ASME SA335 / ASTM A335, Chrome-Moly pipe is the standard for seamless ferritic Alloy-Steel Pipe produced in nominal or minimum wall thickness for high temperature service.
Chrome Moly products are named so due to the presence of the two elements Chromium (Cr) and Molybdenum (Mo). Cr increases the material’s resistance to corrosion and oxidation, and raises the material’s strength at high temperatures. Mo is known to increase tensile and creep strength at high temperatures, reduces brittleness, and improves hardenability. Sometimes referred to as “P Grade” materials or simply “Chrome”, chrome moly pipe comes in more than 17 grades with the most widely used P-Grades being P5, P9, P11, P22 and P91.
It is commonly known that A335 / SA335 material is extensively used in a variety of plants & processes across the globe including refineries, power plants, petro-chemical plants, hydrocrackers, cokers, high and super high temperature lines, reheat lines, distillation, oil field services, etc. In general, the most commonly used P grades in refineries are P5 & P9. The most commonly used P grades in the power generation industry and petro-chemical plants are P11, P22 & P91.