Basic knowledge about duplex steel fittings manufactures

Duplex stainless steel flanges are normally forged to form, as required by the ASTM A182/A182M standard, but may also potentially be machined directly from forged stainless steel bar by duplex steel fittings manufactures. In order to evaluate the integrity of such flanges, axisymmetric elastic-plastic finite element models have been developed, considering static effects such as bolt load and internal pressure. Additionally, tensile testing of a sample forged bar (UNS S31803) has been conducted. The elastic modulus of the forged bar has also been determined, and was found to be lower than anticipated in the axisymmetric models. Some specimens have also been found to exhibit highly non-linear elastic properties.

Duplex stainless steel flanges may potentially be manufactured by forging the source material as close to form as possible, or alternatively by machining the entire geometry from a forged bar source. The forging procedure requires available production time on highly specialized equipment, which may potentially increase the lead time of a flange product forged to form. Manufacturing the flange from bar stock, on the other hand, only requires conventional machining equipment, and available bar stock. Potential benefits to duplex steel flange supplies from using the latter manufacturing method may be a reduction in the lead time, as well as the cost of the finished flange product.

The widely used ASTM (American Society for Testing and Materials) A182/A182M standard specifies that " stainless steel forged flanges wholesale of any type, elbows, return bends, tees, and header tees shall not be machined directly from bar stock", and "The material shall be forged as close as practicable to the specified shape and size".