JPS60122206A - Valve for internal-combustion engine - Google Patents

Abstract

PURPOSE:To prevent crack at the built-up portion where hardening agent harder than the valve body material is built up on the seat face, by placing intermediate material having thermal expansion factor approximately same with that of hardening agent between the valve body material and the hardening agent. CONSTITUTION:Intermediate material 11 composed of such material as having thermal expansion factor approximately same with that of hardening agent 3 is placed between the hardening agent 3 built up on the seat face 2 of valve body 1 and the valve body material. Austenite system heat-resistant stainless steel is employed for valve body material while cobalt alloy is employed for hardening agent 3 and ferrite system iron alloy or maltensite iron alloy is employed for intermediate material. The intermediate material 11 will release transmission of tensile to the hardening agent 3 layer thus to prevent crack in hardening material built-up portion under high temperature usage of valve.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a valve for an internal combustion engine, and more particularly to a valve for an internal combustion engine having an improved hardening material build-up portion on a seat surface.

[Prior Art] A reciprocating internal combustion engine such as a diesel engine is usually provided with an intake valve and an exhaust valve.

These internal combustion valves, especially the exhaust valves, directly receive the high heat of the combustion gas during an explosion, so their base material absorbs the heat well.
It must be made of a material that does not easily oxidize, and stainless steel, particularly austenitic stainless steel, is widely used.

As shown in FIGS. 1 and 2, a cobalt-based or nickel-based hardening material 3 is usually applied to the seat surface 2 of the valve body 1 to improve erosion resistance, wear resistance, and prevent blow-out. It's filled with meat.

As mentioned above, when the engine is driven, the valves, especially the vicinity of the seat surface of the exhaust valve, are heated to extremely high temperatures by the combustion gas (for example, in a marine diesel engine, they are heated to about 500°C). Since the thermal expansion coefficient of the hardened material built up on the sheet surface is smaller than that of the valve base material, thermal stress is generated due to the difference in thermal expansion coefficient, and tensile stress is applied to the hardened material 3. loaded. This thermal stress is considered to be a contributing factor to the radial cracks 4 as shown in FIG. The direction of the maximum stress is estimated from the direction of cracking, and is considered to be the circumferential direction as indicated by the arrow in FIG.

[Object of the Invention] An object of the present invention is to provide a valve for an internal combustion engine that solves the above-mentioned conventional problems and prevents cracking of the built-up portion due to thermal stress.

[Structure of the Invention] In order to achieve this object, the valve for an internal combustion engine of the present invention is provided with an intermediate material for relieving thermal stress in the built-up part, and a base of the valve is provided on the seat surface. In internal combustion engine valves that are built up with a hardened material that is harder than the original material, the valve base material is made of austenitic heat-resistant stainless steel, and the hardened material is made of cobalt-based alloy, nickel-based alloy, ceramics, or tungsten carbide-based alloy. The space between the hardening material and the valve base material has a coefficient of thermal expansion close to that of the hardening material.
A valve for an internal combustion engine, characterized in that an intermediate material of a ferritic iron-based alloy or a martensitic iron-based alloy is interposed.

The main points are as follows.

[Embodiments of the Invention] Examples of the present invention will be described in detail below with reference to the drawings.

FIGS. 3 to 5 are cross-sectional views showing an embodiment of a valve for an internal combustion engine according to the invention. The internal combustion engine valve of the present invention has a third
As shown in the figure, a cross-sectional view of the vicinity of the valve head, there is a thermal expansion coefficient similar to that of the hardened material 3 between the hardened material 3 built up on the seat surface 2 of the valve body and the valve base material. An intermediate member 11 made of a material having the following properties is interposed. (Furthermore, FIG. 4 is an enlarged view of the vicinity of the sheet surface 2 in FIG. 3.) By interposing the intermediate material 11 having a thermal expansion coefficient similar to that of the hardening material 3, the tensile stress applied to the hardening material 3 As a result, the cracks 4 as shown in FIG. 2 described above are less likely to occur.

As a specific example of the intermediate material in the uninvented state, for example, austenitic heat-resistant stainless steel (20 to 500°
Thermal expansion coefficient at C: approx. 19 x lO7°C), and when a cobalt alloy (approximately 14 x lO7°C) or nickel alloy (approximately 13 x 10/'C) is used as the hardening material, the ferritic iron base Steel material (approximately 14x10, /
'c) and martensitic iron-based steel materials (approximately 13
t o'/°C) etc. are suitable.

Examples of the method of joining the intermediate material and the hardening material to the valve base material include a method of overlaying the intermediate material and the hardening material on the valve base material by welding, a method of joining the material by brazing, and the like.

When overlaying, for example, when overlaying a ferritic or martensitic material whose main component is iron as an intermediate material on a valve base material of austenitic heat-resistant stainless steel, depending on the combination of the valve base material and intermediate material. When directly overlay welding,
In some cases, welding defects may occur and it may not be possible to perform sound welding. Specifically, as an example of this, fully austenitic stainless steel is used as the valve base material and carbon steel is used as the intermediate material, but in such a case, as shown in Figure 5, an additional adhesive layer is It is preferable to provide two layers of intermediate materials with an intermediate material interposed therebetween. That is, after the second intermediate material 13 of austenitic stainless steel containing ferrite is built up on the valve base material, the intermediate material 12 of a ferritic or martensitic material containing iron as a main component is built up. Then, by overlaying the hardened material 3 on the intermediate material 12, overlay welding can easily be performed without any overlay.

[Effects of the Invention] As detailed above, the valve for an internal combustion engine of the present invention has an intermediate material having a coefficient of thermal expansion close to that of the hardened material interposed between the hardened material and the valve base material. The intermediate material reduces the transmission of tensile stress to the hardened material layer, and prevents cracking of the hardened material flesh area due to use of the valve at high temperatures.

The internal combustion engine valve of the present invention has excellent heat resistance and wear resistance, and has a long life, making it extremely useful industrially. Therefore, it is particularly suitable for application to exhaust valves.

[Brief explanation of drawings]

FIG. 4 is an enlarged view of the vicinity of the seat surface in FIG. 3, and FIG. 5 is an enlarged sectional view of the vicinity of the seat surface showing another embodiment of the valve for an internal combustion engine according to the present invention. l...Valve body, seat surface for 2..., 3...
...Cured material 54...Crack, 11.12...
...Intermediate material, 13...Second intermediate material. Agent Patent Attorney Shigeno Figure 1 Figure 2 Figure 3 Figure 4 Seal Figure 5

Claims (3)

[Claims] (1) In an internal combustion engine valve in which a hardened material with higher hardness than the valve material is built up on the seat surface, the valve material is made of austenitic heat-resistant stainless steel, and the hardened material is a cobalt-based alloy or nickel-based material. A ferritic iron-based alloy or a martensitic iron-based alloy, which has a thermal expansion coefficient close to that of the hardened material, is formed between the hardened material and the valve material. A valve for an internal combustion engine, characterized in that an alloy intermediate material is interposed. (2) The valve according to claim 1, characterized in that a second intermediate material is interposed between the intermediate material and the valve material to improve the bondability between the intermediate material and the base material. (3) The valve according to claim 1, wherein the intermediate material and the valve gap material are joined by brazing.