JPH02285100A - Method for electrolytically peeling zinc of snow clearing steel pipe without water sprinkling - Google Patents

Abstract

PURPOSE:To peel a zinc coating in a short time with a little supply of electrolyte and without heating at the time of electrolytically peeling the coating on the ends of U-shaped steel pipes TIG-welded to one another by specifying the electrolyte, DC voltage and current value. CONSTITUTION:An electrolyte 7, a 10-13% ammonium nitrate soln., is used, a cathode plate 8 is arranged in the electrolyte, and the end of the U-shaped steel pipe 3 is vertically dipped as an anode. A 30-volt DC voltage is impressed from a DC power source 2, and a current at the maximum of 10A is applied to cause electrolysis. Consequently, only the zinc coating on the surfaces of both ends of the steel pipe 3 is eluted and electrolytically peeled, and the zinc coating on the inner surface of the end of the steel pipe is left. The ends of the steel pipes 3 thus treated are abutted against each other and TIG-welded to form a snow clearing steel pipe without water sprinkling. Even when the electrolyte 7 is deteriorated, the electrolytic capacity is restored by replenishing a little ammonium nitrate soln. Heating is not needed in the electrolytic peeling, and the zinc coating is peeled in a short time without damaging the base material of the steel pipe.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method of manufacturing a waterless snow melting steel pipe for melting snow on roads and the like, and particularly relates to a waterless snow melting steel pipe for melting snow on road surfaces such as roads. This invention relates to a zinc electrolytic stripping method for waterless snow melting steel pipes, in which the zinc coating is electrolytically stripped only from the outer periphery of the ends of the steel pipes, and the ends are joined by TIG welding.

[Conventional technology]

Conventionally, synthetic resin pipes, steel pipes, etc. have been mainly used as heat dissipation pipes for waterless lightning extinguishing. However, among these heat dissipation pipes, synthetic resin pipes have poor thermal conductivity and load capacity.

Steel pipes with excellent load resistance are often used as the heat dissipation pipes. When a steel pipe is used as the heat dissipation pipe in this way, it has excellent thermal conductivity and load resistance, so it can be buried in a relatively shallow part of a snow-covered road surface.
By simply flowing low-temperature water such as groundwater through these steel pipes, it is possible to melt the snow that falls on the road surface. However, in order to form a heat dissipation pipe section on a road surface using steel pipes, a large number of steel pipes must be connected.

In recent years, a method for joining such steel pipes for waterless snow removal is to bring the end faces of the steel pipes for waterless snow removal into contact with each other, and to irradiate the abutting area with a focused high-energy welding beam to melt it, and to melt the melted part. A welding method is used in which cooling gas is blown onto the welding surface. According to this welding method, no convex portion is formed in the welded portion, and the welded joint can have extremely high strength and can withstand bending.

However, in order to completely weld the welded part using this welding method and to produce a high-strength waterless snow melting steel pipe, it is necessary to cover the surface of the steel pipe as a pre-treatment operation in order to cause effective melting with a tungsten electrode. It is necessary to completely remove the existing zinc coating.

This zinc removal method includes a method of mechanically polishing the end surface of the steel pipe, a method of chemically removing the end surface of the steel pipe with hydrochloric acid, an electrolytic method using NaH, PO, 2H, O, One of the electrolytic methods using a mixed solution of ZnCu and NH41,Q has been carried out.

[Problems to be Solved by the Invention] However, these zinc removal methods have the following drawbacks.

That is, the mechanical grinding and removal method has the drawback that uniform grinding is difficult, the zinc coating is incompletely removed, and the welded part cannot be completely melted.

Also, if you try to completely remove zinc using this mechanical grinding removal method, you will end up grinding down to the base steel pipe.

Welding connections under such conditions have the disadvantage of reducing the strength of the steel pipe joints.

In addition, although the zinc coating can be completely removed using the chemical removal method using hydrochloric acid, peripheral equipment may corrode due to the hydrogen chloride gas generated when the zinc coating is chemically removed using salt. In addition, it has the disadvantage that it even dissolves into the base material steel pipe, making the material brittle. In addition, in this chemical removal method using hydrochloric acid, after removing the zinc coating,
It had the disadvantage that the treatment was complicated, such as requiring neutralization treatment and rust prevention treatment. Furthermore, this method of chemically removing the zinc coating using hydrochloric acid has the danger of workers inhaling the generated hydrogen chloride gas during the treatment process.

Further, the electrolytic method using NaH, POl.2H20 has disadvantages such as extremely slow zinc removal rate and high cost unless the electrolytic bath is heated to about 40°C.

Furthermore, ZnCu2. In the electrolytic method using a mixed solution of Met. Furthermore, when using a mixed electrolyte solution of ZnCρ2 and NH4Cl2, zinc crystals precipitate on the cathode plate and gradually grow, contacting the steel tube of the anode installed in the middle part and reducing the electrolytic efficiency. To prevent this, it was necessary to constantly remove crystals formed on the cathode plate. Furthermore, this ZnCu2
．． If you use a mixed electrolyte solution of NH, Cu2 for a long period of time, the electrolyte will deteriorate, and the electrolytic capacity will not be restored to its original level just by replenishing a portion of the electrolyte, so it will be necessary to replace the entire amount, resulting in a large amount of waste solution. was. On top of that is this Z
The mixed electrolyte solution of nCf12 and NH4Cl contains a large amount of the heavy metal zinc, and with the addition of the zinc dissolved from the end of the steel pipe, the concentration of zinc becomes even higher.
It had many drawbacks, including difficult problems in waste liquid treatment in terms of environmental protection.

The present invention has been made in view of the above-mentioned circumstances, and it is possible to easily electrolytically peel off the zinc coating on the outer circumferential surface of the pipe end of a waterless snow-melting steel pipe without damaging the steel pipe base material, and without damaging the steel pipe base material. To provide a zinc electrolytic stripping method for waterless snow melting steel pipes, which can improve the bending workability of steel pipes without causing embrittlement of the base material of steel pipe joints even when used for water spray lightning extinguishing. It is an object.

[Means to solve the problem]

In order to achieve the above object, the present invention arranges a metal plate as a cathode in an electrolyte solution, uses the tube end of a U-shaped steel tube as an anode, and places the tube end of the anode steel tube in the electrolyte solution. In the method of electrolytically stripping the zinc coating coating the surface of the end of the steel pipe by immersing it upright and supplying a direct current, a 10% to 13% ammonium nitrate solution is used as the electrolyte solution, and a direct current voltage is applied. It is characterized in that after electrolytic stripping is performed on only the outer surfaces of both ends at 3o volts and a maximum current value of 10 amperes, each end of the steel pipe is brought into contact and joined by TIG welding.

[Effect]

Next, to explain the operation of the present invention, the ends 1 to 2 of a steel pipe connected to a direct current with a voltage of 30 volts and a maximum current of 10 amperes are treated with 10 to 13% ammonium nitrate to a hydrogen ion concentration of 7.5. ~7 in an electrolyte solution of ~8.5
When soaked upright for a minute.

The zinc coating on the outer surface of the steel pipe end, which has a large tendency to ionize, is eluted into the electrolyte solution as ions, and the zinc coating is electrolytically peeled off, while the zinc coating on the inner surface of the steel pipe end remains as it is without being removed. The eluted zinc precipitates on the surface of the metal plate of the cathode in an amount equivalent to the eluted zinc ions and precipitates in the electrolyte solution. Immediately after preparing the electrolyte solution containing 10% to 13% ammonium nitrate, the hydrogen ion concentration is around 4.5, which is weakly acidic, but it is 1! When used as a solute solution, it soon settles down to a weak alkalinity with a hydrogen ion concentration of 8.0 and stabilizes, and when the electrolyte deteriorates, the electrolytic ability of the electrolyte is quickly restored by adding new ammonium nitrate solution, and the hydrogen ion concentration is 8.0. The concentration is stable around 8.0. Each end of the thus obtained steel pipe for waterless snow removal is abutted and joined by TIG welding to produce a steel pipe for waterless snow removal.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the invention.

In the figure, there is ammonium nitrate (No4N) in the bathtub 1.
oz) of electrolyte solution 7 is filled, and this electrolyte solution 7
Ammonium nitrate has a concentration of 10% to 13%, and the hydrogen ion concentration is around 4.5 immediately after solution preparation, but soon after use, it stabilizes to a slightly alkaline hydrogen ion concentration of 8.0, and the hydrogen ion concentration at the end of the steel pipe By using ammonium nitrate, the hydrogen ion concentration can be easily maintained at a weak alkaline level of 7.5 to 8.5, and this electrolyte solution can be heated at normal temperature (5.5 - 8.5%). (°C to 25°C), the electrolytic peeling effect of the zinc coating is sufficient, and there is no particular need for heating.

A discharge port 11 is provided at the bottom of the bathtub 1.
A pipe line 9 is connected to this outlet.

A filtration device 5 is connected to this conduit 9 via a chemical pump 4. This filtration device 5 is used to always keep the electrolyte solution 7 clear, from which zinc deposited in the electrolyte solution 7 has been filtered. A pipe line 10 is connected to this filtering device 5, and this pipe line 10 is connected to the bathtub 1. In this way, the electrolytic solution 7 is discharged from the bathtub 1 through the pipe line 9 by the chemical pump 4, filtered by the filtration device 5, and then passed through the pipe line 10.
A reflux path is configured through which the water is supplied again to the bathtub 1.

Further, an insulating stand 6 is provided in the bathtub 1 at a position below the surface of the electrolytic solution 7 by a predetermined position. On this insulating stand 6, steel pipes 3 for waterless snow removal formed in a U-shape are vertically erected, and the ends of the pipes are immersed in the electrolytic solution 7. This steel pipe 3 is a galvanized steel pipe having a chemical composition specified by JIS standard G-3452, and the anode of the DC power supply 2 is connected to this steel pipe 3. Further, cathode plates 8 are provided on both sides of the insulating stand 6 in the bathtub 1, and a cathode of DC sg2 is connected to the cathode plates 8.

Since it is configured in this way, now the DC type g
When the end of the steel pipe 3 connected to the steel pipe 2 is immersed in the electrolytic solution 7, a zinc coating with a large ionization tendency only on the outer surface of only 1 to 2 ann of the outer surface of the end of the steel pipe 3 is eluted into the electrolytic solution 7 as ions. The zinc coating is electrolytically removed, and the zinc on the inner surface remains unremoved. This eluted zinc precipitates, floats and precipitates on the surface of the cathode plate 8 as metallic zinc equivalent to the eluted zinc ions.

Therefore, in order to make the concentration of the electrolyte solution 7 in the bathtub 1 uniform, the chemical pump 4 is operated, and the zinc floating in the electrolyte solution 7 is filtered by the filtering device 5, and the electrolyte solution 7 is always kept clear and can be used. Even if the electrolyte solution deteriorates, the electrolytic capacity can be restored with a small amount of replenishment.

The ends of the steel pipe thus obtained are brought into contact with each other and TIG welded to produce a waterless snow melting steel pipe.

As a result of the qualitative test, it is clear that zinc has been completely removed from the outer surface of the end of the steel pipe treated according to this example, and that part is difficult to oxidize, and during tube welding, the outer surface of the steel pipe 1 to Only the ends of the 2aff from which the galvanizing was removed melted and were well joined.

Moreover, generation of toxic gas can be prevented. In addition, the zinc coating on the inner surface of the tube ends is not electrolytically peeled off, and when the tube ends that are in contact with each other are rapidly heated from the outside to 1000°C to 3000°C and melt-bonded, the zinc coating remaining on the inner surface is removed. Once vaporized, it fills the pipe, and as the welded area is rapidly cooled by cooling gas, this vaporized zinc vapor combines with iron to create a new alloy.

This alloy forms a new coating on the inner surface of the tube end joints where they are welded together to protect the inner surface.

Furthermore, there were no protrusions on either the surface or the inner surface of the steel pipe, and it was clear that the welded part had a strength greater than that of the base metal.

Therefore, the heat dissipation tube according to this embodiment will not be damaged by heavy vehicles passing on the road, and will not become brittle even if underground water flows through it for a long period of time.

〔Effect of the invention〕

As explained above, according to the present invention, electrolytic stripping of zinc is carried out by immersing it upright for a short time in an electrolyte solution of ammonium nitrate, which has a high solubility and has the property of dissolving metal oxides. ~2al, and an electrolyte solution with a hydrogen ion concentration of 7.5 to 8.5 (particularly stable around 8.0) can be easily obtained at a concentration of 10% to 13% of ammonium nitrate. Even if the electrolyte solution deteriorates with use, the electrolytic capacity can be restored by simply replenishing a small amount of fresh ammonium nitrate solution. Therefore, unlike replacing the entire electrolyte solution, only a small amount of waste liquid needs to be treated.With this electrolyte solution, there is no need to heat the electrolyte solution during electrolytic stripping of the zinc coating, and the base metal steel pipe is not damaged. In addition, it is possible to electrolytically strip the zinc coating completely in a short period of time at low cost.

In addition, after electrolytic stripping of the zinc coating, the steel pipe base material is less likely to be oxidized by welding. Since the joint is carried out by TIG welding in an active atmosphere, only the ends from which the zinc plating has been electrolytically peeled are heated and melted, resulting in a high-quality joint.

In particular, in the zinc electrolytic stripping method of steel pipes for waterless snow removal according to the present invention, only the zinc on the outer surface of the pipe end is electrolytically stripped, and the zinc on the inner surface remains, so when TIG welding is performed, the zinc remaining on the inner surface is removed. Once heated, the zinc vapor melts into the iron, creating a new alloy coating to protect the inner surface. Furthermore, the generation of toxic gases can be prevented, the welded joint has extremely high strength, and no convex portions are formed on the inner periphery of the welded part.

Since there is no welding unevenness, fluids such as underground water flowing inside the pipe can flow therein without resistance, and it is possible to obtain a waterless snow sliding steel pipe that can sufficiently withstand bending.

As described above, according to the present invention, the heat dissipation pipe made by the zinc electrolytic peeling method of waterless snow sliding steel pipe has a welded part that is stronger than the base material, so it will not be damaged by heavy vehicles passing on the road, and it will not be damaged by underground water. It has the effect of not causing embrittlement even when water is passed for a long period of time.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention. 1... Bathtub, 2... DC power supply. 3... Steel pipe, 4... Chemical pump. 5...filtration device, 6...insulation stand. 7... Electrolyte, 8... Cathode plate. 9.10... Pipe line, 11... Outlet.

Claims (1)

[Claims] (1) During electrolyte welding, a metal plate as a cathode is placed, the end of a U-shaped steel pipe is used as an anode, the end of the anode steel pipe is immersed upright in the electrolyte solution, and a direct current is supplied. In the method of electrolytically stripping the zinc coating coating the surface of the end of the steel pipe, the electrolyte solution is a 10% to 13% ammonium nitrate solution, and the DC voltage is 30 volts and the current value is 10 amperes at the maximum. A method for zinc electrolytic stripping of a steel pipe for waterless snow removal, characterized in that after electrolytically stripping only the outer surfaces of both ends, each end of the steel pipe is brought into contact and joined by TIG welding.