Process for producing heat-resistant alloy for exhaust valve

Abstract

The invention discloses a heat-resistant alloy for an exhaust valve and a process for producing the same. The heat-resistant alloy comprises the following components in mass percentage: 0.04 to 0.10 percent of C, less than or equal to 1.00 percent of Mn, less than or equal to 0.020 percent of P, less than or equal to 1.00 percent of Si, 18.0 to 21.0 percent of Cr, less than or equal to 2.00 percent of Co, less than or equal to 3.00 percent of Fe, 1.80 to 2.70 percent of Ti, 1.00 to 1.80 percent of Al, less than or equal to 0.20 percent of Cu, and the balance being Ni and inevitable impurities. The production process takes the component materials and adopts the process of electric furnace smelting, hardening and tempering, gas refining and continuous casting and rolling. The exhaust valve using the heat-resistant alloy has the advantages of reasonable component design, good product comprehensive performance, in particular high temperature intensity, good high temperature corrosion resistance and extreme resistance to exhaust gas corrosion; besides, the production process greatly reduces the electric power consumption in production, and the production cost is low.

Description

technical field [0001] The invention belongs to the field of preparation of austenitic heat-resistant steel, and is particularly suitable for the production process of heat-resistant alloys for the intake and exhaust valves of internal combustion engines used in large and medium-sized ships, airplanes and tanks. Background technique [0002] At present, 21-4N steel (i.e. 5Cr21Mn9Ni4N) is generally used as the steel for exhaust valves with medium and small cylinder diameters in medium-load internal combustion engines in my country. The working temperature of this steel is between 650-750 °C. At high temperature, there will be more layered precipitates. Since the layered precipitates are chromium carbides and nitrides, a large amount of precipitates will make the gas valve steel matrix poor in chromium, resulting in the steel being used in high temperature gas conditions. The corrosion resistance of the valve is significantly reduced, and corrosion pits will be formed on the nec...

AI Technical Summary

Problems solved by technology

[0002] At present, 21-4N steel (i.e. 5Cr21Mn9Ni4N) is generally used as the steel for exhaust valves with medium and small cylinder diameters in medium-load internal combustion engines in my country. The working temperature of this steel is between 650-750 °C. At high temperature, there will be more layered precipitates. Since the layered precipitates are chromium carbides and nitrides, a large amount of precipitates will make the gas valve steel matrix poor in chromium, resulting in the steel being used in high temperature gas conditions. The corrosion resistance of the valve is significantly reduced, and corrosion pits will be formed on the neck, disk, and cone surface of the valve, which will easily cause air leakage and cracking of the valve steel. Under the action of stress, it is easy to produce fatigue cracks or even fracture

In the prior art, there are also information introductions for high-load exhaust valve steel for internal combustion engines, such as the valve steel introduced in the US Patent 4929419 document. This steel is adjusted for surface division of 23-8N steel. , Mo element and increase the content of C and N to change the performance of the steel grade. In addition, Germany introduced an improved valve steel in the patent document DE3704473A1. This steel is based on 21-4N steel with 5-6 %Al, 1.8-2.5% Nb, 0.8-1.5% W, N increased to 0.4-0.6% composition range, and the technology of improved valve steel is also the Russian SU1650762A1 patent, which introduces a 21 Adding 0.5-1.5% Mo; 0.5-1.5% Nb; 0.5-1.5V and 0.05-0.20% Zr elements on the basis of -4N, the performance of this type of steel is only slightly improved, and it cannot meet the requirements of high-load internal combustion engine exhaust valve steel. need