Preparation method of combined valve rod

Abstract

The invention discloses a preparation method of a combined valve rod, relates to the field of manufacturing of aviation parts, and aims to solve the problem that the combination strength of a traditional threaded connection and welding combination combined valve rod mode is poor. The preparation method comprises the following steps: performing laser cladding on the first valve rod by using powder with the same components as the second valve rod to form a cladding bottom layer; the first valve rod and the second valve rod are correspondingly connected to form an assembly; performing laser cladding on the surface of the assembly by using powder to form a first cladding layer; powder is used for carrying out at least one time of laser cladding on the surface of the first cladding layer, at least one second cladding layer is formed, and the total cladding thickness of the first cladding layer and the second cladding layer ranges from 8 mm to 9 mm. According to the combined valve rod, the cladding base layer is formed by adopting the powder with the same components as the second valve rod, so that the surface components of the first valve rod and the surface components of the second valve rod are closer, then laser cladding of the first cladding layer and the second cladding layer is carried out for multiple times, it is guaranteed that the bonding strength of the combined part is larger than 1000 MPa, and the service life of the combined valve rod is prolonged.

Description

Technical Field

[0001] The invention relates to the field of aviation component manufacturing, and in particular to a method for preparing a combined valve stem. Background Art

[0002] Aviation combination valve stems are usually made of different materials, such as tungsten alloy, martensitic alloy steel, etc., due to the particularity of their use environment and the diversity of their uses. High-strength bonding is required between the components, and the bonding strength must be greater than 1000MPa.

[0003] At present, the existing combined valve stems usually use threaded connection plus brazing or plasma welding to combine the various parts into one, which has poor bonding strength, short service life under specific environments, and replacement increases a lot of labor and time costs. Summary of the invention

[0004] The object of the present invention is to provide a method for preparing a combined valve stem, which is used to ensure the connection strength between various structures of the combined valve stem and to extend the service life of the combined valve stem.

[0005] In order to achieve the above object, the present invention provides the following technical solution: a method for preparing a combined valve stem, comprising:

[0006] S100, performing laser cladding on the first valve stem using powder having the same component as that of the second valve stem to form a cladding base layer;

[0007] S200, connecting the first valve stem and the second valve stem into one piece by corresponding threads to form an assembly;

[0008] S300, performing laser cladding on the entire surface of the assembly using powder to form a first cladding layer;

[0009] S400, performing at least one laser cladding on the entire surface of the first cladding layer using powder to form at least one second cladding layer, so that the total cladding thickness of the first cladding layer and the second cladding layer is 8 mm to 9 mm.

[0010] Optionally, in the method for preparing the combined valve stem, the powder is dried and the cladding base layer is machined so that the thickness of the cladding base layer is 0.4 mm to 0.6 mm.

[0011] Optionally, in the method for preparing the combined valve stem, drying the powder includes: placing the powder in a constant temperature environment of 100° C. to 120° C. for at least 30 minutes to dry the powder.

[0012] Optionally, in the preparation method of the above-mentioned combination valve stem, the laser cladding in step S100, step S300 and step S400 includes: driving the first valve stem or the assembly to rotate around the axis, and at the same time moving the powder and the laser along the axial direction of the first valve stem or the assembly, so that the powder is distributed in a spiral shape on the first valve stem or the assembly, and the powder is clad by the laser.

[0013] Optionally, in the preparation method of the above-mentioned combined valve stem, the powder feeding rate is 20g / min~25g / min, the axial movement speed of the powder along the first valve stem or the assembly is 10mm / s~15mm / s, the powder is transported by powder feeding gas and shielding gas, the gas delivery pressures of the powder feeding gas and the shielding gas are both 0.4MPa~0.6MPa, the flow rate of the powder feeding gas is 6L / min~8L / min, the flow rate of the shielding gas is 13L / min~17L / min, and the power of the laser is 5000W~5500W, so that the single-track height of the cladding base layer, the first cladding layer and the second cladding layer is 0.8mm~1.2mm, the single-track width is 4mm~6mm, the single-layer thickness is 0.9mm~1.3mm, and the overlap rate is 30%~34%.

[0014] Optionally, in the method for preparing the combined valve stem, a connection gap of the combined components is less than or equal to 0.3 mm.

[0015] Optionally, in the preparation method of the above-mentioned combined valve stem, before using powder with the same component as the second valve stem to perform laser cladding on the first valve stem to form a cladding base layer, the preparation method also includes: preheating the first valve stem to 145°C to 155°C.

[0016] Optionally, in the preparation method of the above-mentioned combined valve stem, the first valve stem is a tungsten alloy valve stem, the second valve stem is an A100 martensitic alloy steel valve stem, the components of the powder are the same as those of the A100 martensitic alloy steel valve stem, and the composition of the powder is as follows by mass content: 0.21% to 0.25% C, 13% to 14% Co, 11% to 12% Ni, 2.9% to 3.3% Cr, 1.1% to 1.3% Mo, 0.1% Si, 0.1% Mn, 0.005% S, 0.008% P, 0.005% Al, 0.015% Ti, and the rest is Fe.

[0017] Optionally, in the method for preparing the combined valve stem, before using powder to perform laser cladding on the entire surface of the combined component to form a first cladding layer, the method further comprises: preheating the combined component to 110° C. to 130° C.

[0018] Optionally, in the above-mentioned preparation method of the combined valve stem, before performing at least one laser cladding on the entire surface of the first cladding layer to form at least one second cladding layer, the preparation method further comprises grinding the surface of the first cladding layer to remove the oxide scale on the first cladding layer;

[0019] And / or, after the entire surface of the first cladding layer is subjected to at least one laser cladding operation to form at least one second cladding layer, the preparation method further comprises grinding the surface of the second cladding layer to remove oxide scale on the second cladding layer.

[0020] Compared with the prior art, when the above technical solution is adopted, the powder having the same component as the second valve stem is firstly used to perform laser cladding on the first valve stem to form a cladding base layer, and then the first valve stem and the second valve stem are connected together by corresponding threads to form an assembly, and then the powder is used to continue to perform laser cladding on the entire surface of the assembly to form a first cladding layer, and finally the powder is used to perform laser cladding on the entire surface of the first cladding layer at least once to form at least one second cladding layer, so that the total cladding thickness of the first cladding layer and the second cladding layer is 8mm to 9mm, which is 10mm thick compared with the traditional threaded connection plus brazing or plasma welding. In a combined manner, the preparation method provided in the present application adopts a cladding base layer formed by powder having the same component as that of the second valve stem, so that the surface composition of the first valve stem and the surface composition of the second valve stem are closer. When the entire surface of the assembly is clad, the stress generated by the different amounts of thermal deformation can be reduced to prevent the risk of cracks and peeling of the cladding base layer, thereby improving the bonding strength between the first cladding layer and the assembly; in addition, multiple laser claddings are performed on the entire surface of the first cladding layer using powder, so that the bonding strength of the assembly is greater than 1000MPa, thereby extending the service life of the combined valve stem. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0022] Figure 1 The present invention is a process flow chart of a method for preparing a combined valve stem provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0023] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0024] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0025] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined. The meaning of "several" is one or more, unless otherwise clearly and specifically defined.

[0026] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by the terms "up", "down", "front", "back", "left", "right", etc. are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0027] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] like Figure 1 As shown, an embodiment of the present invention provides a method for preparing a combined valve stem, hereinafter referred to as the preparation method. The method comprises the following steps:

[0029] Step S100, performing laser cladding on the first valve stem using powder having the same component as that of the second valve stem to form a cladding base layer;

[0030] Step S200, connecting the first valve stem and the second valve stem into one piece by corresponding threads to form an assembly;

[0031] Step S300, performing laser cladding on the entire surface of the assembly using powder to form a first cladding layer;

[0032] Step S400, using powder to perform laser cladding on the entire surface of the first cladding layer at least once to form at least one second cladding layer, so that the total cladding thickness of the first cladding layer and the second cladding layer is 8 mm to 9 mm.

[0033] When implementing it, Figure 1 As shown in the figure, firstly, a powder having the same component as that of the second valve stem is used to perform laser cladding on the first valve stem to form a cladding base layer, then the first valve stem and the second valve stem are connected together by corresponding threads to form an assembly, and then the powder is used to continue to perform laser cladding on the entire surface of the assembly to form a first cladding layer, and finally, the powder is used to perform laser cladding on the entire surface of the first cladding layer at least once to form at least one second cladding layer, so that the total cladding thickness of the first cladding layer and the second cladding layer is 8 mm to 9 mm, which is 2 mm thick compared to the traditional method of combining the first valve stem and the second valve stem into one body by thread connection plus brazing or plasma welding. The preparation method provided in the present application adopts a cladding base layer formed by powder having the same component as that of the second valve stem, so that the surface composition of the first valve stem and the surface composition of the second valve stem are closer. When the entire surface of the assembly is clad, the stress generated by the different amounts of thermal deformation can be reduced to prevent the risk of cracks and peeling of the cladding base layer, thereby improving the bonding strength between the first cladding layer and the assembly. In addition, the entire surface of the first cladding layer is laser clad multiple times using powder, so that the bonding strength of the assembly is greater than 1000MPa, thereby extending the service life of the combined valve stem.

[0034] For example, the first valve stem may be a tungsten alloy valve stem, the second valve stem may be an A100 martensitic alloy steel valve stem, the composition of the powder is the same as that of the A100 martensitic alloy steel valve stem, and the composition of the powder is as follows by mass content: 0.21-0.25% C, 13-14% Co, 11-12% Ni, 2.9-3.3% Cr, 1.1-1.3% Mo, 0.1% Si, 0.1% Mn, 0.005% S, 0.008% P, 0.005% Al, 0.015% Ti, and the remainder Fe. By using the powder with the same composition as the surface of the second valve stem for cladding, the bonding strength between the first cladding layer and the assembly and between the first cladding layer and the second cladding layer is improved.

[0035] In some embodiments, before laser cladding, the surface of the first valve stem, the second valve stem or the assembly is wiped clean with industrial alcohol or acetone to remove oil stains attached to the surface of the first valve stem, the second valve stem or the assembly.

[0036] Specifically, in this embodiment, step S100 specifically includes: drying the powder, and machining the cladding base layer so that the thickness of the cladding base layer is 0.4 mm to 0.6 mm. In this step, the powder is first dried to reduce excess moisture and volatile components in the powder, so that the powder is dry, the generation of pores and cracks during the cladding process is reduced, and the quality of the cladding base layer is improved; the first valve stem is a tungsten alloy valve stem, and the second valve stem is an A100 martensitic alloy steel valve stem. Since the tungsten alloy valve stem and the A100 martensitic alloy steel valve stem have different thermal deformation amounts, the connection gap of the assembly formed by the combination of the two will change due to the heat generated during cladding, thereby generating stress to tear the cladding layer, and in step S100, powder is used to clad the base layer on the first valve stem, so that the surface composition of the first valve stem and the surface composition of the second valve stem are closer, and when the entire surface of the assembly is clad, the stress generated by the different thermal deformation amounts can be reduced to prevent the risk of cracks and peeling of the cladding base layer, thereby improving the bonding strength between the first cladding layer and the assembly. Among them, a CNC lathe can be used to turn the cladding base layer so that the thickness of the cladding base layer is 0.4mm, 0.5mm or 0.6mm, etc. The thickness of the cladding base layer after turning is not limited to the above values, as long as the thickness of the cladding base layer meets the processing requirements. Preferably, the thickness of the cladding base layer after turning is 0.5mm.

[0037] Furthermore, in this embodiment, the step S100 of drying the powder includes: placing the powder in a constant temperature environment of 100°C to 120°C for at least 30 minutes to dry the powder. Specifically, the powder can be placed in an oven at 100°C, 105°C, 110°C or 120°C for constant temperature drying, and the holding time can be 30 minutes, 35 minutes or 40 minutes. The drying temperature and drying time of the powder are not limited to the above values. Preferably, the powder is placed in a constant temperature environment of 110°C for 30 minutes, so that the moisture in the powder can evaporate quickly without destroying the components in the powder, thereby improving the drying efficiency.

[0038] In some embodiments, the laser cladding in step S100, step S300 and step S400 includes: driving the first valve stem or assembly to rotate around the axis, and at the same time moving the powder and the laser along the axial direction of the first valve stem or assembly, so that the powder is distributed in a spiral shape on the first valve stem or assembly, and the powder is clad by the laser.

[0039] Specifically, the powder is placed in a powder barrel of a powder feeder and enters the groove of a powder disc through an opening at the bottom of the powder barrel. The powder output is adjusted by changing the rotation speed of the powder disc. The powder disc rotates to deliver the powder to the powder outlet, and then the protective gas and powder delivery gas bring the powder into a powder tube connected to the powder outlet. The other end of the powder tube is connected to a nozzle below the laser head. The nozzle adopts a coaxial annular nozzle. The powder is ejected from the outlet of the annular nozzle and forms a conical powder flow. At this time, the operator can control the first valve stem or assembly to rotate around the axis through a CNC machine tool or other driving method. The powder ejected from the nozzle and the laser move along the axial direction of the first valve stem or assembly, so that the powder is distributed in a spiral shape on the first valve stem or assembly. When the powder is delivered to the surface of the workpiece, the powder is clad by the laser to complete the processing of the cladding base layer, the first cladding layer and the second cladding layer, thereby ensuring the connection strength between the first valve stem and the second valve stem and extending the service life of the combined valve stem.

[0040] Specifically, in this embodiment, the powder feeding rate is 20g / min~25g / min, the axial movement speed of the powder along the first valve stem or the assembly is 10mm / s~15mm / s, the powder is transported by powder feeding gas and shielding gas, the gas delivery pressures of the powder feeding gas and the shielding gas are both 0.4MPa~0.6MPa, the flow rate of the powder feeding gas is 6L / min~8L / min, the flow rate of the shielding gas is 13L / min~17L / min, and the power of the laser is 5000W~5500W, so that the single-track height of the cladding base layer, the first cladding layer and the second cladding layer is 0.8mm~1.2mm, the single-track width is 4mm~6mm, the single-layer thickness is 0.9mm~1.3mm, and the overlap rate is 30%~34%. Exemplarily, the powder feeding rate can be 20g / min, 22g / min, 23g / min, or 25g / min, etc. The axial movement speed of the powder along the first valve stem or the assembly can be automatically adapted to the diameter of the workpiece at the current cladding position by the CNC machine tool to control the chuck speed to ensure that the powder feeding rate remains constant at 10mm / s, 12mm / s, 13mm / s or 15mm / s, etc. The gas delivery pressures of the powder feeding gas and the shielding gas can both be 0.4MPa, 0.5MPa or 0.6MPa, etc. The flow rate of the powder feeding gas can be 6L / min, 7L / min or 8L / min, etc., the flow rate of the shielding gas can be 13L / min, 15L / min, 16L / min or 17L / min, and the power of the laser can be 5000W, 520 0W or 5500W, etc., so that the single-pass height of the cladding base layer, the first cladding layer and the second cladding layer is processed to 0.8mm, 1.0mm, 1.1mm or 1.2mm, etc., the single-pass width is processed to 4mm, 5mm or 6mm, etc., the single-layer thickness is processed to 0.9mm, 1mm, 1.1mm, 1.25mm, 1.3mm, etc., and the overlap rate during processing is 30%, 32% or 34%, etc., and the various process parameters of the laser cladding process in step S100, step S300 and step S400 are not limited to the above values, as long as the total cladding thickness of the first cladding layer and the second cladding layer after processing meets 8mm to 9mm, the above parameters are used to improve the cladding quality of the cladding base layer, the first cladding layer and the second cladding layer, thereby improving the structural strength of the combined valve stem.

[0041] Preferably, when performing cladding base layer processing, the process parameters of laser cladding are as follows: the powder feeding rate is 23 g / min, the axial movement speed of the powder along the first valve stem or assembly is 12 mm / s, the powder is transported by powder feeding gas and shielding gas, the gas delivery pressures of the powder feeding gas and shielding gas are both 0.5 MPa, the flow rate of the powder feeding gas is 7 L / min, the flow rate of the shielding gas is 15 L / min, and the power of the laser is 5500 W, so that the single-track height of the cladding base layer is 1 mm, the single-track width is 5 mm, the single-layer thickness is 1.1 mm, and the overlap rate is 30%. When processing the first cladding layer, the process parameters of laser cladding are as follows: the powder feeding rate is 23g / min, the axial movement speed of the powder along the first valve stem or assembly is 12mm / s, the powder is transported by powder feeding gas and shielding gas, the gas delivery pressure of the powder feeding gas and shielding gas are both 0.5MPa, the flow rate of the powder feeding gas is 7L / min, the flow rate of the shielding gas is 15L / min, and the power of the laser is 5000W, so that the single-pass height of the cladding base layer is 1.1mm, the single-pass width is 5mm, the single-layer thickness is 1.25mm, and the overlap rate is 34%. When processing the second cladding layer, the process parameters of laser cladding are as follows: the powder feeding rate is 23g / min, the axial movement speed of the powder along the first valve stem or assembly is 15mm / s, the powder is transported by powder feeding gas and shielding gas, the gas delivery pressure of the powder feeding gas and shielding gas are both 0.5MPa, the flow rate of the powder feeding gas is 7L / min, the flow rate of the shielding gas is 15L / min, and the power of the laser is 5000W, so that the single-pass height of the cladding base layer is 0.8mm, the single-pass width is 5mm, the single-layer thickness is 0.9mm, and the overlap rate is 34%. Among them, since the tungsten alloy matrix used in the first valve stem has a higher melting point, it is necessary to increase the laser power to ensure that the surface of the first valve stem and the powder are metallurgically bonded, thereby improving the bonding strength between the first valve stem and the cladding base layer; by adjusting the process parameters of laser cladding, such as the laser power, the axial movement speed of the powder along the first valve stem or the assembly, the single-pass height, the single-pass width and the single-layer thickness, the cladding base layer, the first cladding layer and the second cladding layer all have a good overlap rate to ensure that each cladding layer can form a good metallurgical bond, avoid the occurrence of holes, depressions, inconsistent and rough surface heights, and improve the cladding quality of the combined valve stem.

[0042] Specifically, in this embodiment, in step S200, the connection gap of the assembly is less than or equal to 0.3 mm. The connection gap of the assembly can be 0.1 mm, 0.15 mm, 0.24 mm, 0.3 mm, etc., and is not limited to the values ​​listed in this embodiment, as long as the connection gap after the assembly is connected meets the assembly requirements.

[0043] It should be noted that the cladding process at the connection gap of the assembly is the same as the cladding process of the first cladding layer, and the cladding thickness of the first cladding layer is greater than the thickness of each second cladding layer, so that after the first valve stem and the second valve stem are threaded together, having a thicker first cladding layer can improve the connection strength of the assembly and reduce the risk of cracks on the entire surface of the combined valve stem.

[0044] Specifically, in this embodiment, before laser cladding the first valve stem with powder having the same components as the second valve stem in step S100 to form a cladding base layer, the preparation method further includes: preheating the first valve stem to 145°C to 155°C. Before laser cladding the first valve stem with powder, the first valve stem may be preheated to 145°C, 148°C, 150°C or 155°C, etc. The preheating temperature of the first valve stem is not limited to the above values. Since the first valve stem is a tungsten alloy valve stem, the hardness of the material is relatively high. By preheating the first valve stem, the risk of cracks caused by direct cladding is avoided. Preferably, the first valve stem is preheated to 150°C.

[0045] Specifically, in this embodiment, before the powder is used to perform laser cladding on the entire surface of the assembly to form the first cladding layer in step S300, the preparation method further includes: preheating the assembly to 110°C to 130°C. Before the powder is used to perform laser cladding on the entire surface of the assembly, the assembly may be preheated to 110°C, 115°C, 120°C, 126°C or 130°C, etc. The preheating temperature of the assembly is not limited to the above values. By preheating the assembly, the overall temperature of the assembly is uniform, reducing the risk of cracks caused by direct cladding. Preferably, the assembly is preheated to 120°C.

[0046] Specifically, in this embodiment, before the entire surface of the first cladding layer in step S400 is laser clad at least once to form at least one second cladding layer, the preparation method further includes grinding the surface of the first cladding layer to remove the oxide scale on the first cladding layer. That is, after the first cladding layer is laser clad, the oxide scale on the surface of the first cladding layer is polished clean by a grinding device, and then the laser cladding work of the second cladding layer is performed to prevent defects such as pores and slag inclusions, and ensure the connection strength between the first cladding layer and the second cladding layer.

[0047] Specifically, in this embodiment, after the entire surface of the first cladding layer in step S400 is laser clad at least once to form at least one second cladding layer, the preparation method further includes grinding the surface of the second cladding layer to remove the oxide scale on the second cladding layer. That is, after each layer of the second cladding layer is laser clad, the oxide scale on the surface of the second cladding layer is polished clean by a grinding device before the next layer is laser clad to prevent defects such as pores and slag inclusions, and to ensure the connection strength between two adjacent layers of the second cladding layer, so as to extend the service life of the combined valve stem.

[0048] In the description of the above embodiments, specific features, structures, materials or characteristics may be combined in a suitable manner in any one or more embodiments or examples.

[0049] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing a combined valve stem, characterized in that: include: S100, performing laser cladding on the first valve stem using powder having the same component as that of the second valve stem to form a cladding base layer; S200, connecting the first valve stem and the second valve stem into one piece by corresponding threads to form an assembly; S300, performing laser cladding on the entire surface of the assembly using the powder to form a first cladding layer; S400, performing at least one laser cladding operation on the entire surface of the first cladding layer using the powder to form at least one second cladding layer, so that the total cladding thickness of the first cladding layer and the second cladding layer is 8 mm to 9 mm.

2. The method for preparing a combined valve stem according to claim 1, characterized in that: The powder is dried, and the cladding base layer is machined so that the thickness of the cladding base layer is 0.4 mm to 0.6 mm.

3. The method for preparing a combined valve stem according to claim 2, characterized in that: The drying treatment of the powder includes: placing the powder in a constant temperature environment of 100° C. to 120° C. for at least 30 minutes to dry the powder.

4. The method for preparing a combined valve stem according to claim 2, characterized in that: The laser cladding in step S100, step S300 and step S400 includes: driving the first valve stem or the assembly to rotate around an axis, and simultaneously moving the powder and the laser along the axial direction of the first valve stem or the assembly, so that the powder is distributed in a spiral shape on the first valve stem or the assembly, and cladding the powder by the laser.

5. The method for preparing a combined valve stem according to claim 4, characterized in that: The powder feeding rate of the powder is 20g / min~25g / min, the axial movement speed of the powder along the first valve stem or the assembly is 10mm / s~15mm / s, the powder is transported by powder feeding gas and shielding gas, the gas delivery pressures of the powder feeding gas and the shielding gas are both 0.4MPa~0.6MPa, the flow rate of the powder feeding gas is 6L / min~8L / min, the flow rate of the shielding gas is 13L / min~17L / min, and the power of the laser is 5000W~5500W, so that the single-track height of the cladding base layer, the first cladding layer and the second cladding layer is 0.8mm~1.2mm, the single-track width is 4mm~6mm, the single-layer thickness is 0.9mm~1.3mm, and the overlap rate is 30%~34%.

6. The method for preparing a combined valve stem according to claim 1, characterized in that: The connection gap of the assembly is less than or equal to 0.3 mm.

7. The method for preparing a combined valve stem according to any one of claims 1 to 6, characterized in that: Before laser cladding the first valve stem with powder having the same component as that of the second valve stem to form a cladding base layer, the preparation method further includes: preheating the first valve stem to 145° C. to 155° C.

8. The method for preparing a combined valve stem according to any one of claims 1 to 6, characterized in that: The first valve stem is a tungsten alloy valve stem, the second valve stem is an A100 martensitic alloy steel valve stem, the components of the powder are the same as those of the A100 martensitic alloy steel valve stem, and the composition of the powder is as follows by mass content: 0.21% to 0.25% C, 13% to 14% Co, 11% to 12% Ni, 2.9% to 3.3% Cr, 1.1% to 1.3% Mo, 0.1% Si, 0.1% Mn, 0.005% S, 0.008% P, 0.005% Al, 0.015% Ti, and the remainder is Fe.

9. The method for preparing a combined valve stem according to any one of claims 1 to 6, characterized in that: Before using the powder to perform laser cladding on the entire surface of the assembly to form a first cladding layer, the preparation method further includes: preheating the assembly to 110° C. to 130° C.

10. The method for preparing a combined valve stem according to any one of claims 1 to 6, characterized in that: Before performing at least one laser cladding on the entire surface of the first cladding layer to form at least one second cladding layer, the preparation method further includes grinding the surface of the first cladding layer to remove an oxide scale on the first cladding layer; And / or, after performing at least one laser cladding on the entire surface of the first cladding layer to form at least one second cladding layer, the preparation method further includes grinding the surface of the second cladding layer to remove oxide scale on the second cladding layer.

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