JPH0433795A - Composite hard facing by welding material and engine valve and valve seat welded therewith - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a composite metal material used in powder metallization welding, and an engine valve and valve seat made of the same.

[Conventional technology]

The valve face portion of an engine valve for an internal combustion engine and the seat portion of a valve seat are subjected to repeated high loads and high cycles, which causes significant wear due to the strength of the base material alone.

For this reason, we have built-up welding a powdered metal material such as stellite on the valve face and seat to increase mechanical strength such as high-temperature strength and creep resistance, especially wear resistance. There is.

[Problem to be solved by the invention]

Recent engines tend to have higher rotation speeds and higher power output, and from the perspective of exhaust gas purification, there is a tendency to use fuel that does not contain lubricating substances (such as tetraethyl lead) in the face etc. It is in.

Furthermore, diesel engines are required to have excellent corrosion resistance due to the fuel used.

The seat parts of engine valves and valve seats used in such engines are required to have excellent high-temperature properties such as high-temperature strength and corrosion resistance, as well as high wear resistance. It is difficult to obtain the required high-temperature properties, especially wear resistance, with engine valves and the like made of these materials, and the emergence of alternative materials for the materials has been awaited.

The present invention has been made in view of the above-mentioned problems, and its purpose is to provide a composite overlay material based on stellite with excellent wear resistance, and an engine valve and valve seat made by overlay welding the same. It's about doing.

[Means to solve the problem]

In order to achieve the above object, the composite metal material of the present invention is made of C.
It is characterized by being composed of a mixture of a melting powder of a Co-based alloy whose main components are o, Cr, W, and C, and a non-melting powder that is harder and has a higher melting point.

The above mixture is preferably based on stellite, to which chromium carbide or niobium carbide powder is added in a weight ratio of 5 to 50%.

The engine valve of the present invention is characterized in that the above-mentioned composite overlay material is overlay-welded to the valve face portion.

Further, the valve seat of the present invention includes the above-mentioned composite metal material,
It is characterized by overlay welding on the seat part.

[For production]

While supplying the composite metallization material of the present invention to the part to be metallized, the turning part is heated to a temperature higher than the melting point of the powder for melting and lower than or slightly higher than the melting point of the powder for non-melting using plasma arc or the like. When heated to a high temperature, the non-melting powder remains in its powder form or remains to the extent that the surface part melts, and the melting powder is melted, and during subsequent cooling and hardening, the melting powder part remains. Due to the synergistic effect between the precipitation of carbide and the scattering of high hardness non-melting powder, the hardness after build-up increases.

An engine valve whose valve face portion is welded using such a composite overlay material, and a valve seat whose seat portion is similarly welded by overlay welding exhibit excellent physical properties such as hardness, wear resistance, and durability.

〔Example〕

Tables 1 and 2 show the compositions of the powdered Co-based alloy (melting powder) used as the base of the composite metallization material of the present invention, that is, Stellite 112 and J6.

[Table 1] [Table 2] Materials for non-melting powder with high hardness and high melting point that can be added to Stellite #I2 and #16 are 5, for example, Cr, C2, Nb.
Carbide such as C, WC, TiC, TaC, TiN, Ta
Examples include nitrides such as N and oxides such as Al2O3 and ZrO2.

In this example, a composite metal material is constructed by mixing carbide powder, for example, with base materials of Stellite H2 and J6. In other words, Stellite #12 has C
r, C2, and Stellite #6 has NbC added in an amount of 5 to 10% by weight.

Note that the composition ranges of Cr, C2, and NbC are limited for the following reason.

That is, as shown in the experimental example below, when each composite metal material having the above structure is applied to the valve face part of an engine valve or the seat part of a valve seat by plasma welding, carbide is effectively applied to the metal part. In order to obtain sufficient hardness and wear resistance, it is necessary to add at least 5% or more.

However, if too much is added, the proportion of precipitated carbides increases and hardness increases, but on the other hand, the proportion of dissolved carbides remaining increases and the structure becomes unstable. Since cracks may occur and toughness and workability may deteriorate, it is preferable that the content be 50% or less.

Next, the results of investigating the hardness of the composite metallization material of the above-mentioned example applied to the valve face of an engine valve will be explained based on an experimental example.

The metal was deposited on the valve face using a plasma welding method as shown in FIG.

That is, the umbrella part (2a) of the engine valve (2) is placed on the rotary table (1) tilted at approximately 30 degrees and rotated, while the torch (2a) is placed directly above the valve face part (2b). 3
) is generated from the tip of the torch (3), and at the same time, the composite metal material (5) of the above example is supplied from the nozzle at the tip of the torch (3), and the composite metal metal material (5) is heated by the arc heat. By heating and melting at approximately 1,300°C to 1,500°C for a short time, a build-up (6
) was applied.

[Experimental Example 1] Figure 2 shows a composite plate in which stellite l112 is used as a base material, that is, a powder for melting, and chromium carbide (Cr-Cz) is mixed as a non-melting powder with an appropriate addition amount. A gold material was overlaid on the valve face portion (2b) and its hardness was measured.

Note that martensitic heat-resistant steel (SUH3) was used as the material for the engine valve (2).

As is clear from Figure 2, the hardness of Stellite 112 alone with the addition amount of 0r3C2 being O is around 510 (Hv), but when the addition amount of Cr, C, is increased, it is almost proportional to that. As a result, the hardness increases, and at around 45%, which is close to the upper limit of the addition amount, the hardness increases to a value close to 700 (Hv).

This can also be confirmed from an example of a microscopic photograph of the built-up portion shown in FIG. That is, compared to the structure of Stellite 11 alone shown in FIG. The structure is dense with a large amount of particles) and scattered large particles.

Generally, there is a close relationship between hardness and wear resistance, and it is thought that the higher the hardness, the higher the wear resistance.
, C, it can be seen that the wear resistance of the valve face portion (2b) is significantly improved.

[Experimental Example 2] Figure 3 shows the hardness of the built-up part at the boundary with the base material (
The results of an investigation using the distance from A) in the direction of arrow (B) toward the surface layer as a variable are shown.

The base material of the composite metallization material, that is, the powder for melting, was Stellite 1t12, which is the same as in Experimental Example 1 above.

As is clear from Fig. 3, as the non-melting powder, Cr
, C, is added to Stellite 11 without this addition.
Compared to 2 alone, the hardness is higher in all parts,
Furthermore, the greater the amount of Cr3C2 added, the higher the hardness at each location.

Furthermore, regardless of the amount of Cr3C2 added, the hardness tends to be almost constant at a distance of 0.6III11 or more from the boundary. This shows that a stable carbide precipitate layer is formed on the surface layer of the built-up portion.

[Experimental Example 3] Figure 4 shows the base material, that is, the melting powder used as Stellite 16, and the non-melting powder containing niobium carbide (
A composite metal material made by mixing NbC) with an appropriate addition amount was applied to the valve face part (2b) by plasma welding as shown in Figure 1 above, and its hardness was measured. It is something.

The same 5UH3 as mentioned above was used for the engine valve (2).

As is clear from Figure 4, the hardness of Stellite 11 alone without NbC added is around 480 (Hv), but as the amount of NbC added increases, the hardness increases almost in proportion to it, reaching the upper limit. At a near 40% addition, approximately 63
Cures to 0 (Hv).

This is clear from the micrograph shown in Figure 7, and Nb
In an example in which 40% C was added, particles of NbC with a high melting point were scattered in the base of stellite 1G, which was mostly melted, with the melt remaining, and the particles hardened due to the synergistic effect of these particles and the precipitated carbide due to partial melting. layers are formed.

As is clear from the experimental examples explained above, a composite plate made by using Stellite #12 or #6 as a base material, that is, a melting powder, and adding carbide-based Cr5G or NbC as a non-melting powder as appropriate. When gold material is deposited on the valve face of an engine valve by plasma welding, the hardness of the deposit increases significantly compared to Stellite 112 or 1G alone, which does not contain gold materials, and the wear resistance of the valve face decreases. Significantly improved.

Note that Stellite #12, NbC1, and Stellite 1, which are the base materials, are extremely similar in composition and mechanical properties alone.
Although illustration is omitted in an experimental example using a composite metal material made of 6, Cr, and C, almost the same values as in the above experimental example can be obtained even with the combination thereof.

Further, when the composite metal material of the above example is applied to the seat portion (7a) of the valve seat (7) as shown in FIG. 5, the hardness is almost the same as that described above. I'm sure you can get it.

In the embodiment, the material of the engine valve (2) is martensitic heat-resistant steel (SUH3), but it may also be austenitic heat-resistant steel (SUH31) or the like.

The method for welding the composite metal material may be gas welding or other methods.

〔Effect of the invention〕

When the composite metal material of the present invention is used to build up a seat part such as an engine valve or a valve seat, the hardness of the metal part increases significantly compared to conventional CO-based alloys such as stellite alone, and the durability increases. We provide engine valves and valve seats with excellent wear resistance and durability.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram illustrating how to build up a composite metal material according to an embodiment of the present invention on the valve face of an engine valve by plasma welding, and FIG. Figure 3 is a diagram showing the relationship between the amount of Cr and C2 added and the hardness when a composite metal material with varying amounts of Cr and C is built up on the valve face of an engine valve. Figure 4 shows the relationship between the distance between the boundary between the base metal and the built-up part and the hardness. Figure 5 is a diagram showing the relationship between the amount of NbC added and the hardness when overlaying the valve face of the valve. An explanatory diagram of the state. Figures 6 (A) and (B) show Stellite #12 alone,
Figure 7 (A) and (B) are enlarged micrographs showing a comparison of the structure of the built-up part when 25% of Cr and C were added. It is an enlarged microscopic photograph showing a comparison with the structure of the built-up part when % is added. (1) Turntable (2) Engine valve (
2a) Umbrella part (2b) Valve face part (
3) Torch (4) Plasma arc (
5) Composite overlay material (6) (8) Overlay (7)
Valve Seah (7a) Seat part Fig. 1 Fig. 2 Addition amount of chromium carbide (Cr3C2) (wt'10) Distance from boundary (mm) Fig. 4 Addition amount of niobium carbide (NbC) (wt '10) No. 5 Figure 6 (A) (B)

Claims (6)

[Claims] (1) A composite metallization material made of a mixture of a melting powder of a Co-based alloy containing Co, Cr, W, and C as main components and a non-melting powder that is harder and has a higher melting point. (2) The composite metallization material according to claim (1), wherein the mixture is based on a melting powder, to which is added 5 to 50% by weight of a non-melting powder. (3) Claim (1) wherein the non-melting powder is made of chromium carbide.
) or the composite metal material described in (2). (4) Claim (1) wherein the non-melting powder is made of niobium carbide.
) or the composite metal material described in (2). (5) An engine valve characterized in that the composite overlay material according to claim (1) is overlay welded to a valve face portion. (6) A valve seat characterized in that the composite overlay material according to claim (1) is overlay-welded to the seat portion.