» Technical » C-0.5Mo Alloy Steel

C-0.5Mo Alloy Steel

August 14, 2020

General Introduction

The ASTM A204 Grade B (C-0.5Mo steel) plates in stock, 6 m x 1.5 m x 26 mm. Manufacturer: Wusteel.

The C-0.5Mo alloy steels refer to a series of carbon-molybdenum low alloy steel grades that contains 0.5% (nominal composition) of molybdenum alloying element. The C-0.5Mo steels are mainly intended for elevated-temperature service, and the carbon content is usually limited to 0.20%; in some classes of tubing for boilers, however, carbon may be as high as 0.35%. The molybdenum addition in amounts of 0.5% increases the resistance of the ferritic steels to deformation at elevated temperature hence improves the creep strength.

Strengthening Mechanism & Heat Treatment

The carbon and molybdenum atoms in the C-0.5Mo steel act as interstitial and substitutional solutes respectively during the solid solution process and together contributes to substantial enhancement of creep strength. It is also known as interaction solid-solution strengthening. Meanwhile fine precipitates of Mo2C and Mo2N formed may significantly strengthen the carbon-molybdenum steel. This is known as precipitation strengthening.

The C-0.5Mo steels may be furnished in heat-treated conditions of as-rolled, annealed, normalized, normalized and tempered, stress-relived, depending on specific product forms and purchasers’ requirements. Especially, the use of tempering is an important factor that influences the level of precipitation strengthening and solid-solution strengthening in carbon-molybdenum steel. In a normalized C-0.5Mo steel, the initial contribution from solid-solution strengthening is greater than that of the normalized and tempered steel. In the normalized and tempered C-0.5Mo steel, the initial contribution from precipitation strengthening will be larger than that from the normalized steel. In addition, the precipitation-strengthening effect in the normalized and tempered steel will reach a maximum and begin to decline at an earlier stage due to the earlier incidence of overaging in tempered material. This is a potential consideration in applications requiring creep resistance over long times and at high temperatures.

Product Forms & Applications

The C-0.5Mo steels are extensively used in several forms (piping, pressure vessel plates, bolts, structural parts, forgings) in a variety of applications that involve exposure to elevated temperatures. These application include oil & gas industries, fossil-fuel power plants, chemical industries, and petrochemical processing plants, etc.

Standard & GradeProduct Form
ASTM A234/ ASME SA-234 Grade WP1seamless & welded pipe fittings
ASTM A204/ ASME SA-204 Grade A, B, Cpressure vessel plates
ASTM A209/ ASME SA-209 Grade T1, T1a, T1bseamless boiler and superheater tubes
ASTM A250/ ASME SA-250 Grade T1, T1a, T1bERW boiler and superheater tubes
ASTM A335/ ASME SA-335 Grade P1seamless pipes
ASTM A369/ ASME SA-369 Grade FP1forged pipes
ASTM A217/ ASME SA-217 Grade WC1castings
ASTM A352/ ASME SA-352 Grade LC1castings
ASTM A672/ ASME SA-672 Grade L65, L70, L75EFW pipes
ASTM A691/ ASME SA-691 Grade CM-65, CM-70EFW Pipes
ASTM A336/ ASME SA-336 Grade F1forgings
ASTM A182/ ASME SA-182 Grade F1forgings
ASTM A161 Grade T1seamless still tubes

When used in petrochemical operations for continuous service, the suggested maximum temperature based on creep rate of C-0.5Mo steel is 510°C [950°F], while the suggested maximum temperature based on rupture of C-0.5Mo steel is 595°C [1100°F]. Although both Section I and Section VIII of the ASME Boiler & Pressure Vessel Code have defined allowable stresses for C-0.5Mo steel up to 538°C [1000°C], it shall be used for piping and superheater tubes operating at metal temperatures no higher than 455°C [850°F]. Above this temperature, spheroidization and graphitization may increase the possibility of failure in service.

Maybe you like also


    We have been dedicating ourselves to piping and pipeline engineering since the inception. The company provides integrated solution to package supply of various piping & pipeline materials, components, and equipment.


    Room 502, No.448 Heping West Road, Shijiazhuang, Hebei Province, China
    Tel: +86-311-67906676
    Fax: +86-311-67906676
    Email:  sales@pipingpipeline.com
    Whatsapp: 0086-15076331069

  • Service
    Work Time: 8:30-18:00
    Welcome to contact us at your best convenience.