JPH0711112B2 - Unbonding method for PC steel strands - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) There are various methods for unbonding PC strands, but the purpose of unbonding is to reduce frictional resistance with concrete and to prevent rust. .

(Prior Art) The conventional unbonding method for PC stranded wire is broadly classified as follows: (1) As shown in Fig. 3, an oil-based material is applied to the wire surface of PC steel stranded wire, and then an extruder is used. A method of forming vinyl coating, etc. by the method.

(2) As shown in FIG. 4, a method in which a vinyl coating or the like is formed on the surface of a PC steel wire by an extruder method or the like, and then an oil-based material is applied to the surface, and a sheath is used thereon.

(3) As shown in FIG. 5, a method of applying a fluorine-based, polyester-based, or acrylic-based paint to the surface of the PC steel wire and forming a vinyl coating or the like on the surface by an extruder method or the like.

It is divided into the following and will be described with reference to FIGS.
Fig. 5 is a cross-sectional view of a PC steel stranded wire by the conventional unbonding method, and Fig. 3 is a method of applying an oil-based material to the surface of the PC steel stranded wire and then forming a vinyl coating with an extruder. In the figure, 1 is a stranded wire of PC steel, 2 is a coating of vinyl or the like by an extruder method, and 3 is a fat or oil. Fig. 4 shows a method in which vinyl coating etc. is formed on the surface of PC steel wire by an extruder method, then oil-based material is applied on the surface, and a sheath is used on the surface. Lines 2 are coatings of vinyl or the like by an extruder method, 3 are oils and fats, 4 are sheaths, and 5 are hollow portions. Fig. 5 shows the method of applying paint to the surface of the PC steel wire and forming a vinyl coating etc. by the extruder method on it. 1 is a PC steel wire, 2 is a coating of vinyl etc. by the extruder method, Reference numeral 5 is a hollow portion, and 6 is a paint.

Although it was thought that the rust prevention of PC steel strands was perfect by these past unbonding methods, recent studies have revealed that each method has a defect lacking rust preventive power.

That is, in the case of (1), it depends on the oil-based rust preventive material applied to the PC stranded wire as shown in Fig. 3, but it is caused by the aging deterioration of the rust preventive material itself or the incomplete surface application. Therefore, it cannot be said that the rustproof durability is perfect.

In the case of (2), it depends on the vinyl coating etc. formed on the surface of the PC steel strand by the extruder method or the like. However, in the case of the coating by the extruder method or the like, as shown in Fig. 4, the PC steel strand is Spiral grooves are formed between the wires (side wires), and the grooves are often cavities, and the adhesion to iron is poor, resulting in lack of rust prevention.

In the case of (3), as shown in FIG. 5, the surface of the PC steel wire is coated with a fluorine-based, polyester-based, or acrylic-based paint, and the coating is used for rust prevention. In the case of general coating, peeling of the coating film occurs unless the coating is sufficiently pretreated before the coating and finally subjected to the phosphate coating treatment before the coating. Also, with this type of coating, the coating film is thin and scratches and the like occur in the next step, so the rust preventive power cannot be said to be perfect.

(Problems to be solved by the invention) In view of such a situation, the present invention advances research on an unbonding method of PC steel strands, especially rust prevention, for many years,
It was successfully developed with the aim of improving rust prevention.

(Means for Solving the Problems) The present invention provides a coating layer by a fluid immersion powder coating method or an electrostatic powder coating method on the surface of a steel strand, and then thinly coats a fat-based material on the surface, Alternatively, it is a method of unbonding a PC steel wire, which is characterized by forming a thin vinyl coating or the like on the surface thereof by an extruder method or the like without coating. That is, the gist of the present invention is to apply a primary coating layer to the surface including the spiral groove portion between the side wires of the PC steel strand in which a plurality of side wires are twisted around the core wire by a fluid immersion powder coating means or electrostatic powder. It is formed by a coating means, and then a grease-based lubricant is applied to its surface, or without application, and a secondary coating layer is further formed on the surface by an extruder method to form a primary coating layer and a secondary coating layer. It is a method of unbonding PC stranded wire characterized by being configured so that it can freely slide in the axial direction between the two.

FIG. 1 is a sectional view of a PC steel strand according to the unbonding method of the present invention. 1 is a sectional view of a steel strand. 1 is a PC strand having a plurality of side wires twisted around a core wire, and 2 is an extruder. Is a secondary coating of vinyl or the like formed by 3., 3 is a lubricant made of oils and fats, and 7 is a primary coating layer formed by fluidized dip powder coating means or electrostatic powder coating means.

FIG. 2 is a process diagram showing an embodiment of the unbonding method according to the present invention, 1 is a PC steel wire, 8 is a rewinding device, 9 is a heating furnace, 10 is a fluidized dipping tank, or an electrostatic powder coating tank. , 11 is a cooling tank, 12 is an oil and fat application tank, 13 is an extrusion coater, 14 is a cooling tank, 15
Is a winding drum, and 16 is a winding device.

The fluidized dip powder coating or electrostatic powder coating of the unbonding method of the present invention is a special coating method, and is a method of fusing a powder coating having excellent adhesion to iron on the surface of a PC steel wire. The coating thickness can be freely formed to a thickness of 0.1 mm to 1.2 mm depending on the requirement of rustproof durability.

As described above for vinyl coating by the conventional extruder method, etc.
The surface of PC stranded wire forms spiral grooves between the strands (side wires), and even the grooves become cavities without being covered, which is the main cause of deterioration in rust prevention. Such cavities cannot be prevented by increasing the coating thickness.

(Operation) In the case of the fluid immersion powder coating or electrostatic powder coating of the present invention, the powder coating is obtained by heating the PC steel wire to a predetermined temperature and immersing or spraying it in the fluid immersion tank or electrostatic powder coating tank. Since it is fused to the surface of the PC steel strand, the spiral groove between the strands (side wires) is completely covered as shown in Fig. 1 regardless of the coating thickness, and the groove is hollow. There is no.

Also, even if a tensile force is applied to the PC steel wire to pull it, the rustproof coating fused on the surface will be stretched following the elongation of the PC steel wire and the PC steel wire will break. The surface is completely covered and the rust preventive power is not impeded at all.

Also in the case of fixing, if it is a fixing method by a wedge action, it is not necessary to peel off the fluid immersion powder coating or electrostatic powder coating, and fixing can be performed on the coating, which has been a problem in the past. Corrosion of PC steel strand fixing part is also eliminated.

Therefore, the rust preventive power is remarkably improved compared to other methods, and the friction resistance is also very high on the surface of the fluid immersion powder coating or electrostatic powder coating, so that the secondary coating by the extruder method is not necessary. It slides easily without being pinched by a lubricant such as oil or fat, and the friction coefficient is less than half that of conventional unbonded PC steel.

(Example) The contents will be described below with reference to FIG. 2 (processing step) of an example of the present invention.

First, the PC steel strand 1 placed on the rewinding device 8 is a winding device.
16 Sliding up to take-up drum 15. When the slading is completed, the operation is started, the PC steel strand 1 is heated in the heating furnace 9, and the fluidized dipping tank or electrostatic powder coating tank 10 is used.
The powder coating is fused to the surface of the PC steel wire 1 at
At 11, the coating layer 7 is formed by being cooled to such an extent that it does not hinder the next application of oil and fat. In this case, the coating thickness can be adjusted freely according to the heating temperature of the PC steel wire 1 and the dipping time or spraying amount of the fluidized dipping tank or the electrostatic powder coating tank 10.

Next, after the oil and fat of a predetermined thickness is applied in the oil and fat application tank 12,
The extrusion coating machine 13 forms a vinyl coating as a secondary coating on the surface of the fat or oil.

However, the oil and fat application is not always necessary, and when it is not necessary, the vinyl coating by the extrusion coating machine 13 may be directly formed on the fluidized immersion powder or the electrostatic powder coating.
The vinyl coating formed by the extrusion coating machine 13 is cooled in the next cooling tank 14 to such an extent that it does not hinder the winding, and then continuously wound around the winding drum 15 on the winding device 16. .

Note that the above manufacturing process is a process for starting what is connected with a PC steel wire by fluid immersion powder coating or electrostatic powder coating, and when incorporating it into the PC steel wire manufacturing process and performing it continuously. The heating furnace 9 is not necessary if the preheating of bluing in the final process of the PC steel strand manufacturing process is used.

(Effects of the Invention) The present invention is an unbonded processing method for a PC steel wire which has a significantly improved smoothness of the coating surface, has less frictional resistance, and slides easily compared with the conventional processing method and has a large rust preventive force. It is a term invention and its effect is enormous.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of the product of the present invention, FIG. 2 is a process drawing of the present invention, and FIGS. 3, 4, and 5 are cross-sectional views of products of the conventional processing method. 1 ... PC stranded wire, 2 ... secondary coating, 3 ... lubricant, 7
...... Primary coating layer by fluidized-bed powder coating method or electrostatic powder coating method, 8 ... Rewinding device, 9 ... Heating furnace, 10 ... Fluidized immersion tank or electrostatic powder coating tank, 11 ... Cooling tank, 12 ... Oil coating tank, 13 ... Extrusion coating machine, 14 ... Cooling tank, 15 ... Winding drum, 16 ... Winding device.

Claims (1)

[Claims] 1. A PC in which a plurality of side wires are twisted around a core wire.
A primary coating layer is formed on the surface of the stranded steel wire including the spiral groove portion between the side wires by a fluid immersion powder coating means or an electrostatic powder coating means, and then, a grease-based lubricant is applied to the surface, or applied. Without a further, by forming a secondary coating layer on the surface by an extruder method, PC steel characterized in that it is configured so that it can freely slide in the axial direction between the primary coating layer and the secondary coating layer Unbonding method for wire.