A method and device for repairing pores in a powder plasma cladded layer of a valve face of a gas valve

Abstract

The application discloses a kind of gas valve surface powder plasma surfacing layer pore repair method and device, belong to the field of welding additive manufacturing, for solving the problem of surfacing layer pore defect that easily appears in the process of plasma surfacing, specifically for a kind of gas valve surface powder plasma surfacing layer pore repair device and pore repair method, the pore repair device, resistance heating is combined with pressurization mechanism, to promote the pore repair in surfacing layer under certain temperature and pressure conditions.The pore repair method is directly heated by resistance, combined with surfacing layer pressurization device, by accurately controlling heating and pressurization process, promote the pore healing in surfacing layer.

Description

TECHNICAL FIELD

[0001] The application provides a method and device for repairing pores in a powder plasma surfacing layer of a valve face of a gas valve, and belongs to the field of welding additive manufacturing. BACKGROUND

[0002] During service, the valve face of a marine diesel engine needs to have sufficient strength to withstand repeated impact loads, and also needs to have strong high-temperature resistance to adapt to the thermal shock service environment caused by high-temperature and high-pressure combustion gas. In order to improve the wear resistance, corrosion resistance and high-temperature resistance of the valve sealing surface, a plasma surfacing technology is often used for surface strengthening treatment. During the plasma surfacing process, pores may appear in the surfacing layer of the gas valve due to the influence of process parameters, cooling rate of the molten pool and gas inclusions. The pores, which are small bubbles formed by gas or impurities that cannot be completely discharged or dissolved, are usually located inside the welded metal or at the welded joint. In a high-temperature and high-pressure working environment, the existence of pores can cause the valve sealing surface to easily overheat locally, stress to concentrate and fatigue fracture to occur early, thereby significantly reducing the service life of the valve and affecting the safe operation of the diesel engine. In the plasma surfacing process, the repair method for pore defects can draw inspiration from the self-repair mechanism of living organisms. The self-repair phenomenon after tissue damage widely exists in living organisms, and damaged cells repair the wound through division and repair. In the world of inanimate metals, although metals do not have complete self-repairing ability, some studies have shown that under certain conditions, metal alloys can undergo a similar self-repairing process. SUMMARY

[0003] In view of the pore defect repair problem in the plasma surfacing layer described in the background, the application provides a repair device combining resistance direct heating and pressure, which can effectively promote the healing of pores in the surfacing layer and significantly improve the density and mechanical properties of the surfacing layer. The application specifically provides a pore repair device and method for a powder plasma surfacing layer of a valve face of a gas valve.

[0004] The pore repair device combines resistance heating and pressure mechanism, heats the surfacing layer through the heat generated by the current, and at the same time applies uniform pressure, so as to promote the repair of pores in the surfacing layer under certain temperature and pressure conditions. The entire pore repair device includes four systems, namely a resistance heating system, a pressure control system, a temperature monitoring system and a workbench and clamp system. The resistance heating system is composed of an electrode, a heating power supply and a heating controller, the temperature monitoring system is composed of a thermocouple sensor, a temperature data acquisition system and a temperature controller, the pressure control system is composed of a four-petal pressure device and a pressure sensor, and the workbench and clamp system is composed of a stable workbench and a valve fixing clamp

[0005] The resistance heating system, composed of electrodes, heating power supply and heating controller, connects the pressure electrode to the positive pole and the workbench electrode to the negative pole, forming a circuit through the power supply-pressure electrode-deposit layer-workbench, completing the current flow and heating process; the heating controller monitors the temperature in real time and adjusts the current according to the temperature feedback, ensuring that the deposit layer remains within the optimal repair temperature range.

[0006] The temperature monitoring system, the temperature controller adjusts the heating device according to real-time temperature feedback, ensuring that the temperature of the deposit layer is always within the required range.

[0007] The pressure control system, the pressure sensor monitors the pressure applied to the deposit layer in real time and feeds back data to the control system, ensuring stable and uniform pressure to avoid defects in the deposit layer caused by uneven or excessive pressure.

[0008] The workbench and clamp system provides a stable support platform to ensure the gas valve remains in a fixed position throughout the repair process; the gas valve fixing clamp is used to accurately position the gas valve and ensure it is aligned with the heating device, electrodes and pressure device to ensure the heating and pressure effect during repair.

[0009] The pore repair method uses resistance direct heating technology combined with deposit layer pressure device to soften the deposit layer by precise control of heating, improve plastic deformation ability, and deform the metal near the pore in the deposit layer until the pore heals by precise control of pressure, to improve the density of the deposit layer, and thus improve its mechanical properties and high temperature resistance.

[0010] The present application is suitable for powder plasma surfacing of gas valve face, accurately controls the heating and pressure process, promotes the healing of pores in the deposit layer, to improve the density of the deposit layer, and thus improve its mechanical properties and high temperature resistance. The present application uses a combination of resistance heating and pressure mechanism, which heats the deposit layer by the heat generated by the current, while applying uniform pressure, thereby promoting the repair of pores in the deposit layer under certain temperature and pressure conditions. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 It is a schematic diagram of the resistance heating and pressure experimental device.

[0012] Figure 2 It is a layout diagram of the heating and pressure device.

[0013] Figure 3 It is a schematic diagram of the current during repair. DETAILED DESCRIPTION

[0014] The application will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0015] Reference Figure 1 To introduce the resistance heating and pressurizing experimental device in this specific embodiment, first, the plasma surfacing after the gas valve is fixed in the clamp system 1 on the workbench, the clamp 1 aligns the gas valve 2 with the heating device 8, the electrode 5 and the pressurizing device 4, the electrode is installed on the surface of the surfacing layer, according to the behavior of the current passing through the material, the current will preferentially choose the path with lower resistance to flow. Therefore, when the electrode is installed close to the surface of the surfacing layer, it can ensure that the current acts more directly on the pore area, promoting pore repair and healing.

[0016] The specific case of the workpiece and the implementation process will be described below. This implementation case is explained by a gas valve surface powder plasma surfacing layer pore repair.

[0017] The plasma surfacing after the gas valve is fixed in the clamp system on the workbench, ensuring that the gas valve maintains a stable and accurate position during the repair process. The clamp aligns the gas valve with the heating device, the electrode and the pressurizing device, so as to ensure uniform stress and heating of the surfacing layer during heating and pressurizing.

[0018] Start the resistance heating system, the electrode generates heat through the current and transmits heat to the surface of the gas valve surfacing layer. The heating controller adjusts the current intensity in real time according to the feedback signal of the temperature sensor, ensuring that the surfacing layer is always within the optimal repair temperature range.

[0019] In the welding repair, the optimal repair temperature range of the surfacing layer is closely related to the melting point of the material, the heat treatment characteristics, and the physical and chemical changes required for repair. If combined with common surfacing materials (such as stainless steel, nickel-based alloy, etc.) and the repair process, the possible repair temperature range is generally between 300℃ and 1200℃, depending on the material used. In order to obtain an accurate temperature range, it is necessary to consult the standards in this technical field or obtain the data through experiments.

[0020] The temperature monitoring system measures the temperature of the surfacing layer in real time and transmits the data to the temperature data acquisition system, ensuring that the temperature control system accurately maintains temperature stability. By accurately adjusting the heating power, it ensures that the surfacing layer is heated uniformly, avoiding the situation that the repair effect is not ideal due to local overheating or excessive temperature fluctuations.

[0021] After the resistance heating system is started and the surfacing layer is uniformly heated, the pressurizing device is turned on. The four-petal pressurizing device approaches the surfacing layer of the gas valve surface under the action of the driving force until it closely adheres to it, and then stops moving. The driving force will continue to act on the pressurizing device to form a uniform pressure, which is usually not high, between 10 2 N-10 4The actual value is set by considering the material and size of the cladding layer and the pressing device. The lower pressure is set to make the contact force between the four-part pressing device and the cladding layer uniform, to avoid excessive pressure on the cladding layer, and to avoid damage to the pore position.

[0022] The temperature and pressure changes of the cladding layer are monitored to determine whether the pore repair is complete. When the temperature control system keeps the cladding layer in the optimal repair temperature range and the temperature stabilizes at a predetermined value, and the pressure control system uniformly applies pressure, if the pore defects are significantly reduced or disappear, and the surface is smooth and dense, it means that the pores have healed. At this time, the system stops the heating and pressing process.

[0023] For temperature, if we assume that the temperature range is between 300°C and 1200°C, it is likely that the optimal repair effect will be achieved within this range. For pressure, it is usually between a few hundred and a few thousand Newtons, and the exact control is based on the repair requirements. Therefore, the exact values may need to be confirmed through actual engineering design or experimental research.

Claims

1. A method for repairing porosity in the powder plasma overlay layer of a gas valve face, solving the problem of porosity defects in the overlay layer that easily occur after plasma overlay, characterized in that: This invention includes a device for repairing porosity in powder plasma weld overlays on gas valve surfaces. The device comprises a resistance heating system, a pressure control system, a temperature monitoring system, a worktable, and a fixture system. It combines resistance heating with a pressurization mechanism, using heat generated by an electric current to heat the weld overlay while simultaneously applying uniform pressure. Temperature and pressure control promote porosity repair within the weld overlay. The resistance heating system consists of electrodes, a heating power supply, and a heating controller. In this system, the electrodes transfer heat to the gas valve weld overlay via an electric current, ensuring proper repair of the weld overlay during the repair process. Uniform heating is achieved; the heating power supply provides adjustable current to precisely control the temperature during the heating process; the pressure control system in the porosity repair device consists of a four-lobed pressurizing device and a pressure sensor. The four-lobed pressurizing device completely encloses the gas valve weld overlay layer and applies pressure evenly to the surface of the weld overlay layer, ensuring uniform stress on the weld overlay layer during the heating repair process; the temperature monitoring system in the porosity repair device consists of a thermocouple sensor, a temperature data acquisition system, and a temperature controller. The thermocouple sensor is installed on the surface of the weld overlay layer to measure the temperature in real time and transmit the data to the temperature data acquisition system. The porosity repair method specifically employs direct resistance heating technology combined with a weld overlay pressurization device. By precisely controlling the heating and pressurization process, it promotes the healing of porosity in the weld overlay.

2. The method for repairing porosity in the powder plasma overlay layer of a gas valve surface according to claim 1, characterized in that... The workbench and clamping system in the pore repair device consists of a stable workbench and a valve fixing clamp. The workbench provides stable support to ensure that the valve remains in a fixed position throughout the repair process. The valve fixing clamp is used to accurately position the valve and ensure that it is aligned with the heating device, electrode, and pressurizing device to ensure the heating and pressurizing effect during the repair process.

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