TWI392579B - A method for manufacturing an internally polyolefin coated steel pipe - Google Patents

Description

Method for manufacturing inner-coated polyolefin steel pipe Field of invention

The present invention relates to a method for producing a steel pipe coated with a polyolefin inner surface of a polyolefin pipe on the inner surface of a steel pipe which has been galvanized on the inner surface and the outer surface.

This case claims priority based on the special request 2008-184988 filed in Japan on July 16, 2008, and its contents are referred to the case.

Background of the invention

Among the steel pipes used for water supply or drainage, a steel pipe coated with a synthetic resin pipe made of a synthetic resin such as polyolefin on the inner surface of the steel pipe to prevent corrosion of the inner surface of the steel can be used. Since the inner surface of the resin-coated steel pipe is to be used for a long period of time, it is necessary to have sufficient adhesion between the inner surface of the steel pipe and the synthetic resin pipe. In particular, in the case where the temperature or the temperature of the water fluctuates greatly and the freezing and melting occur in the pipe, if the adhesion between the synthetic resin pipe and the steel pipe covered with the inner surface is insufficient, the expansion of the synthetic resin pipe is caused. Or the peeling force caused by the shrinkage causes the synthetic resin tube to be peeled off from the steel pipe, and if the peeling progresses greatly, the pipe is blocked. Therefore, in particular, when the inner surface of the inner surface of the galvanized steel pipe is coated with a synthetic resin pipe made of a synthetic resin such as polyolefin, in order to obtain sufficient adhesion between the zinc and the synthetic resin, the steel pipe is used in advance. The method of pre-treatment of the zinc surface on the inner surface.

For example, Patent Document 1 teaches a method of performing polishing to remove and clean white rust or impurities and oil and fat components.

Further, Patent Document 2 discloses a pretreatment of a galvanized steel pipe by grinding the inner surface of the steel pipe with a wire brush to remove a pure zinc layer to expose an iron-zinc alloy layer containing 6% or more of iron, if the polyolefin pipe is coated. , the polyolefin tube is not easily peeled off in the freeze-thaw test.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] JP-A-58-87045

[Patent Document 2] PCT/JP2007/061256

Summary of invention

However, in Patent Document 1, the specific polishing method and the degree of polishing to the extent that the inner synthetic resin tube is difficult to peel off in a freeze-thaw test or the like are not disclosed at all. Further, in Patent Document 2, the specific wire brush shape, size, suitable conditions for polishing, and inspection methods after polishing are not disclosed at all.

The object of the present invention is to solve the above problems, and to provide a freeze even after repeated occurrences. In a melted environment or a state in which the polyolefin pipe is often filled with warm water, the peeling of the polyolefin pipe is still difficult to occur, and the method of manufacturing the steel pipe coated with the polyolefin having a good water-tightness is also known.

As a result of intensive research to solve the above problems, the present inventors have obtained an iron-zinc alloy layer containing 6% by mass or more of Fe between the surface of the base metal and the galvanized layer of the steel pipe base material. In the inner surface of the hot-dip galvanized steel pipe, the polyolefin is coated with the adhesive as a medium, and in the production of the inner-coated polyolefin steel pipe, in order to improve the adhesion of the polyolefin, it is necessary to contain iron of 6% by mass or more. - The zinc alloy layer is exposed, and the specific conditions of the plating of the inner surface of the hot-dip galvanized steel pipe are observed with a wire brush. The present invention has been completed based on the above findings, and the gist thereof is as follows.

(1) A method for producing a steel pipe coated with a polyolefin on the inner surface, which is an inner plating layer of a hot-dip galvanized steel pipe which has been subjected to hot-dip galvanizing on the inner surface and the outer surface by a wire brush to contain 6 mass% or more of Fe. After the iron-zinc alloy layer is exposed, and in the method for manufacturing a steel pipe coated with a polyolefin inner surface of the polyolefin tube, the wire brush is cylindrical, and is radially radiated from the central axis of the column. The steel wire is placed in a shape, and the inner surface plating layer of the steel pipe is characterized by being rotated by inserting the wire brush with the central axis as a rotating shaft and inserting the molten galvanized steel pipe.

(2) The method for producing a steel pipe coated with polyolefin on the inner surface according to (1), characterized in that the steel wire has a Vickers hardness of 500 or more.

(3) The method for producing a polyolefin-coated steel pipe according to (1) or (2), wherein the chemical composition of the steel wire is C: 0.6 to 1.2% by mass, Mn: 0.2 to 1.2% by mass, Si : 0.1 to 1.5% by mass, P: 0.05% by mass or less, S: 0.04% by mass or less, and the balance being Fe and unavoidable impurities.

(4) The method for producing a steel pipe coated with an inner surface according to any one of (1) to (3), characterized in that the surface of the steel wire is plated with brass.

(5) A method for producing a steel pipe coated with a polyolefin having an inner surface, wherein the method for producing a steel pipe coated with an inner surface of the polyolefin according to any one of (1) to (4) satisfies the following formula 1 to The condition of 5 is characteristic.

F(1): the wiping force of each wire of the wire brush

h(1): the length of the inner surface of the steel wire polished steel pipe (mm) when the wire brush advances its brush length (Lb)

Φ: the product of the total length of the wire brush grinding and the scraping force of the steel wire per unit area when the inner surface of the galvanized steel pipe is passed m times by a wire brush of N steel wires.

K: proportional coefficient

Dpi: inner diameter (mm) of molten galvanized steel pipe

Db: outer diameter of the wire brush (mm)

Lb: length of the wire brush (mm)

Dw: outer diameter (mm) of wire brush wire

Lw: wire length of wire brush (mm)

N: number of wires of the wire brush (root)

n: number of revolutions of the wire brush (r p m)

V: Feeding speed of wire brush (mm/min)

m: number of passes of the wire brush (times)

S: The area of the inner surface of the hot-dip galvanized steel pipe (mm ² ) when the wire brush advances its brush length (Lb) portion

(6) The method for producing an inner-coated polyolefin steel pipe according to any one of the items 1 to 5, characterized in that after the grinding, the metal needle having a Vickers hardness of 60 to 100 is scraped. The inner surface of the steel pipe is used to determine whether the grinding state is good or not.

(7) The method for producing a steel pipe coated with an inner surface according to the item (6), characterized in that the metal needle is made of copper.

According to the present invention, the inner surface of the hot-dip galvanized steel pipe is polished by a wire brush to remove the pure zinc layer, since the iron-zinc alloy layer containing 6 mass% or more of Fe can be surely exposed, so that the polished surface and the polyolefin tube are The adhesion is stabilized and strengthened, and even in the pipeline in which freezing and melting occurs, the inner surface of the polyolefin tube which is not easily peeled off and the polyolefin-coated steel pipe can be industrially produced.

Simple illustration

[Fig. 1] is a cross-sectional view of a hot-dip galvanized steel pipe and a cross-sectional view and a side view of the wire brush.

[Fig. 2] is a schematic diagram showing the relationship between the length h(1) and the brush length Lb of the inner surface of a steel wire-polished hot-dip galvanized steel pipe when the wire brush advances the brush length Lb portion.

The best form for implementing the invention

The inventors of the present invention have produced a steel pipe coated with a polyolefin inner surface of a polyolefin pipe with an adhesive as a medium on the inner surface of the hot-dip galvanized steel pipe, and obtained the inner surface of the hot-dip galvanized steel pipe by a wire brush. The plating layer is subjected to specific conditions in which an iron-zinc alloy layer containing 6% by mass or more of Fe is exposed.

In order to expose the iron-zinc alloy layer containing 6 mass% or more of Fe on the inner surface of the hot-dip galvanized steel pipe, it is necessary to uniformly and surely grind the microscopic irregularities on the inner surface of the hot-dip galvanized steel pipe. Therefore, as shown in Fig. 1, the wire can be transmitted through a cylindrical wire brush, and the steel wire is radially arranged from the central axis of the cylinder in a radial direction, and the wire brush edge is formed by the central axis. The method of inserting the molten galvanized steel pipe into the molten galvanized steel pipe for rotating the shaft is achieved by grinding the inner surface of the molten galvanized steel pipe. This is because the wire of the wire brush conforms to the microscopic irregularities on the inner surface of the hot-dip galvanized steel pipe, and is uniformly and surely ground.

If the Vickers hardness of the aforementioned steel wire is 500 or more, the polishing efficiency is good. This is because if the difference between the Vickers hardness of the steel wire and the Vickers hardness of the zinc is large, the polishing efficiency of zinc is good.

The chemical composition of the steel wire is C: 0.6 to 1.2% by mass, Mn: 0.2 to 1.2% by mass, Si: 0.1 to 1.5% by mass, P: 0.05% by mass or less, S: 0.04% by mass, and the balance is Fe and inevitable The composition of the impurities is preferred. When the lower limit of C, Si, and Mn is less than the above value, the necessary high hardness cannot be obtained, and if the upper limit value exceeds the above value, the toughness is lowered, so these values are set. In addition, when the upper limit of P and S exceeds the above value, embrittlement or the like is caused by segregation, and these upper limit values are set. It is important that the high hardness and the fracture resistance are both necessary for the wire brush, and if it is within this range, such as the inclusion of other elements such as trace amounts, the invention will not be impaired.

The steel wire should be plated with brass as a rust preventive means for the aforementioned steel wire. This is to prevent rust from entering the inner surface of the molten galvanized steel pipe. When the inner surface of the hot-dip galvanized steel pipe is polished under the conditions of the following formulas 1 to 5, an iron-zinc alloy layer containing 6 mass% or more of Fe can be exposed.

The symbols in the above formula are defined as follows, and the partial symbols are also shown in the first and second figures.

F(1): the wiping force of each wire of the wire brush

h(1): the length of the inner surface of the steel wire polished steel pipe (mm) when the wire brush advances its brush length (Lb)

Φ: the product of the total length of the wire brush grinding and the scraping force of the steel wire per unit area when the inner surface of the galvanized steel pipe is melted by the wire brush of the N steel wire m times.

K: proportional coefficient

Dpi: inner diameter (mm) of molten galvanized steel pipe

Db: outer diameter of the wire brush (mm)

Lb: length of the wire brush (mm)

Dw: outer diameter of the wire of the wire brush (mm)

Lw: length of wire of wire brush (mm)

N: the number of wires of the wire brush (root)

n: number of revolutions of the wire brush (r p m)

V: Feeding speed of wire brush (mm/min)

m: number of passes of the wire brush (times)

S: The area of the wire brush grinding the molten galvanized steel pipe (mm ² ) when the wire brush advances its brush length (Lb) portion

The force F(1) of the inner surface of the hot-dip galvanized steel pipe scraped by one wire of the wire brush is as shown in Formula 1.

When the wire brush advances only the brush length Lb, the length h(1) of the inner surface of the one wire-polished molten galvanized steel pipe of the wire brush is as shown in Formula 2.

When the wire brush advances only the brush length Lb, the area S of the inner surface of the wire brush polished molten galvanized steel pipe is as shown in Formula 3.

When the inner surface of the hot-dip galvanized steel pipe is passed through the inner surface of the hot-dip galvanized steel pipe m times, the product of the total length of the wire grinding of the wire brush per unit area and the scraping force of the steel wire is as shown in the following formula 4.

As shown in the first embodiment to the seventh embodiment, it was confirmed that the φ value of the formula 4 is 2.6 or more and 85.4 or less, and the iron-zinc alloy layer containing 6 mass% or more of Fe is exposed, and the polished surface and the polyolefin tube are ensured. The stability of stability. In other words, in the case where the φ value in the formula 4 is less than the polishing condition of 2.6, even if the inner surface of the hot-dip galvanized steel pipe is polished by a wire brush, the pure zinc layer remains, and the iron-zinc alloy layer containing 6 mass% or more of Fe is contained. The exposure becomes insufficient. When the φ value of the formula 4 exceeds the polishing condition of 85.4, the inner surface of the wire brush and the galvanized steel pipe becomes high temperature due to frictional heat generation, the polishing efficiency is remarkably lowered, and the pure zinc layer remains, and the iron-zinc containing 6 mass% or more of Fe is contained. The exposure of the alloy layer is insufficient.

In addition, the inventors of the present invention paid attention to the difference in Vickers hardness between the pure zinc layer and the iron-zinc alloy layer of the surface of the hot-dip galvanized layer, and used it to judge the iron containing 6 mass% or more of Fe by the wire brush. - Examination of the condition in which the zinc alloy layer is exposed on the inner surface of the molten galvanized steel pipe.

That is, since the Vickers hardness of the pure zinc layer is less than 60, and the Vickers hardness of the iron-zinc alloy layer containing 6% by mass or more of Fe exceeds 100, the Vickers hardness in the range of 60 to 100 is utilized. The metal needle is scraped and inspected by the inner surface of the molten galvanized steel pipe polished by the wire brush. When the polishing is insufficient, since a pure zinc layer which is softer than the Vickers hardness of the metal needle remains, the groove can be formed on the surface of the inner surface of the galvanized steel pipe when the surface is scratched by the inspection needle. On the other hand, when the polishing is sufficient, the iron-zinc alloy layer containing Fe of 6 mass% or more hard than the Vickers hardness of the metal needle is exposed, so if the surface is scratched with the metal needle, the front end of the metal needle The metal powder to be cut off is attached to the surface of the iron-zinc alloy layer containing 6% by mass or more of Fe.

Metals with a Vickers hardness of 60 to 100 are known, including aluminum, copper, and brass. Since the color of aluminum and galvanized is the same as silver, it is difficult to judge aluminum and zinc by visual observation, and it is not suitable as a material for the metal needle for inspection. Copper, brass and galvanized tones are different and are suitable as materials for metal needles for inspection. However, because brass has a difference in the mixing ratio of copper and zinc depending on the source, Vickers hardness is prone to high and low, so it is most suitable to check whether the source has a certain Vickers hardness. Material made of metal needles.

[Examples]

An embodiment of the present invention will be described. The conditions of the examples are examples of conditions employed to confirm the implementation possibilities and effects of the present invention, and the present invention is not limited to these conditions. The present invention can adopt various conditions without departing from the gist of the present invention and achieving the object of the present invention.

(Example 1)

The inner surface and the outer surface of the steel pipe (SGP100A × 6000 mm length) were subjected to hot-dip galvanizing to obtain a galvanized steel pipe. At this time, the content of aluminum contained in the galvanization was 0.01% by mass.

The inner surface of the galvanized steel pipe is formed into a cylindrical shape with an outer diameter larger than the inner diameter of the galvanized steel pipe, and the steel wire is radially arranged from the central axis of the cylinder. The wire brush rotates and is inserted into the galvanized steel pipe to grind the inner surface of the galvanizing.

The wire brush wire used in the experiment has a Vickers hardness of 500, and the chemical composition of the wire is C: 0.81% by mass, Mn: 0.47 mass%, Si: 0.20 mass%, P: 0.05 mass%, S: 0.04 quality%.

The grinding conditions are shown in Table 1. In the present embodiment, the feed rate of the wire brush was changed, and 10 sets of molten galvanized steel pipes were internally ground for each type of reference, and a total of five standards were implemented.

The surface temperature of the wire brush shaft was measured immediately after the inner surface was ground and the first and the tenth branch were examined to investigate the frictional heat.

Use a copper metal needle to scrape the inner surface of the inner surface of the galvanized steel pipe and check whether the grinding condition is good or not.

Next, a diameter of the galvanized steel pipe was slightly smaller than that of the galvanized steel pipe, and a high-density polyethylene pipe of maleic anhydride-modified polyethylene having a thickness of 100 μm was laminated on the outer surface. The high density polyethylene has a thickness of 2.0 mm and a melting point of 125 °C.

Insert a high-density polyethylene pipe into the inside of the internally galvanized steel pipe, cover it at both ends, press air inside the high-density polyethylene pipe and seal it, then heat it to 160 ° C in a heating furnace. The high density polyethylene tube is melted and pressed against the inner surface of the galvanized steel pipe.

Then, the galvanized pipe was taken out from the heating furnace to be cooled, and at the time when the temperature became 70 ° C, the sealed air was taken out to obtain a galvanized steel pipe (the steel pipe a of the present invention) having the inner surface covered with the high-density polyethylene pipe.

After the steel pipe a of the present invention was cut, the cross section was polished and observed with an optical microscope, and a freeze-thaw test and a warm water immersion test were carried out.

When observing with an optical microscope, a 20 mm wide circumferential section was taken as a test piece, and after re-polishing the section by resin embedding, the galvanized layer was etched with a 3% nitric acid-alcohol solution, and galvanized was observed with an optical microscope. In the layer, it was investigated whether or not the iron-zinc alloy layer containing 6% by mass or more of Fe was exposed to the outermost layer.

In the freeze-thaw test, a test piece obtained by cutting into a length of 150 mm is immersed in water in a state of about 1/3 of the length in a container filled with tap water, and is placed in a low-temperature tank at -10 ° C together with the container to be frozen. After an hour, the freeze-thaw operation in which the thawing was performed in a high-temperature tank at 60 ° C for 1 hour was repeated for one cycle, and 100 cycles were repeated.

In the warm water immersion test, the test piece obtained by cutting into a length of 150 mm was immersed in a container containing tap water, placed in a thermostat bath at 40 ° C together with the container, and left for 3 months.

After the freeze-thaw test and the warm water immersion test, the test piece was investigated for the peeling of the high-density polyethylene pipe.

According to Table 1, only the case where the φ value of Formula 4 falls within the range of the above formula 5, in the inspection by the metal needle made of copper, the case where the surface of the ground galvanized steel pipe has copper adhesion is confirmed. In the observation of the cross section of the galvanized layer by a microscope, it was confirmed that the iron-zinc alloy layer containing 6 mass% or more of Fe was exposed to the outermost layer. In addition, in the results of the freeze-thaw test and the warm water immersion test, it was also found that the polyethylene pipe was not peeled off.

Friction and heat generation of the wire brush In all of the five types of standards, the surface temperature of the wire brush shaft was measured immediately after the first and tenth grindings, and the result was less than 150 ° C, and the polishing efficiency was good.

(Example 2)

The inner surface and the outer surface of the steel pipe (SGP100A × 6000 mm length) were subjected to hot-dip galvanizing to obtain a galvanized steel pipe. At this time, the content of aluminum contained in the galvanization was 0.01% by mass.

The inner surface of the galvanized steel pipe is formed into a cylindrical shape with an outer diameter larger than the inner diameter of the galvanized steel pipe, and the steel wire is radially arranged from the central axis of the cylinder. The wire brush rotates and is inserted into the galvanized steel pipe to grind the inner surface of the galvanizing.

The wire brush wire used in the experiment has a Vickers hardness of 500, and the chemical composition of the wire is C: 0.81% by mass, Mn: 0.47 mass%, Si: 0.20 mass%, P: 0.05 mass%, S: 0.04 quality%.

The grinding conditions are shown in Table 2. In the present embodiment, the number of passes of the wire brush was changed, and 10 sets of galvanized steel pipes were ground-polished for each type of reference, and five types of standards were collectively implemented.

The surface temperature of the wire brush shaft was measured immediately after the inner surface was ground and the first and the tenth branch were examined to investigate the frictional heat.

Scratch the inner surface of the inner surface of the galvanized steel pipe with a copper metal needle to check whether the grinding state is good or not.

Next, a diameter slightly smaller than the inner diameter of the galvanized steel pipe was prepared, and a high-density polyethylene pipe of maleic anhydride-modified polyethylene having a thickness of 100 μm was laminated on the outer surface. The high density polyethylene has a thickness of 2.0 mm and a melting point of 125 °C.

Insert a high-density polyethylene pipe into the inside of the internally ground galvanized steel pipe, cover at both ends, press air inside the high-density polyethylene pipe and seal it, and then heat it to 160 ° C in a heating furnace. The high density polyethylene pipe is melted and pressed against the inner surface of the galvanized steel pipe.

Then, the galvanized pipe is taken out from the heating furnace and cooled, and at the time when the temperature is changed to 70 ° C, the sealed air is taken out to obtain a galvanized steel pipe coated with a high-density polyethylene pipe on the inner surface (the steel pipe of the present invention) b).

After the steel pipe b of the present invention was cut, the polished section was observed by an optical microscope, and subjected to a freeze-thaw test and a warm water immersion test.

When observing with an optical microscope, a 20 mm wide circumferential section was taken as a test piece, and after re-polishing the section by resin embedding, the galvanized layer was etched with a 3% nitric acid-alcohol solution, and the galvanized layer was observed with an optical microscope. It is investigated whether or not the iron-zinc alloy layer containing 6% by mass or more of Fe is exposed to the outermost layer.

In the freeze-thaw test, a test piece obtained by cutting into a length of 150 mm is immersed in water in a state of about 1/3 of the length in a container filled with tap water, and is placed in a low-temperature tank at -10 ° C together with the container to be frozen. After 23 hours, the freeze-thaw operation of thawing was carried out in a high-temperature tank at 60 ° C for 1 hour, and the operation was repeated for 100 cycles.

In the warm water immersion test, the test piece obtained by cutting into a length of 150 mm was immersed in a container containing tap water, placed in a thermostat bath at 40 ° C together with the container, and left for 3 months.

After the freeze-thaw test and the warm water immersion test, the high-density polyethylene pipe of the test piece was investigated for peeling.

According to Table 2, in the case where the value of φ of Formula 4 exceeds 2.4, in the inspection results by the copper metal needle, it was confirmed that copper adhered to the surface of the ground galvanized steel pipe, and the optical section of the galvanized layer was observed. As a result of microscopic observation, an iron-zinc alloy layer containing 6 mass% or more of Fe was exposed to the outermost layer. In the results of the freeze-thaw test and the warm water immersion test, it was also found that the polyethylene pipe did not peel off.

Friction and heat generation of the wire brush In all of the five types of standards, the surface temperature of the wire brush shaft was measured immediately after the first and tenth grinding of the continuous grinding, and the result was less than 150 ° C, and the polishing efficiency was good.

It is understood that the value of φ of Equation 4 falls within the range of Equation 5 above to set the number of passes of the wire brush.

(Example 3)

The galvanized steel pipe was obtained by performing hot-dip galvanizing on the inner surface and the outer surface of the steel pipe (SGP100A × 6000 mm length). At this time, the aluminum content contained in the galvanization was 0.01% by mass.

The inner surface of the galvanized steel pipe is formed into a cylindrical shape with an outer diameter larger than the inner diameter of the galvanized steel pipe, and the steel wire is radially arranged from the central axis of the cylinder. The wire brush rotates and is inserted into the galvanized steel pipe to grind the inner surface of the galvanizing.

The wire brush wire used in the experiment has a Vickers hardness of 500, and the chemical composition of the wire is C: 0.81% by mass, Mn: 0.47 mass%, Si: 0.20 mass%, P: 0.05 mass%, S: 0.04 quality%.

The grinding conditions are shown in Table 3. In the present embodiment, the number of revolutions of the wire brush was changed, and 10 sets of hot-dip galvanized steel pipes were subjected to inner surface polishing for each type of reference, and a total of five types of standards were implemented.

The surface temperature of the wire brush shaft was measured immediately after the inner surface was ground and the first and the tenth branch were examined to investigate the frictional heat.

Scratch the inner surface of the inner surface of the galvanized steel pipe with a copper metal needle to check whether the grinding state is good or not.

Next, a diameter slightly smaller than the inner diameter of the galvanized steel pipe was prepared, and a high-density polyethylene pipe of maleic anhydride-modified polyethylene having a thickness of 100 μm was laminated on the outer surface. The high density polyethylene has a thickness of 2.0 mm and a melting point of 125 °C.

Insert the high-density polyethylene pipe into the inner surface of the galvanized steel pipe, cover both ends, press the air inside the high-density polyethylene pipe and seal it, then heat it to 160 ° C in a heating furnace to make it high. The density polyethylene tube is melted and pressed against the inner surface of the galvanized steel pipe.

Then, the zinc-coated tube was taken out from the heating furnace and cooled, and the sealed air was taken out at a temperature of 70 ° C to obtain a galvanized steel pipe coated with a high-density polyethylene pipe (the steel pipe c of the present invention) .

After cutting the steel pipe c of the present invention, the polished section was observed by an optical microscope, and subjected to a freeze-thaw test and a warm water immersion test.

In the observation with an optical microscope, a 20 mm wide circumferential section was taken as a test piece, and after re-polishing the section by resin embedding, the galvanized layer was etched with a 3% nitric acid-alcohol solution, and the plating was observed by an optical microscope. In the zinc layer, it was investigated whether or not the iron-zinc alloy layer containing 6% by mass or more of Fe was exposed to the outermost layer.

In the freeze-thaw test, a test piece obtained by cutting into a length of 150 mm is immersed in water in a state of about 1/3 of the length in a container filled with tap water, and is placed in a low-temperature tank at -10 ° C together with the container to be frozen. After 23 hours, the freeze-thaw operation in which the thawing was carried out in a high-temperature tank at 60 ° C for 1 hour was carried out for one cycle, and 100 cycles were repeated.

The warm water immersion test is a test piece obtained by cutting into a length of 150 mm, immersed in a container containing tap water, placed in a thermostat bath at 40 ° C together with the container, and left for 3 months.

After the freeze-thaw test and the warm water immersion test, the high-density polyethylene pipe of the test piece was investigated for peeling.

According to Table 3, in the case where only the value of φ of Formula 4 is within the range of the above Formula 5, it was confirmed in the inspection with a copper metal needle that copper adhered to the surface of the ground galvanized steel pipe, in the galvanized layer section. In the optical microscopic observation, it was confirmed that the iron-zinc alloy layer containing 6 mass% or more of Fe was exposed to the outermost layer. In addition, in the results of the freeze-thaw test and the warm water immersion test, it was also found that the polyethylene pipe was not peeled off.

Friction and heat generation of the wire brush In all of the five types of standards, the surface temperature of the wire brush shaft was measured immediately after the first and tenth grindings, and the result was less than 150 ° C, and the polishing efficiency was good.

(Example 4)

The galvanized steel pipe was obtained by performing hot-dip galvanizing on the inner surface and the outer surface of the steel pipe (SGP100A × 6000 mm length). At this time, the content of aluminum contained in the galvanization was 0.01% by mass.

The inner surface of the galvanized steel pipe is formed into a cylindrical shape with an outer diameter larger than the inner diameter of the galvanized steel pipe, and the steel wire is radially arranged from the central axis of the cylinder. The wire brush is rotated and inserted into the galvanized steel pipe to grind the inner surface of the galvanized steel.

The wire brush wire used in the experiment has a Vickers hardness of 500, and the chemical composition of the wire is C: 0.81% by mass, Mn: 0.47 mass%, Si: 0.20 mass%, P: 0.05 mass%, S: 0.04 quality%.

The grinding conditions are shown in Table 4. In the present embodiment, the length of the wire of the wire brush is changed, and 10 sets of molten galvanized steel pipes are subjected to internal grinding for each type of reference, and a total of five standards are implemented.

The surface temperature of the wire brush shaft was measured immediately after the inner surface was ground and the first and the tenth branch were examined to investigate the frictional heat.

Scratch the inner surface of the inner surface of the galvanized steel pipe with a copper metal needle to check whether the grinding state is good or not.

Next, a diameter slightly smaller than the inner diameter of the galvanized steel pipe was prepared, and a high-density polyethylene pipe of maleic anhydride-modified polyethylene having a thickness of 100 μm was laminated on the outer surface. The high density polyethylene has a thickness of 2.0 mm and a melting point of 125 °C.

Insert the high-density polyethylene pipe into the inner surface of the galvanized steel pipe, cover both ends, press the air inside the high-density polyethylene pipe and seal it, then heat it to 160 ° C in a heating furnace to make it high. The density polyethylene tube is melted and pressed against the inner surface of the galvanized steel pipe.

Then, the zinc coated tube was taken out from the heating furnace and cooled, and the sealed air was taken out at a temperature of 70 ° C to obtain a galvanized steel pipe coated with a high-density polyethylene pipe (the steel pipe d of the present invention) .

After the steel pipe d of the present invention was cut, the polished section was observed by an optical microscope, and subjected to a freeze-thaw test and a warm water immersion test.

When observing with an optical microscope, a 20 mm-wide circumferential section was taken as a test piece, and after re-polishing the cross section by resin embedding, the galvanized layer was etched with a 3% nitric acid-alcohol solution, and the galvanized layer was observed with an optical microscope. It was investigated whether or not the iron-zinc alloy layer containing 6% by mass or more of Fe was exposed to the outermost layer.

In the freeze-thaw test, a test piece obtained by cutting into a length of 150 mm is immersed in water in a state of about 1/3 of the length in a container filled with tap water, and is placed in a low-temperature tank at -10 ° C together with the container to be frozen. After 23 hours, the freeze-thaw operation in which the thawing was carried out in a high-temperature tank at 60 ° C for 1 hour was carried out for one cycle, and 100 cycles were repeated.

The warm water immersion test is a test piece obtained by cutting into a length of 150 mm, immersed in a container containing tap water, placed in a thermostat bath at 40 ° C together with the container, and left for 3 months.

After the freeze-thaw test and the warm water immersion test, the high-density polyethylene pipe of the test piece was investigated for peeling.

According to Table 4, only in the case where the value of φ of Formula 4 is within the range of the above Formula 5, it was confirmed in the inspection with a copper metal needle that copper adhered to the surface of the ground galvanized steel pipe, in the galvanized layer section. In the optical microscopic observation, it was confirmed that the iron-zinc alloy layer containing 6 mass% or more of Fe was exposed to the outermost layer. In addition, in the results of the freeze-thaw test and the warm water immersion test, it was also found that the polyethylene pipe was not peeled off.

Friction and heat generation of the wire brush In all of the five types of standards, the surface temperature of the wire brush shaft was measured immediately after the first and tenth branches were continuously ground, and the results were all less than 150 ° C, and the polishing efficiency was good.

(Example 5)

The inner surface and the outer surface of the steel pipe (SGP100A × 6000 mm length) were subjected to hot-dip galvanizing to obtain a galvanized steel pipe. At this time, the content of aluminum contained in the galvanization was 0.01% by mass.

The inner surface of the galvanized steel pipe is formed into a cylindrical shape with an outer diameter larger than the inner diameter of the galvanized steel pipe, and the wire is radially arranged from the central axis of the cylinder. The wire brush is rotated and inserted into the galvanized steel pipe to grind the inner surface of the galvanized steel.

The wire brush wire used in the experiment has a Vickers hardness of 500, and the chemical composition of the wire is C: 0.81% by mass, Mn: 0.47 mass%, Si: 0.20 mass%, P: 0.05 mass%, S: 0.04 quality%.

The grinding conditions are shown in Table 5. In the present embodiment, the outer diameter of the steel wire of the wire brush is changed, and 10 sets of molten galvanized steel pipes are subjected to inner surface polishing for each type of reference, and a total of five types of standards are implemented.

The surface temperature of the wire brush shaft was measured immediately after the first and tenth branches were ground on the inner surface, and the friction heat was investigated.

Use a copper metal needle to scrape the inner surface of the inner surface of the galvanized steel pipe and check whether the grinding condition is good or not.

Next, a diameter slightly smaller than the inner diameter of the galvanized steel pipe was prepared, and a high-density polyethylene pipe of maleic anhydride-modified polyethylene having a thickness of 100 μm was laminated on the outer surface. The high density polyethylene has a thickness of 2.0 mm and a melting point of 125 °C.

Insert the high-density polyethylene pipe into the inner surface of the galvanized steel pipe, cover both ends, press the air inside the high-density polyethylene pipe and seal it, then heat it to 160 ° C in a heating furnace to make it high. The density polyethylene tube is melted and pressed against the inner surface of the galvanized steel pipe.

Then, the galvanized pipe was taken out from the heating furnace and cooled, and the sealed air was taken out at a temperature of 70 ° C to obtain a galvanized steel pipe coated with a high-density polyethylene pipe (the steel pipe e of the present invention) .

After the steel pipe e of the present invention was cut, the polished section was observed by an optical microscope, and subjected to a freeze-thaw test and a warm water immersion test.

When observing with an optical microscope, a 20 mm wide circumferential section was taken as a test piece, and the cross section was fixed by resin embedding, and then the galvanized layer was etched with a 3% nitric acid-alcohol solution, and the galvanized layer was observed with an optical microscope. It was investigated whether or not the iron-zinc alloy layer containing 6% by mass or more of Fe was exposed to the outermost layer.

In the freeze-thaw test, a test piece obtained by cutting into a length of 150 mm is immersed in water in a state of about 1/3 of the length in a container filled with tap water, and is placed in a low-temperature tank at -10 ° C together with the container to be frozen. After 23 hours, the freeze-thaw operation in which the thawing was carried out in a high-temperature tank at 60 ° C for 1 hour was carried out for one cycle, and 100 cycles were repeated.

The warm water immersion test is a test piece obtained by cutting into a length of 150 mm, immersed in a container containing tap water, placed in a thermostat bath at 40 ° C together with the container, and left for 3 months.

After the freeze-thaw test and the warm water immersion test, the high-density polyethylene pipe of the test piece was investigated for peeling.

According to Table 5, in the case where the value of φ of Formula 4 is within the range of the above Formula 5, it was confirmed in the inspection with the copper metal needle that the copper adhered to the surface of the ground galvanized steel pipe, in the galvanized layer section. In the optical microscopic observation, it was confirmed that the iron-zinc alloy layer containing 6 mass% or more of Fe was exposed to the outermost layer. In addition, in the results of the freeze-thaw test and the warm water immersion test, it was also found that the polyethylene pipe was not peeled off.

Friction and heat generation of the wire brush In all of the five types of standards, the surface temperature of the wire brush shaft was measured immediately after the first and tenth sections were continuously polished, and the results were all less than 150 ° C, and the polishing efficiency was good.

(Example 6)

The inner surface and the outer surface of the steel pipe (SGP100A × 6000 mm length) were subjected to hot-dip galvanizing to obtain a galvanized steel pipe. At this time, the content of aluminum contained in the galvanization was 0.01% by mass.

The inner surface of the galvanized steel pipe is formed into a cylindrical shape with an outer diameter larger than the inner diameter of the galvanized steel pipe, and the steel wire is radially arranged from the central axis of the cylinder. The wire brush is rotated and inserted into the galvanized steel pipe to grind the inner surface of the galvanized steel.

The wire brush wire used in the experiment has a Vickers hardness of 500, and the chemical composition of the wire is C: 0.81% by mass, Mn: 0.47 mass%, Si: 0.20 mass%, P: 0.05 mass%, S: 0.04 quality%.

The grinding conditions are shown in Table 6. In the present embodiment, the outer diameter of the wire brush was changed, and 10 sets of hot-dip galvanized steel pipes were subjected to inner surface polishing for each type of reference, and a total of five types of standards were implemented.

The surface temperature of the wire brush shaft was measured immediately after the first and tenth branches were ground on the inner surface, and the friction heat was investigated.

Use a copper metal needle to scrape the inner surface of the inner surface of the galvanized steel pipe and check whether the grinding condition is good or not.

Next, a high-density polyethylene pipe of maleic anhydride-modified polyethylene having a thickness of 100 μm was prepared to be slightly smaller than the inner diameter of the galvanized steel pipe. The high density polyethylene has a thickness of 2.0 mm and a melting point of 125 °C.

Insert the high-density polyethylene pipe into the inner surface of the galvanized steel pipe, cover both ends, press the air inside the high-density polyethylene pipe and seal it, then heat it to 160 ° C in a heating furnace to make it high. The density polyethylene tube is melted and pressed against the inner surface of the galvanized steel pipe.

Then, the zinc coated tube was taken out from the heating furnace to be cooled, and the sealed air was taken out at a temperature of 70 ° C to obtain a galvanized steel pipe (the steel pipe f of the present invention) whose inner surface was covered with a high-density polyethylene pipe.

After the steel pipe f of the present invention was cut, the polished cross section was observed with an optical microscope, and subjected to a freeze-thaw test and a warm water immersion test.

When observing with an optical microscope, a 20 mm wide circumferential section was taken as a test piece, and the cross section was fixed by resin embedding, and then the galvanized layer was etched with a 3% nitric acid-alcohol solution, and the galvanized layer was observed with an optical microscope. It was investigated whether or not the iron-zinc alloy layer containing 6% by mass or more of Fe was exposed to the outermost layer.

In the freeze-thaw test, a test piece obtained by cutting into a length of 150 mm is immersed in water in a state of about 1/3 of the length in a container filled with tap water, and is placed in a low-temperature tank at -10 ° C together with the container to be frozen. After 23 hours, the freeze-thaw operation in which the thawing was carried out in a high-temperature tank at 60 ° C for 1 hour was carried out for one cycle, and 100 cycles were repeated.

In the warm water immersion test, the test piece obtained by cutting into a length of 150 mm was immersed in a container containing tap water, placed in a thermostat bath at 40 ° C together with the container, and left for 3 months.

After the freeze-thaw test and the warm water immersion test, the high-density polyethylene pipe of the test piece was investigated for peeling.

According to Table 6, only the case where the value of φ of Formula 4 is within the range of the above Formula 5, it was confirmed in the inspection with the copper metal needle that the copper adhered to the surface of the ground galvanized steel pipe, and the galvanized layer was broken. In the optical microscopic observation of the surface, it was confirmed that the iron-zinc alloy layer containing 6 mass% or more of Fe was exposed to the outermost layer. Further, in the results of the freeze-thaw test and the warm water immersion test, it was also found that the polyethylene pipe was not peeled off.

Friction and heat generation of the wire brush In all of the five types of standards, the surface temperature of the wire brush shaft was measured immediately after the first and tenth sections were continuously polished, and the results were all less than 150 ° C, and the polishing efficiency was good.

(Example 7)

The galvanized steel pipe was obtained by performing hot-dip galvanizing on the inner surface and the outer surface of the steel pipe (SGP100A × 6000 mm length). At this time, the content of aluminum contained in the galvanization was 0.01% by mass.

An inner diameter of the inner surface of the galvanized steel pipe having a larger inner diameter than that of the galvanized steel pipe is formed in a cylindrical shape, and the steel wire is radially arranged from the central axis of the columnar shape. The wire brush is rotated and inserted into a galvanized steel pipe to grind the inner surface of the galvanized steel.

The wire brush wire used in the experiment has a Vickers hardness of 500, and the chemical composition of the wire is C: 0.81% by mass, Mn: 0.47 mass%, Si: 0.20 mass%, P: 0.05 mass%, S: 0.04 quality%.

The grinding conditions are shown in Table 7. In the present embodiment, the number of revolutions of the wire brush was changed, and 10 sets of molten galvanized steel pipes were subjected to inner surface polishing for each type of reference, and a total of five types of standards were implemented.

The surface temperature of the wire brush shaft was measured immediately after the inner surface was ground and the first and the tenth branch were examined to investigate the frictional heat.

Use a copper metal needle to scrape the inner surface of the inner surface of the galvanized steel pipe and check whether the grinding condition is good or not.

Next, a high-density polyethylene pipe of maleic anhydride-modified polyethylene having a thickness of 100 μm was prepared to be slightly smaller than the inner diameter of the galvanized steel pipe. The high density polyethylene has a thickness of 2.0 mm and a melting point of 125 °C.

Insert the high-density polyethylene pipe into the inner surface of the galvanized steel pipe, cover both ends, press the air inside the high-density polyethylene pipe and seal it, then heat it to 160 ° C in a heating furnace to make it high. The density polyethylene tube is melted and pressed against the inner surface of the galvanized steel pipe.

Then, the galvanized pipe was taken out from the heating furnace and cooled, and the sealed air was taken out at a temperature of 70 ° C to obtain a galvanized steel pipe coated with a high-density polyethylene pipe (the steel pipe g of the present invention) .

After the steel pipe g of the present invention was cut, the polished cross section was observed by an optical microscope, and subjected to a freeze-thaw test and a warm water immersion test.

When observing with an optical microscope, a 20 mm wide circumferential section was taken as a test piece, and the cross section was fixed by resin embedding, and then the galvanized layer was etched with a 3% nitric acid-alcohol solution, and the galvanized layer was observed with an optical microscope. It was investigated whether or not the iron-zinc alloy layer containing 6% by mass or more of Fe was exposed to the outermost layer.

In the freeze-thaw test, a test piece obtained by cutting into a length of 150 mm is immersed in water in a state of about 1/3 of the length in a container filled with tap water, and is placed in a low-temperature tank at -10 ° C together with the container to be frozen. After 23 hours, the freeze-thaw operation in which the thawing was carried out in a high-temperature tank at 60 ° C for 1 hour was carried out for one cycle, and 100 cycles were repeated.

In the warm water immersion test, the test piece obtained by cutting into a length of 150 mm was immersed in a container containing tap water, placed in a thermostat bath at 40 ° C together with the container, and left for 3 months.

After the freeze-thaw test and the warm water immersion test, the high-density polyethylene pipe of the test piece was investigated for peeling.

According to Table 7, only the case where the value of φ of Formula 4 is within the range of the above Formula 5, it was confirmed in the inspection with a copper metal needle that copper adhered to the surface of the ground galvanized steel pipe, and the galvanized layer was broken. In the optical microscopic observation of the surface, it was confirmed that the iron-zinc alloy layer containing 6 mass% or more of Fe was exposed to the outermost layer. Further, in the results of the freeze-thaw test and the warm water immersion test, it was found that the polyethylene pipe was not peeled off.

Friction and heat generation of the wire brush In all of the five types of standards, the surface temperature of the wire brush shaft was measured immediately after the first and tenth sections were continuously polished, and the results were all less than 150 ° C, and the polishing efficiency was good.

Industry availability

According to the present invention, since the inner surface of the hot-dip galvanized steel pipe is polished by a wire brush and the pure zinc layer is removed, the iron-zinc alloy layer containing 6 mass% or more of Fe can be surely exposed, so that the polished surface and the polyolefin pipe The adhesion is stabilized and strengthened, and industrially, even in the pipeline where freezing and melting occurs, the inner surface of the polyolefin tube is not easily peeled off, and the inner surface of the polyolefin-coated steel pipe is extremely useful in the industry.

1. . . Melt galvanized steel pipe

2. . . Wire brush

2'. . . Wire brush (shows the mode position of the wire brush when advancing its brush length (Lb) portion)

[Fig. 1] is a cross-sectional view of a hot-dip galvanized steel pipe and a cross-sectional view and a side view of the wire brush.

[Fig. 2] A relationship between the length h (1) and the brush length Lb of the inner surface of a steel wire-polished hot-dip galvanized steel pipe when the wire brush advances the brush length Lb portion.

1. . . Melt galvanized steel pipe

2. . . Wire brush

Claims (13)

A method for producing a steel pipe coated with a polyolefin inner surface is an inner plating layer of a hot-dip galvanized steel pipe which has been subjected to hot-dip galvanizing on the inner surface and the outer surface by a wire brush, and is made of iron-zinc containing 6 mass% or more of Fe. After the alloy layer is exposed, and the polyolefin pipe is coated on the inner surface of the polyolefin pipe, the above-described manufacturing method is characterized in that the wire brush is cylindrical and the radial direction is from the central axis of the cylinder. The steel wire is arranged radially, and the inner surface plating layer of the steel pipe is polished by inserting the wire brush into the hot-dip galvanized steel pipe by rotating the wire shaft with the central axis as a rotating shaft, and the method satisfies the following Conditions of Equations 1 to 5: F(1): the wiping force of each wire of the wire brush h(1): the length of the inner surface of the steel wire of the wire brush (mm) when the wire brush advances its brush length (Lb) : When the wire brush of N steel wire passes through the inner surface of the galvanized steel pipe m times, the product of the total length of the wire brush grinding and the scraping force of the steel wire per unit area K: proportional coefficient Dpi: the condition of the molten galvanized steel pipe Inner diameter (mm) Db: outer diameter of the wire brush (mm) Lb: length of the wire brush (mm) Dw: wire diameter of the wire brush (mm) Lw: wire length of the wire brush (mm) N: steel wire Number of wires of the brush (root) n: Number of revolutions of the wire brush (rpm) V: Feeding speed of the wire brush (mm/min) m: Number of passes of the wire brush (times) S: Wire brush advances its brush length (Lb In some cases, the wire brush grinds the area (mm ² ) of the molten galvanized steel pipe. The method for producing an inner-coated polyolefin steel pipe according to the first aspect of the invention, wherein the steel wire has a Vickers hardness of 500 or more. The method for producing an inner-coated polyolefin steel pipe according to the first or second aspect of the invention, wherein the chemical composition of the steel wire is C: 0.6 to 1.2% by mass, Mn: 0.2 to 1.2% by mass, Si: 0.1 ~1.5% by mass, P: 0.05% by mass or less, S: 0.04% by mass or less, and the remainder is Fe and unavoidable impurities. The method for producing a steel pipe coated with an inner surface covered with polyolefin according to the first or second aspect of the invention, wherein the surface of the steel wire is yellow Copper covered. A method for producing an inner-coated polyolefin steel pipe according to the third aspect of the invention, wherein the steel wire is coated on the surface of the steel wire. The method for producing an inner-coated polyolefin steel pipe according to the first or second aspect of the invention, wherein after the grinding, the inner surface of the steel pipe is scraped with a Vickers hardness of 60 to 100 to determine the grinding. The state is good or not. The method for producing a steel pipe coated with an inner surface of a polyolefin according to the third aspect of the invention, wherein after the polishing, the inner surface of the steel pipe is scraped with a metal needle having a Vickers hardness of 60 to 100 to determine whether the state of the steel is good or not. The method for producing an inner-coated polyolefin steel pipe according to the fourth aspect of the invention, wherein after the polishing, the inner surface of the steel pipe is scraped with a metal needle having a Vickers hardness of 60 to 100 to determine the quality of the polished state. The method for producing a steel pipe coated with an inner surface of a polyolefin according to claim 5, wherein after the polishing, the inner surface of the steel pipe is scraped with a metal needle having a Vickers hardness of 60 to 100 to determine whether the state of the steel is good or not. The method for producing an inner-coated polyolefin steel pipe according to the sixth aspect of the invention, wherein the metal needle is made of copper. The method for producing an inner-coated polyolefin steel pipe according to the seventh aspect of the invention, wherein the metal needle is made of copper. The method for producing an inner-coated polyolefin steel pipe according to the eighth aspect of the invention, wherein the metal needle is made of copper. The method for producing an inner-coated polyolefin steel pipe according to claim 9, wherein the metal needle is made of copper.