Method for repairing worn surface of nodular cast iron mold

Abstract

The invention discloses a nodular cast iron mold wear surface repairing method which comprises the following steps: storing prepared transition layer powder and enhancement layer powder in a laser powder feeder, and pretreating the wear surface of a nodular cast iron mold; transition layer powder is sprayed on the surface of the nodular cast iron through a laser cladding system, meanwhile, a laser device emits laser beams to melt the powder to form a molten pool, the molten pool is rapidly cooled to form a transition layer after the laser beams move away, and after the transition layer is formed, the transition layer powder in a powder feeding pipe is blown out, and enhancement layer powder is introduced; enhancement layer powder is sprayed to the surface of the transition layer through a laser cladding system, meanwhile, a laser device emits laser beams to melt the enhancement layer powder to form a molten pool, cooling is conducted to form an enhancement layer, and the thickness ratio of the transition layer to the enhancement layer is about 1: 2. The situation that cracks are prone to being generated in the nodular cast iron surface laser cladding process can be effectively avoided, repairing of the abraded surface of the nodular cast iron mold is achieved, and the service life of the mold is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of surface additive remanufacturing of metal materials, and specifically relates to a method for repairing the worn surface of a ductile iron mold. Background Art

[0002] After long-term service, the surface of a ductile iron mold is severely worn, which greatly affects the processing and forming of subsequent workpieces. The traditional repair method is to use machining for subtractive remanufacturing, but this method is not suitable for multiple re-repairs and problems such as environmental pollution and machining consumables need to be considered, thus increasing the cost; for welding repair, for some complex curved surfaces, the welding repair effect is not ideal, and the composition of the welding material is fixed, while laser cladding can customize the modulation of the powder to meet specific working conditions. The present invention proposes a method for repairing the worn surface of a ductile iron mold to solve the problems existing in the above two processing methods. Summary of the Invention

[0003] To solve the above technical problems, the present invention provides a method for repairing the worn surface of a ductile iron mold that can repair the worn surface of ductile iron and appropriately improve the surface performance.

[0004] The technical solution is as follows: A method for repairing the worn surface of a ball mill cast iron mold, the steps of which include:

[0005] S1: Store the prepared transition layer powder and reinforcement layer powder in a laser powder feeder, and pre-treat the worn surface of the ductile iron mold;

[0006] S2: Spray the transition layer powder on the worn surface of the ductile iron mold through a laser cladding system, and at the same time, the laser emits a laser beam to melt the powder to form a molten pool, so that the molten pool quickly cools to form a transition layer after the laser beam moves away;

[0007] S3: After the transition layer is formed, blow out the transition layer powder in the powder feeding tube, introduce the reinforcement layer powder, spray the reinforcement layer powder on the surface of the transition layer through a laser cladding system, and at the same time, the laser emits a laser beam to melt the reinforcement layer powder to form a molten pool, and cool to form a reinforcement layer.

[0008] Preferably: The material of the ductile iron mold in step S1 is QT500-7, the transition layer powder is In625, the reinforcement layer powder is iron-based powder, and the pre-treatment is to clean and degrease the worn surface of the ductile iron mold with acetone.

[0009] Preferably: The process parameters of the laser cladding system in step S2 are laser power 800W, scanning speed 6mm / s, overlap rate 50%, defocus amount +5mm, distance between the laser head and the working surface 15mm, powder feeding rate 0.3r / min, and spot size 2mm.

[0010] Preferably, the thickness of the transition layer prepared in the step S2 is 0.35 mm.

[0011] Preferably, the process parameters of the laser cladding system in the step S3 are: laser power 800 W, scanning speed 6 mm / s, overlapping rate 50%, defocus amount +5 mm, distance between the laser head and the working surface 15 mm, powder feeding rate 0.3 r / min, and spot size 2 mm.

[0012] Preferably, the thickness of the strengthening layer in the step S3 is 0.65 mm, and the dilution rate of the overall cladding layer is about 28.6%.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: By coating a transition layer and a strengthening layer on the surface of the nodular cast iron mold, it is possible to effectively avoid the occurrence of cracks that are prone to occur during the laser cladding process on the worn surface of the nodular cast iron mold, thereby improving the bonding performance of the cladding layer and achieving the repair of the worn surface of the nodular cast iron mold. Moreover, the surface after repair can significantly improve the surface wear resistance and extend the service life of the mold, facilitating its reuse in production. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the distribution of the repair coating;

[0015] Figure 2 It is a distribution diagram of the laser cladding test coating;

[0016] Figure 3 It is a diagram of the hardness change law;

[0017] Figure 4 It is a metallographic structure diagram at the junction of the transition layer and the matrix;

[0018] Figure 5 It is a metallographic structure diagram at the junction of the strengthening layer and the transition layer;

[0019] Figure 6 It is a schematic diagram of the EDS line scanning position;

[0020] Figure 7 It is a diagram of the cross-sectional EDS line scanning result. DETAILED DESCRIPTION OF THE INVENTION

[0021] The present invention will be further described below in conjunction with the embodiments and the drawings.

[0022] A method for repairing the worn surface of a nodular cast iron mold, the steps of which include:

[0023] S1: Store the prepared transition layer powder and strengthening layer powder in a laser powder feeder, and pretreat the worn surface of the nodular cast iron mold;

[0024] S2: Spray the transition layer powder onto the worn surface of the ductile iron mold through a laser cladding system. Meanwhile, the laser emits a laser beam to melt the powder to form a molten pool, so that the molten pool rapidly cools to form a transition layer after the laser beam moves away;

[0025] S3: After the transition layer is formed, blow out the transition layer powder in the powder feeding tube, introduce the reinforcing layer powder, spray the reinforcing layer powder onto the surface of the transition layer through a laser cladding system. Meanwhile, the laser emits a laser beam to melt the reinforcing layer powder to form a molten pool, and it cools to form a reinforcing layer.

[0026] Example

[0027] In this example, the ductile iron mold used is: 22 mm in length * 22 mm in width * 15 mm in height, the size of the cladding area is 10 mm in length * 10 mm in width, the base material used is QT500-7, the transition layer powder is In625, the reinforcing layer powder is iron-based powder, and the schematic diagram of the morphology after cladding is as Figure 1 shown. The specific method includes the following steps:

[0028] Step 1: Store the prepared transition layer powder and reinforcing layer powder in a laser powder feeder, and clean and degrease the worn surface of the ductile iron mold with acetone;

[0029] Step 2: Conduct experiments through a laser cladding system under the process parameters of laser power 800 W, scanning speed 6 mm / s, overlapping rate 50%, defocus amount +5 mm, distance between the laser head and the working surface 15 mm, powder feeding rate 0.3 r / min, and spot size 2 mm. The laser emits a laser beam to melt the powder to form a molten pool, so that the molten pool rapidly cools to form a transition layer after the laser beam moves away. The thickness of the transition layer is about 0.35 mm, and it can be seen that the surface glossiness is good and the overall transition layer is relatively flat. At this time, the preparation of the transition layer is completed;

[0030] Step 3: After the transition layer is formed, blow out the transition layer powder in the powder feeding tube, introduce the reinforcing layer powder, and conduct experiments through a laser cladding system under the process parameters of laser power 800 W, scanning speed 6 mm / s, overlapping rate 50%, defocus amount +5 mm, distance between the laser head and the working surface 15 mm, powder feeding rate 0.3 r / min, and spot size 2 mm, and it cools to form a reinforcing layer. It can be seen that the cladding surface is slightly reflective, indicating that the preparation of the reinforcing layer is completed at this time. The thickness of the reinforcing layer is about 0.65 mm, and the overall dilution rate of the cladding layer is about 28.6% (coating thickness 1 mm, depth of heat affected zone and remelting zone 0.4 mm). The repair coating of the entire worn surface of the ductile iron is completed. The thickness ratio of the transition layer to the reinforcing layer is 1:2.

[0031] In this example, no obvious cracks are generated at the junction of the transition layer and the matrix, as Figure 2As shown, it indicates that the transition layer powder effectively improves the crack situation during the laser cladding process on the worn surface of ductile iron. To analyze the microstructure and properties of the repaired coating, starting from the top of the cladding layer and moving downwards, the hardness changes were measured at equal intervals of 100 μm in depth. Among them, at the same depth, three points were measured at equal intervals of 300 μm and the average value was taken as the hardness value at that depth. The measurement results are as Figure 3 shown. From the hardness change pattern diagram, it can be seen that the hardness of the strengthening layer is relatively high, about three times that of the matrix, and the hardness of the transition layer is slightly lower than that of the strengthening layer. The metallographic structure at the junction of the matrix and the transition layer is as Figure 4 shown, and the metallographic structure at the junction of the strengthening layer and the transition layer is as Figure 5 shown. To analyze the element change pattern of the coating, the coating was measured by EDS line scanning in the manner shown in Figure 6 , and the results are as Figure 7 shown. The line scanning results show that the In625 powder inhibits the formation of white cast iron structure at the interface through effective mixing with the matrix, thereby inhibiting the formation of cracks. The protrusion of the C element corresponds to the depression of the Fe element, indicating that this is the graphite structure of the matrix part. Through the friction and wear experiment on the repaired surface, it can be seen that the strengthening layer powder effectively improves the surface wear resistance, and the friction coefficient decreases from 0.782 of the matrix to 0.684, indicating that the repaired coating can play a good repair role;

[0032] In this embodiment, the worn surface of a ductile iron mold with a length of 22 mm * width of 22 mm * height of 15 mm was repaired, effectively improving the crack situation at the interface, increasing the wear resistance by 14%, and promoting the remanufacturing application of ductile iron molds.

[0033] Finally, it should be noted that the above description is only the preferred embodiment of the present invention. Under the inspiration of the present invention, those of ordinary skill in the art can make various similar representations without departing from the purpose and claims of the present invention, and such transformations all fall within the protection scope of the present invention.

Claims

1. A method for repairing the worn surface of a ductile iron mold, characterized in that: The following steps are involved: S1: storing the prepared transition layer powder and reinforcement layer powder in a laser powder feeder, and pretreating the wear surface of the ductile iron mold; S2: The transition layer powder is sprayed onto the worn surface of the ductile iron mold by a laser cladding system, and at the same time, the laser emits a laser beam to melt the powder to form a molten pool, so that after the laser beam moves away, the molten pool quickly cools to form a transition layer; S3: After the transition layer is formed, the transition layer powder in the powder feeding pipe is blown out, and the reinforcing layer powder is introduced. The reinforcing layer powder is sprayed on the surface of the transition layer through the laser cladding system. At the same time, the laser emits a laser beam to melt the reinforcing layer powder to form a molten pool, and cools to form a reinforcing layer.

2. A method for repairing the worn surface of a ductile iron mold according to claim 1, characterized in that: The material of the ductile iron mold in step S1 is QT500-7, the transition layer powder is In625, the reinforcement layer powder is iron-based powder, and the pretreatment is to clean and degrease the worn surface of the ductile iron mold with acetone.

3. A method for repairing the worn surface of a spherical cast iron mold according to claim 1, characterized in that: The process parameters of the laser cladding system in step S2 are: laser power 800W, scanning speed 6mm / s, overlap rate 50%, defocus amount +5mm, distance between laser head and action surface 15mm, powder feeding rate 0.3r / min, spot size 2mm.

4. A method for repairing the worn surface of a spherical cast iron mold according to claim 3, characterized in that: The thickness of the transition layer prepared in step S2 is 0.35 mm.

5. A method for repairing the worn surface of a spherical cast iron mold according to claim 1, characterized in that: The process parameters of the laser cladding system in step S3 are: laser power 800W, scanning speed 6mm / s, overlap rate 50%, defocus amount +5mm, distance between laser head and action surface 15mm, powder feeding rate 0.3r / min, spot size 2mm.

6. A method for repairing the worn surface of a spherical cast iron mold according to claim 5, characterized in that: In the step S3, the thickness of the reinforcement layer is 0.65 mm, and the dilution rate of the entire cladding layer is about 28.6%.

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