JPS62284909A - Engine valve and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide excellent resistance to heat and resistance to wear at a low cost, by a method wherein an allowed layer consisting of a specified composition containing an Ni group alloy is alloyed integrally with a valve body on the valve face of the valve body formed by an austenite series heat resistant steel. CONSTITUTION:In a valve body 1 formed by an austenite series heat resistant steel, a shank part 1A and a bevel part 1B are formed integrally with each other, and a face surface 2 making contact with a matching valve seat material is formed to the bevel part 1B. In this case, an Ni group alloy is placed on the valve face 2, and is irradiated from a position above the Ni group alloy with high density energy. The Ni group alloy and the surface layer of its underlaying surface layer are rapidly molten and rapidly re-coagulated to form an alloyed layer 3 consisting of 70% or more Ni, 14-18% Cr, 5-10% Fe, 2-6% Fe, 2-6% Ti, 10.4-1.0% A, and remaining percent inevitable impurity. Thereafter, heat treatment is applied on the alloyed layer 3 at a temperature of 750-850 deg.C.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention Industrial Field of Application This invention relates to an engine valve used for an exhaust valve of an engine such as an automobile, and particularly to an engine valve used for an exhaust valve of an engine such as an automobile. This invention relates to a valve having a stop having excellent heat resistance and wear resistance, and a method for manufacturing the same.

Conventional Techniques 1 As is well known, engine valves are required to be immersed in heat and have high wear resistance, especially for the valve face that contacts the valve seat, as well as high temperature corrosion resistance and high temperature acid resistance. chemical resistance and 1 til thermal shock resistance are also required. In particular, among engine valves, exhaust valves are exposed to extremely high temperatures and are therefore required to have excellent wear resistance under high temperatures.

Conventional exhaust valves have typically been made of austenitic heat-resistant steel (for example, JIS 5UH35), but in recent years there has been a trend toward harsher usage conditions, and to cope with this, the main body has been made of austenitic heat-resistant steel. Made of steel, especially heat resistant on the valve face surface,
Stellite with excellent wear resistance (Co-Cr-W alloy)
Overlay valves with overlays are increasingly being used. In addition, as described in JP-A-49-129016, for example, a Ni-based alloy containing MO as an essential component is overlaid on the face of a valve body made of heat-resistant steel. A valve, or a valve similarly overlaid with a Ni CO-based alloy containing Mo as an essential component, has also been proposed, as described in JP-A-49-129017.

Problems to be Solved by the Invention As mentioned above, engine valves with stellite overlays cannot be used in conventional general valves, since stellite itself is an expensive alloy containing more than zero CO as a basic component. It is difficult to build up thinly using acetylene gas build-up and TIG build-up, which requires more than 1% of Stellite use per engine valve, which significantly increases the cost of the valve. It had to be expensive.

In addition, the valves described in the above-mentioned publications also contain a considerable amount of expensive Mo as an essential alloying component, so they have to be expensive like the stellite overlay valves.

Furthermore, in the conventional Stellite build-up valves and the build-up valves described in the above-mentioned publications, the composition of the meat layer that can exhibit the best heat resistance and wear resistance is determined, and an alloy having that composition is used for the valve body. In order to avoid the inability to obtain the desired characteristics due to changes in the component composition due to the mixing of base material components, especially Fe, into the built-up layer,
During build-up, build-up conditions were usually set so as to prevent the surface of the base material from melting as much as possible. From this,
On the contrary, the metallurgical bond between the m meat layer and the base metal tends to be insufficient, which tends to cause the problem that the meat layer is likely to peel off.

This invention was made against the background of the above circumstances, and is low in cost and exhibits excellent heat and wear resistance equivalent to or better than conventional Stellite domestic valves. It is an object of the present invention to provide an engine valve in which the layer is integrated with the bases 4, 4 so as not to cause peeling due to the properties of the engine, and a method for manufacturing the same.

Means to solve the problem The engine valve of this invention is austenitic heat resistant!
Ni 7 is applied to the valve face surface of the valve body consisting of a threshold.
0% or more, Cr14-18%, Fe5-10%, Ti
An alloyed layer consisting of 2 to 6% Al, 0.4 to 1.0% Al, and the remainder unavoidable impurities is formed integrally with the valve body. .

Further, in the engine valve manufacturing method of the second invention, a Ni1 alloy is placed on the valve face surface of a valve body made of austenitic heat-resistant steel, and high-density energy is irradiated from above the Ni-based alloy to remove the Ni-based alloy and its The surface layer of the lower base material is rapidly melted and rapidly resolidified to produce Ni 70% or more, Cr 14-18%, Fe 5-10%, Ti 2
~6%, Al0.4~1.0%, and the balance formed by unavoidable impurities, and its Q% 750~850
The method is characterized in that the alloyed layer is heat-treated at a temperature within a range of .degree.

Function First, the reason for limiting the composition of the alloyed layer on the valve face surface of the engine valve of the present invention will be explained.

Ni: N1 is the basic component of the valve face alloy layer,
It has the effect of improving high-temperature hardness and high-temperature wear resistance) and also improves lead oxide corrosion resistance in coexistence with Cr.
If it is less than 70%, these effects cannot be sufficiently obtained. 1st
The figure shows the results of a lead oxidation resistance test in which various N1-containing Shiba specimens were immersed in lead oxide (Pb0 100%) heated to 920° C. for 1 hour and the weight loss was measured. 1st
From the figure, it can be seen that when Ni is 70% or more, stable and excellent lead oxide corrosion resistance is exhibited. Therefore, Ni was set at 70% or more.

Cr: Cr forms carbides and has the effect of improving high-temperature hardness, but if it is less than 14%, the desired effect cannot be obtained. Figure 2 shows the results of investigating the Vickers hardness at 800°C when the cr content was varied. From Figure 2, Cr
Stable tlv at ld% or above 300 or above 800
It can be seen that the high temperature hardness at °C is reduced by 1q.

On the other hand, if Or exceeds 18%, thermal shock resistance tends to decrease. Therefore, Cr was limited to a range of 14 to 18%.

Fe: "E has the effect of improving thermal shock resistance, but if it is less than 5%, this effect cannot be sufficiently obtained. On the other hand, if it exceeds 10%, there is a tendency for high temperature hardness to decrease.
was limited within the range of 5 to 10%.

T1: T1 forms carbides, nitrides, and even intermetallic compounds, and is an effective element for improving high-temperature hardness and thermal shock resistance, but if it is less than 2%, these effects are sufficiently reduced by 1q. On the other hand, if it exceeds 6%, the role of carbides becomes too large and the thermal shock resistance decreases. Therefore, Ti was limited to a range of 2 to 6%. Note that T1 is within this range, especially from 2 to
3% is preferred.

Al: Al improves lead oxide corrosion resistance, but if it is less than 0.4%, the desired effect cannot be obtained, while if it exceeds 1.0%, there is a tendency for the alloink property to deteriorate during alloying treatment. Therefore, Al was set within the range of 0.4 to 1.0%.

In the engine valve of the present invention, an alloyed layer having the above-mentioned composition is formed on the face surface of the valve body made of Austety 1~ series heat-resistant steel. An example of this is shown in FIG. In FIG. 3, a valve body 1 made of austenitic heat-resistant steel is integrally formed with a shaft portion 1A and a cap portion 1B, and a face surface 2, which is made in the cap portion 1B and comes into contact with a mating valve seat material, has a , the aforementioned alloyed layer 3 is formed continuously in the circumferential direction.

Here, the austenitic heat-resistant steel constituting the valve body may be one conventionally used for exhaust valves, and is typically JIS 5UH35 (CO, 48~
0.58%, 3i 0.35% or less, Mn 8.00-10
．． 00%, PO, 040% or less, 30.030% or less,
Ni 3.25-4.50%, Cr 20.0-2
2.00%, NO, 35-0.50%, balance Fe) and other 5UH31, Sυt 136.5UH37,5UH
38 etc. can be used.

The alloyed layer is formed by being alloyed integrally with the base material of the valve body through alloying treatment as described below.
By having the above-mentioned composition, heat resistance, abrasion resistance, high temperature corrosion resistance, and thermal shock resistance are equal to or higher than those of the conventional stellite layer formed in a stellite overlay valve.

Since this alloyed layer is formed integrally with the art material through alloying treatment, there is no risk of peeling between it and the base material. In addition, since the alloyed layer does not contain expensive Co or MO, it is inexpensive in terms of cost.
In addition, it can be formed as thin as necessary by alloying treatment using high-density energy such as a laser, TIG arc, or plasma arc, which will be described later, and this is also effective in reducing costs.

Here, it is preferable that the thickness of the alloyed layer be thinner from the viewpoint of cost, or it is usually preferable that the average thickness be 0.2 mm or more. 0.2. If it is less than rnm, the effect of forming the alloyed layer as described above cannot be sufficiently achieved.

In addition, the upper limit of the thickness of the alloyed layer is determined from the viewpoint of cost and workability of alloying treatment, and is usually about 2 layers or less.
Preferably it is 1# or less. Further, in order for the alloyed layer to exhibit its intended function, it is preferable that its hardness be 11/400 or more. Such hardness is achieved by heat treatment as described below.

Next, a method for manufacturing an engine valve according to the present invention will be explained.

First, a valve body made of austenitic heat-resistant steel is prepared in accordance with a conventional method. It is desirable that a concave portion for arranging the alloying material be formed continuously in the circumferential direction on the face surface of the valve body in advance.

Next, N is applied to the face of the valve body as an alloying material.
A Ni-based alloy is placed, and a high-density energy beam is irradiated from above to rapidly melt the Ni-based alloy and the surface layer of the base material (austenitic heat-resistant steel) below it. In this way, N
The i-based alloy and the underlying base material are melted and integrated, that is, alloyed. Subsequently, by moving the irradiation position of the high-density energy beam or stopping the irradiation, heat is rapidly transferred to the base metal side, and the molten alloyed layer is rapidly cooled and rapidly solidified.

Here, the component composition of the N1-based alloy disposed as the alloying material may be determined so that the component composition in the final alloyed state with the base material falls within the above-mentioned range. In other words, alloying is carried out so that the target composition of the alloyed layer falls within the above range, depending on the composition of the austenitic heat-resistant steel as the base material, the fusion depth of the surface of the base material, and the amount of alloying material arranged. It is sufficient to determine the composition of the Ni-based alloy to be used as the material.

Also, examples of high-density energy include laser, TIG,
Plasma arc, electron beam, etc. can be suitably used. In general, the Ni1 alloy as an alloying material can be arranged as a powder kneaded product, for example,
Alternatively, the powder may be placed by thermal spraying, and the method is arbitrary.

After forming the alloyed layer as described above, the alloyed layer is subjected to heat treatment. This heat treatment is an aging treatment for precipitation hardening, and in the temperature range of 750 to 850°C,
Preferably, the mixture is heated and maintained for 4 to 6 hours. In other words, the alloy of the composition of the alloyed layer is a Ni-based alloy containing considerable amounts of T1 and Al, and belongs to a precipitation hardening type alloy, and is treated with aging precipitation to form nitrides, carbides, and even intermetallic materials. Compounds precipitate and these contribute to hardening. Here, if the treatment temperature is less than 750°C, sufficient precipitation hardening will not be obtained, while if it exceeds 850°C, coarsening of the precipitates will occur,
High temperature strength decreases. Therefore, the processing temperature is 750-8
The temperature was within the range of 50°C.

In the case of ordinary precipitation hardening alloys, solution treatment is usually performed before aging treatment, but in the case of the method of this invention, the alloyed layer is rapidly solidified from a molten state during alloying treatment. At that point, an effect similar to that of solution treatment has been obtained, and therefore solution treatment is usually unnecessary.

By performing the heat treatment for age hardening as described above, an alloyed layer 19 having the desired performance of Hv 400 or more is obtained. After the heat treatment or before the heat treatment, the surface of the alloyed layer is usually machined to obtain the desired valve face surface.

Example A valve as shown in FIG. 3 was made in the following manner.

In other words, a valve body 1 is made from JIS 5IJH35 austenitic heat-resistant steel according to a conventional method, and a kneaded mixture of Ni-based alloy powder mixed with PVA (polyvinyl alcohol) is placed on the face surface 2 of the valve body 1. Alloying treatment was performed by irradiating TIG arc.

Is it aging for that alloy layer? After applying A treatment,
The face shape was finished using the machine HROE. The TIG arc irradiation conditions and heat treatment conditions are as follows.

TIG arc irradiation conditions Output 120A/90A; Pulse time o, 5sec feed rate 3mm/SeC: Shield gas 81/ma
n Arc length 2 mm Heat treatment conditions 800°C x 5 hours 1q The composition of the alloyed layer is Ni 75.0%
, Cr15.0%, Fe6.5%, Ti2.3%, Al
016%, the remainder being unavoidable impurities, and the surface hardness after heat treatment was Hv 450. Further, the thickness of the alloyed layer was about 0.2 to 1.0 parts.

On the other hand, an alloyed layer was separately formed on a test piece made of S-35 under the same conditions as above, subjected to the same heat treatment as above, and subjected to a rapid abrasion test. In addition, as a comparative example, a test piece of S-35 was used with stellite (AΔS standard RCoCr-A
> was overlaid and subjected to an ultra-high speed rapid wear test. The test results are shown in FIG.

As is clear from FIG. 4, it was confirmed that the valve according to the example of the present invention had wear resistance equal to or higher than that of the conventional comparative example valve which was overlaid with stellite.

Effects of the Invention The engine valve of this invention has better heat resistance, wear resistance, thermal shock resistance, and
The performance required for the face, such as high-temperature corrosion resistance and high-temperature oxidation resistance, is comparable, and the cost is much lower than that of Stellite overlay valves. Since the coating layer is integrated with the base material by alloying, it has excellent advantages such as no problems such as peeling. Further, according to the method of the present invention, an engine valve having excellent performance as described above and being inexpensive can be manufactured easily in practice.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between N1 content in the alloyed layer and corrosion loss due to lead oxide, Figure 2 is a graph showing the relationship between the Or content of the alloyed layer and high temperature hardness at 800 °C,
FIG. 3 is a partially cutaway side view showing an example of the engine valve of the present invention, and FIG. 4 is a graph showing the results of wear tests on the engine valves of the example and comparative example. 1...Valve body, 2...Face surface, 3...
・Alloyed layer.

Claims (2)

[Claims] (1) On the valve face of the valve body made of austenitic heat-resistant steel, Ni is 70% or more (by weight, the same applies hereinafter), Cr is 14-18%, Fe is 5-10%, and Ti is 2-6%.
, 0.4 to 1.0% Al, the remainder being unavoidable impurities, and an alloyed layer formed integrally with the valve body. (2) A Ni-based alloy is placed on the valve face surface of the valve body made of austenitic heat-resistant steel, and high-density energy is irradiated from above the Ni-based alloy to remove the surface of the Ni-based alloy and the base material below it. Rapid melting and rapid resolidification of the layer results in over 70% Ni, 14-18% Cr, and 5-10 Fe.
%, Ti 2-6%, Al 0.4-1.0%, and the balance is formed by forming an alloyed layer consisting of unavoidable impurities.
A method for manufacturing an engine valve, characterized in that the alloyed layer is heat treated at a temperature within the range of 850°C.