JPS63114954A - Manufacture of surface coated metal - Google Patents

Abstract

PURPOSE:To obtain a surface coated metal having a corrosion, oxidation and wear resistant layer by forming a thermally sprayed layer of a metal on the surface of metallic stock under reduced pressure and carrying out hot working so as to apply compressive force to the thermally sprayed layer at a prescribed reduction in the thickness direction. CONSTITUTION:A metal for thermal spraying such as 'Hastelloy(R)' or an Ni-Cr alloy is thermally sprayed on the surface of a hot workable metal such as carbon steel or low-alloy steel under reduced pressure to form a thermally sprayed layer. Hot working such as hot rolling, hot forging or hot extrusion is then carried out so as to reduce the thickness of the thermally sprayed layer by >=5%. Thus, the thermally sprayed layer is made completely nonporous and a surface coated metal having a uniform satisfactory joining interface is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing a surface-coated metal, and more specifically, a method for coating the surface of a metal with a layer having properties such as corrosion resistance, oxidation resistance, and wear resistance. It's about how to do it.

(Prior Art) With the progress of industry and the development of technology, materials have come to be used in increasingly harsh environments in recent years.

For example, in energy resource development, petroleum and natural gas (so-called sour oil and sour gas) containing large amounts of hydrogen sulfide and carbon dioxide are being developed as production fluids, and the materials used in the development, such as oil country tubular goods and line pipes, are being developed. Since low-alloy steels tend to corrode and crack, nickel alloys such as Hastelloy C-276 and Inconel 625 (trade name) are already in use. However, a major drawback of these alloys is that they are very expensive. Therefore, it has been considered to use so-called clad steel, in which these alloys are used as a laminate only on the surface of the structural material, and the strength is ensured by the underlying metal (for example, low-alloy steel).

Various manufacturing methods have been established or proposed for clad steel, such as seamless pipe or welded pipe when the shape is a pipe, and rolled plate when the shape is a plate. However, in addition to the drawbacks of complicated manufacturing processes and low yields, clad steel pipes made of nickel alloys such as Hastelloy C-276 and Inconel 625 are extremely difficult to manufacture and have not yet been put into practical use. . This is because the deformation resistance of these alloys during hot working is significantly greater than that of the base metals, such as low-alloy steel or carbon steel, so in the normal pipe-making process, the mating material and base metal are uniformly processed and joined. This is because it is difficult to do.

On the other hand, thermal spraying has been known as a type of coating. There are various thermal spraying processes such as plasma spraying and gas flame spraying, which have the advantage of being able to coat the final product and making it easy to control the coating thickness. However, in all of these thermal spraying methods, powder is melted in the atmosphere or an inert gas at atmospheric pressure and sprayed onto the base material, so air or inert gas is drawn into the sprayed layer, creating pores. It has a drawback. These pores not only significantly reduce the ductility of the sprayed layer, but also serve as starting points for corrosion and cracking.Furthermore, some of the pores include through pores, i.e., pores that pass through the sprayed layer, leading to corrosion. There is a serious defect in that the base material is damaged because the solution or oxidizing atmosphere reaches the base material through the through-holes, and the sprayed layer loses its function as a protective layer altogether.

As mentioned in 11η, there is v1 in the sprayed layer sprayed under atmospheric pressure.
Due to the presence of ventilation holes, if normal hot processing is performed, the inside of the through pores and the base material will be oxidized during heating before hot processing, causing cracks in the sprayed layer and surface roughness during hot processing. Moreover, there was a problem in that the through holes were not compressed even by hot rolling and remained as defects. To this end, a conventional method has been to prevent the occurrence of cracks and defects caused by through-holes by, for example, stacking a plurality of thermally sprayed rolled materials so that the thermally sprayed layers are in contact with each other, and then heating and rolling them.

For example, JP-A-59-1003 discloses a method of imparting properties such as corrosion resistance to a surface-coated steel sheet by combining thermal spraying technology and rolling technology. However, this method has a major drawback in that the shape of the product is limited to a plate.

In addition, since a plurality of rolling materials are combined and rolled, processes such as assembly of the materials and peeling after rolling are complicated.

On the other hand, JP-A-59-120276 discloses a method of coating the inner surface of a steel pipe with a thin metal or ceramic with few pores by applying plasma spraying while only the inside of the steel pipe is in a reduced pressure state. However, although this method can reduce pores in the sprayed layer compared to thermal spraying under atmospheric pressure, it still has the disadvantage that the pores are not zero and the ductility and wear resistance of the sprayed layer are inferior.

(Problems to be Solved by the Invention) In view of the current situation, the present invention aims to improve the properties targeted by surface coatings such as corrosion resistance, high-temperature corrosion resistance, oxidation resistance, and abrasion resistance, and to provide a metal with excellent ductility. The present invention provides a method for coating a base metal at a low cost while ensuring excellent properties.

(Means for Solving the Problems) As a result of various experiments and studies in order to achieve the above object, the present inventors found that there were no through-holes in the sprayed layer sprayed onto the metal surface under reduced pressure, and the atmospheric pressure It has been found that the hot workability is significantly superior to that of the thermal sprayed layer produced below, and that the pores in the thermal sprayed layer can be completely eliminated by hot working. Furthermore, in such hot working, it is important to apply compressive force at least in the thickness direction of the sprayed layer in order to eliminate pores in the sprayed layer, and this hot working reduces the thickness of the sprayed layer by 5%. It has been found that it is necessary to reduce the amount of hot working by more than 100%. In addition, we have discovered that it is possible to process the material as it is sprayed, and there is no need to assemble and process multiple materials.

The present invention has been made based on the above findings, and its gist is that after forming a sprayed metal layer on the surface of a metal material under reduced pressure, compressive force is not applied to the sprayed layer at least in the thickness direction. A method of manufacturing a surface-coated metal is characterized in that hot working is performed to reduce the thickness of the sprayed layer by 5% or more.

The present invention will be explained in detail below.

(Function) First, in the present invention, thermal spraying is performed under reduced pressure in order to prevent the formation of through pores in the thermal sprayed layer.
In this case, the degree of vacuum is preferably greater than or equal to I Torr and less than or equal to 300 Torr. This means that the degree of vacuum is I Tor.
If it is less than 300 Torr, the efficiency of thermal spraying is poor, and if it exceeds 300 Torr, it is impossible to prevent the formation of through pores in the sprayed layer. The atmosphere here can be selected from inert gases such as Ar gas and N2 gas, mixed gases such as He, and other gases depending on the spraying conditions, the sprayed metal, the base metal, and the required characteristics of the sprayed layer. I wish I could, but
In either case, it is important that the degree of vacuum be within the above range.

The metal material targeted by the present invention, that is, the metal to be thermally sprayed, can be any metal that can be hot-processed, such as carbon steel, low alloy steel, stainless steel, nickel and nickel alloys, aluminum and aluminum alloys. , titanium and titanium alloys. On the other hand, the thermal spray metal may be selected depending on the required functions such as corrosion resistance, high temperature corrosion resistance, oxidation resistance, and wear resistance, such as Hastelloy, Stellite (all trade names), Ni-Cr alloy. , stainless steel, titanium and titanium alloys.

Examples include nickel and nickel alloys, aluminum and aluminum alloys, and the like.

Next, in the present invention, hot working is performed after forming the sprayed layer, and at this time, it is important to apply compressive force to the sprayed layer at least in the thickness direction in order to eliminate pores. Inter-rolling, hot forging, hot extrusion, etc. can be used. Regarding the amount of hot processing, the thickness of the sprayed layer is 5.
The reason for limiting the reduction to % or more is that if the thickness of the sprayed layer is reduced by less than 5%, the pores in the sprayed layer will not completely disappear. Note that hot working in the present invention refers to processing in the temperature range in which the base metal material and the metal of the sprayed layer are normally processed for purposes such as forming. Appropriate temperatures need to be selected for both layers.

Furthermore, in the present invention, there is no particular upper limit to the amount of hot working;
The reason for this is that for the purpose of the present invention, the amount of hot working only needs to reduce the thickness of the sprayed layer by 5% or more, and can be freely selected as long as it is within the limits of the hot working ability of the sprayed layer or the raw metal. Because you can. Furthermore, since the same effect can be obtained whether the hot working is performed in general or in multiple stages, either method can be selected as required.

In the present invention, when the shape of the metal material is a plate or a pipe, the metal spray layer may be applied to one surface, for example, the upper surface of the plate, the inner surface of the pipe, or the outer surface of the pipe, or both surfaces, that is, the upper and lower surfaces of the plate, the pipe It is also possible to use the inner and outer screens. Depending on the situation in which the product is used, either the - side or both sides may be selected as appropriate.

After the geothermal processing, heat treatments such as quenching, tempering, and normalizing are performed to improve the strength and toughness of the base metal, and solution treatment is performed to further improve the corrosion resistance of the sprayed layer. Other processing may be added as necessary, such as heat treatment such as annealing, and cold processing for the purpose of adjusting the shape of the product. Any of them can be selected depending on the required strength, toughness, corrosion resistance, etc.

The present invention can be applied to manufacture products that require resistance to corrosive substances, products that require resistance to high temperature oxidation, products that require wear resistance, etc., such as pipes, containers, plates, etc. It can be applied to various shapes such as rods and rods. Alternatively, it can also be used as a material for manufacturing products by further performing molding, welding, etc.

Examples of the present invention will be described below.

(Example) Materials to be subjected to hot working were manufactured using the materials and manufacturing conditions shown in Table 1. Here, inventive examples No. 1 to 4 are examples in which a sprayed layer is formed on the upper surface of a slab, inventive examples No. 5 to 6 are examples in which a thermally sprayed layer is formed on both sides of a slab, and inventive example No. 7 is an example in which a thermally sprayed layer is formed on the outer surface of a hollow billet. This is an example of forming layers. In all cases, thermal spraying was carried out under reduced pressure by the Blasme thermal spraying method. The respective shapes are shown in FIGS. 1, 2, and 3, respectively. FIG. 1 shows an example in which a thermal spray layer 2 is formed on the upper surface of a slab 1.

FIG. 2 shows an example in which a thermal spray layer 2 is formed on the upper and lower surfaces of the slab 1. Figure 3 shows a thermal spray layer 2 on the outer surface of a hollow billet 3.
This is an example of forming a .

On the other hand, among the comparative examples, Nos. 8 to IO are examples in which a sprayed layer was formed on the top surface of the slab by plasma spraying under reduced pressure, and Nos. 11 to 12 are examples in which a sprayed layer was formed on the top surface of the slab under atmospheric pressure. be.

Next, these materials were hot-processed under the conditions shown in Table 2 to produce surface-coated metals, and various tests were conducted. The test results are also shown in Table 2. In Table 2, the adhesion strength is JIS
Measured according to N 8664, bending test according to JIS Z
2204 (7) Use No. 1 test piece JISz2248
Those in which cracks did not occur on the surface of the sprayed layer were marked O, and those in which cracks occurred were marked x twII.

Closed. Corrosion test is from sprayed layer 0.2x15x30
(mm) test piece was taken and heated to 100 atm of H2S.
02The corrosion loss after being immersed in a 20% Mail aqueous solution saturated at 100 atm at 250°C for one month is 0.05n.
+m/y or less is marked O, 0.05mIII/
Those whose corrosion loss exceeded y were marked with an X.

In Table 2, Comparative Examples No. 8 and 10 had sprayed layers formed under reduced pressure, but no hot working was performed, whereas Comparative Example No. 9 was hot worked, but the amount of hot working was 5.
%, the pores in the sprayed layer have not completely disappeared, resulting in poor corrosion resistance. Also, comparative example No.
In Nos. 1 to 12, since the sprayed layer was formed under atmospheric pressure, cracks were generated on the surface of the sprayed layer by normal rolling, making it impossible to produce a surface-coated metal.

On the other hand, the samples of Examples Nos. 1 to 7 manufactured according to the present invention are excellent in both the adhesion strength 2 bending test and the corrosion test. Further, from the cross-sectional microscopic observation results, it was confirmed that there were no pores in the sprayed layer and that a uniform and good bonding interface was obtained. Furthermore, present invention example No. 6
It was confirmed that it also has excellent wear resistance.

(Effects of the Invention) As described above, according to the present invention, it is possible to produce a surface-coated metal having excellent properties, and it greatly contributes to the development of industry.

[Brief explanation of the drawing]

FIG. 11, FIG. 2, and FIG. 3 are all cross-sectional views showing the procedure for laminating processed materials according to the method of the present invention. 1... Slab, 2... Thermal spray layer, 3... Hollow billet.

Claims (4)

[Claims] (1) After forming a sprayed metal layer on the surface of a metal material under reduced pressure, hot working is performed to reduce the thickness of the sprayed layer by 5% or more while applying compressive force at least in the thickness direction of the sprayed layer. 1. A method for producing a surface-coated metal, the method comprising: (2) The method according to claim 1, wherein the hot working means is hot rolling. (3) The method according to claim 1, wherein the hot working means is hot extrusion. (4) The method according to claim 1, 2 or 3, wherein the metal spray layer is formed on both sides of the metal material.