KR20170116188A - Mobile wall member and welding method - Google Patents

Abstract

It is an object of the present invention to provide a movable wall member having a fire contact surface having a desired range of corrosion resistance while widening a selection range of materials for the buffer layer. The movable wall member is a movable wall member used in an internal combustion engine,
A corrosion resistant layer (7) having an uppermost surface contact surface on a base material (4), wherein the corrosion resistant layer (7) comprises an alloy containing 50 mass% or more and 60 mass% or less of Ni and 40 mass% And is welded in multiple layers. In the corrosion resistant layer 7, the layer 10 having the uppermost surface contains 40 mass% or more and 50 mass% or less of Cr.

Description

TECHNICAL FIELD [0001] The present invention relates to a movable wall member and a welding method,

The present invention relates to a movable wall member and a welding method used in an internal combustion engine.

The movable wall member used in the internal combustion engine is formed of heat-resisting steel. On the surface of the movable wall member, a layer made of a corrosion-resistant material is provided to prevent high-temperature corrosion (Patent Document 1 and Patent Document 2). Examples of the material component showing corrosion resistance include chromium (Cr) and molybdenum (Mo).

Patent Document 1: Japanese Patent No. 5036879 (paragraph [0030], Fig. 1) Patent Document 2: Registration Utility Model No. 3038802 (paragraph [0004])

When the layer made of the corrosion-resistant material is formed directly on the heat-resistant steel, it is known that the component contained in the corrosion-resistant material forms carbide with the carbon (C) contained in the heat-resistant steel. For example, chromium reacts with carbon (C) to become chromium carbide (CCr). Chromium carbide is hard and tough and does not show corrosion resistance. Therefore, if the amount of chromium carbide to be produced is increased, anticipated corrosion resistance can not be obtained.

In Patent Document 1, a buffer layer is provided between a heat resistant steel (alloy steel) and a layer (outer side) made of a corrosion resistant material so that components contained in the corrosion resistant material prevent carbon and carbide contained in the heat resistant steel from being formed.

However, in Patent Document 1, the carbon content of the alloy steel (base material) and the buffer layer must be limited and the thickness of the buffer layer must be specified. Therefore, there is a problem that the material of the base material and the buffer layer can not be freely selected.

In Patent Document 1, since the buffer layer has a one-layer structure, the influence of the base material is large, and at least the influence of the base material is on the outer side. When the influence of the base material on the outer side portion is deteriorated, the corrosion resistance is lowered, the toughness is lowered, and the reliability as the outer side portion of the movable wall member is lowered.

In Patent Document 2, a layer made of a corrosion-resistant material is directly deposited on the base material. In Patent Document 2, a material having a significantly high Cr content is used as a corrosion-resistant material. However, a corrosion-resistant material having a high Cr content has a problem of low ductility and difficult welding.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a movable wall member and a welding method provided with a fire contact surface having anticipated corrosion resistance while widening the selection range of the material of the buffer layer do.

In order to solve the above problems, the movable wall member and the welding method of the present invention employ the following means.

The present invention relates to a movable wall member for use in an internal combustion engine, wherein the corrosion resistant layer has an uppermost surface on the base material, and the corrosion resistant layer comprises 50% by mass or more of Ni and 60% The present invention provides a movable wall member that is welded in multiple layers by using an alloy including a metal layer.

In the present invention, the corrosion resistant layer is formed using an alloy (hereinafter referred to as a 50Cr-50Ni alloy) containing 50% by mass or more of Ni and 60% by mass or less of Ni and 40% by mass or more and 50% In the present invention, since the corrosion resistant layer is added in multiple layers, the dilution of Cr in the alloy can be stepwise reduced. That is, when the corrosion resistant layer is formed using the same kind of 50Cr-50Ni alloy, the Cr content of the first layer on the base material side becomes lower than that of the 50Cr-50Ni alloy, but the layer including the best surface, It is possible to secure a Cr content of about the same level as the Cr content. This results in a movable wall member having anticipated corrosion resistance. The present invention can form a top surface layer that is a touch screen without being influenced by the base material. Therefore, even if another layer is provided between the base material and the corrosion-resistant layer, the material of the other layer is not limited as in Patent Document 1. Therefore, the operator can freely select an inexpensive material or a material having good availability.

In one embodiment of the present invention, it is preferable that the layer having the uppermost surface among the corrosion resistant layers contains not less than 40 mass% and not more than 50 mass% of Cr.

When the Cr content is in the above range, sufficient corrosion resistance can be obtained while securing ductility.

The present invention relates to a welding method for preheating a base material at a temperature of not lower than 80 ° C and not higher than 120 ° C and then additionally welding an alloy containing 50% by mass or more of Ni and 60% by mass or more of Cr and 40% Is formed at a temperature of 200 DEG C or less.

By preheating (including the base material) it is possible to prevent sudden temperature changes in the lower layer. By determining the upper limit of the temperature between passes, it is possible to suppress the temperature rise of the molten pool. This can prevent high-temperature cracking.

In one embodiment of the present invention, when the alloy is welded in layers, it is preferable to perform surface exposure after formation of the first layer, and then weld the next layer over the first layer.

According to an embodiment of the present invention, after the surface is exposed, the next layer can be formed to provide a corrosion resistant layer in which welding defects are less likely to occur.

The present invention provides a movable wall member provided with a contact surface having anticipated corrosion resistance by forming a corrosion resistant layer added in multiple layers. In such a movable wall member, the selection range of the material of the layer provided under the corrosion resistant layer is wider than that in the prior art.

1 is a perspective view showing a main portion of an engine for a marine vessel.
2 is a front view of an exhaust valve according to the first embodiment.
Fig. 3 is a partial cross-sectional view of the exhaust side of the exhaust valve according to Fig. 2; Fig.
4 is a flowchart showing the procedure for forming the first additional layer of the corrosion resistant layer.
5 is a view for explaining bead formation.
6 is a view for explaining bead formation.
7 is a partial cross-sectional view of the movable wall member according to the experimental example.
8 is a front view of the exhaust valve according to the second embodiment.

1 is a perspective view showing a main portion of an engine for a marine vessel. The engine includes a cylinder 1, a piston 2 slidably fitted in the cylinder, an exhaust pipe 3 coupled to the upper portion of the cylinder, and an exhaust valve 4 inserted into the exhaust pipe 3 . The space surrounded by the cylinder 1, the exhaust valve 4 and the piston 2 is the combustion chamber 5. The engine is provided with a fuel supply means for supplying fuel to the combustion chamber 5 and an air supply means for supplying air to the combustion chamber 5 and the like.

The present invention can be applied to the exhaust valve 4 or the piston 2, which is a movable wall member as shown in Fig. The internal combustion engine in which the movable wall member is used may be a two-cycle engine or a four-cycle engine. In the case of a four-cycle engine, the movable wall member of the present invention is also applicable to an intake valve.

(First Embodiment)

In this embodiment, an exhaust valve of a marine diesel engine will be described as an example. 2 is a front view of the exhaust valve according to the embodiment. Fig. 3 is a partial cross-sectional view of the exhaust side of the exhaust valve according to Fig. 2; Fig.

The exhaust valve 4 includes a shaft portion 4a and a disk-shaped flange portion 4b provided at an end portion of the shaft portion 4a. The flange portion 4b has a buffer layer 6 and a corrosion resistant layer 7 on the surface facing the combustion chamber side.

The exhaust valve 4 (base material) is a heat resistant alloy. As the heat resistant alloy, for example, stainless steel such as SUH31, SNCrW or Ni based alloy such as Nimonic80A (all manufactured by Daido Steel Co., Ltd.) can be used. The main component of the stainless steel may be Fe and may contain inevitable components such as Mn, P, and S. Table 1 shows the main subcomponents (% by mass) of the stainless steel used as the base material.

Symbol of kind C Si Ni Cr W SUH31 0.35 to 0.45 1.50 to 2.50 13.00 - 15.00 14.00-16.00 2.00 to 3.00 SNCrW 0.20-0.30 1.00 to 2.00 8.00-10.00 18.00 - 21.00 1.50 to 2.50 Nimonic80A ~ 0.10 ~ 1.00 Honey. 18.00 - 21.00 -

The buffer layer 6 is a layer capable of buffering the influence of the base material when the corrosion resistant layer 7 is formed. "Influence of base metal" means that Cr contained in the welding material used for forming the corrosion resistant layer is diluted by reacting with C contained in the base metal. Or that the components contained in the weld material are diluted by merely mixing the components intended to be melted by welding. The buffer layer (6) is made of a heat resistant alloy different from the base material and the corrosion resistant layer (7). Although not particularly limited, the C content of the buffer layer 6 is smaller than that of the base material, and is preferably in the range of 0.15 mass% or less. The C content of the buffer layer 6 may exceed 0.09 mass%. The buffer layer 6 may have one or two or more layers. The total thickness of the buffer layer 6 may be appropriately set in accordance with the size of the exhaust valve or the like.

The corrosion resistant layer 7 is a layer formed by welding a multi-layered 50Cr-50Ni alloy as a welding material. 50Cr-50Ni alloy contains 50% by mass or more of Ni and 60% by mass or less of Ni, and 40% by mass or more and 50% by mass or less of Cr with respect to the total mass of 100%. 50Cr-50Ni alloy has a composition of C0.10 mass% or less, Fe 0.50 mass% or less, Si0.20 mass% or less, Mn0.20 mass% or less, P0.02 mass% or less, Cu0.50 mass% To 1.0 mass%.

The corrosion resistant layer (7) is constituted by stacking two or more additional layers. The content of Cr in the corrosion resistant layer (7) is higher as the additional layer is detached from the base material. It is preferable that the Cr content of the additional layer having the uppermost surface is equal to or close to the Cr content of the weld material.

The corrosion resistant layer 7 according to the present embodiment has a structure in which a first reinforcement layer 8, a second reinforcement layer 9 and a third reinforcement layer 10 are sequentially stacked on a cushioning layer 6 ). The third additional layer (10) includes the uppermost surface of the corrosion resistant layer (7) and becomes the contact surface of the exhaust valve (4). The Cr content of the third additional layer 10 is 40 mass% or more and 50 mass% or less. The Cr content of the second additional layer (9) is lower than the Cr content of the third additional layer (10). The Cr content of the first additional layer 8 is lower than the Cr content of the second additional layer 9.

The total thickness of the corrosion resistant layer 7 can be appropriately set by the size of the exhaust valve 4. [ If the corrosion resistant layer 7 is too thick, the production cost is increased. Therefore, the total thickness of the corrosion resistant layer 7 is preferably set to the minimum thickness at which the desired corrosion resistance is obtained.

For example, in the case of an exhaust valve having an outer diameter of about 470 mm of the plunge portion 4b, the corrosion resistant layer 7 has a multilayer structure of two or more layers, and if the total thickness of the corrosion resistant layer 7 is about 4 mm to 5 mm, Corrosion resistance is obtained. The total thickness of the corrosion resistant layer 7 is preferably about 6 mm to 8 mm. When the corrosion resistant layer 7 has a single-layer structure, the Cr content does not change in the thickness direction, so that the same effect can not be obtained even if the total thickness is the same.

Next, a manufacturing method of the exhaust valve will be described.

The cushioning layer 6 and the corrosion resistant layer 7 are provided in order on the surface (contact surface side) of the flange portion 4b of the exhaust valve 4 facing the combustion chamber side. The buffer layer 6 may be suitably formed by a method suitable for the material constituting the buffer layer 6.

The corrosion-resistant layer 7 is formed by welding and welding multiple layers (layers) using a welding material. For the welding material, wire or rod-shaped 50Cr-50Ni alloy is used.

The first additional layer 8 to the third additional layer 10 are formed using the same kind of welding material under the same conditions. The final Cr content differs depending on each layer. The first additional layer 8 formed directly on the buffer layer 6 is strongly influenced by the base material, so Cr is diluted. When the second and third overlaid layers are sequentially stacked on the first overlay layer, the influence of the base material is gradually reduced and the dilution (diffusion) of Cr is suppressed in stages. Therefore, by stacking the layers in multiple layers, it is possible to make the Cr content of the additional layer having the contact surface equal to the weld material component.

The welding can be performed by gas shielded metal arc welding (MIG welding or MAG welding), laser welding, TIG welding, or PTA (plasma welding), but the corrosion resistant layer 7 is most preferably formed by MAG welding.

The shield gas used for MAG welding may be a gas containing Ar as a main component and mixed with He and CO ₂ . As a result, the bead shape can be made uniform and the occurrence of welding defects can be reduced. CO ₂ is dissociated into carbon and oxygen by heat at the time of welding, and at this time, since heat is taken away, there is an effect of suppressing the temperature rise of the molten pool. By using shield gas mixed with CO ₂ , heat loss of arc can be suppressed and spatter can be suppressed.

The current value at the time of welding may be set to a value that is 0.8 or more and 0.9 or less when the base current of the welding apparatus to be used is 1. It is possible to prevent the high-temperature crack by lowering the current value and suppressing the temperature rise of the molten pool as compared with the conventional method.

In the step of forming the corrosion resistant layer, one additional layer is formed on the buffer layer, and then one additional layer is exposed by machining. Subsequently, another additional layer is formed on the additional layer of 1, and then the surface of the other additional layer is exposed by machining. After the formation of the additional layer and the surface exposure are repeated until the corrosion resistant layer becomes a desired thickness, annealing and finishing are performed in the same manner as in the conventional method.

By exposing the overlaid layer as a base when laminating the additional layers, it is possible to reduce the entry of impurities when the next layer is welded, thereby preventing the occurrence of welding defects.

Next, a method of forming the additional layer will be described. Fig. 4 shows the procedure for forming the first additional layer of the corrosion resistant layer. Figs. 5 and 6 show diagrams for explaining bead formation. Fig. 5 is a sectional view of the exhaust valve. 6 is a view of the exhaust valve on the side of the flange portion (the flange surface side on which the corrosion resistant layer is provided).

First, the exhaust valve (base material) 4 provided with the buffer layer 6 is preheated at a temperature of 80 ° C or higher and 120 ° C or lower, preferably about 100 ° C or so. Burners or electric furnaces can be used for preheating. By preheating, it is possible to gently change the temperature of the lower layer (base material and buffer layer) at the time of forming the beads, so that the difference in thermal expansion can be alleviated even with a material having a high Cr content and cracking of the base material due to tensile can be prevented.

After the preheating, the first bead 8a is formed along the outer periphery of the flange portion 4b on the buffer layer 6 (first pass). In order to prevent high temperature cracking, the air is cooled until the temperature between the passes becomes 200 DEG C or less, and then the center of the bead is shifted to the inside of the first bead 8a and the second bead 8b is brought into contact with the first bead 8a (Second pass). In order to prevent high-temperature cracking, the third bead 8c is formed inside the second bead 8b after air-cooling again until the temperature between passes becomes 200 deg. Bead formation and air cooling are repeated until the surface of the buffer layer 6 is covered with the weld metal.

The pass-to-pass temperature is the temperature of the weld metal (bead) immediately before welding the next pass and the adjacent workpiece. The inter-path temperature is obtained by using a non-contact thermometer and measuring the temperature of the weld metal. By air-cooling until the temperature between the passes becomes 200 DEG C or lower, the temperature rise in the lower layer is suppressed, so that high-temperature cracking can be prevented.

In the present embodiment, the first additional layer is formed so as to be directed inward from the outer peripheral side of the flange portion, but it may be formed so as to extend from the inner side to the outer peripheral side of the flange portion.

(Experimental Example)

A corrosion resistant layer was formed according to the above embodiment and the Cr content of each layer of the corrosion resistant layer was confirmed. 7 is a partial cross-sectional view of the movable wall member according to the experimental example. The material of the exhaust valve 4 (base material) was 15Cr-14Ni-2Si-2.5W-0.4C (SUH31). The buffer layer 6 was formed by MAG welding using an alloy steel having a carbon content exceeding 0.09 mass%. The buffer layer 6 is composed of 4 to 5 layers (total thickness 10 mm to 12 mm).

The corrosion resistant layer 7 was formed using a 50Cr-50Ni alloy. The 50Cr-50Ni alloy used the wire 11 having a Cr content of 44%. The welding was MAG welding, and the current value was 140A.

The first bead was formed along the outer periphery of the flange surface. The second bead was formed on the inner side of the first bead, waiting for the temperature between the passes to become 200 DEG C or less. Bead formation and air cooling were repeated to form the first reinforcement layer 8. The bead height was about 2 mm to 4 mm.

The upper surface of the first reinforcement layer 8 was cut off to expose the surface. The thickness of the first reinforcement layer 8 after the surface exposure was 1.5 mm to 2.5 mm. The second rewriting layer 9 was formed on the first rewiring layer 8 in the same manner as the first rewiring layer 8 and surface exposure was performed.

The Cr content of the first additional layer 8 and the second additional layer 9 was measured. The content of Cr was 33% by mass for the first additional layer 8 and 40% by mass for the second additional layer 9. From these results, it was confirmed that by accumulating the corrosion resistant layer in multiple layers, it is possible to secure a Cr content of about the same level as the weld material on the uppermost surface of the corrosion resistant layer.

(Second Embodiment)

8 is a front view of the exhaust valve according to the present embodiment. In the present embodiment, the corrosion-resistant layer 17 is formed directly on the exhaust valve (base material) 4. Other than that, the structure is the same as that of the first embodiment.

The corrosion resistant layer 17 is a layer formed by welding a multi-layered 50Cr-50Ni alloy as a welding material. 50Cr-50Ni alloy contains 50% by mass or more of Ni and 60% by mass or less of Ni, and 40% by mass or more and 50% by mass or less of Cr with respect to the total mass of 100%. 50Cr-50Ni alloy has a composition of C0.10 mass% or less, Fe 0.50 mass% or less, Si0.20 mass% or less, Mn0.20 mass% or less, P0.02 mass% or less, Cu0.50 mass% To 1.0 mass%.

The corrosion resistant layer 17 has a multilayer structure of two or more layers, preferably three layers or more. The total thickness of the corrosion resistant layer 17 is preferably about 6 mm to 9 mm.

1 cylinder
2 piston
3 exhaust pipes
4 Exhaust valve (base material)
4a shaft portion
4b flange portion
5 combustion chamber
6 buffer layer
7, 17 Resistance layer
8 First rewrite layer
9 Second reinforcement layer
10 third additional layer
11 Wire (Welding material)

Claims (6)

1. A movable wall member used in an internal combustion engine,
The uppermost surface of the base material has a corrosion resistant layer which is a fire contact surface,
Wherein the corrosion resistant layer is welded in multiple layers using an alloy containing 50% by mass or more of Ni and 60% by mass or less of Ni and 40% by mass or more and 50% by mass or less of Cr. The method according to claim 1,
Wherein the layer having the uppermost surface among the corrosion resistant layers comprises at least 40 mass% and not more than 50 mass% of Cr. A method of welding a base material by preheating the base material at a temperature of not lower than 80 ° C and not higher than 120 ° C, and then adding an alloy containing not less than 50 mass% and not more than 60 mass% Ni and not less than 40 mass% and not more than 50 mass%
Wherein a temperature between passes at the time of forming the layer is 200 占 폚 or less. The method of claim 3,
Wherein when the alloy is welded in layers, the surface is exposed after the formation of the first layer, and then the next layer is overlaid on the first layer. The method according to claim 3 or 4,
Wherein the over welding is welded by MAG welding, and the shield gas contains Ar as a main component and a mixture of He and CO ₂ is used. 6. The method of claim 5,
A welding method in which a current value is set to a value that is 0.8 or more and 0.9 or less when a base current of a welding apparatus to be used is set to 1.

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