JPH0555233B2 - - Google Patents

Description

[Detailed description of the invention]

Technical Field The present invention relates to a method for manufacturing an engine valve, and in particular, a martensitic material containing Fe and Cr as main components is used as the engine valve material, and a valve face surface is formed by hardfacing the engine valve material. The present invention relates to a method of manufacturing the desired engine valve. BACKGROUND OF THE INVENTION Engines such as automobiles are provided with engine valves that open and close intake ports and exhaust ports in order to supply mixed gas into the combustion chamber or discharge combustion exhaust gas from the combustion chamber. Since this engine valve is used in a high temperature environment, it is required to have excellent heat resistance and wear resistance. For this reason,
Traditionally, austenitic heat-resistant steels, such as
Using SUH36 material etc. as engine valve material,
Engine valves with excellent heat resistance and wear resistance are manufactured by hardfacing the engine valve material to form a valve face that seats on the valve seat of the intake or exhaust port. On the other hand, austenitic heat-resistant steels such as the SUH36 material mentioned above are generally expensive, so in recent years relatively inexpensive
Martensitic heat-resistant steels containing Fe and Cr as main components, such as SUH11 material and SUH3 material, have come to be used as the engine valve material. Problems to be Solved by the Invention However, martensitic heat-resistant steel whose main components are Fe and Cr has high quench hardenability, and in hardfacing using conventional gas or TIG methods, sufficient preheating is not required. If this was not done, welding cracks could occur. In addition, the main components, Fe and Cr, are easily oxidized, and their oxides may get mixed into the molten metal during welding, causing pinholes or impairing the bond strength between the overlay material and the engine valve material. , there were problems such as poor fusion. Means for Solving the Problems In order to solve the above-mentioned problems, the method for manufacturing an engine valve according to the present invention provides a method for hardfacing an engine valve material made of a martensitic material containing Fe and Cr as main components. To form the valve face surface and manufacture the desired engine valve, a plasma arc is formed between the plasma arc torch and the engine valve material, while a predetermined powder material is The powder material is guided into a plasma arc to melt it and form a predetermined hard overlay on the engine valve material, and the nozzle diameter of the plasma arc torch: _D1 is the groove width of the hard overlay: For D ₂ ,
It is characterized by satisfying the following formula: 0.6D ₂ ≦D ₁ ≦1.2D ₂ . Furthermore, in the present invention, the welding speed at which hardfacing is performed, that is, the relative movement speed in the welding direction between the plasma arc torch and the engine valve material, although it varies depending on the magnitude of the welding current, etc. In order to perform hardfacing with a good bead shape, it is desirable to set the speed to 4 mm/sec or more. Note that this welding speed is generally 20
The upper limit is about mm/sec, but if conditions such as welding current are appropriately set, even higher speeds can be used. At this time, if necessary, the plasma arc torch and the engine valve material are moved relative to each other in a direction perpendicular to the welding direction (oscillate).
You can also do it. Furthermore, the valve face surface of an engine valve is generally formed in a tapered shape on the outer periphery of the valve bulk. If hardfacing is performed by placing a plasma arc torch above the inclined engine valve material while rotating around the axis, the bead shape will not be damaged due to gravity acting on the molten metal. do not have. In addition, various types of overlay material powders such as stellite type (Co-based), colmonoid type (Ni-based), and Fe-Cr type (Fe-based) can be used as the powder material to be hardfacing. The size is also set appropriately considering the difficulty of melting, etc.
In general, spherical particles with a mesh size of -100 to +350 are preferably used. Effects of the Invention If hard overlay is applied to an engine valve material made of martensitic material in this way, weld cracks and pinholes may occur in the hard overlay, as will be clear from the examples described later. This solves the problem of poor fusion between the filler material and the engine valve material. Further, since a powder material is used as the overlay material, the time required for hard overlay can be shortened compared to the case where a bar material is used, and the hard overlay can be easily automated. Furthermore, since hardfacing is performed using a plasma arc, hardfacing with a good bead shape can be obtained even if the depth of the groove to be hardfacing is shallow, and the amount of hardfacing material used can be reduced. Significant savings can be made. EXAMPLES Next, examples of the present invention will be described in order to clarify the present invention more specifically. However, in order to facilitate understanding, first, plasma overlay welding in which the present invention can be suitably carried out will be explained. The apparatus will be explained based on FIG. In the figure, 10 is a plasma arc torch (hereinafter referred to as a torch) arranged vertically.
This is the tip of the Such a torch 10 is equipped with a tungsten electrode 12 in the center, and this electrode 1
2, a torch inner cylinder 14 and a torch outer cylinder 16 are coaxially arranged at a predetermined distance from each other. Annular passages 18 and 20 are formed between the electrode 12 and the torch inner cylinder 14 and between the torch inner cylinder 14 and the torch outer cylinder 16, respectively. The passage 18 is connected to a plasma gas supply device 24 via a pipe 22, and is supplied with plasma gas such as argon gas. The plasma gas supplied into this passage 18 is then passed through a nozzle 3 provided at the tip of the torch inner cylinder 14.
It is ejected downward from 0. Further, the passage 20 is connected to a carrier gas supply device 34 via a pipe 32, and the pipe 32 is further connected to a carrier gas supply device 34.
A powder supply device 36 is connected to the intermediate portion of the device 2, and a predetermined powder material is supplied from the powder supply device 36. That is, a carrier gas containing a predetermined amount of powder material is supplied to the passage 20 and is ejected downward from a nozzle 38 provided at the tip of the torch outer cylinder 16.
As the powder material, it is possible to use various hardfacing material powders for hardfacing such as stellite type, colmonoy type, and Fe-Cr type, and as the carrier gas, non-containing materials such as argon gas and helium gas can be used. An active gas is used. On the other hand, cooling water passages 40 and 42 are provided in the nozzles 30 and 38 of the torch inner cylinder 14 and the torch outer cylinder 16, respectively.
0 and 38. Furthermore, a shielding gas made of an inert gas such as argon gas or helium gas is supplied to the tip of the torch outer cylinder 16 from a shielding gas supply device 44 via a pipe 46. By blowing out in a substantially cylindrical shape in the axial direction of the torch 10, the welding part is shielded from the atmosphere. An engine valve material 48 to be subjected to hardfacing welding is attached below the torch 10 configured as described above. This engine valve material 48 is a material for an engine valve that opens and closes an intake port and an exhaust port in order to supply mixed gas into the combustion chamber of an engine such as an automobile or to discharge combustion exhaust gas from the combustion chamber. SUH11 material whose main components are Fe and Cr,
Made of martensitic heat-resistant steel material such as SUH3 material. The engine valve material 48 includes a shaft portion 50 and an umbrella portion 52, and the outer peripheral portion of the shoulder portion of the bulk portion 52 located on the shaft portion 50 side has an annular recess 54 to which hardfacing is applied. (grooves) are formed. In addition, the broken line shown in the recessed part 54 in FIG. 1 shows the state where the hardfacing was applied. The engine valve material 48 has a mounting shaft 56 inclined at an angle θ with respect to the vertical direction.
, its axis A via the cooling backing 58.
is attached so as to coincide with the axis of the mounting shaft 56, and is configured to rotate together with the mounting shaft 56 around the axis A at a predetermined speed.
In the state of being attached to the mounting shaft 56 in this manner, the uppermost portion of the recess 54 formed in the bulk portion 52 of the engine valve material 48 is located vertically below the nozzle 38 of the torch 10. When the engine valve material 48 is rotated around the axis A, hardfacing is sequentially applied to the annular recess 54. Here, the nozzle diameter D ₁ of the nozzle 38 is
The groove width D ₂ of the recess 54 is set to satisfy the following formula: 0.6D ₂ ≦D ₁ ≦1.2D ₂ . Note that the electrode 12 of the torch 10 and the torch inner cylinder 14
A predetermined pilot current is supplied from a pilot power source 60 between the electrode 12 and the backing 58 to which the engine valve material 48 is attached. Current is being supplied. Further, a high frequency oscillator 64 for ignition is inserted between the power source 12 and the torch inner cylinder 14 in parallel with the pilot power source 60. Next, a procedure for applying hard overlay to the engine valve material 48 using the above-mentioned plasma overlay welding apparatus will be described, which constitutes one embodiment of the present invention as it is. First, a pilot current is supplied from the pilot power source 60 to generate a pilot arc between the tip of the power source 12 and the nozzle 30 of the torch inner cylinder 14, and at the same time, plasma gas is supplied from the plasma gas supply device 24 into the annular passage 18. supply As a result, a plasma arc is formed at the tip of the electrode 12. Thereafter, a welding current is supplied from the main power source 62 between the electrode 12 and the bucking 58 to transfer the plasma arc formed at the tip of the electrode 12 to the engine valve material 48, and at the same time, the carrier gas supply device 34 and the powder supply A device 36 supplies a carrier gas containing a predetermined powder material into the passageway 20 . The powder material supplied into the passage 20 is ejected from the nozzle 38 and melted by a plasma arc, and is melted into the recess 5 of the engine valve material 48.
4 is overlay welded. In addition, at this time, torch 10
A shielding gas is blown out from the tip of the recess 54 to prevent the molten powder material and the recess 54 from being affected by oxygen in the air. In this state, by rotating the engine valve material 48 around its axis A, the portion of the recess 54 to be overlaid welded moves.
An annular recess 5 formed on the outer periphery of the umbrella portion 52
Hardfacing will be sequentially applied to the entire circumference of 4.
At this time, it is also possible to reciprocate (oscillate) the torch 10 in a direction perpendicular to the welding direction, that is, in the left-right direction in FIG. 1, if necessary. Here, if hardfacing is performed on the engine valve material 48 made of martensitic heat-resistant steel material in this way, weld cracks or pinholes may occur in the hardfacing part, or the overlaying material and engine valve material may 48, there is almost no possibility of fusion failure occurring between the two. Further, since a powder material is used as the overlay material, the welding time can be shortened compared to the case where a bar material is used, and the automation of hard overlay can be facilitated. In the above example, the recess 54 is formed in the part of the engine valve material 48 that is to be hard-faced welded, but such a recess is not necessarily necessary when hard-faced welding is performed using a plasma arc. For example, even on a flat surface, a good bead-shaped hardfacing can be obtained. Therefore, compared to the conventional gas method or TIG method, which requires forming predetermined recesses and performing hardfacing, the amount of overlaying material used can be significantly reduced. Then, the engine valve material 48 that has been hard faced in this way is then subjected to a predetermined process such as grinding on the hard faced part, and is then installed at the intake or exhaust port of the combustion chamber. The valve face surface that sits on the valve seat is formed, and an engine valve with excellent heat resistance and wear resistance is manufactured. In the above explanation, the case where the engine valve material 48 is made of a mantensite heat-resistant steel material such as SUH11 material or SUH3 material is explained, but even if it is made of an austenitic heat-resistant steel material such as SUH36 material. Of course, it can be implemented in the same way. Further, the engine valve material 48 is attached to the mounting shaft 56 via a buckling 58 for cooling, but the buckling 58 is designed in consideration of the size of the engine valve material 48 and welding conditions such as welding current. Therefore, it may be provided as necessary. Furthermore, the above-mentioned plasma overlay welding device is only an example of a device that can suitably carry out the present invention, and manufacturing an engine valve using the device is one embodiment of the present invention. It goes without saying that the present invention is not limited in any way by these descriptions, and may be implemented with various modifications and improvements based on the knowledge of those skilled in the art. The method for manufacturing an engine valve according to the present invention has been described above in detail.Next, in order to specifically clarify the effects of the present invention, we will explain the bead of the hardfacing part formed according to the above example. The results of investigations regarding shape, hardness (H _R C), weld cracks, pinholes, and poor fusion will be specifically explained in comparison with comparative examples. Example 1 SUH3 material (0.4%C-11%Cr-1%Mo-residue
Fe) valve diameter (outer diameter of bulk part 52) 40
When hardfacing Stellite #6 spherical powder material (-100 to +350 mesh) to 48 mm of automotive engine valve material, the welding current was 80 to 100 A.
The supply rate of plasma gas is 1.5 to 1.8/min, the supply rate of powder carrier gas is 5.0/min, the supply rate of shield gas is 25.0/min, the inclination angle θ of the axis A of the engine valve material 48 is 45°, and the hardened meat The groove width _D2 of the built-up part was set to 5.3 mm, the nozzle diameter _D1 and welding speed were changed as appropriate, and the bead shape of the hardfacing part was also investigated with and without oscillation. The results are shown in Table 1. Comparative Example No. 10 is a case in which hardfacing was performed using a Stellite # rod material by a gas method.

[Table] *:○...good △...usable ×...bad As is clear from Table 1, No. 1 according to the present invention
In the case of hard overlay of 7 to 7, no weld cracks or pinholes occur in the hard overlaid portion, and no fusion failure occurs. In addition, the welding speed is 3mm/sec.
In the case of No. 4, which is relatively slow, the penetration amount of the base material (engine valve material 48) increases and the overlay material is diluted, the bead shape is slightly impaired and the hardness of the overlay part decreases. There is no problem in practical use,
In other cases where the welding speed is 4 mm/sec or more,
It can be seen that hardened build-up with a good bead shape and sufficient hardness can be obtained. In this example, the welding speed was only 12 mm/sec, but depending on the welding conditions such as welding current, the welding speed could be 20 mm/sec.
A fully satisfactory hardened build-up can be obtained even if the hardfacing is higher than sec. On the other hand, in Comparative Example No. 8, the nozzle diameter D ₁ is smaller than the range of the present invention, which impairs the bead shape and causes poor fusion. Also, No. 9 where the nozzle diameter D ₁ is larger than the range of the present invention.
In this case, the penetration amount of the base material (engine valve material 48) increases and the overlay material is diluted, resulting in a decrease in hardness of the formed hard overlay part and poor fusion. Furthermore, in case No. 10, in which hardfacing was performed using the gas method, weld cracks, pinholes, and even poor fusion occurred in the hardfacing, making it impossible to obtain a satisfactory hardfacing. . Example 2 Powdered materials of various overlay materials are hard-clad onto an automobile engine valve material 48 made of SUH11 material (0.5% C-8.5% Cr-remaining Fe) and having a valve diameter (outer diameter of the bulk part 52) of 55 mm. When welding current is 80~100A,
The plasma gas supply rate is 1.5 to 1.8/min, the powder carrier gas supply rate is 5.0/min, the shielding gas supply rate is 25.0/min, and the welding speed is 10mm/min.
sec, nozzle diameter D ₁ , groove width D ₂ and engine valve material 4 on the condition that oscillation is not performed.
Table 2 shows the results of examining the bead shape of the hardfacing portion when the inclination angle θ of the axis A of No. 8 was changed as appropriate. In addition, Comparative Examples Nos. 19 to 21 are cases where hardfacing was performed using a bar material by a gas method.

[Table] *:○...good △...usable ×...bad As is clear from Table 2, No. 11 according to the present invention
In the case of hardfacing of ~18, no weld cracks, pinholes, or poor fusion occur in the hardfacing. In addition, in the case of No. 13 where the inclination angle θ of the axis line A is as large as 65 degrees, and in the case of No. 14 as small as 5 degrees, the bead shape is damaged due to the gravity acting on the molten metal, but this is not a practical problem. It can be seen that in other cases where the angle is within the range of 10° to 60°, hardfacing with a good bead shape and sufficient hardness can be obtained.
In addition, VMS585-B is an Fe-based overlay material.
However, although Nimonic 80A is used as the Ni-based overlay material, it is of course possible to use other overlay materials, and Co-based overlay materials include not only Stellite #32 and #12 but also other overlay materials. , #6 of Example 1, etc. can be used. On the other hand, in the case of comparative examples No. 19 to 21,
In either case, weld cracks or pinholes occurred in the hardfacing portion, or poor fusion occurred, so that a satisfactory hardfacing could not be obtained. Example 3 In the same manner as in Example 1, Stellite #6 spherical powder material (-100 to +350 mesh) was applied to an automobile engine valve material 48 made of SUH3 material with a valve diameter of 40 mm (outer diameter of the bulk portion 52). When hardfacing, the plasma gas supply rate is constant at 1.5/min, the powder carrier gas rate is 5/min, the shielding gas supply rate is 25/min, and the welding current is set to two types: 80A and 150A. However, the relationship between the nozzle diameter D ₁ and the groove width D ₂ under different welding currents was evaluated using the bead shape of the hardfacing part, and the results are shown in FIG. In addition, hardfacing was performed in the same manner as above except that the welding current was kept constant at 100A and the plasma gas supply rate was set to two types, 1.0/min and 1.8/min. The relationship between the nozzle diameter D ₁ and the groove width D ₂ under the gas supply amount was evaluated based on the bead shape of the hardfacing portion, and the results are shown in FIG. 3. Regarding the symbols in Figures 2 and 3, the ○ mark indicates that the bead shape of the hardfacing part was good, and the △ mark indicates that the bead shape is slightly impaired, but it can be used practically. In addition, the x mark indicates that the bead shape of the hardfacing portion was poor. As is clear from the results shown in FIGS. 2 and 3, the relationship between the nozzle diameter D ₁ and the groove width D ₂ can be seen from the welding conditions' current and plasma gas supply amount. Despite the changes, under the conditions of 0.6D ₂ ≦D ₁ ≦1.2D ₂ according to the present invention, it was possible to obtain a good hardfacing part with excellent properties.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating an example of an apparatus that can suitably implement the present invention. Figure 2 shows the nozzle diameter for different welding currents obtained in Example 3.
It is a graph showing the result of investigating the relationship between _D1 and groove width _D2 . Figure 3 shows the nozzle diameter for different plasma gas supply amounts obtained in Example 3.
It is a graph showing the result of investigating the relationship between _D1 and groove width _D2 . 10: Plasma arc torch, 38: Nozzle,
48: Engine valve material, D ₁ : Nozzle diameter,
D ₂ : Groove width, θ: Incline angle.

Claims (1)

[Claims] 1. When manufacturing a target engine valve by hardfacing an engine valve material made of a martensitic material containing Fe and Cr as main components to form a valve face surface, plasma arc A plasma arc is formed between the torch and the engine valve material, while a powder carrier gas guides a predetermined powder material into the plasma arc to melt the powder material and form a predetermined powder material on the engine valve material. While performing hardfacing, the nozzle diameter of the plasma arc torch: _D1 is set to the groove width of the hardfacing part: _D2 ,
A method for manufacturing an engine valve characterized by satisfying the following formula: 0.6D ₂ ≦D ₁ ≦1.2D ₂ . 2. The manufacturing method according to claim 1, wherein the welding speed of the hardfacing is 4 mm/sec or more. 3 The engine valve material is rotated around its axis with its axis inclined at an angle of 10° to 60° with respect to the vertical direction, and a plasma arc torch is placed above the inclined engine valve material to perform hardfacing. The manufacturing method according to claim 1 or 2, which performs the following.