JP2007327077A - Method for manufacturing heat-resistant component by chromizing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method capable of suppressing roughness of a surface of a chromium cementation layer formed on a surface of a heat-resistant component by the chromizing. <P>SOLUTION: In the manufacturing method, a work such as SUS is embedded in a cementation agent consisting of a chromium powder, a carrier and an activator and subjected to chromizing, and a chromium cementation layer is formed on the surface of the work to enhance the heat resistance of the work. The activator contains chloride of 0.1-1.0 wt.% the cementation agent, and fluoride of 0.1-1.0 wt.% the cementation agent, and the surface roughness Ry of the work after the chromizing can be suppressed to ≤6.3 μm. The work can be applied to a sliding surface as it is without polishing the work after the chromizing, and is favorable for manufacturing components such as a variable wing 1 in a VGS turbocharger and a turbine frame 2 for turnably holding the wings. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a chromization treatment (chromium diffusion permeation treatment) for forming a chromium diffusion permeation layer on the surface of a metal product such as stainless steel. In particular, in order to narrow down a small amount of exhaust gas appropriately in a high temperature / exhaust gas atmosphere. The present invention relates to a novel manufacturing method suitable for manufacturing components of a so-called VGS type turbocharger in which the variable blades are repeatedly rotated.

  For example, chromization treatment is known as a kind of surface heat treatment for improving heat resistance such as high-temperature surface hardness, wear resistance, and corrosion resistance of metal products. Several methods are known for this chromization treatment, and among them, a powder pack method is generally used. This is done by placing a mixture of metallic chromium powder as a chromium source, chloride such as ammonium chloride as an activator (accelerator), and alumina powder as a support agent in a container, and processing the metal product (hereinafter referred to as a coated product). The processing material is embedded in the above mixture, and the container is sealed, and then accommodated in a heating furnace, and heated and held at a high temperature for a predetermined time. As a result, a chromium diffusion layer is formed on the surface of the material to be treated, and the heat resistance such as high temperature hardness, wear resistance, and corrosion resistance of the material to be treated (surface) is improved.

A metal part improved in heat resistance by such a chromizing treatment is suitable as a component part of an apparatus used in a high temperature atmosphere. As this type of apparatus, for example, a turbocharger used in an automobile engine or the like. Is mentioned. A turbocharger is a turbocharger used as a means to increase the output and performance of an engine. The turbocharger is driven by the exhaust energy of the engine, and the compressor is rotated by the output of the turbine. It is a device that brings about a supercharging state. However, in the turbocharger, when the engine is rotating at a low speed, the exhaust turbine hardly works due to a decrease in the exhaust flow rate, and the engine power cannot be increased. In addition, a diesel engine having a low engine speed originally has a drawback that it is difficult to obtain a turbo effect.
For this reason, a VGS type turbocharger (hereinafter simply referred to as a VGS turbocharger) that operates efficiently even in a low-speed rotation range has been developed. And a variable mechanism for rotating a plurality of variable blades at once, and by rotating the variable blades, a small amount of exhaust gas is appropriately throttled to amplify the exhaust speed, thereby increasing the work of the exhaust turbine. It is a turbocharger that can achieve high output even at low speed rotation by increasing the.

As a constituent member of the VGS turbocharger, for example, austenitic stainless steel subjected to chromization treatment is used. However, when such a stainless steel is subjected to a general chromization treatment, there are the following problems. That is, the stainless steel subjected to the chromization treatment has a problem that fine irregularities are formed on the surface (chromium diffusion permeation layer) and the skin surface (treated surface) is rough. For this reason, the stainless steel after the chromization treatment is not used for assembling as it is, and it is common to receive a finishing process such as polishing before assembling. That is, in the manufacture of the VGS turbocharger, if the component parts are subjected to chromization treatment, then finishing processing such as polishing is inevitably required, which becomes a factor that hinders mass productivity and production cost. It was.
In particular, since the VGS turbocharger repeatedly performs the operation of rotating the variable blades under high temperature and exhaust gas, in order to reliably control the exhaust gas and maintain smooth rotation over a long period of time, In a member or the like that holds this rotatably, high surface smoothness is required to reduce frictional resistance as much as possible.

Of course, as other materials to be applied to the material to be treated, non-austenitic stainless steel, for example, martensitic stainless steel may be used and subjected to chromization treatment. For example, in the case of a variable blade of a VGS turbocharger, the required surface roughness (smoothness) is extremely high, and thus polishing processing (finishing processing) after processing cannot be excluded.
VGS turbochargers are used not only in high temperatures but also in an exhaust gas environment, and in many cases the operating temperature exceeds 750 ° C. If martensitic stainless steel is subjected to normal chromization treatment, corrosion resistance will not It was still insufficient in terms of high temperature oxidation resistance.

  The present invention has been made in view of such a background, and by applying a novel chromization treatment using a diffusion penetrating agent containing chloride and fluoride, the surface of the material to be treated is provided. This is an attempt to develop a new manufacturing method that can form a chromium diffusion layer with high smoothness, especially suitable for the manufacture of heat resistant parts that repeatedly slide (friction) in a high temperature atmosphere, such as VGS turbochargers. It is a thing.

  That is, in the method for manufacturing a heat-resistant member by chromization treatment according to claim 1, the metal material to be treated is embedded in a diffusion penetrating treatment agent comprising chrome powder, a support agent and an activator, and chromization treatment is performed. , A method of improving the heat resistance of a material to be treated by forming a chromium diffusion and permeation layer on the surface of the material to be treated, wherein the activator comprises 0.1 to 1.0% by weight of chloride And 0.1 to 1.0% by weight of a fluoride of the diffusion penetrating agent.

  Further, in the method for producing a heat-resistant member by chromization treatment according to claim 2, in addition to the requirement of claim 1, the chloride is ammonium chloride, and the fluoride is aluminum fluoride or sodium fluoride. Is a feature.

  Moreover, in addition to the requirement of the said Claim 1 or 2, the manufacturing method of the heat-resistant member by the chromization process of Claim 3 suppresses the surface roughness Ry to the to-be-processed material after the said chromization process to 6.3 micrometers or less. It is characterized by this.

  According to a fourth aspect of the present invention, there is provided a method for producing a heat-resistant member by chromizing treatment. In addition to the requirements of the first, second, or third aspect, the chromizing treatment is performed by appropriately reducing a small amount of exhaust gas and increasing an exhaust speed. It is characterized in that it is applied to a component of a VGS type turbocharger that can achieve high output even when the engine is in a low speed rotation range by increasing the work amount of the engine.

The above-described problems can be solved by using the configuration of the invention described in each of the claims.
That is, according to the present invention, a chromium diffusion / penetrating layer having a very smooth surface is formed on the heat-resistant component (material to be treated) after the chromization treatment. The reason is as follows. That is, the characteristic of the active action of chloride on the high temperature reaction of chromize is fast-acting, while the characteristic of the active action of fluoride is slow-acting. Therefore, by mixing both, the activity / promoting action is controlled to an appropriate averaging speed during the chromizing process, and as a result, a smooth surface is obtained.
Therefore, the heat-resistant parts after the treatment can be widely applied as sliding parts used in a high temperature atmosphere and other machine parts without requiring surface polishing. In addition, the chromium diffusion layer formed on heat-resistant parts by chromization treatment has a chromium carbide layer formed near the surface (surface surface) and a diffusion layer (alloy layer) having a high Cr concentration below it (inside the surface layer) Therefore, the heat-resistant component can sufficiently exhibit wear resistance and oxidation resistance even in a high-temperature oxidizing atmosphere.
Such a heat-resistant component is a component of a VGS turbocharger (exhaust guide assembly), specifically, variable blades for appropriately reducing exhaust gas, a turbine frame that rotatably holds the variable blades, or a plurality of variable members. Application to a variable mechanism or the like that rotates the wings to the same extent at once is preferable. In addition, it can also be applied to peripheral members of the exhaust guide assembly, such as a wastegate valve that releases excess exhaust gas when the supercharging pressure rises above a certain value, and a bearing that receives the shaft portion of the exhaust turbine. It can also be applied to engine exhaust parts.

  In addition, when each component part of the VGS turbocharger is manufactured by the manufacturing method of the present invention, each component member is used in the assembling process as it is without requiring polishing (finishing processing) that is often performed after chromizing treatment. Therefore, the mass productivity of the entire turbocharger can be improved. In addition, since the surface of the chromized member is extremely smooth, the frictional resistance when rotating the variable blades is kept low, and the smooth operation of the variable blades and consequently the flow control of the exhaust gas are stable and reliable over a long period of time. Can be done.

BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out the present invention includes one described in the following examples, and further includes various methods that can be improved within the technical idea. In the description, the material (steel material) applied to the chromizing process according to the present invention will be described first, then the substance of the chromizing process will be described, and then the VGS turbocharger manufactured by such a process will be described.
As the material to be treated applied to the present invention, a steel material which originally contains chromium or nickel in the base material itself and has already been heat-resistant before the chromization treatment is preferable. Moreover, in order to improve corrosion resistance, low carbon steel is preferable, specifically, the carbon content is 0.2% or less, more preferably 0.08% C or less. This is because if the carbon content in the material to be treated exceeds 0.2%, the probability of reaction with external oxygen increases, so that the corrosion resistance, particularly oxidation resistance, of the material to be treated at high temperatures decreases.
On the other hand, the lower limit of carbon in the material to be treated is preferably 0.05% or more. This is because the minimum necessary amount as a carbon source exists in the material to be treated. That is, if it is above this value, a chromium carbide layer can be formed on the surface of the chromium diffusion and penetration layer.

Examples of such steel materials include austenitic stainless steel, and SUS304 and SUS316 are exemplified by steel symbols specified in JIS. Other examples include 25Cr-20Ni-based SUS309S, SUS310S, SUH660, SCS13, and the like, in which the contents of nickel and chromium are further increased, but SUS310S is more desirable.
In addition to the above-mentioned materials, heat-resistant cast steel can also be applied as the material to be treated. For example, SCH21 (25Cr-20Ni system) defined in JIS, SCH22 and SCH23 having a higher carbon content than these (both 25Cr-20Ni). SCH24 (25Cr-35Ni system and higher carbon than SCH21), etc. can be applied.

A part (material to be processed) formed into a finished shape from such a metal material is subjected to the chromization process according to the present invention to obtain a desired heat-resistant part. This chromization process will be described below. The chromization treatment according to the present invention is a powder pack method, in which a material to be treated is heated in a diffusion penetrating treatment agent comprising a chromium source, a support agent, and an activator. Here, chromium powder is used as the chromium source, alumina particles are used as the supporting agent, 0.1 to 1.0% by weight of chloride and 0.1 to 1.0% by weight as the activator. % Fluoride. In addition, a support agent bears the sintering prevention effect | action and the adsorption | suction prevention effect | action to a to-be-processed material in the cooling process of an activator. Further, the activator will be described in more detail. For the chloride, ammonium chloride (NH ₄ Cl) can be used, and for the fluoride, aluminum fluoride (AlF ₃ ) or sodium fluoride (NaF) can be used. Although applicable, it is also possible to use minerals containing these or mixtures thereof (eg cryolite).

  In the present invention, the above-mentioned fluoride is included in the diffusion penetrating agent together with the chloride, and this is for appropriately controlling the active reaction. As a result, chromium decomposes and precipitates on the surface of the material to be treated (surface surface), and then uniformly forms a chromium carbide layer, and also forms a diffusion layer (alloy layer) by diffusion and penetration inside the material to be treated (inside the surface layer). Generate uniformly. In this specification, the chromium carbide layer and the diffusion layer are collectively referred to as a chromium diffusion / permeation layer (see FIG. 1).

Further, regarding the addition ratio of chloride and fluoride, the technical significance of the upper limit and the lower limit will be described. If the chloride is less than 0.1% by weight, the reaction of chromium precipitation is small and the formation of the chromium carbide layer is inhibited, On the other hand, even if the chloride is added in an amount of more than 1.0% by weight, it sublimates and causes loss, which is uneconomical.
Also, if the fluoride content is less than 0.1% by weight, the surface smoothing is not effective, and unevenness of the surface cannot be prevented. On the other hand, even if the fluoride is added in an amount of more than 1.0% by weight, the chromium precipitation is accelerated. This is because it is not useful for preventing surface roughness.

In addition, chromium as a chromium source may contain a chromium component in a chromium alloy in addition to metallic chromium, and can be contained in a diffusion infiltration treatment agent in an amount of 20 to 99% by weight.
Moreover, since the diffusion penetrating agent contains 0.2 to 2.0% by weight of the above-mentioned activator, the remainder contains the above-mentioned carrier and may contain other additives.

  Then, such a diffusion penetrating agent is spread in a heat-resistant container, and after the material to be treated is embedded in the treating agent, the container is sealed. Next, this container is accommodated in a heating furnace, and the temperature in the container (furnace temperature) is kept constant. The heating temperature at this time is preferably 900 ° C. to 1100 ° C. If the heating temperature is kept in this temperature range for 2 to 20 hours, a diffusion / penetration layer having a thickness of about 3 to 30 μm can be formed on the material to be processed.

  Here, the heating temperature by the powder pack method is set to 900 ° C. to 1100 ° C. If the heating temperature is less than 900 ° C., the amount of chromium deposited on the surface of the material to be processed is small, and the thickness of the chromium carbide layer as the diffusion and penetration layer is also thin. On the other hand, if the heating temperature exceeds 1100 ° C., the metal chromium or carrier powder in the treatment agent is directly applied to the surface of the material to be treated. This is because it adheres and causes rough skin.

By subjecting the material to be treated to such a chromization treatment, a chromium diffusion / permeation layer is formed on the surface of the material to be treated, and in particular, the surface layer portion contains homogeneous precipitated chromium carbide particles. A hardened layer (chromium carbide layer) is formed. The surface roughness of the chromium diffusion layer is preferably 6.3 μm or less in terms of Ry (maximum height) defined in JIS B 0601 (1994). When the surface roughness Ry exceeds 6.3 μm, for example, in the case of a VGS turbocharger, the frictional resistance (rotational sliding resistance) with the turbine frame serving as a bearing increases when the variable blade (heat resistant part) is rotated. However, a large driving force is required for rotation, and the chromium carbide layer is greatly worn due to surface friction between the parts. On the contrary, if the surface roughness Ry is 6.3 μm or less, the heat-resistant component can maintain low sliding resistance without surface polishing after chromizing treatment, and in particular, in the case of a VGS turbocharger, the variable blade Or it can be used conveniently as a member which hold | maintains a variable wing | blade rotatably.
The surface roughness Ry of the diffusion / penetration layer is preferably 5.0 μm or less, and more preferably 3.0 μm or less.

Hereinafter, the effect of the chromization treatment of the present invention using the diffusion penetrating agent containing chloride and fluoride will be described with reference to specific examples.
As a material to be treated, a test piece having a thickness of 4 mm, a width of 7 mm, a length of 20 mm and a surface roughness of 0.5 μm was prepared from SUS310S (25Cr-20Ni austenitic stainless steel). Chromized.

  The diffusion and penetration treating agent was prepared by mixing 75% by weight of metal chromium powder as a chromium source and 1.0% by weight of activator, and mixing and adjusting alumina powder as a supporting agent in the balance. In addition, as for the activator, the sum (total) of ammonium chloride and aluminum fluoride was constant at 1.0% by weight of the diffusion penetrating agent, and the respective weight percents were five as shown in Table 1. Among these, the chromization process using the processing agents of Nos. 1 to 3 corresponds to the present invention, and the chromization process using the processing agents of Nos. 4 and 5 is a reference example showing the effect of the present invention.

In the chromization treatment, such five kinds of diffusion penetrating treatment agents are spread in a heat-resistant container, and then the specimen is embedded in the treatment agent, and the container is placed in an electric furnace in an inert gas atmosphere at 1050. After heating at 10 ° C. for 10 hours, the vessel was allowed to cool outside the furnace.
The specimen (material to be treated) obtained by such chromization treatment was subjected to surface roughness (Ry) measurement specified in JIS B 0601 (1994), and the results are shown in Table 1.

  From Table 1, it was found that the surface roughness Ry of Nos. 1 to 3 (test pieces) containing ammonium chloride and aluminum fluoride as the activator was less than 3.0 μm, and these exhibited smooth and good surface properties. . Furthermore, it can be discriminated from this table that numbers 4 and 5 (test specimens) containing 1.0% by weight of ammonium chloride or aluminum fluoride alone have a surface roughness Ry of 10 μm or more, resulting in remarkable skin roughness. It will occur.

  FIG. 1 shows an SE image obtained by observing the diffusion / penetration layer of No. 1 (specimen) with EPMA. From FIG. 1, it can be seen that when the chromization treatment according to the present invention is performed, the thickness of the diffusion / penetration layer formed on the surface of the material to be processed is relatively uniform and the surface is also smooth.

  The concentration distribution of the component by the EPMA line analysis of No. 1 (test piece) is shown in FIG. In FIG. 2, the concentrations of Cr, Ni, and Fe in the internal parts are values of SUS310S that is the base material. However, on the surface of the surface layer, Cr is concentrated and the contents of Ni and Fe are reduced. This portion is a chromium diffusion / penetration layer formed on the surface of the material to be treated, and its thickness is about 20 μm. That is, it can be seen from FIGS. 1 and 2 that the diffusion and permeation layer of the chromization treatment according to the present invention is composed of a high concentration chromium layer.

  FIG. 3 shows an example of an SE image obtained by observing a cross section of a test piece of No. 5 subjected to chromization treatment only with chloride with EPMA. In FIG. 3, there are large protrusions (actually fine irregularities) on the surface of the specimen as compared with FIG. 1, which contributes to hindering the surface smoothness (surface roughness) after the treatment. ing. Moreover, the line analysis result of this thing is shown in FIG. The protrusions show a very high Cr concentration and appear to be metallic chromium deposits or chromium compounds.

  FIG. 5 shows the analysis result by SEM of the material to be processed in which SUS310S was subjected to the conventional chromization treatment only with chloride, as in FIG. This figure (A) is a SEI image, and (B) to (D) are Al, O, and Cr surface analysis mapping images of this SEI image in sequence. Reference numerals 1, 2, and 3 in FIG. 5 (A) represent protrusions formed on the surface of the chromium diffusion and penetration layer. 5 (B) and 5 (C), it is suggested that reference numeral 1 is a composite Cr particle made of metal Cr or Cr oxide, and reference numerals 2 and 3 are Al, O, and Cr. Thus, in the material to be treated (heat-resistant parts) subjected to the conventional chromization treatment, the presence of Cr, Al, and O is observed in the protrusions, and the cause of various protrusions is accompanied by abnormal precipitation of chromium, It is thought that there is adhesion between the alumina particles as the support agent and Cr. However, in the material to be treated (numbers 1 to 3 in Table 1) subjected to the chromization treatment according to the present invention, the protrusions caused by such excessive precipitation of chromium or adhesion of composite alumina particles to the diffusion and permeation layer are It is not formed, and its surface roughness Ry can be secured to 6.3 μm or less.

  The chromization treatment according to the present invention is a kind of manufacturing technique for imparting further heat resistance, oxidation resistance, corrosion resistance, and the like to a material to be treated (heat resistant component). Moreover, since the surface smoothness after the treatment can be realized at a high level, the treated material after the treatment can be used as it is without being polished. For this reason, the chromizing process according to the present invention is suitable for the chromizing process on the constituent members of the VGS turbocharger, in particular, the components having the finished shape. The VGS turbocharger will be described below.

  The VGS turbocharger adjusts the exhaust gas flow by restricting the exhaust gas G especially when the engine is rotating at a low speed, and the exhaust gas guide assembly A is a main component. As shown in FIG. 6 as an example, the exhaust guide assembly A includes a plurality of variable blades 1 that are provided on the outer periphery of the exhaust turbine T and substantially throttle exhaust gas, and a turbine frame 2 that rotatably holds the variable blades 1. And a variable mechanism 3 for rotating the variable blade 1 by a certain angle so as to appropriately set the flow rate of the exhaust gas G. Hereinafter, each component will be further described.

First, the variable blade 1 will be described. As an example, as shown in FIG. 6, a plurality of these are arranged in an arc shape along the outer periphery of the exhaust turbine T (approximately 10 to 15 with respect to one exhaust guide assembly A). The exhaust flow rate is adjusted appropriately by rotating approximately the same degree. The variable wing 1 includes a wing portion 11 and a shaft portion 12, which will be described below.
The blade portion 11 is formed to have a constant width mainly in accordance with the width dimension of the exhaust turbine T, and the cross section in the width direction is formed in a substantially airfoil shape so that the exhaust gas G can be effectively exhausted. It is configured to go to the turbine T. Here, the width dimension of the wing part 11 is referred to as a wing width h for convenience.
Further, the shaft portion 12 is formed integrally and continuously with the wing portion 11 and serves as a rotating shaft when the wing portion 11 is moved.

In addition, a tapered portion 13 that is narrowed from the shaft portion 12 toward the wing portion 11 and a flange portion 14 that is somewhat larger in diameter than the shaft portion 12 are connected to the connection portion between the wing portion 11 and the shaft portion 12. Is formed. Note that the bottom surface of the flange portion 14 is formed on substantially the same plane as the end surface of the blade portion 11 on the shaft portion 12 side, and this plane serves as a seating surface when the variable blade 1 is attached to the turbine frame 2. The turbine T is responsible for regulating the position in the width direction (the direction of the blade width h).
Further, a reference surface 15 serving as a reference for the mounting state of the variable wing 1 is formed at the tip of the shaft portion 12. The reference surface 15 is a part fixed to the variable mechanism 3 to be described later by caulking or the like. As an example, as shown in FIG. 6, two planes formed by cutting away the shaft portion 12 are formed on the wing portion 11. On the other hand, it is formed in a substantially constant inclined state.

Next, the turbine frame 2 will be described. This is configured as a frame member that rotatably holds a plurality of variable blades 1. As an example, as shown in FIG. 6, the variable blade 1 (blade) is constituted by a frame segment 21 and a holding member 22. Part 11).
The frame segment 21 includes a flange portion 23 that receives the shaft portion 12 of the variable wing 1 and a boss portion 24 that fits the variable mechanism 3 described later on the outer periphery. Because of this structure, the flange portion 23 is formed with the same number of bearing holes 25 as the variable blades 1 at equal intervals in the peripheral portion.
In addition, the holding member 22 is formed in a disk shape having an open central portion as shown in FIG. The dimension between the two members is substantially constant (generally the blade of the variable blade 1 so that the blade portion 11 of the variable blade 1 sandwiched between the frame segment 21 and the holding member 22 can be rotated smoothly at all times. As an example, the distance between the two members is maintained by caulking pins 26 provided at four locations on the outer peripheral portion of the bearing hole 25. Here, a hole opened in the frame segment 21 and the holding member 22 to receive the caulking pin 26 is referred to as a pin hole 27.

  In the embodiment shown in FIG. 6, the flange portion 23 of the frame segment 21 has two flange portions, that is, a flange portion 23 </ b> A having substantially the same diameter as the holding member 22 and a flange portion 23 </ b> B having a slightly larger diameter than the holding member 22. These are formed with the same member, but when processing with the same member is complicated, two flange parts with different diameters are formed separately, and then caulking or brazing is performed. It is also possible to join by processing or the like.

Next, the variable mechanism 3 will be described. This is provided on the outer peripheral side of the boss portion 24 of the turbine frame 2 and appropriately rotates the variable blade 1 in order to adjust the exhaust flow rate. As an example, as shown in FIG. In addition, a rotating member 31 that causes the variable wing 1 to rotate and a transmission member 32 that transmits the rotation to the variable wing 1 are provided.
As shown in the figure, the rotating member 31 is formed in a substantially disk shape with an open central portion, and the same number of transmission members 32 as the variable blades 1 are provided at equal intervals on the peripheral portion. The transmission member 32 includes a driving element 32A that is rotatably attached to the rotating member 31, and a passive element 32B that is fixedly attached to the reference surface 15 of the variable blade 1, and these driving elements 32A. The rotation is transmitted in a state where the passive element 32B and the passive element 32B are connected. Specifically, a square piece drive element 32A is rotatably pinned to the rotation member 31, and a passive element 32B formed in a substantially U shape so as to receive the drive element 32A is provided. The rotating member 31 is attached to the boss portion 24 so as to be fixed to the reference surface 15 at the tip of the variable wing 1 and to be fitted with the square-shaped drive element 32A into the U-shaped passive element 32B.

In the initial state where a plurality of variable blades 1 are attached, in order to align them in a circumferential shape, each variable blade 1 and the passive element 32B must be attached at a substantially constant angle, as shown in FIG. In the embodiment, the reference surface 15 of the variable wing 1 is mainly responsible for this function. Further, if the rotating member 31 is simply fitted in the boss portion 24, there is a concern that the engaging of the transmission member 32 is released when the rotating member 31 is slightly separated from the turbine frame 2. In order to prevent this, a ring 33 or the like is provided so as to sandwich the rotating member 31 from the opposite side of the turbine frame 2, and a tendency to press the rotating member 31 toward the turbine frame 2 is imparted.
With such a configuration, when the engine rotates at a low speed, the rotation member 31 of the variable mechanism 3 is appropriately rotated and transmitted to the shaft portion 12 via the transmission member 32, as shown in FIG. The variable vane 1 is rotated and the exhaust gas G is appropriately throttled to adjust the exhaust flow rate.

  In such a VGS turbocharger, since it is necessary to repeatedly rotate the variable blade 1 in accordance with the rotational speed of the engine, for example, the variable blade 1 (shaft portion 12) and the turbine frame 2 (bearing hole 25). ) Is constantly in sliding contact. Applying the chromization treatment according to the present invention to the parts having such a relationship not only can be used for assembly without undergoing a polishing step after the treatment, but also the surface of the parts can be formed with extremely high smoothness. Therefore, it brings about special effects such as reduction of driving force when rotating the variable blade 1, reduction of frictional resistance during rotation, smooth and reliable control of the variable blade 1, and the like.

  In the manufacturing method of the present invention, when the material to be treated is subjected to chromization treatment, the surface of the material to be treated is mixed with fluoride with a chloride as an activator, thereby mixing homogeneous chromium with high smoothness. The diffusion / penetration layer can be formed, and can be applied to the production of heat-resistant parts, particularly heat-resistant parts that slide in contact with other members, and various machine parts.

  In addition, since the surface roughness Ry of the processed material after the treatment can be formed to 6.3 μm or less, the present invention can be used for assembling without grinding or grinding the processed material after the chromizing treatment. It is suitable for the manufacture of turbocharger components.

It is the EPMA observation photograph showing the metal structure of the cross-sectional site | part containing the chromium diffusion penetration layer of the to-be-processed material to which this invention is applied. It is a graph which shows the density | concentration distribution of the component by the EPMA analysis of the to-be-processed material shown in FIG. It is the EPMA observation photograph showing the metal structure of the surface part in which the protrusion was formed in the to-be-processed material (comparative example) which performed the conventional chromization process only with a chloride. It is a graph which shows the density | concentration distribution of the component by the EPMA analysis of the to-be-processed material shown in FIG. It is the analysis result by the scanning electron microscope of the to-be-processed material which performed the conventional chromization process, Comprising: (A) is a SEI image, (B)-(D) is an area analysis mapping image of Al, O, and Cr, respectively. It is. FIG. 2 is a perspective view (a) of an exhaust guide assembly formed by assembling a heat-resistant component manufactured according to the present invention, and a perspective view (b) of a VGS type turbocharger incorporating the exhaust guide assembly.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Variable wing | blade 2 Turbine frame 3 Variable mechanism 11 wing | blade part 12 axial part 13 taper part 14 collar part 15 reference plane 21 frame segment 22 holding member 23 flange part 23A flange part (small)
23B Flange (Large)
24 Boss portion 25 Bearing hole 26 Caulking pin 27 Pin hole 31 Rotating member 32 Transmission member 32A Drive element 32B Passive element 33 Ring A Exhaust guide assembly G Exhaust gas h Blade width T Exhaust turbine

Claims (4)

A metal material to be treated is embedded in a diffusion and permeation treatment agent comprising chromium powder, a support agent, and an activator, and subjected to chromization treatment, and a chromium diffusion and permeation layer is formed on the surface of the treatment material to be treated. A method for improving the heat resistance of a treatment material,
The activator comprises 0.1 to 1.0% by weight of a chloride of the diffusion penetrating agent and 0.1 to 1.0% by weight of a fluoride of the diffusion penetrating agent. To manufacture heat-resistant parts by chromizing treatment.   The method for producing a heat-resistant component by chromization treatment according to claim 1, wherein the chloride is ammonium chloride, and the fluoride is aluminum fluoride or sodium fluoride.   The method for manufacturing a heat-resistant component by chromization treatment according to claim 1 or 2, wherein the material to be treated after the chromization treatment has a surface roughness Ry of 6.3 µm or less.   The chromizing process is a VGS type turbo engine that is capable of exerting high output even when the engine is in a low speed rotation region by appropriately reducing the amount of exhaust gas to increase the exhaust speed and increasing the work of the exhaust turbine. 4. The method for producing a heat-resistant component by chromization treatment according to claim 1, wherein the method is applied to a component of a charger.