JPS61276772A - Build-up welding method for engine valve for automobile - Google Patents

Abstract

PURPOSE:To prevent the generation of a pin hole by placing a nickel super-alloy powder to which a calcium component is added by a specified quantity, on a valve face part, sealing an irradiating part by a shield gas, and irradiating a high density energy. CONSTITUTION:A nickel super-alloy powder to which a calcium component is added by 1.5-3wt% is supplied to a recessed part of a valve face part 2 of an automobile use engine valve 1 from a build-up alloy supply device 4, and the engine valve 1 is rotated. At the same time, an argon gas being a shield gas is supplied to the recessed part of the valve face part 2 from a shield gas supply device, and a build-up welding is executed by irradiating a laser beam 5 to the recessed part.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method of overlaying an automobile engine valve, and in particular, a method of overlaying an automobile engine valve suitable for overlaying using a high-density energy source such as a laser. Regarding.

[Conventional technology]

Intake valves used in automobile engines,
An engine valve such as an exhaust valve is a valve that controls intake or exhaust air in a combustion chamber, and consists of a bulk part and a shaft part. The bulk of this engine valve is installed inside the combustion chamber, and repeatedly comes into contact with and separates from the valve seat that is press-fitted into the cylinder head on the valve face surface. That is,
The temperature of the valve face in the combustion chamber is 700°C to 800°C.
Because they are exposed to high temperatures (°C) and repeatedly collide with valve seats, they are required to have heat resistance, corrosion resistance, and abrasion resistance.

Conventionally, one way to provide the valve face of an engine valve with the above-mentioned properties such as heat resistance is to use a material with excellent heat resistance, corrosion resistance, and wear resistance, such as a nickel-based superalloy or a nickel-based material, on the valve face surface. A method of overlaying superalloy etc. is adopted.

Currently, the main method of overlaying the valve face is gas overlay using acetylene gas, and there are other methods that use a TIG welding power source or a plasma power source. In such build-up, it is desirable to prevent internal defects in the build-up, that is, pinholes, in order to ensure the desired heat resistance and wear resistance of the superalloy that is the material of the valve face. It is rare. The reason for this is that if a pinhole exists on the valve face or just below the valve face, the thermal conductivity around the pinhole decreases while the car engine is rotating, and the area around the pinhole becomes a heat spot. This is because there is a risk of melting and damage, resulting in a blow-through in the valve train.

In the conventional build-up method using acetylene gas, pinhole defects appearing on the valve face after processing the build-up portion are approximately 20%. Here, the pinhole defect rate (
%) is the percentage of defective products in the total, with a product having even one pinhole on the valve face as a defective product and a product with no pinhole on the valve face as a good product. In the overlay method 1 using acetylene gas, for the approximately 20% of defective products mentioned above, after processing the valve face surface where pinholes have occurred, rework is performed such as overlaying with acetylene gas again. was necessary. The conventional acetylene gas overlay method has problems such as the high cost of rework and the need for manual inspection processes such as color checking.

On the other hand, recently, as a build-up method using a high-density energy source, a method using a laser or the like in addition to the conventional TIG or plasma has been considered. When overlaying is performed using such a high-density energy source, the structure of the overlay portion becomes finer, as the method using the high-density energy source involves rapid heating and rapid cooling, and improvement in wear resistance can be expected.

[Problem that the invention seeks to solve]

However, the overlay method using this high-density energy source requires rapid heating and cooling, so compared to the conventional acetylene gas overlay method, the overlay method uses a high-density energy source.
G,) There are many chances that bubbles, mainly oxygen, due to supersaturated dissolved gas components generated during solidification cannot float up and remain as internal defects. Therefore, the build-up method using a high-density energy source has a problem in that the pinhole defect rate is higher than that of the conventional acetylene gas build-up method.

Therefore, there has been a desire for a device to prevent pinhole defects while taking advantage of the advantages of a high-density energy source.

[Means for solving problems]

The above problem is solved by the following method of overlaying an automobile engine valve according to the present invention.

That is, the method for overlaying an automobile engine valve of the present invention is as follows:
A method of overlaying a nickel-based superalloy on a valve face portion of an engine valve using a high-density energy source, the method comprising depositing a calcium component on the valve face portion in an amount of 1.5 to 3.
It is characterized by arranging nickel-based superalloy powder added with 0% by weight and irradiating with a high-density energy source while sealing the irradiation part with a shielding gas.

In the present invention, a nickel-based superalloy is used as the base of the overlay material. This nickel-based superalloy is a precipitation-strengthened alloy that contains around 20% chromium (Cr), and is further added with aluminum (Alt), titanium (Ti), and niobium (Nb) for high-temperature strength. As a nickel-based superalloy, for example, (a) in weight% (hereinafter, all units are weight%), Co<'l, 5%, Cr: 14-2
3%, MO: 5-16%, W<4.0%, Fe<
5.0%, St<0.8%, Mn<1.0%, C:0.
05-0.1%, Ca: 0.1-2.0% and balance N
i, (b) Co < 5゜0%, Cr: 18
~22%, Mo: 3~6%, Fe < 4.0%, Si
<1.0%, Mn<1.0%, C: 0.05-0.1%
, Ca: 0.1 to 2.0%, A x <1°0%, and the balance Ni, etc. can be used.

In the present invention, calcium component (element) is added to the nickel-based superalloy in the form of a Ca-Si alloy or the like in an amount of 1.5% to 3.0%.
It is characterized by the addition of 0%. Of course, an alloy obtained by dissolving a nickel-based superalloy and a calcium component may also be used.Here, the lower limit is set to 1.5% because the addition amount is 1.5
This is because if it is less than 3.0%, the pinhole suppressing effect will not be sufficient, and the reason why the upper limit was set at 3.0% is that if it exceeds 3.0%, sputtering will become intense due to the reaction with oxygen entangled in the shielding gas. In addition to lasers, TIGt8 is a high-density energy source that increases the scattering of alloy powder.
Contact or plasma can be used.

[Effect]

According to the method of overlaying an automobile engine valve of the present invention,
By adding a predetermined amount of calcium as a deoxidizer to conventional nickel-based superalloys, the occurrence of pinholes is prevented or significantly reduced. That is, in the overlay boule melted by a high-density energy source, oxygen in the atmosphere mixed into the shielding gas.

It is adsorbed on the surface of nickel-based superalloy powder.

Oxygen is present as a solid solution in the nickel-based superalloy powder. Normally, this oxygen becomes bubbles and is drawn out of the overlay boule, but when a high-density energy source is used, the process involves rapid heating and cooling, so that the oxygen is completely solidified before it leaves the overlay boule. However, it may be incorporated into the overlay alloy and form a pinhole.

However, when calcium is present, it combines with oxygen to form oxides such as CaO, which float up as slag. Therefore, the amount of oxygen present in the form of bubbles is significantly reduced, and the occurrence of pinholes is prevented or significantly reduced.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

Here, FIG. 1 is a schematic diagram showing one step of the overlay method for an automobile engine valve according to an embodiment of the present invention.
Figure 2 is a graph showing the relationship between cooling rate and pinhole generation rate when the amount of added calcium is changed, and Figure 3 is a graph showing the relationship between the oxygen concentration in the filler and filler alloy powder and the pinhole generation rate when the amount of added calcium is changed. It is a graph showing the relationship between ball occurrence rates.

Heat resistant TM (full length 94mm, bulk diameter 30m, shaft diameter 6R)
EXHAUST VALVE I consisting of SU83B) was prepared. This exhaust valve 1 has a shaft portion 1a and an umbrella portion 1b.
A concave portion is formed in the valve face portion 2 of the bulk portion 1b for overlaying. This exhaust valve 1 is tilted until the upper valve face portion 2 becomes horizontal, and the tip of the shaft portion 1a is held rotatably around the shaft.

Then, an overlay alloy supply device 4 for supplying overlay alloy powder 3 is installed directly above the upper valve face portion 2 . Also,
Although not shown, shielding gas is supplied toward the upper valve face portion 2 from a shielding gas supply device. Furthermore, the upper valve face portion 2 is irradiated with laser light 5 from a laser device (not shown).

Overlay alloy powder 3 is CO: 1.0%, CR: 20%, M
o: 10%, W: 3. Q%, Fe: 3. Q%, Si:Q
, 5%, Mn<l, Q%, C: 0.1%, Ca71.
The base material was a nickel-based superalloy consisting of 0% Ni and the balance Ni, to which a calcium component was added in the form of Ca-3t alloy powder.

Next, the overlay method will be explained.

The exhaust valve 1 was gradually rotated while supplying the overlay alloy powder 3 from the overlay alloy supply device 4 to the recessed portion of the valve face portion 2 . At the same time, argon gas was supplied as a shielding gas from a shielding gas supply device (not shown), and laser light 5 was irradiated.

At this time, the laser build-up conditions were as follows: laser irradiation crab 2.5
KW, beam scanning width t': 20 On/min, beam diameter: φ5. The above laser build-up was performed by changing the sealing performance and the amount of calcium component added. That is, the atmospheric content in the shielding gas is assumed to be 30%, and the amount of calcium component added is 0%, 1.5%, and 3.0%.
The air content in the shielding gas was set to 15% to provide a relatively good seal, and the amount of calcium added was changed to 0.75% and 1.5%, and cooling was performed in each case. The pinhole occurrence rate was investigated at various speeds. The results are shown in FIG. As is clear from FIG. 2, the pinhole prevention effect is not sufficient unless the amount of calcium component added is 1.5% or more.

Although it depends on the conditions, the pinhole occurrence rate decreases as the amount of calcium component added increases.

In addition, if the amount of calcium added exceeds 3%,
Spatter became so intense that it became impossible to carry out the process. Moreover, when the amount of residual calcium exceeded 2.0%, cracks occurred in the overlaid bead.

Furthermore, using various materials with different oxygen concentrations in the overlay alloy powder and changing the amount of calcium added in four ways, the relationship between the oxygen concentration and the pinhole generation rate was investigated.

At this time, the cooling rate was kept constant at 60° C./sec.

The results are shown in FIG. From FIG. 3, it can be seen that the lower the oxygen concentration in the overlay alloy powder, the lower the pinhole generation rate. Further, even when the oxygen concentration in the overlay alloy powder is high, the pinhole generation rate can be significantly reduced by increasing the amount of added calcium.

From the above, according to the overlay method for automobile engine valves of this embodiment, by adding a predetermined amount of calcium, even when overlay is performed by rapid heating and cooling using a high-density energy source such as a laser, The pinhole occurrence rate can be reduced to less than half that of conventional acetylene gas build-up. Furthermore, by controlling the amount of calcium and sealing properties, it is possible to completely prevent the occurrence of pinholes. Furthermore, even if a low-grade and inexpensive overlay alloy powder with a high oxygen content is used, the pinhole generation rate can be kept low.

Although specific embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, but includes various embodiments within the scope of the claims.

For example, although the example uses a laser as a high-density energy source, other high-density energy sources such as TI
Similar effects can be obtained with G arc, plasma, etc.

〔Effect of the invention〕

From the above, according to the overlay method for automobile engine valves of the present invention, oxygen that causes pinholes is turned into slag as CaO etc. by adding a predetermined amount of calcium component, so that almost no oxygen exists as bubbles. pinholes are prevented or significantly reduced. For this reason,
The time and effort required to repair defective products can be significantly saved, and costs can be reduced.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram showing one step of the overlay method for automobile engine valves according to an embodiment of the present invention, and Fig. 2 shows the oxygen concentration and pinholes in the cooled alloy powder when the amount of added calcium is changed. It is a graph showing the relationship between incidence rates. 1--------One extreme valve (engine valve) l a --------- One shaft portion 1b --- Umbrella portion 2 --- Valve face portion 3 --- - Overlay alloy powder 4 - Overlay alloy supply device 5 - Laser light applicant Toyota Motor Corporation Daiichi 1 sec)

Claims (1)

[Claims] (1) A method of overlaying a nickel-based superalloy on the valve face portion of an engine valve using a high-density energy source, the method comprising applying a calcium component of 1.5 to 3.5% to the valve face portion.
A method for overlaying an engine valve for an automobile, characterized in that nickel-based superalloy powder added at 0% by weight is placed, and a high-density energy source is irradiated while the irradiated part is sealed with a shielding gas.