JPS6067651A - Metal material having graphite fluoride penetrated layer and preparation thereof - Google Patents

Abstract

PURPOSE:To suppress corrosion and scale adhesion, by forming a graphite fluoride penetrated layer with a predetermined thickness to the surface of a metal material. CONSTITUTION:For example, a metal material is embedded in a mixture of hard charcoal particles and a solid carburizing agent and heated for a prescribed time to form a carbide penetrated layer to the surface of the metal material. This carburized metal material is heated at 370-570 deg.C in a fluorine gas stream. By this method, the corrosion of the metal material is prevented and scale adhesion to the metal material is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a metal material on which a permeated layer of graphite fluoride is formed and a method for manufacturing the same. It consists in restraining what one does.

Conventionally, metal materials such as rolled steel, copper strips, round bars, steel pipes, and iron plates have been subject to gradual corrosion and collapse depending on the environment in which they are used. As a phenomenon other than the above, the solute in the solution precipitates and comes to cover the material surface.

For example, over time, calcium carbonate, silica, and other inorganic components polymerize and precipitate from service water on the surface of the metal material that constitutes the heat transfer surface of a boiler or heat exchanger, resulting in a decrease in heat transfer efficiency.

Although scale inhibitors have been developed as a means to prevent this, no definitive agent has been found to date to prevent the formation and adhesion of silica scale.

Furthermore, although much research has been conducted on the quality of metal materials, it has been concluded that material selection alone cannot provide a complete countermeasure. In addition, metal materials whose surfaces are coated with fluororesins such as tetrafluoroethylene are known, and although these fluororesin coatings are highly effective as a means of preventing scaling and corrosion, It has the disadvantage that it peels off from the surface of the metal material and is eroded from the peeled part.

The present invention provides a metal material that has corrosion resistance and can prevent scale adhesion by having the structure described in the claims, and a method for manufacturing the same.

That is, the invention of Application No. 1 is a metal material having a permeation layer of graphite fluoride, characterized in that a permeation layer of graphite fluoride with a thickness of 10 to 300 μm is formed on the surface;
The invention involves carburizing a metal material in advance by a conventional method to form a carbide permeation layer on the surface, and then heat-treating the metal material at a temperature of 370 to 570°C in a fluorine gas stream. Metal materials that have a permeated layer of graphite fluoride on their surfaces include rolled steel strips, copper strips, round steel bars,
These metal materials, such as steel pipes and iron plates, pig iron, cast iron, and iron plates, are first subjected to carburizing treatment.

This soaking and ashing treatment may be carried out by a conventional carburizing method. That is, hard charcoal particles such as oak charcoal, chrysanthemum charcoal, and pine charcoal contain Na2 Cog,
Mix 10-3'0% of a solid carburizing agent such as Ba2COs, put the carburizing agent in an iron carburizing box, embed the metal material in it, make it airtight, and heat it in a heating furnace for a predetermined period of time to carburize it. Solid carburizing method or natural gas, methane, ethane,
A carbide layer is formed on the surface of the metal material by a gas carburizing method in which a gas such as propane is passed through a carburizing furnace and the metal material is heated and carburized in the air flow. Next, fluorine gas or pressurized fluorine gas is passed through the metal material having the carbide layer on the surface obtained by the above operation at a temperature of 370 to 620°C in a heating furnace, and the carbide layer is fluorinated by heating for a predetermined period of time. It can be made into a layer of fluorinated graphite (CF→-n), with 10 to 300 μm of fluorinated graphite on the surface of the metal material.
rn osmotic diffusion is obtained.

In the layer of fluorinated graphite formed on the surface of the metal material in this way, the carburized layer is gradually transformed into a fluorinated graphite layer to form a layer of fluorinated graphite, and some or most of the carburized layer remains intact with defects. It is characterized by being a layer of fluorinated graphite with a small amount of carbon dioxide, and forms a kind of diffusion permeation layer, so there is no problem with adhesion, unlike when a separate coating is applied.

However, if the thickness of the fluorinated graphite layer exceeds 300 μm, peeling phenomenon tends to occur from weak bonds between the fluorinated graphite layers, so it is disadvantageous to form a fluorinated graphite layer with a thickness of 300 μm or more. Furthermore, if the thickness is less than 10 μm, it is practically difficult to form a complete layer of fluorinated graphite without defects.

Therefore, as a first step, the conditions for carburizing a metal material and forming a carburized layer on the metal material are generally 800
1 by heat treatment at ~950℃ for 1 hour or more.
A carburized layer is formed by penetrating and diffusing into the surface of the metal material to a thickness of about 0 to 300 μm.Then, in the second step, this is heated in a heating furnace at a temperature of 370 to 570°C in a fluorine gas stream to carburize it. The layer gradually becomes a layer of fluorinated graphite.

The heating conditions for forming the carburized layer into a layer of graphite heptafluoride were set at 370~$1°C because there are two types of #A fluoride lead, and the carbon represented by C For example, there are many types such as natural graphite, 9 artificial graphites, 1 petroleum coke, activated carbon, charcoal, and carbon black, each of which has a different structure, so the optimal reaction conditions also differ.

nc + −Fz → (CF)n −−=・(1)2
nc + '-Fx → (CxF)n --- (2) Equation (1) proceeds at a temperature of 400° C. or higher, and Equation (2) proceeds at a temperature of 400° C. or lower under the condition that the fluorine pressure is not too low.

The material of the present invention may be either type (1) or (2) of fluorinated graphite, but in order to produce fluorinated graphite industrially and economically, it must be heated to a temperature of 370°C or higher. (CF)n is necessary, and (CF)n is (C2F) at 630°C.
) Since decomposition starts at 1600°C, the burial temperature for heating and moxibustion is set at 570°C.

By heating in a reactor within the above temperature range for about 30 minutes to 4 hours, it is possible to obtain a gold-chocolate material in which the carburized layer is a layer of fluorinated graphite having an arbitrary thickness.

The metal material obtained in the above manner is stable even in an oxidizing or reducing atmosphere, and is thermally stable.

It is chemically stable and has good adhesion with the metal material, making it useful as a corrosion-resistant material.In particular, heat exchangers using the metal material on the heat transfer surface are suitable for heat exchangers such as geothermal hot water. It has a high salt concentration, does not increase flow resistance due to calcium-based or silica-based scale adhesion, and does not require maintenance for a long period of time.
Hot water pipe.

If 7-liquor is generated on valves as the temperature of hot water decreases, scale adhesion can also be prevented on these valves.

Furthermore, it is possible to suppress the adhesion of calcium-based scale that occurs deep in the well.

In addition, as an additional effect of the present invention, since the metal material of the present invention is used for the sliding parts I of compressors, cylinders, pistons, shafts, bearings, etc., it does not require lubricant, but is free from oil, water, and water. It has the advantage that there is no adhesion of dust, etc., and the sliding surface is always kept clean, making it extremely useful for maintenance.

Furthermore, when used in the chute portion of the tank, the angle of rest of the powder becomes zero, and the powder can be taken out smoothly.

The present invention will be explained below with reference to Examples.

Example 5 Cr22 round bar (,19y3X 100) f: 70% coke + 20% Bacos, NagCO3
Embedded in carburized material consisting of 10% and sealed in a carburized box.
It was heated at 850° C. for 3 hours in an electric resistance furnace.

The hypereutectoid structure (hypereutectoid carburized layer) was approximately 300 tim deep.

Next, this round bar was placed in a horizontal cylindrical rotating fluorination container made of nickel, and heated at 550 to 600°C and under a fluorine pressure of 760 m
When heated at mHg for 2 hours, a round steel bar was obtained in which a layer of fluorinated graphite was formed up to about 10 μm from the surface of the graphite and carbide layer of the carburized layer.

When this round steel bar was immersed in a geothermal hot water pipeline at 117°C for three months and taken out, there was no peeling of the fluorinated graphite layer and almost no scale adhesion. Meanwhile, Ti immersed for a while
183 for plate test piece (30 x 50 x 0.5')
mg scale was attached.

Claims (1)

[Claims] 91. A metal material having a permeated layer of graphite fluoride, characterized in that a permeated layer of graphite fluoride with a thickness of 10 to 300 μm is formed on the surface. 2. Carburize the metal material in advance by a conventional method,
After forming a carbide permeation layer on the surface, the metal material is subjected to heat treatment at a temperature of 370 to 570°C in a fluorine gas stream. Production method.