing (annealing temperature 450℃, holding for 1.5h). Then, the roller surface is machined to be flat, controlling the thickness of the weld layer to 2mm on each side and the roller surface size to the pre-spray welding size Φ277mm. The edges of the roller surface are rounded.

[0044] 2. First preheating: The slender rollers are preheated in a trolley-type heating furnace. Three-point support is provided at the shaft ends on both sides and the middle of the roller body to prevent bending. The temperature is raised to 250℃ with the furnace and held for 2 hours before being taken out of the furnace. The roller surface temperature is checked to be ≥200℃ after being taken out of the furnace. The grease and moisture on the roller surface are cleaned.

[0045] 3. Sandblasting: The roller is clamped on the sandblasting machine tool, the sandblasting can is filled with No. 8 brown corundum sand, and the roller enters the sandblasting room with the tooling for sandblasting and roughening until the surface roughness reaches Ra10-12μm;

[0046] 4. Cleaning: After sandblasting, use a wire brush to clean the residual sand particles on the roller surface;

[0047] 5. Secondary preheating: The roller is clamped onto the powder coating machine, the roller body is rotated, and the roller surface is reciprocated and heated to 260-280℃ using a flame spray gun, which provides the temperature conditions for the deposition of flame-sprayed powder.

[0048] 6. Flame powder spraying: The roller rotates on the powder spraying machine and the roller surface is sprayed with powder through a flame spray gun (7-9 times in total). After powder spraying, the diameter of the roller surface increases to Φ282.8~Φ283.2mm. The temperature of the roller surface after powder spraying is about 290-320℃, and the temperature of the shaft head and the core of the roller body is about 100-120℃.

[0049] 7. Three preheating processes: The trolley heating furnace is preheated to 320℃. The powder-coated rollers are preheated in the trolley heating furnace. The rollers are supported at three points on both sides of the slender roller head and in the middle of the roller body to prevent bending. First, the rollers are kept at 320℃ for 1.5 hours to ensure that the roller head and the core of the roller body are heated to the same temperature. Then, the rollers are heated to 660℃ in the furnace. The heating rate is controlled at 60℃ / h. After reaching the temperature, the rollers are kept at 6-8 hours. The roller surface temperature is checked after exiting the furnace and found to be ≥650℃, so that the solid rollers are thoroughly heated inside and out.

[0050] 8. Pre-remelting: The heat preservation device is pre-installed on the machine tool. The preheated rollers are clamped onto the remelting machine tool. When placing them, the roller surface of the workpiece is within the length of the furnace cavity of the heat preservation device. An auxiliary support roller device is placed on the chuck side and the tailstock side of the machine tool. The shaft head of the chuck clamps one side. The tailstock ejector pin is slightly attached to the ejector pin hole of the workpiece without being tightly pressed. The auxiliary support roller can provide load-bearing assistance and effectively prevent the bending deformation of the slender roller after high temperature treatment. The roller rotates and the induction coil is used at low power (50kW) to pre-remelt the roller surface until the coating on the roller surface is dark red and unmelted (800-850℃). During the process, the power of the heat preservation device is turned on simultaneously to start heating and raise its displayed temperature to 620-640℃.

[0051] 9. Remelting: Increase the coil power (100-110kW) to begin remelting. Remelting uses a spiral stepping method, starting from one end face. The induction coil is energized to create an eddy current magnetic field that heats the coating on the roller surface. When the coating temperature reaches 1080-1130℃, it will become a bright, molten mirror surface. Then, the coil moves forward step by step. After the coil moves away, the molten coating will gradually cool, solidify, and crystallize, forming a dense coating. This process is repeated until the entire roller surface coating is remelted. During remelting, to control the temperature difference of the coating along the length of the roller, the already melted coating... The coefficients of thermal expansion of the solidified coating and the base material are similar within a certain temperature range. To prevent cracking, the solidified coating must be maintained at a temperature of 630±10℃. A dedicated auxiliary heat preservation device was designed and manufactured. The upper part of the heat preservation device is open, and the furnace is filled with resistance wires and equipped with two thermocouples. When energized, the resistance wires heat up. The heating temperature of the heat preservation device is adjusted by controlling the current (the temperature display maintains a range of 620-640℃). The remelting parameters of the auxiliary heating and heat preservation device (as shown in the diagram above) are as follows.

[0052]

[0053] 10. Slow cooling in the furnace: Preheat the trolley-type heating furnace to 630℃ in advance. After the coating on the entire roller surface is remelted, the workpiece is immediately put into the furnace and multiple supports are provided to prevent bending. First, keep it at 630℃ for 2 hours to release stress. Then, start slow cooling. The cooling rate must be controlled at 10-12℃ / h. After the furnace temperature cools down to ≤30℃, measure the surface temperature of the workpiece. The surface temperature of the workpiece must be kept below 30℃ before it can be taken out of the furnace for subsequent processing.

[0054] 11. Machin the coated portion of the workpiece roller surface to a dimension of Φ280mm, and machine the remaining parts to the drawing specifications.

[0055] Comparative Example

[0056] The conventional spray welding and remelting process (heating → remelting → cooling: no transition layer, excessively rapid heating before remelting without heat preservation, no preheating separation, no accurate temperature maintenance during remelting, and uncontrolled cooling rate after remelting) cannot successfully prepare a high-hardness nickel-based alloy coating on the base material and solid rollers described in this case. The resulting coating has numerous cracks and is extremely prone to peeling during use, failing to meet normal operating requirements.

[0057] This application achieves relatively stable thermal expansion and contraction between the high-hardness nickel-based alloy coating and the solid roller by pre-preparing a low-carbon, low-alloy transition layer, gradient and controlled preheating before remelting, maintaining high temperature during remelting, and controlling the cooling rate. This results in sufficient stress release in the coating, a crack-free coating that is more uniform and dense, and exhibits good wear resistance during use.

[0058]

[0059] The above description is merely a preferred embodiment of the present invention and is illustrative rather than restrictive. Those skilled in the art will understand that many changes, modifications, and even equivalents can be made within the spirit and scope defined by the claims of the present invention, all of which will fall within the protection scope of the present invention.

Claims

1. A method for spray welding and remelting slender solid roller components, characterized in that, Includes the following steps: S1, Roller body manufacturing and processing: After the roller body is tempered, the roller surface is processed to the size before welding. The remaining shaft head positions are processed after the coating is prepared. S2. First, a low-carbon, low-alloy steel weld layer is prepared on the surface of the slender solid roller using the submerged arc welding method to provide a transition for the subsequent high-hardness nickel-based alloy layer. During the welding process, a support roller is used to rotate the welding to prevent bending. After welding, the roller is annealed to relieve stress. Then, the roller surface is machined to be flat, retaining a weld layer thickness of 2mm on each side, controlling the roller surface size to the size before spray welding, and rounding the edges of the roller surface. S3, First preheating: The slender roller is preheated in a trolley-type heating furnace. After preheating, the temperature is raised to 250℃ and kept at that temperature for 2 hours before being taken out of the furnace. The grease and moisture on the roller surface are then cleaned. S4, Sandblasting: Sandblasting roughens slender rollers; S5, Cleaning: Clean the surface of the slender rollers after sandblasting; S6, Secondary Preheating: The cleaned slender rollers are clamped onto the powder spraying machine, the rollers are rotated, and the roller surface is reciprocated and heated to 260-280℃ using a flame spray gun to provide the temperature conditions for the deposition of flame sprayed powder. S7, Flame Powder Spraying: The rollers rotate on the powder spraying machine and the roller surface is sprayed with powder one layer at a time using a flame spray gun; S8, three preheating: The bogie furnace is preheated to 320℃. The roller after powder spraying is preheated in the bogie furnace. The slender roller is supported at three points on both sides of the shaft head and the middle of the roller body to prevent bending. It is first kept at 320℃ for 1.5h to ensure that the shaft head and the core of the roller body are heated to the same temperature. Then it is heated to 660℃ with the furnace. The heating rate is controlled at 60℃ / h. After reaching the temperature, it is kept for 7h. The roller surface temperature is tested after exiting the furnace and is ≥650℃, so that the solid roller body is thoroughly heated inside and out. S9, Pre-remelting: The heat preservation base is pre-installed on the machine tool. The preheated rollers are clamped onto the remelting machine tool. When placing them, the roller surface of the workpiece is within the length of the furnace cavity of the heat preservation device. An auxiliary support roller device is placed on the chuck side and the tailstock side of the machine tool. The shaft head of the chuck clamps one side. The tailstock ejector pin is slightly attached to the ejector pin hole of the workpiece without being tightly pressed. The auxiliary support roller can provide load-bearing assistance and effectively prevent the bending deformation of the slender roller after high temperature treatment. The roller rotates and the moving induction coil is pre-remelted back and forth on the roller surface until the coating on the roller surface is dark red and unmelted. During the process, the power supply of the heat preservation device is turned on simultaneously to start heating and raise its displayed temperature to 620-640℃. S10, Remelting: Increase the coil power to start remelting. Remelting is carried out by rotating the roller and stepping the induction coil. Starting from one end face, the induction coil is energized to form an eddy current magnetic field to heat the coating on the roller surface. When the coating temperature reaches 1080-1130℃, the coating becomes a bright molten mirror surface. Then the coil moves forward step by step. After the coil moves away, the already melted coating will gradually cool, solidify and crystallize to form a dense coating. This process is repeated until the entire roller surface coating is remelted. During the remelting process, the heating power of the heat preservation device is adjusted to ensure that the workpiece is in an atmosphere of 630℃. S11, Slow Cooling: Preheat the trolley-type heating furnace to 630-660℃ in advance. After the coating on the entire roller surface is remelted, the workpiece is immediately put into the furnace and held at 650℃ for 2 hours to release stress. Then, start slow cooling. The cooling rate must be controlled at 10-12℃ / h. After the furnace temperature cools down to ≤30℃, measure the surface temperature of the workpiece. The surface temperature of the workpiece must also be below 30℃ before it can be taken out of the furnace. S12, Machining: Machin the coated part of the workpiece roller surface to a size of Φ280mm, and machine the remaining parts to the drawing.

2. The spray welding and remelting method for a slender solid roller as described in claim 1, characterized in that, In step S3, the temperature of the roller surface after preheating is ≥200℃.

3. The spray welding and remelting method for a slender solid roller as described in claim 1, characterized in that, The surface roughness of the slender solid roller after sandblasting in step S4 is Ra10-12μm.

4. The spray welding and remelting method for a slender solid roller as described in claim 1, characterized in that, In step S7, the number of powder spraying passes is 7 to 9, and the diameter of the roller surface increases to Φ282.8 to Φ283.2 mm after powder spraying.

5. The spray welding and remelting method for a slender solid roller as described in claim 1, characterized in that, In step S9, the power of the induction coil during pre-remelting is 50kW, and the roller surface temperature is 830℃ when the coating on the roller surface is in a dark red, unmelted state.

6. The spray welding and remelting method for a slender solid roller as described in claim 1, characterized in that, The power of the induction coil during remelting in step S10 is 105kW.

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