JPS5937697B2 - Method for forming threads for pipes or pipe fittings - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming threads on pipes or pipe joints used in piping work such as gas pipes.

A pipe or a pipe joint is required to have high airtightness and durability in consideration of its usage condition, and in particular, the dimensional accuracy of the threaded portion constituting the joint plays a large role in determining whether the airtightness is good or not.

Therefore, when applying corrosion-resistant treatment to pipes or pipe fittings, sufficient consideration must be given to the corrosion-resistant treatment of threaded parts that require a high degree of dimensional accuracy due to airtightness issues. Conventionally, a corrosion-resistant treatment method using electroplating, which can easily form a relatively thin and uniform coating, has been adopted as a method for corrosion-resistant treatment while maintaining the corrosion resistance.

However, when this conventional method is used, the coating is likely to peel off during the joining process by screwing, so the necessary corrosion resistance cannot be maintained after joining, and the corrosion resistance of the pipe or fitting body is not good enough. Even if the pipe is a pipe, it is undeniable that the durability of the piping system deteriorates due to local corrosion of the threaded portion, and therefore, sufficient anti-corrosion management and anti-corrosion retreatment are required after the piping is installed.

(b) Moreover, the insufficient corrosion resistance of the threaded portion has a negative effect on the airtightness, which is particularly strictly required for piping systems, as described above.

(c) Also, from the viewpoint of the manufacturing process, it is necessary to perform the above-mentioned electroplating after machining the threaded portion, which has the drawback of increasing manufacturing costs.

The present invention was developed in view of the above-mentioned circumstances, and it is possible to inexpensively form a screw with excellent corrosion resistance, maintain a high degree of dimensional accuracy, and ensure airtightness as a piping system. It is an object of the present invention to provide an effective method for forming threads for pipes or pipe joints.

The method for forming threads for pipes or pipe fittings according to the present invention is to apply hot-dip plating to the pipe or pipe fitting in advance, and then plastically deform the alloy layer at the portions of the plated layer that require thread forming using a rolling machine. Since it is characterized by thread forming, it has the following advantages.

In other words, ■ The base material of the pipe or pipe joint, including its threaded portion, can be treated with hot-dip plating to reduce corrosion resistance.This reduces the cost of corrosion resistance treatment, and eliminates the need for corrosion resistance treatment after thread processing, which improves manufacturing efficiency. Cost can be reduced.

■ Moreover, since the corrosion-resistant treatment is hot-dip plating, an alloy layer with excellent mechanical strength is formed between the base material and the coating, and the threaded part is formed by plastic deformation of this alloy layer. , while maintaining a high degree of dimensional accuracy to maintain airtightness, without impairing the corrosion resistance of the screw capital.

In other words, due to the presence of the alloy layer, it is possible to form a threaded portion with high quality in terms of dimensional accuracy while maintaining sufficient corrosion resistance.

■ Also, because the molded threaded part and its corrosion-resistant coating have excellent mechanical strength, there is no risk of peeling or damage to the coating during screw-jointing work, as well as rough handling during the process leading up to piping. Since there is almost no damage due to piping, it is possible to save time and money on maintenance such as piping work, and subsequent corrosion prevention management, airtightness management, and corrosion prevention reprocessing.

As described above, the present invention has been able to propose a method that is extremely effective in forming threaded portions for pipes or pipe fittings that have high requirements for airtightness and corrosion resistance.

Hereinafter, an embodiment of the method of the present invention will be described in detail based on the drawings. As shown in FIG. As shown in FIG. 2, a thread rolling machine 3 having three rolling rolls 3a arranged at a center angle of 120 degrees is used to apply the plating to the part 2 where thread forming is required. The alloy layer formed by the treatment is thread-formed so as to be plastically deformed, thereby producing a corrosion-resistant pipe or a corrosion-resistant pipe joint 11 having a joining thread IA' as shown in FIG.

Incidentally, the method of the present invention is more effective in forming a tapered screw, which is likely to have errors in terms of dimensional accuracy.

Further, the number of rolling rolls of the rolling machine 3 may be two, three or more, but in the case of a pipe material, three is suitable.

[Brief explanation of drawings]

The drawings illustrate an embodiment of the method for forming threads for pipes or pipe fittings according to the present invention, and FIG. 1 is a partially cutaway perspective view of the plated state, and FIG. 2 is a thread-rolled state. FIG. 3 is an enlarged cross-sectional view of a threaded pipe or pipe fitting. 1... Pipe or pipe joint, 2... Location where thread forming is required, 3... Rolling machine, 4... Plating layer.

Claims (1)

[Claims] 1. After applying hot-dip plating to 11 pipes or pipe fittings,
A method for forming threads for pipes or pipe fittings, which comprises thread-forming portions 2 of the plating layer 4 that require thread forming using a rolling machine 3 so that the alloy layer is plastically deformed.