Method for improving hardness of conical surface of air valve of medium-speed internal combustion engine

Abstract

The invention discloses a method for improving the hardness of a conical surface of an air valve of a medium-speed internal combustion engine, after the conical surface of a valve disc of the air valve subjected to upsetting heat treatment is slotted, surfacing is carried out by using alloy powder through laser cladding, and the alloy powder comprises the following chemical components in percentage by mass: 0.054% of C, 0.46% of Si, 0.41% of Mn, 0.026% of P, 0.009% of S, 16.13% of Cr, 4.31% of Ni, 3.39% of Cu, 0.0042% of B, 0.075% of Co, 0.0081% of Al, 0.0025% of Zr, 0.014% of Ti, less than 0.001% of Mo and 67.4% of Fe. The laser cladding process is adopted to replace a traditional surfacing process, the production efficiency can be greatly improved, the production quality is guaranteed, novel alloy powder is adopted for laser cladding surfacing, the hardness of a cladding layer of the manufactured air valve reaches 390-430 HV, the crack-free requirement is met under ultrasonic flaw detection, and laser cladding and a base body are free of micro cracks.

Description

Technical Field

[0001] This invention belongs to the technical field of medium-speed internal combustion engine components, specifically relating to a method for improving the hardness of the valve cone surface of a medium-speed internal combustion engine. Background Technology

[0002] Currently, the valve disc conical surface of medium-speed internal combustion engines is typically constructed using a welding process. This process suffers from low efficiency, poor forming quality, and significant difficulty in controlling the welding process. Therefore, we propose using a laser cladding process. However, laser cladding generally uses GH864 high-temperature alloy material. GH864 is a nickel-based high-temperature alloy, which often exhibits poor bonding and microcracks during laser cladding. Furthermore, when its hardness is below 400 HV, it is difficult to meet the requirements for wear and corrosion resistance. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a method for improving the hardness of the valve cone surface of a medium-speed internal combustion engine. This method uses a novel alloy powder and laser cladding process to treat the valve cone surface, which can increase the hardness of the cladding layer to 390-430 HV and meet the requirement of no cracks under ultrasonic testing.

[0004] The technical solution adopted in this invention is: a method for improving the hardness of the valve cone surface of a medium-speed internal combustion engine, wherein after slotting the valve disc cone surface after upsetting heat treatment, alloy powder is used for laser cladding welding.

[0005] Preferably, the chemical composition of the alloy powder, by mass percentage, is: C: 0.003%-0.007%, Si: 0.1%-0.8%, Mn: 0.1%-0.6%, P: 0.001%-0.004%, S: 0.005%-0.010%, Cr: 12%-18%, Ni: 2%-7%, Cu: 1%-5%, B: 0.001%-0.006%, Co: 0.03%-0.10%, Al: 0.005%-0.015%, Zr: 0.001%-0.005%, Ti: 0.01%-0.03%, Mo: less than 0.001%, with the balance being Fe.

[0006] Preferably, the chemical composition of the alloy powder, by mass percentage, is: C: 0.054%, Si: 0.46%, Mn: 0.41%, P: 0.026%, S: 0.009%, Cr: 16.13%, Ni: 4.31%, Cu: 3.39%, B: 0.0042%, Co: 0.075%, Al: 0.0081%, Zr: 0.0025%, Ti: 0.014%, Mo: less than 0.001%, Fe: 67.4%.

[0007] Preferably, the chemical composition of the alloy powder, by mass percentage, is: C: 0.006%, Si: 0.5%, Mn: 0.3%, P: 0.002%, S: 0.009%, Cr: 14%, Ni: 4%, Cu: 3%, B: 0.002%, Co: 0.08%, Al: 0.005%, Zr: 0.004%, Ti: 0.03%, Mo: less than 0.001%, with the balance being Fe.

[0008] Preferably, the chemical composition of the alloy powder, by mass percentage, is: C: 0.004%, Si: 0.3%, Mn: 0.45%, P: 0.0035%, S: 0.0087%, Cr: 13.4%, Ni: 3.6%, Cu: 4.2%, B: 0.0034%, Co: 0.088%, Al: 0.013%, Zr: 0.002%, Ti: 0.01%, Mo: less than 0.001%, with the balance being Fe.

[0009] The beneficial effects of this invention are as follows: This invention uses laser cladding process to replace traditional welding process, which can greatly improve production efficiency and ensure production quality. Furthermore, the use of new alloy powder for laser cladding welding results in a cladding layer hardness of 390-430 HV for the gas valve, which meets the requirement of no cracks under ultrasonic testing, and there are no microcracks in the laser cladding and the substrate. Attached Figure Description

[0010] Figure 1 This is a metallographic image of the weld overlay layer of the present invention. Detailed Implementation

[0011] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0012] Example 1

[0013] like Figure 1 As shown, the method for improving the hardness of the valve cone surface of a medium-speed internal combustion engine provided in this embodiment involves slotting the valve disc cone surface after upsetting heat treatment, and then using alloy powder for laser cladding welding. The chemical composition of the alloy powder, by mass percentage, is as follows: C: 0.054%, Si: 0.46%, Mn: 0.41%, P: 0.026%, S: 0.009%, Cr: 16.13%, Ni: 4.31%, Cu: 3.39%, B: 0.0042%, Co: 0.075%, Al: 0.0081%, Zr: 0.0025%, Ti: 0.014%, Mo: less than 0.001%, Fe: 67.4%.

[0014] A fiber laser is selected, with a laser power of 1500-2500W, a spot diameter of 2.0-3.0mm, a scanning speed of 5-10mm / s, a powder feeding rate of 15-25g / min, and an overlap rate of 40%-50%. After preheating to 300-400℃, laser cladding begins. During the cladding process, the laser beam is kept perpendicular to the curvature of the valve disc cone. After cladding is completed, the valve is post-heated to 350-450℃ and then slowly cooled. After slow cooling, the cladding layer is precision machined to achieve the final dimensional accuracy and surface finish of the valve.

[0015] The valve cone surface prepared in Example 1 was subjected to a high-temperature tensile test according to GB / T228.2-2015. The test results are shown in Table 1.

[0016] Table 1

[0017]

[0018] The valve cone surface prepared in Example 1 was subjected to a high-temperature creep test according to GB / T2039-2012. The test results are shown in Table 2.

[0019] Table 2

[0020]

[0021] The valve cone surface prepared in Example 1 was subjected to matrix hardness testing according to GB / T231.1-2018. The test results are shown in Table 3.

[0022] Table 3

[0023]

[0024] The valve cone surface prepared in Example 1 was subjected to a hardness test of the cladding layer according to GB / T4340.1-2009. The hardness test results of the cladding layer, transition layer and substrate along a straight line are shown in Table 4.

[0025] Table 4

[0026]

[0027] The metallographic structure of the valve cone surface prepared in Example 1 was tested at the laser cladding site according to GB / T13298-2015. The test results are shown in Table 5.

[0028] Table 5

[0029]

[0030] Example 2

[0031] This embodiment is basically the same as Embodiment 1, except that the composition of the alloy powder is different. The chemical composition of the alloy powder, by mass percentage, is as follows: C: 0.006%, Si: 0.5%, Mn: 0.3%, P: 0.002%, S: 0.009%, Cr: 14%, Ni: 4%, Cu: 3%, B: 0.002%, Co: 0.08%, Al: 0.005%, Zr: 0.004%, Ti: 0.03%, Mo: less than 0.001%, with the balance being Fe.

[0032] Example 3

[0033] This embodiment is basically the same as Embodiment 1, except that the composition of the alloy powder is different. The chemical composition of the alloy powder by mass percentage is as follows: C: 0.004%, Si: 0.3%, Mn: 0.45%, P: 0.0035%, S: 0.0087%, Cr: 13.4%, Ni: 3.6%, Cu: 4.2%, B: 0.0034%, Co: 0.088%, Al: 0.013%, Zr: 0.002%, Ti: 0.01%, Mo: less than 0.001%, and the balance is Fe.

[0034] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications and substitutions based on the technical solutions and inventive concepts provided by the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for improving the hardness of the valve cone surface in a medium-speed internal combustion engine, characterized in that: After the valve disc of the gas valve has been grooved at the conical surface after upsetting and heat treatment, it is overlaid by laser cladding using alloy powder.

2. The method for improving the hardness of the valve cone surface of a medium-speed internal combustion engine according to claim 1, characterized in that: The chemical composition of the alloy powder, by mass percentage, is as follows: C: 0.003%-0.007%, Si: 0.1%-0.8%, Mn: 0.1%-0.6%, P: 0.001%-0.004%, S: 0.005%-0.010%, Cr: 12%-18%, Ni: 2%-7%, Cu: 1%-5%, B: 0.001%-0.006%, Co: 0.03%-0.10%, Al: 0.005%-0.015%, Zr: 0.001%-0.005%, Ti: 0.01%-0.03%, Mo: less than 0.001%, with the balance being Fe.

3. The method for improving the hardness of the valve cone surface of a medium-speed internal combustion engine according to claim 2, characterized in that: The chemical composition of the alloy powder, by mass percentage, is as follows: C: 0.054%, Si: 0.46%, Mn: 0.41%, P: 0.026%, S: 0.009%, Cr: 16.13%, Ni: 4.31%, Cu: 3.39%, B: 0.0042%, Co: 0.075%, Al: 0.0081%, Zr: 0.0025%, Ti: 0.014%, Mo: less than 0.001%, Fe: 67.4%.

4. The method for improving the hardness of the valve cone surface of a medium-speed internal combustion engine according to claim 2, characterized in that: The chemical composition of the alloy powder, by mass percentage, is as follows: C: 0.006%, Si: 0.5%, Mn: 0.3%, P: 0.002%, S: 0.009%, Cr: 14%, Ni: 4%, Cu: 3%, B: 0.002%, Co: 0.08%, Al: 0.005%, Zr: 0.004%, Ti: 0.03%, Mo: less than 0.001%, balance Fe.

5. The method for improving the hardness of the valve cone surface of a medium-speed internal combustion engine according to claim 2, characterized in that: The chemical composition of the alloy powder, by mass percentage, is as follows: C: 0.004%, Si: 0.3%, Mn: 0.45%, P: 0.0035%, S: 0.0087%, Cr: 13.4%, Ni: 3.6%, Cu: 4.2%, B: 0.0034%, Co: 0.088%, Al: 0.013%. Zr ： 0.002%, Ti: 0.01%, Mo: less than 0.001%, balance Fe.

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