Kurosawa Construction Co., Ltd.

Kei Hirai

Ryohei Kurosawa

Naoki Matsubara

In a method for forming a rustproof film on a PC strand, the thickness of the resin film is set to 200&#xb1;80 &#x3bc;m, the pre-heating is performed within a temperature range from 60 to 150&#xb0; C. to prevent an occurrence of a cob-webbing phenomenon as a result of melting of the synthetic resin powder coating material and the post-heating is performed within a range from 150 to 250&#xb0; C. in order to uniformize the thickness of the coats adhered to the outer peripheral surfaces of the core wire and the surrounding wires, and the temperature of the pre-heating is set to be lower than the temperature of the post-heating, and the synthetic resin powder coating material including particles having diameters in a range from 0.1 to 250 &#x3bc;m is used, and the line speed in the series of steps is set to 5 to 10 m/min.

Method for forming rustproof film on PC strand and PC strand

A double rustproof PC strand has superior durability and semi-permanent rustproof performance. A core wire and surrounding wires are formed of wires subjected to a wire drawing treatment and a plating treatment to be formed with a plated layer. A rustproof treatment is applied by forming a synthetic resin coat on an outer peripheral surface thereof. In order to uniformize and regulate the twisting pitch, the core wire and the surrounding wires are adjusted under the conditions of:

Double rustproof PC strand

A PC strand is untwisted to separate surrounding wires from a core wire, a synthetic resin powdered coating material is uniformly adhered by being applied and heated over the outer periphery of the core wire and surrounding wires in this untwisted state, the product is cooled to form a resin film, and then the surrounding wires are twisted back to the original state with respect to the core wire. Pre-heating is performed before the coating step and post-heating is performed after the coating step, the pre-heating temperature is set 30 to 130&#xb0; C. higher than the post-heating temperature, a synthetic resin powdered coating material having an average grain size of 40 to 50 &#x3bc;m is used, and the process line speed is 5 to 10 m/min.

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Tokyo, Japan

Kei Hirai