This specification covers chrome-molybdenum (4135) seamless steel tubing of aircraft quality.

Classification:

Tubing shall be of the following types and physical conditions, as specified (see 6.2):

Type I - Round

Type II - Rectangular or square

Type III - Streamline

Type IV - Oval

Physical condition:

(A) - Annealed

(N) - Normalized or stress relieved

(HT-125) - Heat treated to a minimum tensile strength of 125,000 psi

(HT-150) - Heat treated to a minimum tensile strength of 150,000 psi

(HT-180) - Heat treated to a minimum tensile strength of 180,000 psi

(HT-200) - Heat treated to a minimum tensile strength of 200,000 psi

Unless otherwise specified, tubing shall be furnished in type I, condition (N).