ThePipingMart Blog Grades P12 Alloy Steel (ASTM A335 P12) – Composition, Properties, and Uses

P12 Alloy Steel (ASTM A335 P12) – Composition, Properties, and Uses

P12 Alloy Steel Grade - Composition, Uses, Properties.

ASTM A335 P12 is a type of steel alloy that is known for its superior strength and durability. It is used in various industrial applications, from automotive parts to medical implants. In this blog post, we will discuss the chemical, physical, and mechanical properties of Alloy Steel Grade P12. We will also cover its uses, corrosion resistance, heat resistance, heat treatment, machining, and welding.

P12 Alloy Steel Chemical Composition

ASTM A335 P12 comprises 0.3-0.5% carbon content and 1-2% manganese content with trace amounts of other elements such as chromium and vanadium. The composition can vary slightly depending on the application or manufacturer’s desired outcome.

C, % Mn, % P, % S, % Si, % Cr, % Mo, %
0.015 max 0.30-0.61 0.025 max 0.025 max 0.50 max 0.80-1.25 0.44-0.65

P12 Alloy Steel Chemical Properties

ASTM A335 P12 includes corrosion resistance due to its high chromium content (13%) and good weldability due to its low carbon content (0.3-0.5%). It also has good creep resistance at high temperatures because of its high manganese content (1-2%).

P12 Alloy Steel Mechanical Properties

The mechanical properties of ASTM A335 P12 include a yield strength range between 200MPa and 600MPa with an ultimate tensile strength of 650MPa to 800MPa. Additionally, it has good abrasion resistance due to its hardness range between 28 HRC and 32 HRC.

Tensile Strength, MPa Yield Strength, MPa Elongation, %
415 min 205 min 30 min

P12 Alloy Steel Physical Properties

The physical properties of ASTM A335 P12 include excellent ductility with elongation up to 15%. It has a melting point between 1450°C and 1530°C and a density range between 7800 kg/m³ and 8000 kg/m³ depending on the grade chosen.

P12 Alloy Steel Equivalent

ASTM ASME Equivalent material JIS G 3458 UNS BS DIN ISO ABS NK LRS
A335 P12 SA335 P12 T12 STPA 22 K11562 3604 P1 620-440 17175
ABS 12 KSTPA 22 Sec 2
1Cr 1/2Mo440
Sec 3
1Cr 1/2Mo440

P12 Alloy Steel Uses

Alloy Steel Grade P12 is used in many industries, including automotive manufacturing for cylinder heads, engine blocks; shipbuilding for pressure vessels; aerospace components; power plants; off-shore drilling rigs; valves; oil pipelines; pumps; general engineering components; construction; heavy machinery components; medical implants such as hip replacements, etc.; military applications such as armour plates, etc.; oil & gas industry components such as flanges, etc., among others.

  • Alloy steels are made by combining carbon steel with one or several alloying elements, such as manganese, chromium, nickel, molybdenum, vanadium, silicon, or boron.
  • The resulting steel contains higher levels of these other elements than what is found in carbon steel and is therefore referred to as being alloyed.
  • Alloy steels are stronger and harder than carbon steel and can be heat treated to improve their strength and hardness further.
  • One of the most popular alloy steels is grade P12, which contains chromium and molybdenum.
  • Grade P12 steels are often used in applications where high temperatures are a concern, such as in power plants and chemical plants.
  • Grade P12 steels can also be used in oil and gas pipelines, as well as in pressure vessels and boiler drums.
  • Another popular use for grade P12 steels is in the construction of welding wire and electrodes.
  • Grade P12 steels are also sometimes used to manufacture cutting tools, such as saw blades and drill bits.
  • Finally, grade P12 steels can also be used in the production of wear-resistant coatings.

Corrosion Resistance

Due to its high chromium content (13%), it has excellent corrosion resistance in most environments, including seawater-resistant applications like marine propellers or anchors when properly treated through heat treatment or surface coating techniques like galvanizing or painting, etc. It can be used in acidic environments; however, additional precautions, such as proper coating, must be taken.

Heat Resistance

The alloy steel grade P12 offers good heat resistance up to 500°C thanks to its increased silicon content (up to 080%), which provides improved oxidation stability at elevated temperatures when subjected to air cooling cycles during processing operations like welding or machining etc.

Heat Treatment

This grade can be hardened by heating it above 860°C followed by rapid cooling, but it does not require further quenching after hardening because it has sufficient retained austenite after cooling, providing improved toughness with reasonable strength levels.


This grade can easily be machined using conventional cutting tools like turning inserts, milling cutters, etc.; however, high cutting speeds are recommended due slow thermal conductivity resulting in increased cutting temperatures leading to potential tool wear if cutting parameters are not optimized accordingly.


Alloys steel grade P12 can be welded using any standard welding technique without preheating, but post-weld heat treatment should always be done at subcritical temperatures below 500°C together with stress relieving cycles whenever possible in order to reduce residual stresses caused by welding, decreasing chances for potential cracking, especially in highly restrained assemblies subject extreme loading conditions.


In conclusion, Alloy Steel Grade P12 is an excellent choice for many industrial applications thanks to its superior strength and durability combined with excellent corrosion, heat, fatigue, wear, and abrasion resistances. Its composition provides great weldability along with good machinability allowing for quick fabrication times even under complex geometries. Finally, proper selection, fabrication, installation, maintenance, inspection, and safe operating procedures must always be considered when designing any assembly involving this type of steel.

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