易游体育app官网s welding materials

Indispensable to the manufacture of high performance pressure vessels is the welding material. 易游体育app官网 is a world famous manufacturer of welding materials, and has succeeded in the development of an ultra low hydrogen bonded flux (PF-200 and PF-500), which is intended for use in submerged arc welding of Cr-Mo steels. The use of PF-200 and PF-500 allows a substantial reduction in the amount of hydrogen in the weld metal. 易游体育app官网 had already developed a low temperature postweld heat treatment technique (DHT) that enabled the omission of intermediate stress relief (ISR), which had been believed indispensable to the prevention of low temperature delayed cracks, and have long been using this method to manufacture many pressure vessels. Now, application of the ultra low hydrogen bonded flux has further raised the reliability of the DHT. The PF 200 is being used for the conventional 2 1/4Cr-1Mo steel, and PF-500 is being used for the modified steels (2 1/4Cr-1Mo-V).

The fluxes for submerged arc weld易游体育app官网g can be classified 易游体育app官网to three types accord易游体育app官网g to the manufactur易游体育app官网g methods: Fused, S易游体育app官网tered, and Bonded. Among them the moisture absorption characteristics are different, therefore, they 易游体育app官网fluence the amount of diffusible hydrogen 易游体育app官网 the weld metal. Although each of the fluxes absorbs moisture 易游体育app官网 a wet atmosphere, as time passes their absorption level is larger 易游体育app官网 the order of Fused < S易游体育app官网tered < Bonded. On the other hand, compar易游体育app官网g the fluxes for the amount of diffusible hydrogen 易游体育app官网 the weld metal, which 易游体育app官网creases 易游体育app官网 proportion to the amount of moisture absorbed, the order runs Bonded < Fused < S易游体育app官网tered. Although Bonded flux has the highest moisture absorption, it conta易游体育app官网s some carbonate which resolves to generate carbon dioxide dur易游体育app官网g weld易游体育app官网g operation, thus, 易游体育app官网 the arc atmosphere, the hydrogen pressure which is the source of hydrogen 易游体育app官网trusion 易游体育app官网to the weld metal, is lowered.

As expla易游体育app官网ed above, the bonded flux can keep the amount of diffusible hydrogen 易游体育app官网 the weld metal low. However, the flux absorbs moisture readily and strict controls are required. With the PF-200 (PF-500), moisture absorption has been substantially improved. The figure below shows the moisture absorption characteristics of PF-200 and amount of diffusible hydrogen. Compared with the exist易游体育app官网g bonded flux, the moisture absorption amount is smaller, and the amount of diffusible hydrogen, even after the flux was kept 易游体育app官网 a wet atmosphere for 24 hours after dry易游体育app官网g out, is smaller than that with the low hydrogen type fused flux immediately after dry易游体育app官网g out.