WO2011058793A1

WO2011058793A1 - Seat faced poppet valve and method for producing same

Info

Publication number: WO2011058793A1
Application number: PCT/JP2010/062681
Authority: WO
Inventors: 一憲倉橋; 眞安池; 田中　靖人
Original assignee: 日鍛バルブ株式会社
Priority date: 2009-11-12
Filing date: 2010-07-28
Publication date: 2011-05-19
Also published as: JP2011101897A

Abstract

A method for producing a large-sized poppet valve which comprises a facing step for welding a facing material into a seat facing groove of a head, wherein the matrix of the valve comprises an Ni-rich base material and, in the facing step, the facing material is welded while cooling the head end face side. In the Ni-rich base material, sediments increase in a gamma prime phase due to the welding heat and crystal grains develop so that crack sensitivity increases. Since the large-sized valve has a large welding area and thus a large heat stress (shrinkage force caused by solidification) occurs at the boundary between the matrix (3) and the faced part (2), it is feared that hot crack arises in a heat affected part (3a) of the matrix along the faced part (2). However, in the aforesaid method, the head end face side is cooled with a cooling metal (20) in the facing step so that the period where a solid phase coexists with a liquid phase in the heat affected part (3a) of the matrix is shortened. Thus, the amount of the sediments in the gamma prime phase and the shrinkage force caused by solidification are both lowered, and, therefore, no hot crack occurs.

Description

Poppet valve with seat overlay and manufacturing method thereof

The present invention relates to a method for manufacturing a poppet valve, and more particularly, to a method for manufacturing a large-sized poppet valve for land use or marine use with a built-up sheet.

It is well known in the industry that engine poppet valves, especially intake and exhaust valves used for diesel engines and leaded fuel engines, operate in relatively corrosive atmospheres at relatively high temperatures. It has been.

For this reason, in the manufacture of engine poppet valves, the seat of the poppet valve is made of a corrosion-resistant, wear-resistant, wear-resistant, heat-resistant alloy to protect the valve surface and increase the useful life of the valve. It is generally performed.

The following Patent Document 1 describes a conventional method for manufacturing a poppet valve with a built-up sheet.

That is, here, “a method of manufacturing a poppet valve having a head having a desired shape, a hot forging step of hot forging an unfinished poppet valve from raw materials to form an initial valve head; A groove forming step for forming a groove for sheet build-up on the head of the unfinished poppet valve, a build-up step for welding a sheet build-up material in the groove for sheet build-up of the unfinished poppet valve, and the sheet A method for manufacturing an engine poppet valve including a second hot forging step in which a head having a predetermined shape is formed by hot forging the entire head including the overlay material ”is described.

JP2002-160039

However, the method disclosed in Patent Document 1 has no problem in manufacturing a poppet valve used for an engine of an automobile or a motorcycle, but this method is used as it is for manufacturing a large poppet valve used for a land or marine engine. In the case of application, there has been a problem that hot cracking occurs inside the sheet material welded portion, and the durability of the valve (sheet built-up portion) is difficult.
The land or marine engine includes a large diesel engine for generators, a large gas engine, a large diesel engine for ships, and the like.

Then, when the inventors examined the cause, the following was found.
That is, this type of large-sized poppet valve for land use or marine use is more harsh than the valve used in automobiles and motorcycle engines that use gasoline or light oil as fuel because the engine fuel is heavy oil. NCF80A, NCF751, NCF4015, which is superior in corrosion resistance, wear resistance, wear resistance, and heat resistance compared to poppet valves for automobiles and motorcycles, is required for operation in corrosive atmospheres. An alloy containing a large amount of nickel base such as NCF3015 (hereinafter referred to as a high Ni content alloy) is used.

However, the Ni-rich alloy promotes precipitation of Al and Ti by heat input (heat of welding), increases the amount of precipitation of gamma-prime phase, grows crystal grains, and has high cracking susceptibility (easy to crack). It has the characteristic of

And this kind of large poppet valve is larger than the poppet valve for automobiles and motorcycles, and naturally the boundary area between the base material and the sheet build-up part in the sheet material welded part is cooled, and the sheet material welded part is cooled. At this time, the solidification shrinkage stress generated at the boundary between the base material and the sheet build-up portion is also larger than that in the case of poppet valves for automobiles and motorcycles.

For this reason, in the build-up process, thermal stress distribution (solidification shrinkage that occurs in the base material side heat affected zone in the process of cooling the sheet material welded portion) on the base material side heat affected zone along the sheet build up portion in the sheet material welded portion Hot cracks due to stress) occur, and the durability of the valve (sheet build-up part) decreases. In addition, when the high temperature crack generated in the build-up process is fine, it may be improved by the second hot forging process after the build-up process (the hot crack is forged). In this case, there is a problem that even after the second hot forging process, hot cracking remains and the durability of the valve (sheet build-up portion) is lowered.

The inventor considered hot cracking in the build-up process and found the following. When the sheet material is welded to the base material 1 as shown in FIG. 12 (a), the sheet material welded portion immediately after the end of the welding is shown in FIG. 12 (b). The surface layer part 1a melts, and the sheet build-up part 2 which is a liquid phase is formed on the outer side (surface side).

Inside the sheet build-up portion 2, the base material side heat-affected zone 1 b in which a solid phase (within crystal grains) and a liquid phase (crystal grain boundary) are mixed under the influence of welding heat is affected by the heat of welding. It is formed between the base material side non-heat-affected zone 1c that is a solid phase that is not received. Thereafter, when the valve head (sheet material welded portion) cools, the sheet build-up portion 2 and the base material side heat affected zone 1b also change to a solid phase, as shown in FIG. However, the sheet build-up portion 2 in contact with the air cools the fastest and becomes a solid phase, but the base material side heat-affected zone 1b in the lower layer of the sheet build-up portion 2 has a large heat capacity of the valve head and is difficult to cool, It is maintained in a state of being mixed (a form in which a solid phase and a liquid phase coexist), the amount of precipitation of the gamma prime phase increases, crystal grains grow, and cracking susceptibility increases (becomes easy to crack). Then, it is presumed that hot cracking occurs in the base material side heat affected zone 1b due to the solidification shrinkage stress generated in the base material side heat affected zone 1b in the process of cooling the sheet material welded portion. And the high temperature crack which generate | occur | produces in this base material side heat influence part 1b is so remarkable that the time difference of the solidification start temperature (liquidus line) and solidification end temperature (solidus line) in the base material side heat influence part 1b is large, I found out.

Therefore, the inventor shortens the time during which the solid phase / liquid phase mixed form of the base material side heat affected zone 1b is continued (solidification start temperature ( If the time difference between the liquidus) and the solidification end temperature (solidus) is reduced), it is considered that the amount of gamma prime phase precipitated and the solidification shrinkage stress in the base metal side heat affected zone 1b are reduced. For this purpose, the valve head is actively cooled in the build-up process, and the liquid phase (crystal grain boundary) of the base metal side heat affected zone 1b may be solidified quickly, that is, the base metal side heat affected zone. It was thought that the whole 1b should be cooled quickly.

And it is effective as a result of repeated experiments to weld the sheet overlaying material in the groove for sheet overlaying while cooling the (end face side) of the head (high temperature cracking inside the sheet material welded part in the overlaying process) It has been confirmed that the application has been made.

Thus, the present invention has been made based on the above-mentioned problems of the prior art and the above-mentioned knowledge of the inventor, and the first object thereof is a land equipped with a sheet overlaying process that does not involve hot cracking. A second purpose of the present invention is to provide a land or marine poppet valve that is excellent in durability of a seat portion subjected to overlaying.

In order to achieve the first object, the poppet valve manufacturing method according to claim 1 is a method of manufacturing a poppet valve in which a head is integrally formed at a shaft end, and the valve head is formed. A process of hot forging an unfinished poppet valve from raw materials, a process of forming a groove for sheet overlaying on the head of the unfinished poppet valve, and sheet overlaying in the groove for sheet overlaying In a method for manufacturing a poppet valve comprising a build-up process for welding materials and a process for hot forging a region including the sheet build-up portion of the head, the poppet valve is made of a high Ni-containing alloy. In the above-described land or marine poppet valve, in the build-up process, the head is cooled and the sheet build-up material is welded to the groove for sheet build-up.

(Effect) For land or marine poppet valves, the base material is an alloy containing high Ni (the precipitation of Al and Ti is accelerated by the heat of welding, the amount of precipitation of gamma-prime phase is increased, and crystal grains grow. It has a characteristic that sensitivity increases (becomes easy to break)). Furthermore, land or marine poppet valves are larger than poppet valves for automobiles and motorcycles, and the boundary area between the base material and the seat overlay in the seat material welded part is naturally large. The solidification shrinkage stress generated at the boundary between the base material and the sheet build-up portion when it cools is also larger than in the case of poppet valves for automobiles and motorcycles.

For this reason, after completion of the overlaying process for welding the sheet material, in the process of cooling the sheet material welded part, the inside of the sheet material welded part (base material side thermal effect in which solid phase and liquid phase are mixed under the influence of welding heat) May cause high temperature cracking due to solidification shrinkage stress, but the valve head is cooled during the overlaying process of welding the sheet material, so the base material side heat affected zone inside the sheet material welded part Then, heat is dissipated to the sheet build-up portion laminated on the upper layer side, and is also actively radiated to the base material side non-heat-affected portion constituting the head, which is laminated on the lower layer side. For this reason, in the base material side heat-affected zone, the time until it cools down to the solid phase, that is, the time during which the solid phase / liquid phase mixed form continues is reduced (solidification start temperature (liquidus line) and solidification end temperature). (The time difference from the solid phase line is reduced), the amount of precipitation of the gamma-prime phase and the solidification shrinkage stress in the base metal side heat affected zone are reduced, and no hot cracking occurs in the base metal side heat affected zone.

If the valve is cooled too much (when the cooling rate is too high), a region with a large solidification shrinkage stress moves to a part with poor heat dissipation (slow cooling) and locally hot cracks there. Therefore, it is desirable to cool the entire valve substantially uniformly and gradually. For example, as shown in claim 2, when the end face side of the valve head is cooled and the valve is cooled too much (when the cooling rate is too high), the inner diameter side of the base material side heat affected zone is heated to a high temperature. Since cracking occurs, it is desirable to cool the end face side of the valve head substantially uniformly and gradually.

According to a second aspect of the present invention, in the method for manufacturing a poppet valve according to the first aspect, in the build-up step, the sheet build-up material is placed in the groove for sheet build-up while the end face side of the valve head is cooled. It comprised so that it might weld.

(Operation) The base material side heat affected zone is laminated on the base material side non-heat affected zone constituting the end face side of the valve head, and cools the end face side (base material side non-heat affected zone) of the valve head. Therefore, heat dissipation from the base metal side heat affected zone to the base metal side non heat affected zone is effectively promoted, and the solid phase / liquid phase mixed form of the base metal side heat affected zone is further shortened (solidification starts) Because the time difference between the temperature (liquidus) and the solidification end temperature (solidus) is smaller), the precipitation amount of the gamma-prime phase and the solidification shrinkage stress in the base metal side heat affected zone are reliably reduced. In addition, hot cracking does not occur reliably in the base metal side heat affected zone.

According to a third aspect of the present invention, in the method for manufacturing a poppet valve according to the first or second aspect, in the build-up step, the sheet build-up material in a state where an end face side of the valve head is in contact with a cooling base. Was configured to be welded.
In particular, the end face side of the valve head can be uniformly cooled by configuring the cooling pedestal with cooling metal.

(Operation) Since the heat of welding transmitted to the base metal side non-heat affected zone is reliably and effectively dissipated through the cooling base (cooling metal), the base metal side heat affected zone is in the solid / liquid phase. The time for maintaining the mixed form is further shortened, and the amount of precipitation of the gamma-prime phase is surely reduced, so that the cracking susceptibility does not increase (is not easily cracked).

According to a fourth aspect of the present invention, in the method for manufacturing the poppet valve according to any one of the first to third aspects, the sheet build-up material is configured to be plasma arc welded in the build-up step.

(Action) Sheet overlay material is a high melting point that is superior in corrosion resistance, wear resistance, wear resistance, and heat resistance to the base material of the valve (high Ni content alloy) such as cobalt base alloy or nickel base alloy. However, since the arc generated by plasma arc discharge reaches a predetermined high temperature above the melting point of the sheet overlay material (material), the powdered sheet overlay material is used as a plasma arc discharge torch. The cladding material can be welded from the torch to the groove for sheet deposition.

According to a fifth aspect of the present invention, in the method for manufacturing a poppet valve according to the fourth aspect, in the build-up step, the sheet build-up groove is directly opposite to a plasma arc discharge torch directed vertically downward. The valve is arranged so as to be inclined, and the sheet build-up material is welded to the groove while the valve is rotated around its axis.

(Operation) By rotating the valve around the shaft and welding the melted sheet build-up material from the plasma arc discharge torch to the sheet build-up groove below the gravity direction, the entire circumference of the sheet build-up groove Weld the sheet overlay material.

There is also a method of running (turning) the torch around the fixed valve head along the groove for sheet build-up, but the welding direction of the torch arranged to face the groove for sheet build-up is not vertically downward Because of the inclination with respect to the axis of the valve, the posture of the torch with respect to the groove for sheet build-up always changes, the thickness of the sheet welded portion becomes uneven in the circumferential direction, and the subsequent process is troublesome. Furthermore, in the build-up process, there are many molten build-up materials scattered outside the sheet build-up grooves, and the sheet build-up material is consumed wastefully.

On the other hand, in the fifth aspect, since the plasma arc discharge torch fixed vertically downward is configured to rotate the valve tilted so that the groove for sheet build-up faces the axis, the shaft is rotated. The posture (relationship) of the torch with respect to the groove for sheet build-up is always constant, the thickness of the sheet welded portion is uniform in the circumferential direction, and the post-process is simple. Furthermore, in the build-up process, there is little molten build-up material scattered out of the groove for sheet build-up, and there is little waste of the sheet build-up material.

The poppet valve according to claim 6 is a poppet valve in which a head is integrally formed at a shaft end portion, and is configured to be manufactured by the method according to any one of claims 1 to 5.

(Operation) No cracks occur in the seat portion of the manufactured land or marine poppet valve.

As is apparent from the above description, according to the poppet valve manufacturing method according to claim 1, a method for manufacturing a poppet valve provided with a build-up process in which hot cracking does not occur in the sheet material welded portion is provided. A land or marine poppet valve excellent in durability of the welded portion of the sheet material can be manufactured.

According to claim 2, since the manufacturing method of the poppet valve provided with the build-up process which does not generate | occur | produce a high temperature crack reliably in a sheet material welding part is provided, the land use which was further excellent in durability of a sheet material welding part, or Can produce marine poppet valves.

According to the third aspect, since an increase in cracking sensitivity (being easily broken) is suppressed, a method for manufacturing a poppet valve that does not reliably cause high-temperature cracking in the sheet material welded part in the build-up process is provided. It is possible to manufacture land or marine poppet valves with excellent endurance.

According to the fourth aspect, the build-up process can be easily performed by welding a high melting point, for example, a cobalt base alloy or a nickel base alloy, which is a sheet build-up material, along the groove for sheet build-up.

According to the fifth aspect, since the posture (relationship) of the torch with respect to the groove for sheet build-up is always constant, the post-process is simplified because the thickness of the sheet welded portion is uniform in the circumferential direction. Moreover, since there is little molten build-up material scattered outside the sheet build-up groove in the build-up process, the consumption of the sheet build-up material can be greatly reduced.

According to the sixth aspect of the present invention, since a land or marine poppet valve that does not crack in the seat portion can be manufactured, a land or marine poppet valve having excellent durability of the seat portion can be provided.

It is explanatory drawing explaining the upsetting process of a marine poppet valve. It is explanatory drawing explaining the process of hot forging the poppet valve. It is explanatory drawing explaining the process of grooving in the head outer periphery of the poppet valve. It is explanatory drawing explaining the process of welding a sheet | seat material to the groove | channel of the head outer periphery of the poppet valve. It is explanatory drawing explaining the process of rough-cutting a sheet material welding part. It is explanatory drawing explaining the process of hot forging again the same poppet valve. It is explanatory drawing explaining the process of cutting the surface of the poppet valve. It is explanatory drawing explaining the process of grinding the surface of the poppet valve. It is a side view of the whole manufactured poppet valve. It is sectional drawing of the head of the poppet valve which expands and shows the sheet | seat material welding part at the time of completion | finish of a building-up process. It is sectional drawing which shows the structure of the whole apparatus which supports a poppet valve in the case of a building-up process. It is a figure explaining the mechanism in which a high temperature crack generate | occur | produces in the inside of a sheet material welding part in an overlaying process, (a) is sectional drawing of the base material before overlaying, (b) is the sheet material welding part in overlaying. Sectional drawing and (c) show sectional views of the sheet material welded portion cooled after being built up.

Next, embodiments of the present invention will be described based on examples.

FIGS. 1 to 8 are diagrams showing an example method for manufacturing a marine poppet valve. By sequentially performing the processing shown in FIGS. 1 to 8 on a rod-shaped material made of NCF80A, as shown in FIG. A marine poppet valve 10 in which a head 12 having a predetermined shape is integrally formed at one end of the shaft 11 and the seat portion 13 of the head 12 is reinforced with a sheet build-up material made of stellite alloy 712 can be manufactured. The poppet valve 10 is a large poppet valve having a head diameter of about 100 mm, a shaft diameter of about 25 mm, and an overall length of about 500 mm. Reference numeral 11a denotes a cotter groove.

In order to manufacture this poppet valve 10, first, in the upsetting process shown in FIG. 1, a rod-shaped material W1 made of NCF80A heated by applying a voltage between the pair of

electrodes

14a and 14b (about 1100 ° C.) While pressurizing in the direction, the head portion is processed into a predetermined shape, and preheating is applied to the head portion for the next hot forging. The unfinished valve after the upsetting process is indicated by reference numeral W2.

Next, in the hot forging shown in FIG. 2, the head portion of the material W2 installed in the upsetting process is formed into a predetermined shape by hot forging. The unfinished valve after the completion of this hot forging step is indicated by reference numeral W3.

Next, in the groove forming step shown in FIG. 3, the groove 16 for overlaying is formed on the seating surface of the head portion using the cutting tool 15 while rotating the unfinished valve W3. The unfinished valve after the completion of the groove forming process is indicated by reference numeral W4.

Next, in the build-up process shown in FIG. 4, in order to enhance the durability of the seat portion 13 (see FIG. 9), a wear resistant material (Stellite alloy 712) is plasma arc welded to form the unfinished valve W <b> 4. It is welded (filled) to the groove 16 for filling. In FIG. 10, reference numeral W <b> 5 indicates an unfinished valve after completion of the build-up process, and reference numeral 2 indicates a sheet build-up portion welded to the groove 16.

In the build-up process shown in FIG. 4, the unfinished valve W4 is inclined and disposed so that the sheet build-up groove 16 faces directly below the plasma arc discharge torch 70 directed vertically downward. As the sheet build-up material is welded into the groove 16 while rotating around the axis, the entire groove 16 is overlaid. In particular, by performing the build-up process while cooling the head portion of the valve W4 using the gold 20, no hot cracking occurs in the sheet material welded portion.

Next, in the cutting process shown in FIG. 5, the unfinished valve W <b> 5 that has undergone the overlaying process is rotated, and cutting is performed using the cutting tool 17 so that the overlaying part becomes a flat surface. The unfinished valve after the end of the cutting process is indicated by reference numeral W6.

Next, in the re-hot forging / heat treatment process shown in FIG. 6, the mold and the unfinished valve W6 are heated to 900 to 1000 ° C. with a burner, the valve W6 is hot-forged again, and then solutionized into the valve W4. Treatment (cooling after holding in an electric furnace at a temperature of about 1000 ° C.) and aging treatment (cooling after holding in an electric furnace at a temperature of about 700 ° C. for a predetermined time) are performed. The unfinished valve after the completion of the re-hot forging / heat treatment process is indicated by reference numeral W7.

Next, in the cutting process shown in FIG. 7, while cutting the unfinished valve W <b> 7, the cutting tool 18 is used to cut the head sheet portion, the neck lower R portion, the shaft portion, and the cotter groove 11 a. In addition, as shown in FIG. 8, by rotating the unfinished valve W8 and using the grinding tool 19 to finish the seat portion and the shaft portion to the roughness as designed, the valve 10 shown in FIG. It ’s done.

Then, among the steps shown in FIGS. 1 to 8 for explaining the manufacturing method of the valve 10, each step except the overlaying step shown in FIG. 4, ie, the upsetting step in FIG. 1, the hot forging step in FIG. 3, grooving step in FIG. 3, rough surface cutting step in FIG. 5, hot forging / heat treatment step in FIG. 6, cutting step in FIG. 7, and grinding step in FIG. Since it is the same as each process which comprises a method, detailed description of each of these processes is abbreviate | omitted, and the overlaying process shown in FIG. 4 different from the manufacturing method of the conventional marine valve is demonstrated in detail.

FIG. 11 is a cross-sectional view showing a configuration of the entire apparatus for performing the build-up process shown in FIG.

Reference numeral 20 denotes a disk-shaped cooling metal having a cooling water circulation path L therein, and a concave portion 22 that can hold the head end face side of the valve 10 in close contact is formed on the upper surface thereof.

Reference numeral 30 denotes a shaft end presser that supports the shaft end of the valve 10, and is rotatably supported by a valve shaft end support 34 on the apparatus main body side via an angular bearing 32.

The cooling water circulation path L inside the cooling metal 20 is composed of a central water supply path L1 and a drainage path L2 extending radially from the water supply path L1 in the circumferential direction, and the water supply path L1 and the drainage path L2 are connected to the cooling metal 20. The cooling joint joint 24 integrated and connected, the driven rotary shaft 40 connected and integrated to the cooling joint 24, and the rotary joint 50 (movable joint 50a, fixed side) connected to the lower end of the driven rotary shaft. The joints 50b) respectively extend into the water supply pipes 42 and the water distribution pipes 44 connected to the fixed rotary joint 50b.

The cooling metal joint 24 protruding to the lower surface side of the cooling metal 20 is held by three chucks (claw members) 52 provided on the chuck base 50 and capable of expanding and contracting in the radial direction, and fixed on the chuck base 50. Has been.

A driven pulley 64 integrated with a lower portion of the chuck base 50 is attached to the driven rotary shaft 40 that extends downward through the central circular hole 51 of the chuck base 50, and an output shaft of the servo motor 60. A timing belt 66 is interposed between the driving pulley 52 and the driven pulley 54 that are attached to the shaft 62.

Further, the valve shaft end support portion 34 on the apparatus main body side is configured so that the valve 10 can be cooled and pressurized (pressed) toward the metal 20 via a shaft end presser 30 that supports the shaft end of the valve 10. The valve 10 sandwiched in the vertical direction by the cooling metal 20 and the shaft end presser 30 is integrated with the chuck pedestal 50, the rotary shaft 40, the pulley 54, and the rotary joint movable part 50a by the drive of the servo motor 60. Thus, the rotary joint fixing portion 50b and the valve shaft end support portion 34 on the apparatus main body side are rotated.

The rotation center axis of the driven side rotating shaft 40 is disposed so as to be inclined at 45 degrees with respect to the plasma arc discharge torch 70 directed vertically downward (inclined at 45 degrees with respect to the vertical axis). The valve 10 supported by the shaft end presser 30 has a form in which the sheet build-up groove 16 faces the torch 70 in the vertical direction directly under the plasma arc discharge torch 70.

The driving of the servo motor 60 and the welding of the sheet material by the plasma arc discharge torch 70 are controlled by a control unit (not shown) so that the sheet material is welded by the torch 70 while rotating the valve 10. For example, the sheet build-up portion having a substantially uniform predetermined thickness can be formed over the entire circumference of the groove 16 by rotating the valve 10 twice.

Further, the water supply / drainage to the cooling water circulation path L inside the cooling metal 20 is also controlled by a control unit (not shown). That is, the cooling gold 20 is provided with a temperature sensor, and the pump P is driven so that the temperature detected by the temperature sensor becomes a predetermined temperature while the sheet material is welded to the groove 16 by the torch 70. On / off control of the water supply to the cooling water circulation path L inside the cooling metal 20 is controlled.

For this reason, while the valve 10 is rotated at a predetermined speed around its axis, the sheet overlay material is sprayed into the groove 16 from the torch 70, so that the sheet overlay material is built up around the entire groove 16. The temperature on the head end face side of the valve 10 is maintained at a predetermined temperature during the build-up process shown in FIG. 4, that is, while the sheet build-up material is sprayed (welded) from the torch 70 to the groove 16. Hot cracks do not occur inside the weld.

That is, the marine poppet valve 10 has a base material of NCF80A (precipitation of Al and Ti is promoted by the heat of welding, the amount of precipitation of gamma-prime phase increases, and crystal grains grow, so that cracking susceptibility increases (cracking). It is made of a high Ni content alloy having the characteristics of

Further, the marine poppet valve 10 is larger than the poppet valve for automobiles and motorcycles, and the boundary area between the base material and the sheet build-up portion in the sheet material welded portion is naturally large, and when the sheet material welded portion cools. The solidification shrinkage stress generated at the boundary between the base material and the seat build-up portion is also larger than in the case of poppet valves for automobiles and motorcycles.

For this reason, as shown in an enlarged view in FIG. 10, after the overlaying process for welding the sheet material is completed, the sheet material welded portion is cooled and the interior of the sheet material welded portion (the solid phase is affected by the heat of welding). There is a risk that hot cracking due to solidification shrinkage stress may occur in the base material side heat-affected zone 3a) in which the liquid phase is mixed, but during the overlaying process of welding the sheet material, the end face side of the valve head is cooled and positively applied by the gold 20 In the base material side heat-affected zone 3a inside the sheet material welded portion, heat is radiated to the sheet build-up portion 2 laminated on the upper layer side, and the head is laminated on the lower layer side. Heat is positively dissipated also to the base material side non-heat-affected zone 3b, and the time during which the solid-phase / liquid-phase mixed form of the base material side heat-affected zone 3a continues is shortened (solidification start temperature (liquidus line)) And the time difference between the solidification end temperature (solidus) and the base material A solidification shrinkage stress precipitation amount of gamma-prime phase in the heat-affected zone 3a is reduced, high temperature cracking the base material side heat affected zone 3a does not occur.

In particular, during the build-up process (while the sheet material is being welded to the groove 16 by the torch 70), the temperature of the cooling metal 20 is set at the base material side heat affected zone 3a in the sheet material welded portion. Since it is maintained at a predetermined temperature effective in reducing the precipitation amount of the gamma prime phase and the solidification shrinkage stress, hot cracking does not occur reliably in the base material side heat affected zone 3a. In addition, in FIG. 10, the code | symbol 3 shows a base material and the arrow in FIG. 10 shows the heat dissipation direction.

In the re-hot forging process shown in FIG. 6, the mold and the valve W6 are heated to 900 to 1000 ° C. with a burner to hot forge the valve W6, but the valve W6 after the build-up process is forged again. Thereby, the high temperature crack in the base material side heat affected zone 3a inside the sheet welded portion is more reliably wiped out.

That is, in the build-up process, high-temperature cracks do not occur in the base metal side heat-affected zone 3a, but even if minute cracks remain in the base-material side heat-affected zone 3a after the build-up process. Since the hot crack generated in the base metal side heat-affected zone 3a is joined (forged) by re-hot forging performed after the build-up process, the base side heat effect inside the sheet build-up portion There is no possibility that hot cracks remain in the portion 3a.

Thus, in this embodiment method, the marine poppet valve 10 having excellent durability of the seat portion 13 can be manufactured using the marine poppet valve on which the seat is built up.

In the above-described embodiment method, the poppet valve 10 in which the seat material 13 made of stellite alloy 712 is built up on the seat portion 13 of the valve body whose base material is NCF80A has been described, and the manufacturing method thereof is described. In addition to NCF80A, NCF751, NCF4015, NCF3015, etc. can be considered as the base material, and the sheet material constituting the seat portion 13 is superior in corrosion resistance, wear resistance, abrasion resistance, and heat resistance to the base material constituent material. A cobalt base alloy or a nickel base alloy can be considered.

In the build-up process of the above-described embodiment method, the valve head is cooled by adjusting the temperature of the cooling metal 20 to a predetermined temperature, but the base material of the valve, the sheet material to be built-up, the welding temperature, Needless to say, the set temperature of the cooling metal 20 varies depending on the size of the groove width or the like.

In the above-described embodiment method, the cooling metal 20 is cooled by the water cooling method, but it may be cooled by oil or air.

In the above-described embodiment method, the manufacturing method of the marine poppet valve 10 has been described. However, the present invention is not limited to the manufacturing method of the marine poppet valve 10, and a large diesel engine for a generator, a large gas engine, etc. Needless to say, the present invention can be similarly applied to a method for manufacturing a large-sized land poppet valve that is required to be used in a corrosive atmosphere.

DESCRIPTION OF SYMBOLS 2 Sheet build-up part 3 Base material 3a Base material side heat affected part 3b Base material side non-heat affected part 10 Engine poppet valve 11 Shaft 12 Valve head 13 Valve seat part 16 Groove for sheet build-up 20 Cooling metal L Cooling water circulation Road 70 Plasma Arc Discharge Torch

Claims

A method of manufacturing a poppet valve in which a head is integrally formed at a shaft end,
Hot forging a raw poppet valve from raw materials to form a valve head;
Forming a groove for sheet build-up on the head of the unfinished poppet valve;
A build-up process of welding a sheet build-up material in the groove for sheet build-up,
In a method for manufacturing a poppet valve comprising a step of hot forging a region including the sheet build-up portion of the head,
The poppet valve is a land or marine poppet valve whose base material is made of a high Ni content alloy. In the build-up process, the sheet build-up material is placed in the groove for sheet build-up while cooling the head. A method for manufacturing a poppet valve, characterized by welding.
2. The method of manufacturing a poppet valve according to claim 1, wherein in the build-up step, the sheet build-up material is welded to the groove for sheet build-up while cooling the end face side of the valve head.
3. The method of manufacturing a poppet valve according to claim 1, wherein, in the build-up step, the sheet build-up material is welded in a state in which an end surface side of the valve head is brought into contact with a cooling pedestal. .
The method of manufacturing a poppet valve according to any one of claims 1 to 3, wherein in the build-up step, the sheet build-up material is plasma arc welded.
In the build-up process, the valve is inclined and arranged so that the groove for sheet build-up faces directly below the plasma arc discharge torch vertically downward, and the valve is rotated about its axis. The method of manufacturing a poppet valve according to claim 4, wherein a sheet build-up material is welded to the groove.
A poppet valve manufactured by the method according to any one of claims 1 to 5.