RU2339822C2 - Ice exhaust valve, method of its production and high-temperature alloy for its production - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: invention relates to engine building and can be used in piston-type aircraft and automotive ICEs. The proposed ICE exhaust valve comprises a stem with a tip, an umbrella-like heat with stiffening ribs, their number not exceeding eight. Note that the rib has a chamfer to horizontal surface not exceeding 20°. The valve is cast in vacuum in heated ceramic molds with the further thermal treatment in the protective gas atmosphere at 1200°+20°C for, at least, 4.5 hours, mechanically processed and coated thereafter. The invention comprises the alloy composition used in the valve production.

EFFECT: ease of manufacture, better manufacturability, smaller labour input, higher valve reliability, wear resistance, longer life, optimum weight.

3 cl

Description

The invention relates to mechanical engineering, namely to engine building, and can be used in piston aircraft internal combustion engines.

Known intake valve of an internal combustion engine having a stem, a fungal-shaped head and a transition section between them with stiffeners (Japanese patent No. 61-229908 IPC F01L 3/20, F02B 31/00). In this prototype, the stiffener inlet valves develop a surface for the vaporization of the air-fuel mixture, reducing its adhesion to the valve head during engine operation.

For a valve of an exhaust internal combustion engine (ICE), stiffeners eliminate warping of its working chamfer, play an additional heat-releasing role from it, and intensify the forced rotation of valve springs, an additional reaction of exhaust gases, contributing to a more tight fit of the valve in its seat and erasing soot from the working chamfer , increasing the reliability and service life of the valve without burnout at its optimum weight.

This technical problem is solved using the valve of the exhaust internal combustion engine, having a rod with a tip, an umbrella-shaped head with stiffeners in its bottom part, evenly spaced up to 8 ribs on the circumference with the rise of the crest of each rib no more than 20 ° towards the horizontal.

Figure 1 shows the exhaust valve, figure 2 - its section aa, figure 3 - casting diagram of the exhaust valve of the internal combustion engine in vacuum in a heated ceramic mold.

The exhaust valve consists of a rod 1, an umbrella-shaped head 2 with 4 stiffeners 3 in its bottom part from the rod side.

To maintain optimum valve mass, the number of stiffeners is sufficient no more than 8 with a rise (bevel) of each to 20 ° to the horizontal. Under the valve pusher roller, at the end of the stem opposite the head, there is a tip 4 made of metal of greater hardness than the stem, for better wear resistance of this end of the stem. The umbrella-shaped head 2 has a working chamfer 5, the surface of which is rubbed against the valve seat during assembly to ensure tightness and engine power in operation.

The valve of the exhaust internal combustion engine is a highly heat-stressed part of the engine, and it is the above design, which is distinguished by simplicity, stably provides no less working thermal load than in a valve with an internal heat-removal cavity filled with sodium to balance the transfer of heat from the fungus to the stem (pp. 402-403 P. I.Orlov "Design of aircraft engines", Oborongiz, 1940, v.2). Stiffening ribs increase the heat sink from the zone of the working chamfer 5 to the rod 1 during engine operation, which is very important, and, in addition, under the influence of a turbulent gas flow from the combustion of the air-fuel mixture, the valve rotates more intensively, positively complementing the effect of valve springs on its rotation which contributes to a denser and sealed fit into its seat, erasing from the working chamfer the adhering particles of soot and eliminating the occurrence of chamfer burnouts, ensuring reliable tightness of the valve during operation of the engine at the most heat-stressed modes.

A known method of manufacturing a valve of an exhaust internal combustion engine obtained by investment casting in heated ceramic molds (UK patent No. 2110299, IPC F01L 3/02 - prototype).

The disadvantage of this method is the need for stabilizing heat treatment to maintain high strength characteristics of the material.

The technological task of this development is to simplify the valve manufacturing technology with an increase in its manufacturability, reduce the complexity and reduce the necessary dimensional accuracy with high quality strength characteristics of the material for reliable operation of such a critical and highly loaded engine part.

A method of manufacturing a valve of an exhaust internal combustion engine, comprising casting a valve according to investment casting into heated ceramic molds without machining the finned part of the head and with an allowance of up to 1-2 mm on other surfaces. After casting, a stabilizing heat treatment is carried out in a shielding gas at a temperature of 1200 + 20 ° C for at least 4.5 hours, followed by mechanical processing and applying a nitride-titanium coating, which ensures a dense, homogeneous, equiaxed and stable structure of the valve metal with a density of 8, 9 g / cm ³ with a high level of strength characteristics and dimensional accuracy at operating temperatures. Figure 3 shows a casting diagram of a valve of an exhaust internal combustion engine in vacuum into heated ceramic molds. The equiaxed dense macrostructure of the cast exhaust valve provides high characteristics of its mechanical properties, are shown in table 1.

After heat treatment and preliminary finishing of the chamfer and stem, a tip made of high-chromium steel is welded to the end of the valve stem, then the end of the stem is cut, ground and subjected to surface hardening and tempering at high hardness HRC≥50. Then follow the operations of grinding, polishing and superfinishing of the stem and valve head to the final sizes and coating with titanium nitride. After coating with titanium nitride, the rod is re-superfinished, and the working facet of each valve is rubbed to its seat in the cylinder during assembly.

Known casting heat-resistant alloy based on Nickel, containing carbon, chromium, titanium, aluminum, cobalt, niobium, tungsten, molybdenum, iron, lanthanum, hafnium, boron, cerium and yttrium, additionally contains tantalum and rhenium in the following ratio of 16 alloying elements, wt .%:

carbon 0.12-0.18 chromium 4.3-5.6 titanium 0.9-1.3 aluminum 5.65-6.25 cobalt 8.0-10.0 niobium 4.0-4.8 tungsten 10.9-12.5 molybdenum 2.5-3.5 iron 0.1-1.0 lanthanum 0.005-0.015 hafnium 0.01-0.1 boron 0.005-0.015 cerium 0.005-0.025 yttrium 0.005-0.025 tantalum 0.15-0.35 rhenium 0.15-0.35 nickel the rest (≥60%)

(US Pat. No. 2081930, С22С 19/05 - analogue)

The disadvantage of this multicompact alloy is its low resistance to abrasion and wear at temperatures above 900 ° C, despite the abundance of alloying elements.

The closest analogue is (US patent No. 3497349, IPC С22С 19/05) a heat-resistant alloy for the exhaust valve of the internal combustion engine (nickel-based) containing nickel, carbon, chromium, molybdenum, iron, tungsten, boron, niobium, silicon, manganese in the following the ratio of components, wt.%:

carbon up to 0.1 chromium 15-30 niobium 4.0-8.5 silicon up to 1 manganese up to 1 molybdenum no more than 2 iron to 10 tungsten no more than 5 boron up to 0.1 nickel rest

The disadvantage of the above alloy is the presence of niobium, impurities of silicon and manganese, which does not guarantee the formation of oxides even in a vacuum, does not contribute to the formation of a strengthening intermetallic phase, and does not allow to obtain an alloy with a dense fine-grained structure.

The technical task of this invention is to increase the resistance of the alloy to wear on the working facet of the exhaust valve of the internal combustion engine at temperatures above 900 ° C and to obtain an alloy with a dense fine-grained structure.

To solve this problem, a heat-resistant alloy of intermetallic hardening is used, without allotropic transformations in a dense equiaxial structure, stabilized after casting in vacuum by heat treatment to 1200 ° C + 20 ° C, of a relatively simple chemical composition containing nickel, carbon, chromium, molybdenum iron, tungsten, boron. This alloy additionally contains aluminum, titanium, zirconium and cerium, which affects the crystallization process and the formation of a strengthening intermetallic phase during stabilizing heat treatment and the following ratio of all components in the alloy, wt.%:

nickel  not less than 66 carbon  0.17 ± 0.05 chromium 16 ± 2 tungsten  5.5 ± 0.5 molybdenum  4 ± 0.5 iron  no more than 5 boron  0.2 ± 0.005 aluminum  2 ± 0.25 titanium  2 ± 0.25 zirconium  0.1 ± 0.025 cerium  0.01 ± 0.005

Thus, the exhaust valve of an internal combustion engine of this design, made of this alloy and in this way, is high-tech, has little laboriousness, is reliable in operation, allows to obtain a dense fine-grained structure, has great resistance to wear, has a long service life, and optimal weight. The interchangeability of cast and forged valves during operation and repair of engines is maintained.

Claims (3)

1. The valve of the exhaust internal combustion engine containing a rod with a tip, an umbrella-shaped head with stiffeners in its bottom, characterized in that the stiffeners are not more than 8, and each rib has a bevel to a horizontal surface of not more than 20 °. 2. A method of manufacturing a valve of an exhaust internal combustion engine, comprising casting a valve according to investment casting into heated ceramic molds, characterized in that after casting a stabilizing heat treatment is carried out in a shielding gas at a temperature of 1200 ° C + 20 ° C for at least 4.5 h, machining and coating. 3. Heat-resistant alloy for the valve of the exhaust internal combustion engine, containing nickel, carbon, chromium, molybdenum, iron, tungsten, boron, characterized in that it additionally contains aluminum, titanium, zirconium and cerium in the following ratio of components, wt.%: Nickel not less than 66 Carbon 0.17 ± 0.05 Chromium 16 ± 2 Aluminum 2 ± 0.25 Titanium 2 ± 0.25 Tungsten 5.5 ± 0.5 Molybdenum 4 ± 0.5 Iron no more than 5 Boron 0.2 ± 0.005 Cerium 0.01 ± 0.005 Zirconium 0.1 ± 0.025

Images