JPS6263679A - Treatment of inside of tubular metallic material - Google Patents

Abstract

PURPOSE:To make a flux for etching unnecessary and to prevent the corrosion of the inside of a tubular metallic material by sticking alloy powder having a lower m.p. than the material to the inside of the material and by heat treating the material in an atmosphere of a reducing gas. CONSTITUTION:Metallic powder having a lower m.p. than a tubular metallic material to be treated is stuck to the inside of the material. The powder may be mixed with a liq. substance which is decomposed and volatilized during heat treatment before the sticking. The material having the stuck powder is heat treated at a temp. between the m.p. of the powder and the m.p. of the material in an atmosphere of a reducing gas.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Fields] The present invention relates to a treatment method for coating the inner surfaces of various metal pipe materials with different metals, such as water and sewage water passage,
Improving the corrosion resistance of the inner surfaces of supply pipes for liquids such as hot water and oil, supply pipes for gas bodies such as fuel gas, heat transfer pipes that utilize heat transfer inside and outside the pipe, pressure transfer pipes, etc., and improving the strength of pipe materials. It can be used as a processing method for

[Prior art and its problems] Conventional methods for coating the inner surface of pipe materials include the following methods, but each method has the following drawbacks.

(1) Method using extrusion method This method uses a composite extrusion billet in which an inner layer and an outer layer are combined in advance, and the inner surface of the tube is coated with dissimilar metals by extrusion molding to form a composite tube (double tube). This method is disadvantageous in terms of manufacturing cost because the manufacturing process includes a composite billet manufacturing process, an extrusion process, and an ignition process for reducing the diameter according to a predetermined method. Furthermore, if the metal covering the inner surface is a low melting point metal, it may melt due to the heat of deformation during extrusion molding, making it impossible to obtain a normal composite tube. Furthermore, if the difference in deformation resistance during extrusion between the tube base material and the coating material is large, the extrusion is normal.
There are disadvantages such as difficulty in flame forming.

(Z Inner surface plating method) This method covers the inner surface of the tube.Although it is possible to cover the inner surface of the tube by electroplating the inner surface of the tube by pouring a metal coating solution, plating is necessary for treating long tube materials. The management of liquid concentration and current density becomes complicated, making it unsuitable for industrial production.

(3) Welding method This method seam-welds the pipe material and the sheathing material into a tubular shape with the sheathing material side inside. Furthermore, the coating metal is exposed on the outer surface of the tube at the seam weld, making it impossible to obtain a uniform coating layer on the inner surface of the tube.

[Object of the Invention] An object of the present invention is to eliminate the drawbacks of the prior art described above and to provide a processing method with excellent industrial productivity.

[Approximate number of inventions 1] In order to achieve the above object, the present invention uses a metal to be coated in a powder state, and coats the inner surface of a tube material in a molten state in a reducing gas environment.

As metal pipe materials, Cu, Af, "e", "lower i", MQ, Ni
, Nb, Co, ΔΩ, Hf, "'l-a, Pt, V, (
When targeting pure metals such as r, Zr, etc. or alloys whose main components are these, the metals that are most effective for metal powder binding are:
AJ! , Cu, Zn, Mq, AQ, Cd, In, Sn
, Sb, Au, Pb, and other pure metals, as well as alloys containing these as main components. These metal powders are preferably used in the form of a mixture with a liquid substance that decomposes and vaporizes at the temperature during heat treatment because it can be easily applied to the inner surface of the tube material.

The heating temperature is higher than the temperature at which the metal powder melts.

The upper limit should theoretically be below the melting point of the tube H, but in practice it is preferably about 50 m lower than the melting point of the tube material. The atmosphere must have the ability to reduce the oxides on the inner surface of the tube material and the surface of the metal powder to a metallic state when the metal powder is melted, and must contain hydrogen, carbon fluoride, ammonia-modified gas, and metal gases (metals with a stronger affinity for oxygen than the tube material). ) or a mixture of these with an inert gas is suitable.

By heating under such conditions, a metal coating is formed on the inner surface, and a diffusion layer is also partially formed. Depending on the heat treatment conditions, diffusion is promoted and an alloy layer with the fabric is formed on the surface. A separate heating step may be added to promote diffusion.

Depending on the condition of the inner surface of the tube, when the metal powder melts, there is a risk that it will shift in one direction due to gravity. In order to prevent this, it is desirable to provide a plurality of grooves or projections extending in the longitudinal direction of the tube on the inner surface of the tube. It is desirable that the grooves have a depth of 0.01 to 5 m and a width of 0.03 to 10 m.

[Embodiments of the invention] The present invention will be explained in detail below.

Example 1 On the inner surface of a copper tube with an outer diameter of 25%, a wall thickness of 1#, and a length of 25#,
50 mesh of Zn powder was sprayed on) and the steel pipe was heated at 550°C in a mixed gas consisting of 3% CO, 2% Hz, 20% CO2, and the balance Nz.
By heating for 0 minutes, a thickness of 15 μm (0,
A C1,1-Zn alloy layer of 0.015 m> was formed.

Example 2 The inner surface of a steel pipe with an outer diameter of 161M1, a wall thickness of 0.7m, and a length of 50m has a depth of 0.051rvIl and a width of 0.05#! Grooves were installed continuously in the longitudinal direction of the pipe at a pitch of 0.05 m, and a paste made by mixing 250 mesh of Sn powder and flammable lubricant polybutene was applied almost uniformly to the inner surface of the pipe. It was applied to. After that, this tube material was heated to Hz: 80
%, balance N2 at 800'C for 30 minutes. As a result, 50% of the Cu-3m alloy layer was formed on the inner surface of the copper tube.
μm (0,05#1) was formed.

Example 3 After spraying 100 mesh of A1 powder on the inner surface of an iron pipe with an outer diameter of 15s++, a wall thickness of 1.2#I, and a length of 10m, the iron pipe was heated to 700m in the same gas as in Example 2. 'C
Heat 7JO for 115 minutes. As a result, the inner surface of the tube has a thickness of 5
A μm thick A coating layer was formed.

[Effects of the Invention] Since the present invention is a method of coating the inner surface of a pipe material by attaching metal powder and heat-treating it in a reducing gas atmosphere, corrosive flux is not indigo and its residue can be removed. No additional work is required, there is no need to worry about internal corrosion due to insufficient removal of flux residue, and reliability can be increased.

Furthermore, the method according to the present invention is suitable for industrial production because the inner surface of thin tubes and long tubes can be easily treated.

Claims (3)

[Claims] (1) After attaching metal powder with a lower melting point than the metal tube material to the inner surface of the tube material, the tube material is heat-treated in a reducing gas atmosphere at a temperature higher than the melting point of the metal powder and lower than the melting point of the tube material. A method for treating the inner surface of metal pipe material. (2) The method according to item 1 above, wherein the metal powder is attached to the inner surface of the pipe material in the form of a mixture with a liquid substance that decomposes and vaporizes during heat treatment. (3) The method according to item 1 or 2, wherein the tube material has a plurality of grooves or protrusions extending in the longitudinal direction of the tube on the inner surface.