JPH0613750B2 - Apparatus and method for chromizing an object - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to coatings of objects, and in particular to devices and methods for applying a chromizing coating to one or more surfaces of an object as a protective measure, in particular against corrosion.

From the standpoint of being able to resist various types of corrosion, it has long been known in the prior art that the most important alloying element, as far as steel is concerned, is probably chromium. Further, one means of providing the surface of chromium necessary to impart such resistance to corrosion and / or oxidation to steel is the treatment of which the term chromizing has heretofore been commonly used in the prior art. It has long been known to be used.

As used in the prior art, the term chromizing has come to mean a high temperature diffusion treatment of the treated surface of steel by alloying with chromium. Briefly, in accordance with this process, a steel body is embedded in a chromium-containing powder in a retort, which is then heated with its contents to a high temperature in a furnace for several hours. This heating gasifies the chromium in the powder and deposits it on the steel body, which is concentrated in the base metal of the steel body over a depth at a concentration that depends on a number of metallurgical and process variables. Spread it. The process described above results in a steel object in which the coating iron-chromium alloy is metallurgically bonded, such as in the integral part of the base material of the steel object. Since chromizing is a diffusion process, the structural alterations that occur with this process occur within the surface of the matrix and not on the surface itself. The significance of this is that the diffused chromium physically and metallurgically penetrates into the base metal surface of the steel body and replaces some of the iron atoms in the base metal, so that the diffused chromium is present in the steel body. As an integral part of the matrix, it will not be exposed to the characteristic cracks or delaminations of the mechanical bond coating. As is known, there are numerous fields of application in which it is desirable to use components that have a chromized or chrome coating. A non-limiting example of this is known to arise in situations where it is necessary to combat many types of general and / or local gas-side corrosion and vapor-side oxide scale delamination resulting in solid particle vapor erosion. The various boiler-related fields that have been mentioned can be mentioned in particular.

For example, the chemical recovery boiler is one of the boiler related fields.
Take as an example. A chemical recovery boiler is a device that recovers and processes chemicals used in pulp mills. A special problem with chemical recovery boilers concerns so-called black liquor, a cooling effluent produced during pulp production. It is this black liquor that is burned as fuel in the chemical recovery boiler. For many years, black liquor was burned in a chemical recovery boiler as a means of chemical recovery, which at the same time generated steam. The value of the chemicals recovered by use of the chemical recovery boiler is usually more than three times the value of the steam generated in this chemical recovery boiler. Needless to say, the amount of steam generated in the chemical recovery boiler reaches a substantial amount, perhaps half of the amount of steam required in the pulp mill. Unfortunately, however, the black liquor burned as fuel in the chemical recovery boiler creates an environment that is highly corrosive to the carbon steel water wall of the chemical recovery boiler. As a result, boiler tubes used for water wall panels in chemical recovery facilities have, until now, often had to be replaced and / or metallized for the purpose of resisting this corrosion. In order to do so, it is necessary to suspend the operation of the chemical recovery boiler so that it can enter and leave it. Another option is to use a special composite tube of carbon steel with 304 stainless steel outer cladding.
Such a composite pipe is relatively expensive. An alternative to this is to use a chromized boiler tube, i.e. a boiler tube with a chrome coating.

Another example of a boiler-related field that may be particularly suitable for using chromized or chrome-coated parts is in the field of resource recovery boilers. As the number of landfills that can accept municipal solid waste is decreasing, more and more communities are relying on the incineration of municipal solid waste. The means of carrying out the municipal waste incineration adopted by such communities often uses a type of boiler called a resource recovery boiler in the general industry. Unfortunately, however, due to the composition of municipal solid waste, or the nature of the various antibiotics considered to be contained in the municipal solid waste, it is often at least necessary to burn such municipal waste with a resource recovery boiler. This produces conditions that expose some to corrosion. Boiler burning of municipal waste on a scale currently being attempted is a relatively recent development field as a field of use where boilers have historically been adopted, so the boiler tube of resource recovery boilers is There is much to learn about the nature of the corrosion that is exposed as a result of the incineration of municipal solid waste, and the extent to which this boiler tube of a resource recovery boiler is exposed to corrosion. Nevertheless, there is sufficient information to suggest that it may be possible to sufficiently resist corrosion by using chromized boiler piping, ie chromium coated boiler piping, in the resource recovery boiler.

Another example of a boiler-related field that uses chromized or chrome-coated components is gasifier components designed for use in coal gasification processes. The development and practical application of coal gasification, which produces synthetic gas from coal, has attracted considerable attention in the United States, especially in the 1970s. Many large US companies, as well as the US government, were funding during this period to support the development of such technologies. The degree of relevance in the United States to carry out coal gasification on a commercial scale declined significantly with the subsequent decline in oil prices. On the other hand, while there is currently little interest in achieving coal gasification on a commercial scale in the United States, there has been relatively recent considerable interest abroad. As a result,
In particular abroad, there has been a focus on how to combat the corrosion that occurs in the internal parts of a gasifier during its operation. As with the resource recovery boiler described above, one must learn about the nature of the corrosion that gasifier internal components are exposed to during gasifier operation and the extent to which gasifier internal components are exposed to this corrosion. Many remain. Nevertheless, it is sufficient to conclude that it is possible to successfully resist such corrosion by chromizing the internal parts of the gasifier, i.e. by applying a chromium coating. Information exists.

Coal-fired general boilers represent another example of a boiler-related field that may be particularly suitable for using chromized components, that is, components having a chromium coating.
Coal-fired general-purpose boilers, especially supercritical pressure type boilers of this type, suffer from total and / or local erosion of their water walls. Furthermore, it was found that metallization was not an effective means to combat this highly aggressive sulfidation environment. On the other hand, parts with a chrome coating have been found to be resistant to such sulfidation erosion and metal loss, even in areas where previously significant metal loss was noted.

Proceeding with the boiler, it was known that its superheater and reheater sections suffered corrosion and oxidation by hot ash. This hot ash corrosion and oxidation in the superheater and reheater sections of such boilers can in some cases be addressed by upgrading the material from ferritic steel to austenitic stainless steel. However, due to the difference in coefficient of thermal expansion between ferritic steel and austenitic stainless steel, it is possible to continue to use ferritic steel as a material for some or all of the components of the boiler superheater and / or reheater sections. It may be desirable or even necessary. In such cases,
The use of chromizing, i.e. providing a chromium coating on such ferrite alloy members, is advantageous in conferring resistance to ash corrosion, whereby the matrix of these parts, i.e. the ferrite alloy material from which they are made, is This will significantly increase the oxidation limit. Further referring to the problem of different coefficients of thermal expansion, materials that expand at different rates become a particularly significant problem in retrofitting boilers. That is, the original design is based on the use of a ferrite material, and this ferrite material is replaced by an austenite material, or vice versa, the original design is based on the use of an austenite material and this austenite material is replaced by a ferrite material. Things may not be feasible. Thus, there is a need to employ components made of ferrite alloy materials. However, in doing so, some work needs to be done to raise the oxidation limit of this ferrite alloy material. Such results are obtained by using parts which are chromized on the inside and outside, that is to say made of a ferrite alloy material with a chromium coating on the inside and outside. This provides a part that is expected to have a significantly longer life than parts made of non-chromized ferrite alloy material.

To further mention the problem of oxidation, it is known that steam side oxidation products formed in the tubes of the superheater and reheater sections of boilers that come into contact with gas can create significantly higher metal temperatures. ing. Further, a thick oxide may be formed on the inner surface of the boiler tube, resulting in failure of the boiler tube. In contrast, the oxide scale formed on the chromium coated surface was found to be extremely thin. As a result, the oxide scale is extremely thin so that the metal temperature of boiler tubes made of chromized or chromium-coated ferrite alloy material does not increase significantly, even during long-term operation.

Next, we will describe the problem of a kind of metal wear, which is often referred to as corrosion fatigue, peripheral grooving, and elephant hiding. Cracking often occurs circumferentially in conventional boiler tubes, which have a fire side, ie, the side facing the flame in the boiler, which is exposed to high front and back temperature differences, eg, the side which is normally exposed to radiant heat. The cause of such circumferential cracking is not fully understood, but it is believed to be induced by thermal stress. The mechanism of penetration of the base metal, that is, cracking is said to be a result of repeated cracking of the semi-protected oxidation product formed on the boiler tube surface. The water wall pipes of general-purpose coal-fired boilers, especially the water wall pipes of supercritical pressure type boilers of this kind, are subject to sulphidic wear attack, but at the same time are areas outside the area subject to corrosion fatigue cracking, especially severe metal loss. Is known to undergo corrosion fatigue cracking. Furthermore, the radiant wall tubes of the reheater section of a coal fired boiler also produce this type of cracking, ie thermally induced corrosion fatigue cracking. Once again, chromizing the boiler tube, i.e. applying a chromium coating on its surface, is itself quite resistant to the type of corrosion fatigue cracking mentioned above, i.e. the thermally induced corrosion fatigue cracking mentioned above. It was shown to be.

In summary, the areas where it is necessary to provide a material with protection against oxidation and sulphurization, which are known to occur on heat transfer surfaces, and it is effective to provide a chromium coating or chromizing treatment to protect the material surface. It will be readily apparent from the foregoing description that non-limiting examples of known fields include industries such as power supply, papermaking, petrochemicals, coal gasification and the chemical industry.

Continuing further, it is known in the art to apply a chromium coating to the surface of the material as described above. For example, U.S. Pat. No. 2836513 discloses a hydrated dispersion of chromium and ammonium and a complex fluoride of chromium and a passivating material applied to the surface of an object to provide an adhesive bond on the iron-based metal object. Form a chromizing layer and then attach this ferrous metal object
Heating to a temperature of 1600 ° F to 2200 ° F (857 ° C to 1079 ° C) and maintaining this body in a closed space at this temperature to protect it by exposing it to the gaseous environment generated by complex fluorides To make the coating fragile for easy removal. In carrying out such a method, as shown in FIG. 2 of U.S. Pat. No. 2,8365,513, a work piece 20 'is placed in a container 26 having a bottom and a side closed and a top open, with a suitable lid. Put 27 loosely on top, not airtight. By doing so, the possibility of the chromizing gas disappearing due to the action of cleaning or scavenging is further reduced. This is because the relatively heavy chromizing gas tends to fill the lower vessel portion 26. Today, however, the application of such a chromium coating on the surface of a material has two disadvantages, first of all. One is the fact that up until now it has only been possible to coat the outer surface of relatively small components, for example components with dimensions such as turbine blades, with chromium, as far as the outer coating of the component is concerned. is there. The reason is due to the fact that if a chromium coating is to be applied to the surface of the material, this has to be done at a certain temperature. Therefore, as the size of the component increases, it becomes increasingly difficult to maintain the entire surface of the component at this particular temperature for the time required to apply the chrome coating.

Regardless of whether the chromium coating is applied to the outer surface or the inner surface of the material, another drawback of the conventional chromium coating method is that this conventional chromium coating does not It derives from the feature of containing grain boundary carbide. In this regard, U.S. Patent No.
See 4208453 and U.S. Pat. No. 4,290,391. The reason why the presence of large amounts of grain boundary carbides in chromium coatings is considered to be detrimental was found to be that such grain boundary carbides make chromium coatings more susceptible to intergranular erosion in harsh environments. . Efforts have been made to overcome this drawback by minimizing the presence of grain boundary carbides in chromium coatings. One approach taken to minimize the presence of grain boundary carbides in chromium coatings is to co-diffuse vanadium into chromium. The idea of co-diffusing vanadium in chromium is based on a U.S. patent application filed on July 1, 1987 with E.Clyde Lewis, one of the inventors of the present application, as one of the co-inventors. It is the gist of No. 68922. Another approach has been to use a carbon-stabilized low alloy matrix as the chromium coating material.

Thus, one or more surfaces of an object, whether external or internal, may be provided with a chrome coating, especially those used in fields of application subject to corrosion. There has previously been a need for improved apparatus and methods. Further, there has been a long-felt need for apparatus and methods that can provide a chromium coating on the surface of an object that is thicker than the chromium coating that can be obtained using conventional chromium coating methods. Moreover, there has been a long-felt need for chromium coating apparatus and methods that provide higher chromium concentrations than can be obtained using conventional chromium coating methods. Furthermore, if the size of the object whose surface is to be chrome coated is larger than the size of the object that could be chrome coated on the surface using conventional chrome coating methods, then the surface of this object There is a need for an apparatus and method for applying chromium coatings to steel.

Accordingly, it is an object of the present invention to provide a new and improved apparatus for providing a chromium coating on the surface of an object as a means of protecting the object.

Another object of the present invention is to provide a new and improved method of providing a chromium coating on the surface of an object as a means of protecting the object.

Yet another object of the present invention is to provide an apparatus and method for applying a chrome coating to the surface of an object where the surface to be chrome coated is the outer and / or inner surface of the object.

Another object of the present invention is to provide a chromium coating apparatus and method in which the applied chromium coating thickness is greater than the chromium coating thickness that can be obtained using conventional chromium coating methods.

Yet another object of the present invention is a chrome coating wherein the size of the object whose surface is to be chrome coated is greater than the size of the object whose surface could be chrome coated using conventional chrome coating methods. An apparatus and method are provided.

Yet another object of the present invention is to provide a chromium coating that is relatively inexpensive, relatively easy to use, and more resistant to corrosion than the chromium coatings conventionally used for the same purpose. The present invention provides a chromium coating apparatus and method.

SUMMARY OF THE INVENTION One aspect of the invention is the novel application of chromium coatings to one or more surfaces of an object, particularly those surfaces intended for use in applications subject to corrosion. It is to provide an improved device. The device preferably includes a fixed foundation formed of cast refractory material. On the fixed base is a retort that is supported by a plurality of support members that are spaced apart from each other. In this retort is placed the object to be chrome coated. An inlet opening is appropriately formed at a certain position of the retort, and the fluid medium is supplied to the inside of the retort through the inlet opening. An outlet opening is appropriately formed in the other place of the retort, and the fluid medium entering from the above-mentioned inlet opening flows out of the outlet opening after flowing in the retort. The apparatus of the present invention further comprises heating means for moving to and from one location, and when in this location, the heating means actuates the retort at a predetermined temperature for a predetermined time. It includes a furnace adapted for uniform heating. Like the retort, the furnace has an inlet opening at one location through which the fluid medium is fed into the furnace. The furnace also has an outlet opening formed elsewhere so that the fluid medium entering through the inlet opening exits the outlet opening after flowing through the furnace. Finally, the device according to the invention is suitably arranged in a sealing relationship between the furnace and the fixed foundation and acts to seal the furnace, whereby the retort is sealed from the environment surrounding the furnace and the retort is installed in the furnace. It includes a sealed portion adapted to be heated by the heating means provided.

Another aspect of the present invention is to provide a new and improved method of applying a chromium coating to one or more surfaces of an object intended for use in applications where the object is particularly subject to corrosion. is there. This method preferably comprises providing a fixed base formed of a molded refractory material, a plurality of support members spaced apart from each other on the fixed base, and a retort in a supporting relationship on the support members. A layer of powder consisting of a mixture of ammonium chloride, alumina and ferrochrome on the bottom of the retort, the layer of the object to be chromium-coated is placed on top of the powder layer in the retort, Cover the layers with a layer of powder, thus alternatingly adding to the retort a layer of the object to be chrome coated and a layer of the powder until the retort contains the desired number of objects,
This last layer of material is covered with powder of a given thickness, the retort is capped and sealed in place, a furnace with heating means is placed around the retort and the furnace is sealed. As a result, the retort is sealed from the environment surrounding the furnace, and while the heating of the retort is started by the heating means of the furnace, the fluid medium is supplied to the inside of the retort and the surroundings of the retort to expel the air for a predetermined time Heat the retort uniformly at a first predetermined temperature, then cool the retort to the predetermined temperature in Figure 2, remove the furnace from the location surrounding the retort, remove the lid from the retort, remove the powder residue from the retort and the chrome coating. Take out the object. Cleaning the remaining powder from these chrome coated objects is included.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of an apparatus for applying a chrome coating to one or more surfaces of an object according to the present invention.

2 is an enlarged schematic view of the retort portion of the apparatus of FIG. 1 according to the present invention.

3 is a cross-sectional view of the retort portion of the apparatus of FIG. 1 according to the present invention, taken substantially along the line 3-3 of FIG.

FIG. 4 is a perspective view of a pair of tubular members chrome coated on both the outer and inner surfaces by an apparatus and method for chrome coating one or more surfaces of an object in accordance with the present invention.

FIG. 5 is a perspective view of a tubular member having a chromium coating on its outer surface by an apparatus and method for chromium coating one or more surfaces of an object according to the present invention.

FIG. 6 is a perspective view of a non-tubular member having a chromium coating on its outer surface according to an apparatus and method for applying a chromium coating on one or more surfaces of an object in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings and to FIG. 1, there is shown an apparatus generally designated by the numeral 10. In accordance with one aspect of the present invention, the apparatus 10 is designed to operate for the purpose of providing a chrome coating on one or more surfaces of an object intended for use in applications where the object is particularly subject to corrosion. I am doing it.

First, the structural properties of the device 10 will be described. To this end, please refer in particular to FIGS. 1, 2 and 3 of the drawings. As best seen in FIG. 1, device 10 includes a fixed foundation. This fixed foundation is shown generally at 12 in FIG. According to the best mode of the invention, the fixed foundation 12 is preferably formed of a cast refractory material. The fixed foundation 12 is designed to perform two functions. That is, this fixed base 12 has the properties of a support base for the device 10. Second, because it is formed of a mold refractory material, the fixed foundation 12 forms a heat insulating barrier between the device 10 and the facility in which it is located, such as the factory floor (not shown). Acts like.

With further reference to FIG. 1 of the drawings, a fixed foundation 12 supports a plurality of support members thereon with a distance between adjacent support members. For simplicity, each of these plurality of support members is designated with the same reference numeral or reference numeral 14 in FIG. As with the fixed foundation 12, the plurality of support members 14 are preferably each formed of a cast refractory material. Moreover, like the fixed foundation 12, the plurality of support members are designed to act both as a support surface function and as a heat insulating barrier function.

The support surface provided by the plurality of support members is for the retort indicated at 16 in FIGS. 1, 2 and 3. In this retort 16 is placed an object whose one or more surfaces are to be chrome coated. retort
Another aspect of the present invention is a method of providing a chromium coating on the surface of an object placed inside 16. This method will be described in detail below. However, for purposes of describing the structural nature of the apparatus 10 of FIG. 1, the retort 16 may contain objects having chromium coatings on one or more surfaces for a predetermined period of time to form chromium coatings on those objects. Suffice it to say that it is designed to have the function of an enclosure that allows it to be heated to a predetermined temperature that is uniform across it. Thus, in accordance with the preferred embodiment of the present invention, the retort 16 is preferably a large number of relatively large objects, such as a number of relatively long tubular metal objects heated to a temperature on the order of 2100 ° F (1135 ° C). Shall be formed of any suitable conventional material of sufficient strength to support. Further, in order to simplify the structure of the retort 16, the preferred embodiment of the present invention preferably has a square structure formed by a base designated by the reference numeral 18. This base
18 has four upright sidewalls, designated by the reference numeral 20. These are joined by any conventional connecting means (not shown) to form a closed box type structure. In addition, the retort 16 includes a lid indicated at 22. The lid 22 is removably attached to the top of the box structure formed by the base 18 and the upstanding sidewalls 20 associated therewith to hold the object in which the chrome coating is to be applied on one or more surfaces. The inside of the retort 16 is made to come close to the inside of the retort 16 for the purpose of putting it in and taking out the chrome-coated object from the inside.
The lid 22 is further referred to when it is used to heat the object to be chromium-coated on one or more surfaces once it is set in the retort and heated as described below. Is designed to seal in-situ the box structure formed by the base 18 and the upstanding sidewalls 20.

In completing the description of the structural nature of the retort 16, it will be pointed out that the retort 16 is provided with inlet passage means in a first position, as will be described in more detail below. This inlet passage means is designated by the numeral 24 in FIG. The inlet passage means 24 is suitably formed in a first position such that it is operative to allow an inert fluid medium to be fed therethrough into the interior of the retort 16. In addition, the retort 16 has outlet passage means in another position. This outlet passage means is shown schematically at 26 in FIG. The outlet passage means 26 serve to allow the inert fluid medium supplied to the interior of the retort 16 via the inlet passage means 24 to flow out of the retort 16 after it has flowed into the retort 16. According to the best embodiment of the present invention,
The inlet passage means 24 and outlet passage means 26 may be of any suitable conventional type as long as they can perform their desired functions as described above.

Continuing with the nature of the construction of the apparatus 10, as best seen in FIG. 1, the apparatus 10 includes a furnace, generally designated 28. According to the preferred embodiment of the present invention, the furnace 28 is preferably substantially rectangular in shape. More specifically, the furnace 28 is made to provide a shape that is complementary to the shape of the retort 16, but its dimensions are
Larger than 16 dimensions allows the furnace 28 to be moved between a first position that covers the retort 16 and a second position (not shown) that does not cover the retort 16. Appropriate gripping means are provided to move the furnace 28 relative to the retort 16. The gripping means is in the form of a plurality of conventional lugs, as indicated at 30 in FIG. The lugs 30 are preferably suitably spaced apart from one another so that they project from the top 32 (FIG. 1) of the furnace 28. The lug 30 is brought into or out of the position of the furnace 28 relative to the retort 16 by an industrial type crane or by any other similar equipment suitable for such purposes. Designed to perform moving. However, without departing from the spirit of the invention, the lug 30 could be replaced by any conventional gripping means suitable for use for the purposes described above.

To further describe the nature of the structure of the furnace 28, as is apparent from FIG. 1, the furnace 28 has heating means. The heating means is designated by 34 in FIG. Heating means 34
In the best mode of the invention, comprises a number of electrical heating elements 36 suitably disposed in supporting relationship within a furnace 28. When the furnace 28 is positioned over the retort 16 as shown in FIG.
To uniformly heat the retort 16 to a predetermined temperature for a predetermined time, thereby heating the contents of the retort 16, that is, the object to be chromium coated on one or more surfaces. In addition to the predetermined temperature and the predetermined time, the predetermined temperature is preferably 2100 ° F (1135 ° C) in the best embodiment of the present invention, and the predetermined time is preferably 10 hours. is there. Thus, according to the present invention, in order to successfully achieve the desired quality, thickness, etc. of the chrome coating on one or more surfaces of the object, this object and thus the surface of this object to be chrome coated 2100 It must be heated uniformly to a temperature of ° F (1135 ° C). This temperature must be maintained uniformly for 10 hours, whatever the overall dimensions, ie the length, width and height of the object. In this regard, the larger the size of the object, the more uniformly the entire 2100 ° F (1135 ° C)
It was found to be more difficult to maintain that temperature for 10 hours continuously. Finally, according to the invention, especially for relatively large objects, 2100 ° F (1
The surface is uniformly heated to a temperature of 135 ° C, and then approximately 2100 °
Forming a chromium coating by continuously maintaining this body at a temperature of F (1135 ° C.) for 10 hours is accomplished by the aforementioned multiple electric heating elements 36 as heating means 34 suitably provided in the furnace 28. Can be achieved. It has been found that gas or oil heating means do not work as a uniform heating means for the purpose of successfully forming the desired chromium coating on the surface of an object.

Referring again to the structural nature of the furnace 28, as is apparent from FIG. 1, the furnace 28 has inlet passage means similar to the retort 16 described above. This inlet passage means is shown at 38 in FIG. The inlet passage means 38 is appropriately the first of the furnace 28.
At the position where the fluid medium is fed into the furnace 28. Further, the furnace 28 also has outlet passage means in another location. This outlet passage means is designated by the reference numeral 40 in FIG. The outlet passage means 40 serves to cause the fluid medium supplied to the interior of the furnace 28 from the inlet passage means 38 to flow through and then exit through the furnace 28. In accordance with the preferred embodiment of the present invention, the inlet passage means 38 and the outlet passage means 40
Both can employ any suitable conventional structure that can function as desired, ie, function as described above.

To conclude the description of the nature of the construction of the furnace 28, in accordance with the preferred embodiment of the present invention, a number of electrical heating elements 36 of the heating means 34 supported within the furnace 28 are provided with conventional insulating means (not shown). )
In the retort 16 the heat generated by these multiple electric heating elements 36 does not escape to the outside of the furnace 28 and does not heat the retort 16 and the objects located in this retort as desired. The object is successfully coated with a chrome coating as described above. Any conventional insulating means can be used for this purpose, as described above.

Finally, as far as the structural nature of the device 10 is concerned, the device 10 includes sealing means, as best seen in FIG. This sealing means is shown at 42. As shown in FIG. 1, this sealing means 42 is designed to be interposed between the furnace 28 and the fixed foundation 12. Therefore, the sealing means
1, the retort 16 is arranged on a plurality of supporting members 14 as shown in FIG. 1 and supported on the fixed foundation 12, and the furnace 28 is moved to a position surrounding the retort 16.
When occupying a relative position to the retort 16 shown in
It is designed to act as a seal between the fixed base 12 and the fixed base 12. That is, the sealing means 42 seals the furnace 28,
As a result, the retort 16 is hermetically sealed from the external environment surrounding the furnace 28, and the object within the retort 16 is heated as described below.
It is intended to serve to enable heating to a desired temperature for a desired time by means of a number of electric heating elements 36 of heating means 34 provided in 28. Any known sealing means that acts in this way, ie, able to withstand the weight applied to the furnace 28 and withstand high temperatures for extended periods of time, could be used as the sealing means for the device 10. Further, for convenience of use, the sealing means 42 is appropriately installed in the furnace 28.
It may be mounted on and may be moved therewith for sealing engagement with or disengagement from the fixed foundation 12.

Now turn to another aspect of the invention. As will be described in more detail below, the present invention is directed to a method of applying a chrome coating to one or more surfaces of an object, particularly one or more objects of the type used in such applications as subject to corrosion. There is a method of coating the surface with chromium. In order to carry out this method, according to the best mode of the invention, it is preferred to use the apparatus 10 described above and illustrated in whole or in part in each of FIGS. 1, 2 and 3.

To describe this aspect of the invention, a method of applying a chromium coating to one or more surfaces of an object comprises the steps set forth below. In order to explain these steps, FIG. 1, FIG. 2 and FIG.
Refer to. The first of these steps is to first provide a fixed foundation, for example a fixed foundation in the form of fixed foundation 12 shown in FIG. According to the preferred embodiment of the present invention, the fixed foundation is preferably made from any suitable conventional shaped refractory material. Next, a plurality of supporting members, for example, the supporting members 14 shown in FIG. 1, are arranged on the fixed foundation at a suitable distance from each other. Then a retort with a lid,
In accordance with the preferred embodiment of the present invention, the retort 16 shown in FIGS. 1, 2 and 3 is placed in a suitably supported relationship on a plurality of support members with the lid removed.

Continuing with the description of the steps of the method of the present invention, remove the lid from the retort to bring it closer to the interior of the retort,
Then spread a layer of powder on the bottom of the retort. According to the best mode of the invention, this powder preferably comprises a mixture of ammonium chloride, alumina and ferrochrome. Then a layer of objects, for example a plurality of objects, ie in the form of pairs of joined tubular members such as that shown in FIG. 4, or a plurality of single tubular members shown in FIG. 5 or shown in FIG. A plurality of objects, such as a plurality of non-tubular members, are placed on the layer of powder described above laid on the bottom of the retort. However, it should be understood that the objects illustrated in each of FIGS. 4, 5 and 6 are merely examples of objects for carrying out the method of the present invention to provide a chromium coating on a surface. That is, other types of objects, such as, but not limited to, I-beam shaped objects, cup shaped objects, etc., like the objects shown in FIGS. 4, 5 and 6, respectively,
Without departing from the spirit of the invention, the method of the invention can be carried out to provide a chromium coating on its surface. Now, the layer of parts placed in the retort is covered with a layer of powder identical to the layer of powder described above spread on the bottom of the retort, namely a layer of a mixture of ammonium chloride, alumina and ferrochrome. Subsequent to this step, a layer of the object and a powder of the same mixture as described above are applied until the volume of the retort is full, or if the number of objects required is less than the number of objects that fill the retort. Alternately formed in the retort until the number of objects is reached. The top or last body layer is then covered with a powder layer of the same mixture as described above. According to the best mode of the invention, this powder layer is of a predetermined thickness. Once the last object layer has been covered with a powder layer of a given thickness, the lid or retort lid is appropriately positioned over the retort to keep away from the interior of the retort, and then suitable for sealing purposes. Sealing is accomplished by any conventional sealing means such as welding, ie, welding the lid in place on the retort.

In this way, the retort is filled with the desired number of objects whose surface is to be coated with chrome, the retort is capped, and then the furnace containing the heating means is placed in a relation surrounding the retort. For this reason, the furnace is designed so that it can be moved into and out of relation with the retort. According to the preferred embodiment of the present invention, the furnace is preferably implemented as a structure such as furnace 28 illustrated in FIG. Whether or not the furnace 28 is the furnace used in carrying out the method of the present invention is important to the successful execution of the method of the present invention in which a relatively large object is heated to a predetermined temperature for a predetermined time. Is. According to the present invention, each object is once heated to this predetermined temperature quite uniformly, and thereafter, this object is heated to this uniform predetermined temperature for a predetermined time, that is, 10
It is continuously maintained for a relatively long time of about a time or more. Once the furnace is placed in the relevant position surrounding the retort as described above, the furnace or retort is sealed from the external environment surrounding the furnace. According to the preferred embodiment of the present invention, this furnace and retort closure is preferably accomplished using sealing means, such as the sealing means shown in FIG.

Then, the process of heating the object placed in the retort to a predetermined temperature for a predetermined time is started. The heating of this object is done by heating means provided in the furnace for this purpose. Simultaneously with the initiation of this object heating, the fluid medium is supplied to the interior of the retort via conventionally constructed inlet passage means which are suitably formed in the retort for this purpose. This fluid medium is designed to act to drive air out of the interior of the retort. After flowing through the retort, the fluid medium exits through conventional outlet passage means suitably provided in the retort for this purpose. In addition to this fluid medium which is supplied to the interior of the retort, at the same time another fluid medium is supplied to the interior of the furnace, i.e. around the retort, by means of conventionally designed inlet passage means formed in the furnace for this purpose. . The fluid medium supplied to the inside of the furnace, that is, the fluid medium supplied to the periphery of the retort, has the same air-discharging action as the fluid medium supplied to the inside of the retort. More specifically, the fluid medium supplied to the interior of the furnace or around the retort is adapted to expel air from the area supplying the fluid medium. The fluid medium exits the furnace through the interior of the channel and through outlet passage means provided in the furnace for this purpose, if appropriate.

From this time, the heating of the objects inside the retort by the heating means provided in the furnace is continued until these objects are uniformly heated to a first predetermined temperature, and then these objects are heated to this first predetermined temperature. Is continuously maintained for a predetermined time. After this predetermined time, the heating means provided in the furnace are deactivated and the retort and the objects placed in the retort are allowed to cool. This cooling of the objects placed in the retort continues until the objects are uniformly cooled to the second predetermined temperature.

When this second predetermined temperature is reached, the furnace is removed from the position surrounding the retort. The lid is then removed from the retort. When the lid is removed, the remainder of the powder mixture and the surface-chrome coated object are removed from the retort.
After that, the powder still remaining on the surface of these objects is cleaned off. The removal of the remaining powder from the objects in this manner then adds to these objects a heat treatment and / or any other manufacturing step that it may be desirable to apply to these objects.

Now, by way of non-limiting illustration, an example of implementation of the method according to the invention will now be described. In this embodiment, the object whose chrome coating is to be formed on one or more surfaces is the tubular member 44 shown in FIG. Furthermore, for the purposes of this exemplary implementation of the method according to the invention, the surface of this tubular member 44 to be chromium coated is its outer peripheral surface,
It is assumed that 44 is provided with a chromium coating indicated by reference numeral 46 in FIG.

In order to apply a chrome coating, such as the chrome coating shown in FIG. 5 at 46, to the outer peripheral surface of a tubular member such as the tubular member 44 shown in FIG. To execute. First, a fixed base, such as the fixed base 12 made of the preferred mold refractory material shown in FIG. 1, is provided. Then
A plurality of support members, such as the plurality of support members 14 shown in FIG. 1, are arranged on a fixed foundation adjacent to each other and at appropriate intervals. Thereafter, preferably, a lid-equipped retort having a structure such as the retort 16 shown in FIGS. 1, 2 and 3 is appropriately placed on a plurality of support members in a state where the lid is removed, and a fixed foundation is provided. To support it appropriately.

Since the lid is removed from the retort and you can access the inside of this retort, it is roughly 1/2 on the bottom of the retort.
Spread evenly the powder layer with inch (12.7mm) thickness.
The powder used for this is in the form of a mixture of 3% ammonium chloride, 55% alumina and 42% ferrochrome. In this regard, the residue of the powder remaining after applying the chromium coating on the surface of the object according to the invention is
It is possible to mix new powder with a ratio of approximately 25% for reuse. After spreading the powder layer as described above, a layer of the first tubular member 44 is formed on the powder layer on the bottom surface of the retort. However, this first tubular member 44
Prior to placing this layer and the next layer of similar tubular member 44 in the retort, air is first expelled by passing an inert gas, such as argon, into each of the tubular members 44. Further, once air is once removed from the inside of each tubular member 44 of each layer thus formed in the retort, a plug having an appropriate structure, preferably a plug made of sheet metal, is attached to each of these tubular members 44. Fit tightly on the end.

Once this layer of the first tubular member is formed in the retort, the layer of the same powder mixture laid down at the bottom of the retort is approximately 1/2 inch (12.7 mm) thick and the first tubular member is formed. Formed on the layer of. Following this, the tubular member
Alternately, 44 layers and approximately 1/2 inch (12.7 mm) thick powder layers are formed in the retort to reach the capacity of the retort to accommodate the layers of tubular member 44 or the desired number. When the layer of tubular member of is formed, it is stopped. In the embodiment of the invention illustrated in FIGS. 2 and 3, the layers of tubular member 44 are
Reference numeral 50 indicates a powder layer having a thickness of approximately 1/2 inch (12.7 mm) including 6 layers of 48 and the powder layer spread on the bottom of the retort. After forming the last or sixth layer of tubular member 44 in the retort in the illustrated embodiment, this last layer
The powder layer 50 previously described as containing 48 into the retort.
Powder of the same mixture as above is laid down to a thickness of approximately 4 inches (101.6 mm) to form a powder layer indicated by reference numeral 52 in FIG.

The retort is then capped and sealed by welding.
Subsequent to this, the inlet passage means and outlet passage means, suitably formed in the retort, are provided as a suitable source for the supply of a fluid medium, which is an inert gas such as argon, suitable for expelling air from the interior of the retort. To a fluid flow forming relationship. The furnace is then moved to a position over the retort, for example using a conventional industrial crane with lugs, whereby the heating means of the furnace causes the bed of tubular members 44 placed in the retort as described above. Allow 48 to be heated. After moving the furnace to a position surrounding the retort, the inlet passage means and the outlet passage means are connected in fluid communication with a suitable source of a fluid medium, which is an inert gas such as argon, for example in the furnace. Allows air to be expelled from the area surrounding the retort.

The heating of the layer 48 of the tubular member 44 by the heating means of the furnace is then started. Simultaneously with the start of heating of the tubular member layer by the furnace heating means, an inert gas is flowed from the retort inlet passage means into the retort and through the furnace inlet passage means into the area within the furnace surrounding the retort. start. Fumes are generated during this stage of heating the layer 48 of tubular member 44 placed in the retort. The fumes are carried away by the inert gas flowing in the retort to the outside of the retort via the outlet passage means, and further carried out by the inert gas flowing in the furnace to the outside through the outlet passage means of the furnace.
Preferably, these fumes and inert gases exiting through the retort outlet means and the furnace outlet passage means, according to the illustrated embodiment of the invention, are allowed to flow to a chimney before being released to the atmosphere. . This chimney is shown in the drawing at 54. Once the fume is formed, it is ignited as appropriate using any conventional ignition device (not shown). The ignition of the fume takes place after the fume leaves the retort and the surrounding furnace area so that it burns before it is released from the chimney to the atmosphere. Tubular member placed in retort by heating means of furnace
The heating of 44 layers 48 and the flow of the inert gas through the furnace area and the retort surrounding the retort include:
In this case, for example, the chrome coating to be applied is the tubular member 44.
It continues until it is formed on the outer peripheral surface. Even at the coldest point in the retort, the first predetermined temperature of 2100 ° F (1135 ° C) is reached. In addition, this predetermined temperature of 2100 ° F (1135 ° C) is then maintained for the desired 10 hours. In this regard, if the chrome coating to be applied is not the chrome coating applied to the outer peripheral surface of tubular member 44, the predetermined surface to be heated to successfully apply the chrome coating to the surface of such other objects. The temperature is different from the above 2100 ° F (1135 ° C), for example 2
1700 ° F (912 ° C) or 2100 ° F (113 ° C below 100 ° F (1135 ° C)
The temperature may be in the range of 5 ° C). Similarly, except when chromium coating is applied to the outer peripheral surface of the tubular member 44, the time to be continuously maintained at the predetermined temperature may require a time other than 10 hours, for example, 10 hours or more. .

When the tubular member 44 is heated to a predetermined temperature, that is, 2100 ° F (1135 ° C) and maintained at this temperature for a predetermined time, that is, 10 hours, the heating means of the furnace is turned off, and the retort and the furnace surrounding the retort are closed. The flow of inert gas through the area is stopped and the layer 48 of tubular member 44 placed in the retort begins to cool. This cooling of layer 48 of tubular member 44 placed in the retort continues until the hottest portion in the retort has cooled to a second predetermined temperature. In the case of layer 48 of tubular member 44 placed in the retort, this second predetermined temperature is
It is 400 ° F (190 ° C). If the chrome coating to be applied is not the chrome coating on the outer surface of the tubular member 44, this second predetermined temperature for successfully applying the chrome coating to the surface of the particular object in question is 400 ° F. Temperatures other than (190 ° C) are possible. The hottest place in the retort is the second predetermined temperature 40
Upon cooling to 0 ° F (190 ° C), the furnace inlet and outlet passage means are suitably removed to allow the furnace to be removed from the location surrounding the retort. Then this furnace
A conventional industrial crane with lugs is used to move it from the position surrounding the retort. When the furnace is moved from the retort in this manner, the inlet passage means and the outlet passage means are also removed. Finally, remove the lid from the sealed relationship with the retort.

Layers of powder remaining in the retort and tubular member 44 left in the retort after removing the lid from the retort
Issue 48. Then, each tubular member 44 is cleaned,
The powder adhering to this is removed. If necessary, the tubular member 44 is heat-treated. After heat treating the tubular member 44, check its physical integrity and, if necessary, bend the tubular member 44 to correct any deformation that may have occurred when chrome coating the outer peripheral surface. To do. Thereafter, the tubular member 44 is provided with any necessary welded connections, and any other associated processing required to the tubular member. Following this, the tubular member 44 is again subjected to the necessary heat treatment. Then, the final step of applying a chrome coating to the outer surface of each tubular member 44, the final inspection of each tubular member 44, is performed.

Although the implementation of the method of the present invention has been described in detail above with respect to the tubular member 44 for applying the chromium coating 46 to the outer peripheral surface, it goes without saying that the method of the present invention does not depart from the spirit of the present invention as described above. It can also be applied to apply a chrome coating to one or more surfaces of an object. Thus, the method of the present invention is intended to provide a chrome coating on one or more surfaces of an object, such as a non-limiting example of joined tubular members such as 58,59 shown in FIG. It can be used for the same purpose. In FIG. 4, the inner and outer peripheral surfaces of the joined tubular members 56 and 58 are illustrated with chrome coatings 60 and 62.
Further, FIG. 6 shows an example in which a chromium coating shown by the reference numeral 66 is formed on the entire outer surface of the non-tubular member shown by the reference numeral.

Next, a modified example in which the method of the present invention can be carried out without departing from the spirit of the present invention as described above will be described. According to this
The chrome-coated surface is shot peened to provide the chrome coating with additional strength to one or more surfaces. The effects of shot peening in the manufacturing process are well known to those skilled in the art. Prior to the present invention, it was entirely unknown that it was possible to shot peen a surface provided with it without adversely affecting the effectiveness of the chromium coating provided according to the invention. However, regardless of whether the chromium coating is applied as a result of the chromium component being applied in a slurry to the surface of the object, or the chromium component is mixed as a powder with ammonium chloride and alumina and applied as a layer, The chromium coating formed as a result of the practice of the present invention is shot peened, thereby providing all the advantages known to be obtained by shot peening a surface without adversely affecting the effectiveness of the chromium coating. That is, it can be achieved without compromising the chromium coating's ability to resist corrosion.

Therefore, in a very brief summary, the chromizing treatment involves embedding a steel object, which is to have a chromium coating on one or more surfaces, in a powder mixture containing a chromium component in a retort, The retort is then sealed, from which the retort and its contents are heated in a furnace to a predetermined elevated temperature for a predetermined time, for example several hours. As a result of this heating, the chromium component in the powder mixture is gasified and deposited on the surface of the steel object embedded in the powder mixture in the retort, which chromium is in the metal, i.e. in the surface of the steel object, It diffuses at depths and concentrations that depend on various metallurgical and process variables. As a result, an iron-chromium alloy coating is formed on the surface of the steel body, which is an integral part of the base metal and is metallurgically bonded. Since it is a diffusion process, structural transformations occur inside the surface rather than on the surface.

It has long been known that grain boundary carbides are characteristically present in chromized structures. It is also known that such grain boundary carbides increase the susceptibility of chromium coatings to grain boundary erosion under harsh environments. So, at least in these harsh environments,
It is desirable to minimize the amount of grain boundary carbide present in the chromium coating. In a method of applying a chromium coating to one or more surfaces of an object according to the present invention, the presence of grain boundary carbides in the chromium coating resulting from the practice of this method is substantially reduced, which results in
The chromizing coating is characterized in that it maximizes resistance to intergranular corrosion, which is known to make the chromium coating more susceptible to corrosion.

Thus, in accordance with the present invention, there is provided a new and improved device for providing a protective chromium coating on one or more surfaces of an object. Further according to the invention,
A new and improved method of providing a protective chromium coating on one or more surfaces of an object is provided.
Further in accordance with the present invention, there is provided an apparatus and method for applying a chrome coating to one or more surfaces of an object such that the chrome coating is applied to the outer and / or inner surface of the object. Furthermore, the apparatus and method of the present invention for applying a chromium coating to the surface of an object is characterized in that the chromium coating is applied in a thickness greater than that obtainable by the use of conventional chromium coating methods. Further in accordance with the present invention, there is provided an apparatus and method for applying a chromium coating to the surface of an object with a chromium concentration higher than that which can be achieved using conventional chromium coating methods. The apparatus and method of the present invention for applying a chromium coating to the surface of an object is such that the object whose surface is to be chromium coated is
It is characterized in that it is larger than the size of an object whose surface can be chromium coated using conventional chromium coating methods.
Further in accordance with the present invention, an apparatus for applying a chromium coating to the surface of an object that is relatively inexpensive, relatively easy to apply, and that the chromium coating formed is more resistant to corrosion than the chromium coatings previously used for the same purpose. And a method is provided.

Although the preferred embodiment of the present invention has been described above, the present invention is
The invention is not limited to these particular embodiments, but of course encompasses numerous variations and modifications without departing from the spirit of the invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References Japanese Patent Publication No. 46-13604 (JP, B1) Japanese Patent Publication No. 45-26207 (JP, B1) US Patent 2836513 (US, A)

Claims (43)

[Claims] Claims: 1. A support means and (12,14); b) A chromium coating (46,60,62,64) on one or more surfaces supported on this support means (12,14). Retort (1) that contains the goods (44, 56, 58, 60)
6), c) first inlet passage means (24) formed at a first position of the retort (16) for supplying a fluid medium to the inside of the retort (16), and d) the retort (16). Formed in the second position of the first
First outlet passage means (26) for discharging the fluid medium supplied from the inlet passage means (24) of the retort (16) to the inside of the retort (16), and e) the retort Is movable between a first position surrounding the retort (16) and a second position surrounding the retort (16), the retort being in the first position.
A furnace (28) provided with heating means (34) for uniformly heating the (16) to a first predetermined temperature and then maintaining the retort (16) uniformly heated to the first predetermined temperature for a predetermined time. And f) supplying a fluid medium into the furnace so as to surround the retort (16) when the furnace (28) is formed at the first position and the furnace (28) occupies the first position. G) second inlet passage means (38), and g) the fluid medium formed at the second position of the furnace (28) and supplied from the second inlet passage means (38) is in the furnace (28). Flow through the retort (16) to surround the furnace (28)
Second outlet passage means (40) for allowing discharge from said furnace; and h) said furnace (28) when said furnace (28) occupies said first position.
And a support means (12, 14) interposed between the furnace (28) and, as a result, a sealing means (42) for sealing from the ambient environment of the retort (16). , 56, 58, 64) and a chromium coating (46, 60, 62, 66) on one or more surfaces (10). 2. Device according to claim 1, characterized in that said support means (12, 14) comprise a fixed foundation (12). 3. The apparatus of claim 2, wherein the fixed foundation (12) is capable of functioning as a heat insulating barrier and is sufficient to support the furnace (28) and the retort (16) thereon. An apparatus (10) characterized by being formed of a molded refractory material having a sufficient strength. 4. The apparatus according to claim 3, wherein said supporting means (12, 14) are further arranged on said fixed foundation (12) at a distance from each other.
A device (10) comprising (14). 5. The apparatus of claim 4, wherein each of the plurality of support members (14) is capable of functioning as a heat insulating barrier, and further thereon the furnace (28) and the retort (16). A device (10), characterized in that it is made of a molded refractory material having sufficient strength to support the. 6. The apparatus of claim 1, wherein said retort (16) has a removable lid (22) and a plurality of adjacent ones interconnected to give said retort (16) a box shape. A device (10) characterized in that it includes an individual side wall member (18). 7. The apparatus of claim 6, wherein the furnace (28).
An apparatus (10) characterized in that said heating means (34) comprises a plurality of electric heating elements. 8. The apparatus according to claim 7, wherein the predetermined temperature for heating the retort is 2100 ° F. (1135 ° C.). 9. The apparatus of claim 8 wherein the retort (16) is maintained at a uniform temperature of 2100 ° F (1135 ° C) for a predetermined time of 10 hours. 10. The apparatus of claim 1, wherein the fluid medium supplied to the retort (16) acts to expel air from the interior of the retort (16). 11. The apparatus according to claim 10, wherein the fluid medium supplied to the retort (16) is an inert gas. 12. The apparatus according to claim 11, wherein the inert gas is argon. 13. The apparatus according to claim 1, wherein the furnace (2
Device (10) characterized in that the fluid medium supplied to (8) acts to expel air from the area surrounding said retort (16). 14. The apparatus according to claim 13, wherein the furnace (2
The device (10) characterized in that the fluid medium supplied to 8) is an inert gas. 15. The apparatus according to claim 14, wherein the inert gas is argon. 16. A) a support means (12, 14) is provided, and b) a retort (16) having a removable lid (22) is mounted on the support means (12, 14), and c) this. Spread uniformly on the bottom of the retort (16) a first predetermined thickness layer (50) of powder containing a chromium source, and d) coat one or more surfaces with chromium (46,
A layer (48) of the object (44,56,58,64) to be subjected to (60,62,66) is placed on the powder layer (50) of the retort (16), and Objects placed in the retort (16) (4
4,56,58,64) layer (48) with a second powder layer (52) of a predetermined thickness containing a chromium source, and f) covering the retort (16) lid (22) with the retort (16). Placed on top of (16), this lid (22) is sealed in place, g) a furnace (28) with heating means (34) is placed in a relationship surrounding the retort (16), and h) the furnace. (28) is sealed so that the retort (16)
Is sealed (42) from the environment surrounding the furnace (28), and i) the retort (16) is heated by the heating means (34) of the furnace (28).
Therefore, the heating of the objects (44, 56, 58, 64) placed therein is uniformly started to the first predetermined temperature, and j) inside the retort (16) simultaneously with the start of heating in step i. A) supplying a fluid medium, k) allowing the fluid medium to flow through the retort (16) and then discharging it; Supplying a medium, m) the furnace in which the fluid medium surrounds the retort (16)
(28) After flowing through the furnace (28), it is discharged from the furnace (28), and n) when uniformly heated to the first predetermined temperature, the retort (16) and thus the retort (16) are placed. Object (4
4,56,58,64) continuously maintained at the first predetermined temperature for a predetermined time, and o) after the predetermined time, the retort (16) and thus the retort (16) placed in the retort (16). End heating of the objects (44, 56, 58, 64), and p) both the flow of fluid medium to the retort (16) and the flow of fluid medium to the furnace (28) at the same time as the heating of step o is finished. Q) to cool the retort (16) and thus the object (44,56,58,64) placed in the retort (16) to a second predetermined temperature, and r) to retort the retort (16) When the object (44, 56, 58, 64) placed in the retort (16) cools to a second predetermined temperature, the furnace (28) is removed from the position surrounding the retort (16), s) the retort Removing the lid (22) from (16), t) the object placed in step d from the retort (16)
Chromium coating (46, 60, 46, 60, on one or more surfaces of the object (44, 56, 58, 64) comprising the step of removing the layer (48) of (44, 56, 58, 64) 62, 66). 17. The method of claim 16, wherein the object
After removing the layer (48) of (44,56,58,64) from the retort (16), a step of further removing the adhered powder from the layer (48) of these objects (44,56,58,64) is further performed. A method of including. 18. The method according to claim 17, wherein after removing the adhering powder, one or more objects (44,56) of the layers (48) of the object (44,56,58,64). , 58, 64), which further comprises the step of heat-treating. 19. The method of claim 18, further comprising the step of shot peening the surface of the article (44, 56, 58, 64) coated with chromium (46, 60, 62, 66). A method characterized by. 20. The method according to claim 16, wherein the supporting means (12, 14) are formed of a molded refractory material.
A method characterized by including 2). 21. The method according to claim 20, wherein said supporting means (12, 14) are further arranged on said fixed foundation (12) with a space between adjacent supporting members (14). ) Is included. 22. The method of claim 21, wherein the powder layer (50) has a first predetermined thickness and contains a chromium source and one or more surfaces are coated with chromium (46, 60, 62, 66). The method further comprising the step of alternately adding layers (48) of the objects (44, 56, 58, 64) to be subjected to) to the retort. 23. The method of claim 22, wherein the powder layer (50) has a first predetermined thickness of 1/2 inch (12.7 mm). 24. The method of claim 23, wherein the second predetermined thickness of the powder layer (50) is 4 inches (101.6 mm). 25. The method according to claim 24, wherein the layer (4
8) each of the objects (44, 56, 58, 64) is a tubular member,
A method characterized in that the surface to which chromium coating (46, 60, 62, 66) is applied is an outer peripheral surface. 26. The method of claim 25, wherein the first predetermined temperature is 2100 ° F. (1135 ° C.). 27. The method of claim 26, wherein the predetermined time period is 10 hours. 28. The method of claim 27, wherein the second predetermined temperature is 400 ° F. (190 ° C.). 29. The method of claim 28, wherein the fluid medium fed to the retort is an inert gas. 30. The method according to claim 29, wherein the inert gas supplied to the retort is argon. 31. The method of claim 28, wherein the furnace (2
The method characterized in that the fluid medium supplied to 8) is an inert gas. 32. The method of claim 31, wherein the furnace (2
The method characterized in that the inert gas supplied to 8) is argon. 33. The method of claim 32, wherein the object
Prior to placing the layer (48) of (44,56,58,64) in the retort (16), each individual object (44,56) of the layer (48) of these objects (44,56,58,64) , 58, 64) and further purging air from the inside of the inert gas. 34. The method of claim 33, wherein the object
Further comprising the step of expelling air from the inside of each individual object (44,56,58,64) of the layer (48) of (44,56,58,64) and then sealing its ends. how to. 35. The method according to claim 34, wherein each of the powder layers (50, 52) contained in the retort contains a mixture of 3% ammonium chloride, 55% alumina and 42% ferrochrome. how to. 36. The method of claim 16, wherein the retort (16) and an object (44,) placed within the retort (16).
As the layer (48) of (56,58,64) is heated, the retort (1
6) A method characterized in that fumes are generated within. 37. The method of claim 36, wherein the fluid medium flowing in the retort (16) causes the retort (1) to flow.
6) A method further comprising the step of carrying out the fumes generated in the inside of the retort (16). 38. The method of claim 37, further comprising the step of igniting the fumes after they have been carried out of the retort (16) by a fluid medium flowing within the retort (16). A method characterized by the following. 39. The method of claim 16, wherein the retort (16) and an object (44,) placed within the retort (16).
Fume is generated in the furnace (28) as the layer (48) of (56,58,64) is heated. 40. The method according to claim 39, wherein the fumes generated in the furnace (28) are generated by the fluid medium flowing in the furnace (28) in a relationship surrounding the retort (16).
The method, which further comprises the step of carrying away to the outside of 8). 41. The method of claim 40, wherein the fumes are carried out of the furnace (28) by a fluid medium flowing in the furnace (28) in a relationship surrounding the retort (16). A method further comprising the step of igniting. 42. a) A support means (12, 14) is provided; b) A retort (16) having a removable lid (22) is mounted on this support means (12, 14); c) This Evenly spread a layer (50) of the first predetermined thickness of the powder, which contains something other than a chromium source, on the bottom of the retort (16) and d) apply the chromium coating (46,60,62,66). The object to try (44,5
6,58,64) one (1) or more surfaces of each body (44,56,58,64) in the layer (48) is coated with a slurry containing a chromium source, and e) one or more. Number of surfaces with chrome coating (46,
A layer (48) of the object (44,56,58,64) to be subjected to the treatment (60,62,66) is placed on the layer of powder of the retort (16), and f) the retort (16) according to step e. ) Object (4
4,56,58,64) layer (48) covered with a powder layer (52) of a second predetermined thickness, containing other than chromium source, g) lid (22) of said retort (16) Is placed on the retort (16) to seal the lid (22) in place, and h) a furnace (28) with heating means (34) is placed in a relationship surrounding the retort (16), i. ) The furnace (28) is sealed so that the retort (16)
Is sealed from the environment surrounding the furnace (28), and j) the retort (16) is heated by the heating means (34) of the furnace (28).
Therefore, the heating of the objects (44, 56, 58, 64) placed therein is started uniformly to a first predetermined temperature, and k) inside the retort (16) simultaneously with the start of heating in step j. A) supplying a fluid medium, 1) allowing the fluid medium to flow through the retort (16) and then discharge it, m) at the same time when the heating in step j is started, the fluid is introduced into the furnace (28) surrounding the retort (16) Supplying a medium, n) the furnace in which the fluid medium surrounds the retort (16)
After flowing through the inside of the (28), it is discharged from the furnace (28), and o) When uniformly heated to a first predetermined temperature, the retort (16) and thus the retort (16) are placed in the retort (16). Object (4
4,56,58,64) continuously maintained at the first predetermined temperature for a predetermined time, and p) after the predetermined time has passed, the retort (16) and thus the retort (16) placed in the retort (16). End heating of the objects (44, 56, 58, 64), and q) both the flow of the fluid medium to the retort (16) and the flow of the fluid medium to the furnace (28) at the same time as the heating of the step p ends. R) letting the object (44, 56, 58, 64) placed in the retort (16) and thus the retort (16) cool to a second predetermined temperature, and s) thus retort (16) When the objects (44, 56, 58, 64) placed in the retort (16) cool to a second predetermined temperature, the furnace (28) is removed from the position surrounding the retort (16), and t) the retort Removing the lid (22) from (16), u) the object placed in step e from the retort (16)
A layer (48) of (44,56,58,64) comprising removing chromium coating (46,60,64) on one or more surfaces of the object (44,56,58,64). 62, 66). 43. The method according to claim 42, characterized in that each layer (50, 52) of the powder mixture disposed in the retort (16) is composed of ammonium chloride and alumina.