JP2010106351A - Treatment method for article including container by hip process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a treatment method which reduces a container portion that must be removed after the treatment, and also solves problems occurring due to thermal stress in a cooling stage and residual stress in service, when diffusion-bonding an interface between contents themselves and an interface between the content and the container. <P>SOLUTION: The content contained in the container 1 is a powder 1A of A40, which becomes a bearing material that is a component of a main bearing, and stainless-steel SUS304 that becomes a back metal 1B. The stainless-steel SUS304 which is the content 1B has such a structure as to also serve as an outer tube 2 that is a part of the container. A metallic foil made from stainless steel SUS304 with the thickness of 50 &mu;m is inserted as a release material 6 in an interface between the content 1A and an inner tube 3 in a doubly wound form so as not to form any gap as much as possible so that the powdery content 1A does not enter a gap between the metallic foils and a gap between the metallic foil and the inner tube 3, and is fixed to the inner tube 3 by spot welding. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a processing method by a HIP method of a processing object composed of a container and contents contained in the container.

  The HIP method is a high-precision joint and near-net shape that can perform functions in a wide range of applications, such as diffusion bonding at the interface between bulk bodies having complex interfaces, high-density sintering between powders, and removal of internal defects in cast materials. This is an effective means for manufacturing molded articles.

  However, since the HIP method is based on pressurization with an atmospheric gas that is a pressure medium, the atmospheric gas in which the contents are pressurized, such as diffusion bonding at the interface between bulk bodies and high-density sintering between powders. In order to prevent gas intrusion, the container contains all or part of the contents, and the container is outside the scope of the product. The container needs to be removed from the product.

  In the HIP method, inclusion of contents in a container is called canning, and the HIP method not containing in a container is also called a canless HIP method, and the above-described internal defect removal of cast material is often performed by canless.

  This canning is technically and economically burdensome, and depending on the canning method, not only the quality and characteristics of the processed product but also the number of manufacturing steps, manufacturing cost, and delivery time are strongly affected.

  In other words, depending on the structure and material of the container used for canning, not only the necessary temperature and pressure cannot be applied to the contents contained in the container, but also excessive thermal stress in the cooling stage during HIP processing. This may cause peeling of the bonding interface, which may cause problems such as interface deterioration during use due to residual stress, and may fail to obtain predetermined quality and characteristics.

  In particular, when the container is not covered by the product and needs to be removed after processing, the process of manufacturing, filling, degassing, enclosing and removing the container leads to an increase in the number of manufacturing steps and manufacturing cost. However, this is an economically disadvantageous manufacturing method.

  Furthermore, in the cooling stage of the HIP process, it becomes a cause of a serious problem in product quality that the thermal stress tends to cause defects such as separation of the product interface and occurrence of cracks in the base material.

  In order to eliminate the disadvantages of the HIP method, for example, in Patent Document 1, as a method of manufacturing a contact of a vacuum circuit breaker, it is also possible to form a treatment material as a composite material that leaves a part of a metal container. Document 2 discloses a method of manufacturing a heat sink composite member, in which a composite alloy powder is charged into a container made of a single metal and the container and the composite alloy powder are integrated by diffusion bonding. The container in this case is limited to a copper component having a composition common to the contents and relatively easy to interface.

  However, when the contents having different characteristics in the container are diffusion-bonded at the bonding interface by the HIP method, not only the contents in the container to be joined but also the container, these material characteristics are the quality of the processed material. Strongly affects. For example, the thermal expansion coefficient and Young's modulus are typical indicators of the elastic properties of materials at high and low temperatures, but the generation of thermal stress due to the difference in these material properties strongly affects the interface properties. In other words, in a processed product in which a plurality of contents are interface-bonded by the HIP method, thermal stress acts on the bonding interface during cooling, so the strength of the base material in the content matrix and the interface bonding strength at the bonding interface is deteriorated. Even after the temperature reaches room temperature, a part of the thermal stress continues to act on the joint interface as a residual stress, and this residual stress has a great influence on the quality and characteristics of the processed product. In other words, when thermal stress or residual stress acts on the joint interface or in the material, the joint strength is weakened to cause interfacial peeling, and when it acts on harmful defects in the material as residual stress, the fatigue strength may be lowered.

  As a means for removing the effect of residual stress on the joint interface, Patent Document 3 discloses a method for manufacturing a multi-axis composite cylinder by the HIP method, which is a single material made of a metal material having a larger thermal expansion coefficient than that of the cylinder-constituting metal material. Inserted into the core through deposition of release material such as ion plating or ceramic plating, and the inner surface guard metal powder is integrally deposited in the space between the outer peripheral surface of the core and the inner diameter surface of the cylinder. It is described.

The formation of the release material has a problem that it must be performed by a special surface treatment such as ion plating or ceramic plating. In addition, spray coating films of heat-resistant powders such as ceramics are desirable as a release material because they can contaminate the inside of the container and in the worst case enter the bonded interface of the treated material and hinder good interface bonding. Absent.
JP 08-124462 JP 11-323409 A JP 05-338809

  The problem to be solved by the present invention is that, when a processed product containing the contents in a container is processed by the HIP method, the diffusion between the contents and the interface between the contents and the container must be removed after the processing. The purpose is to reduce the portion of the container that must be used, and to solve problems caused by thermal stress in the cooling stage and residual stress during use.

  The present invention includes the contents of bulk or granular materials in a container, and when dissimilar materials with different material properties are diffusion-bonded and integrally joined by HIP, the contents are in the cooling stage of HIP processing. Differences in material properties between the materials often have a strong influence on the material matrix and interface properties. For example, the coefficient of thermal expansion and Young's modulus are typical indicators of the elastic properties of the contents at high and low temperatures, but the occurrence of thermal stress and residual stress due to the difference in these material characteristics is particularly due to multiple contents. In the case of the processed material constituted by, it strongly affects the interface characteristics.

  In other words, a processed product in which a plurality of contents are interface-bonded by the HIP method is subject to thermal stress during cooling, which may deteriorate the strength of the base material in the base material of the content or the interface joint strength at the joint interface. Even after the temperature reaches room temperature, it continues to act on the bonding interface as residual stress, and the fatigue strength of the base material and the interface is also reduced.

  By the way, when Δα is a difference in thermal expansion coefficient, ΔE is a Young's modulus difference, ΔT is a temperature difference from room temperature, and K is a constant, generally, the thermal stress σT between two different materials is It is represented by the following formula (1).

σT = K × Δα × ΔE × ΔT (1)
Therefore, as a method for relaxing or reducing the thermal stress and the residual stress, the manufacturing condition in the HIP method is to first lower the holding temperature, which requires that ΔT in the equation (1) be reduced.

  However, since the diffusion bonding in the HIP method is directly related to the interface reaction in the diffusion phenomenon at the holding temperature, the interface reaction is a phenomenon at a temperature higher than the temperature range in which thermal stress and residual stress are generated and act. There are some aspects that cannot be determined only by thermal stress or residual stress.

  However, for example, when the contents are composed of a plurality of different materials, if the difference in thermal expansion coefficient (Δα) and the Young's modulus difference (ΔE) between the materials can be set as small as possible, clearly from the equation (1), Thermal stress can be relaxed. Eventually, the residual stress when the temperature and the restrained state become a steady state can also be reduced.

  In other words, when aluminum bearings are targeted, if the bearing material is an aluminum alloy with a low Young's modulus and a large thermal expansion coefficient, instead of carbon steel with a high Young's modulus and a low thermal expansion coefficient as the back metal, If stainless steel with a Young's modulus lower than that of carbon steel and a coefficient of thermal expansion greater than that of carbon steel is selected, both Δα and ΔE can be reduced, so that thermal stress can be relaxed relatively easily compared to changing the holding temperature. Become.

  First, when there are a plurality of contents, the means is simple and the effect is obvious. By sharing the container and the contents, the interface area between the container and the contents is reduced.

  In other words, when aluminum bearings are the target, instead of carbon steel with a high Young's modulus and a low thermal expansion coefficient as the back metal, stainless steel with a lower Young's modulus than carbon steel and a larger thermal expansion coefficient than carbon steel And adopting a container method that adopts stainless steel as a backing metal in part of the container, and adopting a mild steel equivalent to carbon steel as Young's modulus and thermal expansion coefficient as a container, Since the interface area between the container and the contents can be surely reduced, the thermal stress and residual stress in the entire processed product can be reduced.

  In addition, the common use of the container and contents described above leads to a reduction in the number of parts in the processed product and a reduction in material loss as a container removed after the HIP process. The effect of this is obvious and should be used to the full extent within the tolerances of the container design and product specifications.

  Furthermore, in order to reduce the thermal expansion coefficient difference (Δα) and the Young's modulus difference (ΔE) between the container and the contents, and between the contents, the material composition in the processed material is changed to the above (1 ) In addition to reducing the thermal stress (σT) between materials, the conventional container method is not changed significantly, and more versatile and inexpensive carbon steel and mild steel are used as conventional containers. While being used, it is also possible to reduce thermal stress and residual stress by peeling the contents from the container.

  In other words, in order to peel the container interface for the purpose of reducing thermal stress and residual stress, the container side surface of the container interface in the processed material is subjected to a peeling treatment, or a metal foil is disposed as a peeling material on the container interface. Is also an effective method.

  By the way, it is obvious that the action of thermal stress and residual stress acts on a continuous body such as a single body or between a plurality of integrated components, and does not act on a discontinuous body or a peeling interface. Therefore, if there is a peeled interface even in a part of the processed material, stress transmission at the interface should be insufficient.

  Therefore, although it cannot be applied to the bonding interface included in the product, it is possible to reduce thermal stress and residual stress by positively peeling the interface if it is a container interface that is removed as an object of the product. .

  Specifically, in order to inhibit the conformability and reactivity at the container interface, the surface on the container side is coated with a non-metallic film and roughened as a peeling treatment, and oxides, nitrides, carbides, etc. The purpose can be achieved by coating the non-metallic thin film and increasing the surface roughness. The simplest of these is a process in which the relevant container side surface is heated in the atmosphere to provide an oxide film, and the surface of the container is subjected to shot blasting to roughen the surface roughness. Is more effective.

  The thickness of the non-metal film is not specified, but the function is exhibited if the film is coated with a film thickness that is about the surface roughness. However, the container is deformed during the HIP process and cracks are allowed to occur on the surface subjected to the peeling process on the container surface. is necessary.

  In addition, there is no special requirement for the surface roughness at the time of roughening, but even when the container surface is curved, the surface of the container is deformed during the HIP process. Even so, it is necessary that the non-metallic film on the surface of the container is broken and the new surface does not appear at the convex portion having the surface roughness.

  And since the metal foil is flexible, it can be easily adhered to the container interface, it can be easily cut to a predetermined size, and there is no possibility of intrusion into the joint interface that is not involved in peeling. If there are, it is more preferable to stack a plurality of sheets because an effect of promoting peeling of the container and contents can be obtained at the time of taking out after the HIP process. The heat resistant metal foil referred to here is functionally provided that it is a high melting point metal such as chromium (Cr), molybdenum (Mo), tungsten (W) alone or an iron (Fe) alloy containing these alone or in plural. Satisfied. In particular, from the viewpoint of versatility, stainless steel, which is an Fe—Cr-based iron alloy, is suitable, and even if nickel (Ni) is contained, it is functionally equivalent and inhibits familiarity at the container interface. In addition to imparting releasability due to, a thermal expansion coefficient is lower than that of iron, so a composite effect can be expected from the viewpoint of thermal stress relaxation. That is, Cr, Mo, and W have a characteristic that the thermal expansion coefficient is low in common in addition to the property that the conformability is low because the melting point is high.

  Compared with the prior art, the HIP method of the present invention has a smaller number of steps, is more advantageous in terms of cost and delivery time, and can provide a product with stable quality and high reliability.

  Hereinafter, one of the embodiments of the present invention is a journal bearing type marine main bearing in which an aluminum bearing is used as a bearing material and an aluminum alloy A40 (Al-40 wt% Sn-1 wt% Cu) and steel are used as components. This is shown in the applied example.

  In the HIP method, the processed product is vacuum-sealed in a processing vessel. In the present invention, mild steel, carbon steel or stainless steel is selected as the material of the processing vessel, and the HIP processing according to the present invention is performed. gave.

  FIG. 1 is a simplified drawing showing the structure and dimensions of a processed product 1 for manufacturing a main bearing as an example, and the contents contained in the container become a bearing material which is a constituent material of the main bearing. Stainless steel SUS304 used as A40 powder 1A and back metal 1B. The powder of the aluminum alloy A40 is a spherical gas atomized powder, and the particle size distribution is less than # 100 mesh. Incidentally, in FIG. 1, the stainless steel SUS304 that is the contents 1B has a structure that also serves as the outer tube 2 that is a part of the container, and has a size of outer diameter φ480 mm × inner diameter φ448 mm × height about 400 mm. The inner tube 3 constituting the container other than the outer tube is stainless steel SUS304 (plate thickness 4 mm), and the lid 4 is carbon steel S25C. Before the HIP treatment, the outer tube 2, the inner tube 3 and the lid 4 constituting the container containing the contents are welded and assembled at the welded portion 5 in the electron beam welding apparatus maintained in a vacuum atmosphere. The object is vacuum-sealed in the container.

  Further, a metal foil made of stainless steel SUS304 and having a thickness of 50 μm is wound twice as a release material 6 at the container interface, and the content 1A as a powder is placed in the gap between the metal foil and the gap between the metal foil and the inner tube 3. It is inserted with as little gap as possible so as not to enter, and is fixed to the inner tube 3 by spot welding. This is because the double winding of the metal foil can achieve the peeling effect more reliably.

  The processed product 1 is placed in a HIP apparatus and subjected to HIP processing under appropriate conditions. As the HIP processing conditions, a holding temperature of 500 ° C. × a holding pressure of 98 MPa × a holding time of 90 minutes is adopted. In addition, no special consideration is required for the pressurization and cooling patterns, and any HIP device having a general function as a device can be sufficiently applied.

  If a part of the outer tube 1B, which is also the inner tube 2, the lid 4, the welded part 5, the release material 6, and the contents 1B, which is excluded from the product after the HIP process, is removed by cutting, it is included in the container and integrated. The converted contents can be easily taken out as a product.

  Immediately after the HIP treatment, an ultrasonic flaw detection test was performed on the treated material as a nondestructive test, and the state of the bonding interface and the container interface was inspected. As a result, the bonding interface consisting of the contents 1A and the contents 1B was bonded to the entire surface. 95% or more of the container interface was peeled off from the container interface composed of the inserted contents 1A and the inner tube 3.

Further, the inside of the bulk of the content 1A made of A40 powder was sufficiently sintered and integrated with the content 1B made of stainless steel. Various specimens were collected for destructive testing and subjected to metallographic observation, cross-sectional hardness measurement, and peel test. As a result of observing the metal structure with an optical microscope at a magnification of 100, there was no interface defect at the bonding interface, and the A40 powder was also sintered and integrated. As a result of measuring the cross-sectional hardness, the Vickers hardness in the sintered part of the A40 powder was a value satisfying Hv = 45 or less, which is the customer specification, Hv (1) = 37 to 42. Then, as the bond strength at the bond interface, the peel strength corresponding to the tensile strength was examined at five points in the product by a peel test, which is a test method of a method of pushing at right angles to the bond interface. A sufficient value of 7.7 to 8.8 kgf / mm ² was obtained.

  1 is the same as Example 1 except that the inner tube 3 is mild steel STKM13A and the release material is single wound.

  Immediately after the HIP treatment, an ultrasonic flaw detection test was performed as a non-destructive test on the processed material, and the state of the bonding interface and the container interface was inspected. As a result, the bonding interface consisting of the contents 1A and the contents 1B was entirely bonded. 60% or more of the container interface was peeled off from the container interface composed of the inserted contents 1A and the inner tube 3.

As a result of observing the metal structure at a magnification of 100 using an optical microscope, there was no interface defect at the bonding interface, and the aluminum alloy A40 powder was also sintered and integrated. As a result of measuring the cross-sectional hardness, the Vickers hardness in the sintered part of the A40 powder was Hv (1) = 35-40, which satisfies the customer specification Hv = 45 or less. Then, as the bond strength at the bond interface, the peel strength corresponding to the tensile strength was examined at five points in the product by a peel test, which is a test method of a method of pushing at right angles to the bond interface. The thickness showed a slight variation of 5.3 to 8.8 kgf / mm ² , but a sufficient value was obtained.

  2 is the same as in Example 1 except that the inner tube 3 is mild steel STKM13A and the peeling process to the container side surface at the container interface is heating in air and shot blasting.

  Immediately after the HIP treatment, an ultrasonic flaw detection test was performed as a non-destructive test on the processed material, and the state of the bonding interface and the container interface was inspected. As a result, the bonding interface consisting of the contents 1A and the contents 1B was entirely bonded. 40% or less of the container interface was peeled off from the container interface consisting of the inserted contents 1A and the inner tube 3.

As a result of observing the metal structure with an optical microscope at a magnification of 100, there was no interface defect at the bonding interface, and the A40 powder was also sintered and integrated. Further, as a result of measuring the cross-sectional hardness, the Vickers hardness in the sintered part of the A40 powder was Hv (1) = 39 to 43, which satisfies the customer specification of Hv = 45 or less. Then, as the bonding strength at the bonding interface, the peeling strength corresponding to the tensile strength was examined at two points in the product by the peeling test, which is a test method of pushing out at a right angle to the bonding interface. In both cases, a value of 5.2 kgf / mm ² was obtained.

The form and the cross-sectional shape in the 1st and 2nd Example which applied this invention to the processed material of the journal bearing type | mold are shown. The form and the cross-sectional shape in the 3rd Example which applied this invention to the processed material of the journal bearing type | mold are shown.

Explanation of symbols

1 Processed products 1A and 1B having a container interface and containing contents The contents 2 constituting the product contained in the container 2 Outer tube 3 Inner tube 4 Lid 5 Welded part 6 Release material

Claims (6)

  In the case where the contents contained by the container are integrated by diffusion bonding by the HIP method, this is a processing method by the HIP method that reduces the thermal stress and residual stress between the constituent materials. In addition, a treatment method using an HIP method in which one material at an interface formed of different materials reduces the difference in Young's modulus and the thermal expansion coefficient from the other material.   The processing method by HIP method of Claim 1 which reduces the interface area between a container and a content by making a content and a container common, when the content included with a container is plurality.   The processing method by the HIP method according to claim 1, wherein at least a part of the container containing the contents is a material mainly composed of iron, and a part of the contents contained by the container is aluminum or an aluminum alloy. .   The processing method by the HIP method according to claim 1, wherein the means for reducing the thermal stress and residual stress between the materials is a peeling treatment applied to the container side surface, or an arrangement of a metal foil at the interface as a peeling material.   The processing method according to the HIP method according to claim 4, wherein the peeling treatment is roughening after the surface on the container side is coated with a non-metallic thin film such as oxide, nitride, or carbide.   The processing method by the HIP method according to claim 4, wherein the metal foil is chromium (Cr), molybdenum (Mo), tungsten (W) alone, or an iron (Fe) alloy containing one or more of these.

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