JPS62149887A - Surface coated steel pipe having superior corrosion resistance and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture a surface coated steel pipe having superior corrosion resistance and bendability at a low cost by forming a brass coating layer of a specified thickness having a specified composition as a top layer on one side or both sides of a steel pipe. CONSTITUTION:A coating layer of 3-1,000mum thickness contg., by weight, 40-70% Cu, 15-50% Zn, 2-15% Al and 0.1-3% Mn as essential components is formed as a a top layer on one side or both sides of a steel pipe by thermal spraying or spray coating. The coating layer may be heat treated as required.

Description

[Detailed Description of the Invention] <Object of the Invention> Industrial Field of Application The present invention relates to a surface-coated steel pipe with excellent corrosion resistance, and more specifically, a surface-coated steel pipe with extremely excellent corrosion resistance and low cost, and a method for manufacturing the same. Pertains to.

Conventional technology In recent years, the environments in which steel pipes are used have diversified, and the fields of application are vast, such as raw material or fuel gas and liquid transportation piping, seawater cooling piping, steam piping, and water and sewage piping. It is necessary to pay sufficient attention to the corrosion resistance of these piping materials.
Steel pipes made from low-alloy steel or Kodai Kinsei, which are suitable for the usage environment and characteristics, have been used.

However, the manufacturing efficiency of steel pipes made of low-alloy steel and high-alloy steel is much lower than that of Jintong steel pipes, and the material costs are high, making them expensive.

Under these circumstances, a method for producing inexpensive and high quality surface wave 1 steel pipes has been proposed in Machima 115747 Publication. This method involves thermally spraying N+, Or, or an alloy of these onto the surface of the steel pipe. After forming the covering layer,
Heat treatment is performed at a heating temperature of 800° C. or higher to improve adhesion through mutual diffusion at the interface between the mouth coating and the material, thereby improving bending workability and corrosion resistance. However, in this method, the porosity of the thermally sprayed coating layer hardly changes even if it is heated at 800 to 1200°C because N1, Or, or Ni-Cr alloy has a high melting point, and the porosity of the thermally sprayed coating layer is usually 4 to 10% as sprayed. The porosity is close to this value even after heating.

This may allow transport fluids or gases to enter the pores of the mouth and accelerate corrosion.

Problems to be Solved by the Invention The present invention aims to solve these problems,
Specifically, the purpose is to provide a dense surface-coated steel pipe with excellent corrosion resistance and bending workability at a low cost.

<Structure of the Invention> Means for Solving the Problems and Their Effects The present invention provides a method for solving the problems and its operation.
・70 heavy lifting I? 6 (hereinafter simply referred to as %. lcu, 15
~50%2n, 2・~15%Al, 0.1・”3%un
The present invention comprises a surface-coated steel pipe with excellent corrosion resistance, and a method for manufacturing the same, characterized in that a coating of brass having a thickness of 3 to 1000 μm is thermally sprayed or spray-coated and then heat-treated.

As a result of many studies, the present inventors have discovered Carbon Tears, M.

A coating m is formed on both or one of the inner and outer surfaces of a steel pipe made of steel, Cr-Mo steel, stainless steel, etc., and the outermost layer of the coating layer contains 40 to 70% Cu and 15 to 50% 7.
Surface-coated steel pipes made of brass containing n, 2 to 15% Mn, and 0.1 to 3% Mn as essential components and having a coating pattern with a thickness of 3 to 1000μ have excellent corrosion resistance and bending workability. They discovered this and completed the present invention. The coating layer can be formed on the inner and/or outer surface of the steel pipe, and in the case of A, a single layer coating of brass, or
It is also possible to form a base layer of metal or ceramic and then coat the outermost layer with brass. This brass has an appropriate range of ingredients to improve corrosion resistance and bending workability.

The appropriate component range will be explained below.

CIJ: The content range of Cu is preferably 40% to 70%. Cu is 40%
If it is less than 70%, bending workability deteriorates and cracks occur in the NH material, while if it exceeds 70%, bending workability is good, but seawater corrosion resistance is deteriorated, which is not preferable.

ln: The component range of 2n is preferably 15% to 50%. 7 mouths is 15%
If it is less than 50%, the seawater corrosion resistance will deteriorate.
When the amount is more than 1, ductility decreases and bending workability deteriorates.

8L: The preferred Al component range is 2% to 15%. If the Al content is less than 2%, it will be easily corroded, and if it is more than 15%, the ductility will decrease, the bending workability will deteriorate, and cracks will occur in the coating pattern.

Mn= The component range of Mn is preferably o,i% to 3%. 1Jnff0
．． If it is less than 1%, the effect of improving corrosion resistance is small, and 3%
If the amount is more than that, it will harden and the bending ductility will deteriorate.

The above component ranges are essential conditions, but in addition, Sn,
Si, Ni, P%Fe, etc. can be added. In particular, Sn further improves corrosion resistance, so 5
% or less, $1 is effective when added in a range of 1% or less to prevent Zn evaporation.

A coating layer is formed on one or both sides of the steel pipe using brass having such a composition, and the thickness thereof is 3 to 1000 μm.
The range is appropriate. If it is less than 3μ, if the coating pattern is physically damaged, cracks may occur in this area, which may deteriorate the corrosion resistance. On the other hand, if it is thicker than 1000 μm, it is not preferable because it may peel off from the interface between the steel pipe and the coating after one bending process.

The surface 9Q steel pipe having the coating pattern shown above has excellent corrosion resistance and bending resistance, but the method for forming the coating layer must be one that is suitable for large-scale production and can be carried out at low cost.

For this purpose, brass powder and wire are sprayed using plasma spraying.
The coating can be carried out by arc melting, gas spraying, gas combustion melting, etc., or by spray coating with a coating agent in which the above powder is mixed in a solvent with compressed gas or air. The coating layer formed in this way is porous and has poor adhesion at the interface with the steel pipe or the base, so after forming this coating layer, it is necessary to heat it with IJD heat using arc or flame, high frequency heating, a heat treatment furnace, etc. By performing the treatment, a coating layer with excellent density and adhesion can be formed.

Example This will be further explained below with reference to Examples.

Example 1゜Outer diameter 25.4 mm, thickness 3.5 mm, chemical composition 0゜14
%C50゜30%Si, 0.50%Mn, 0,014%
After plasting the outer surface of a P, 0,007% S steel pipe with Al2O3 powder, 20-100 μ diameter powder of brass solder having the composition shown in Table 1 was applied to a thickness of 30-4 μm by plasma spraying.
A coating layer of 0Ii was formed, and then a heat treatment was performed using a plasma arc so that the surface temperature of the coating became 850°C.

Table 1 After a surface-coated steel pipe was formed in this manner, the surface properties of the coating layer were observed when this steel pipe was bent at a radius of 20 mm. As shown in Table 2, the fill material of the present invention exhibited good ductility and no cracking, but cracks occurred in Comparative Examples F and H.

Table 2 Example 2゜Outer diameter: 356 mm, thickness: G: 3 mm, chemical composition: 0.15
%G, 0.32%Si, 1.26%Mn, 0.016%
Both the inner and outer surfaces of the P, 0.008% S steel pipe are coated with Al2O.
After Plast treatment with 3 powders, a coating layer with a thickness of 125μ was formed using the brass brazing powder of Comparative Example G, which had excellent bending ductility in Table 2, and B of the present invention, respectively, by plasma spraying, and then 800W It was heated by irradiating it with laser light.

The inner and outer surfaces of the steel pipe treated in this way are 3% N
It was immersed in an aCl solution and the time of rust formation was observed. As shown in Table 3, the oral results are as follows: Inventive Example 8 is about 3 Comparative Example G
It turned out that there was twice as much longevity.

Table 3 <Effects of the Invention> [As explained above, the present invention provides 40 to 70% Cu, 15 to 50% In, and
2-15% A1. ．． A surface-coated steel pipe in which a coating layer of 3 to 1000 μm in thickness is formed from brass containing 0.1 to 3% Mn as an essential component, and a method for manufacturing the same, the method comprising: A surface-coated IJ4 pipe with excellent density and corrosion resistance and excellent bending workability was obtained.
It has become possible to fully respond to the increasingly diverse usage environments of recent years.

Claims (1)

[Claims] 1) The outermost layer of one or both sides of the steel pipe contains 40 to 70
wt%Cu15-50wt%Zn2-15wt%Al
A surface-coated steel pipe with excellent corrosion resistance, characterized by forming a coating layer of 3 to 1000 microns thick made of brass containing 0.1 to 3% by weight of Mn as an essential component. 2) On the outermost layer of one or both sides of the steel pipe, 40 to 70
Between molds %Cu, 15-50% by weight Zn, 2-15% by weight A
A surface coating treatment with excellent corrosion resistance characterized by thermal spraying or spray coating a coating layer made of brass with a thickness of 3 to 1000μ containing 0.1 to 3% by weight of Mn as an essential component, and then heat treatment. Method of manufacturing steel pipes.