Laser overlaying method for engine valve conical surfaces

Abstract

The invention discloses a laser overlaying method for engine valve conical surfaces. Valve workpieces to be overlaid are formed through machining, and are preheated in a heat treatment furnace; the preheating temperature is 200-300 DEG C; the preheating time is 15-30 min; the valve workpieces to be overlaid are fixed by using a tool; the tool is mounted on a rotating shaft, and is used for drivingthe valve workpieces to be overlaid to rotate; the valve workpieces are overlaid by laser through a laser overlaying machine; due to self rotation of the valve workpieces, a scanning trajectory of laser beams emitted by the laser overlaying machine is spiral; and the laser overlaying machine comprises the following parameters: 5-8 mm of the light spot diameter, 2000-3000 W of the laser power, 5-15 mm / s of the scanning speed, 10-16 g / min of the powder feeding speed, 5-15 L / min of the flow of tail blowing gas, 5-10 L / min of the flow of protective gas, and 35-45% of the joint rate. The method not only can effectively reduce the loss of overlaying powder and increase the utilization rate of the overlaying powder, but also can effectively reduce thermal stress.

Description

technical field [0001] The invention relates to a laser surfacing method, in particular to a laser surfacing method for an engine valve conical surface. Background technique [0002] With the ever-increasing performance requirements and environmental protection requirements, the working conditions of the engine are becoming more and more complex and harsh, and the working conditions of the valves are also becoming more severe, especially the working conditions of the exhaust valve. Because the valve moves in the engine cylinder, the working condition of the valve is more complicated. The main working conditions of the cone surface of the valve disc are as follows: (1) The valve disc is in a state of rapid opening and closing, so every time it is opened and closed, the cone surface of the valve will contact the valve seat ring, and due to the explosion pressure of the gas in the cylinder, the valve will The conical surface forms an impact with the seat ring. (2) The high te...

AI Technical Summary

Problems solved by technology

[0005] At present, there are mainly three surfacing welding methods in the world. The first one is the traditional arc powder surfacing technology. Due to the influence of the arc blowing force, it is difficult to achieve the goals of high efficiency and low dilution rate at the same time. In order to improve efficiency, it will inevitably lead to heat input. increase, resulting in increased penetration of the base material, decreased performance of the surfacing layer, and greater tensile thermal stress

The second is the powder surfacing technology based on the plasma arc-based high-energy-density heat source, which is also the surfacing technology currently used for valves. This technology has a low dilution rate (5% to 10%), but the surfacing efficiency is low. , After surfacing welding, the machining allowance is large, the surfacing layer is difficult to process, the utilization rate of surfacing welding powder is not high, and the processing tools are easy to wear out, etc.

The third is the high-energy beam surfacing technology represented by laser surfacing, the energy utilization rate is as high as 30%, the base material is not affected by the metal vapor when heated, the cladding metal cooling speed is fast, and the cladding layer has good wear resistance. The disadvantage is that the laser equipment is expensive and the operating cost is high. At present, this technology has not been used in valve products.

However, the equipment is relatively complicated and the gas consumption is large, so plasma arc surfacing is suitable for mass production

The disadvantage of plasma surfacing welding is that it is difficult to guarantee the stability of the arc during the manufacturing process, there are many parameters affected, and the precision of the formed parts is low, so it is necessary to leave sufficient machining allowance after surfacing welding

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