Reducing pipe, also known as reducer, is one of the chemical pipe fittings used for connecting two different pipe diameters. The roundness of the reducing pipe should not exceed 1% of the corresponding end outer diameter, and the allowable deviation is ± 3mm. The material of the reducer shall comply with SY/T5037, GB/T9711, GB/T8163, American standard ASTM A106/A53 GRB, API 5L, APT5CT, ASTM A105, ASTM A234, ASTM A106, DIN German standards, and customer requirements.