Welding P5 Material 5Cr-0.5Mo

Welding P5 Material 5Cr-0.5Mo

When welding P5 material, it is important to use the correct filler metal and welding procedure to avoid cracking, formation of hard microstructure and other weld defects.

welding P5 material can be difficult, as the high Cr-Mo content of the alloy can lead to high hardness, hydrogen cracking and other weldability issues. However, with careful pre-heating and post-weld heat treatment, welders can successfully weld P5 steels.

P5 Material (5Cr-0.5Mo Alloy)

P5 or commonly called as 5Cr-0.5 Mo alloy steel is a chromium-molybdenum alloyed steel that finds use in high temperature, high pressure environments. The material is strong and resistant to heat, oxidation and corrosion with creep resistance.

P5 material Specification

P5 steel UNS number is K41545. ASME Section IX P Number for P5 material is 5B, Group Number 1. The P5 material is available in various forms such as plate, sheet, strip, bar, and pipe.

P5 material (5Cr-0.5 Mo) specification and Grades are:

  1. ASTM A182, A336: Forgings, Grade F5
  2. A199: Seamless tubes, Grade T5
  3. A213: Seamless tubes, Grade T5
  4. A234: Piping fittings, Grade WP5, Cl1 & Cl3
  5. A335: Seamless Pipes, Grade P5
  6. A369: Forged Pipes, Grade FP5
  7. A387: Plate, Grade 5Cl1, Cl2
  8. A691: Fusion welded pipe, Grade 5CR Cl1 & Cl2

These specifications cover different aspects of the material such as the chemistry, mechanical properties and heat treatment.

P5 Material Chemical Composition

P5 is a chromium-molybdenum alloy steel that is used in high-pressure, high-temperature applications.

The material has good weldability and resistance to corrosion. The composition of the steel includes chromium, molybdenum, manganese, silicon, carbon, and iron are shown in the below table:

P5 (5Cr-0.5Mo) Material Chemical Composition
C % Mn % Si % Cr % Mo % S % P %
 0.15 Max.  0.30- 0.60  0.50 Max.  4.0- 6.0  0.45- 0.65  0.030 Max   0.030 Max
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P5 Welding Rod & Electrodes

Welding Rods for P5 Material Welding, 5Cr-0.5Mo Welding are listed below:

  1. E8018-B6
  2. E8015-B6
  3. E8016-B6
  4. E9018-B6 (For welding ASTM A182 Grade F5a)
  5. ER80S-B6
  6. G CrMo5Si
  7. F9PZ-EB6-B6 (SAW Flux-wire combination)
  8. E80C-B6 (Metal Cored wire for welding P5 Material)
Welding P5 Material 5Cr-0.5Mo A335 P5

P5 Material Welding Procedure

P5 Material is a high strength, low alloy ferritic steel. It is classified as a martensitic stainless steel and is commonly used in the construction of power plants & high temperature piping in oil & gas.

The P5 Material Welding Procedure is a set of welding instructions that are followed in order to safely weld P5 material. You can find recommended welding preheat, PWHT and welding electrode in API 582 for P5 material welding.

The P5 Material Welding Procedure consists of four steps:

Preparation, welding, post-welding heat treatment, and inspection.

  • Preparation includes ensuring that the materials to be welded are clean and free of contaminants.
  • Welding must be performed in an inert gas environment to prevent oxidation of the material if welding with TIG or MIG. Root purging is mandatory for P5 material welding.

No purging is required if welding using Stick Welding (SMAW) Process.

  • Post-welding heat treatment is necessary to relieve stress in the material and ensure that the final product meets all strength requirements and hardness requirements.
  • Inspection is performed to ensure that the weld meets all quality standards.

Welding P5 (A335 P5) to Carbon Steel

Welding P5 to Carbon steel is carried out using E8018-B6 welding electrode and should not be welded with E7018 electrode.

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The reason is:

Welding with E8018-B6 will provide higher weld strength compared to base metal. This will ensure the weld is superior compared to carbon steel side base material. This will reduce the chances of failure in weld region.

Welding P5 to P8

Welding of P5 to P8 material is carried out using E309L-15/16 or ENiCrFe-2/ ENiCrMo-3 type filler rods.

Following welding electrodes can be used for welding Cr-Mo steel (P5,P11 P22) to stainless steel (P8 steels) materials:

  1. E309L-15/16/17
  2. E309-15/16/17
  3. ENiCrFe-2
  4. ENiCrMo-3
  5. ERNiCrMo-3
  6. ER309L/ ER309

Welding 316 Stainless to ASTM A335 P5

Welding 316 Stainless to ASTM A335 P5 material is carried out using E309L-15 or ERNiCrFe-2 or ENiCrMo-3 electrodes.

Equivalents TIG welding rods can also be used for the welding of 316 stainless steel to ASTM A355P5 steel. Examples: ER309L, ERNiCrMo-3.

Welding of P5 to P9 Steel

When welding P5 and P9 materials, different welding processes can be employed, and specific welding consumables are recommended for each process. Here are the details for each welding process and the corresponding welding consumables:

  1. Shielded Metal Arc Welding (SMAW):
    • Process: SMAW (Stick Welding)
    • Recommended Consumable: E8018-B6
    • Description: E8018-B6 is an electrode specifically designed for welding chromium-molybdenum alloy steels, such as P5 and P9 materials. It provides excellent strength and creep resistance at elevated temperatures. The “B6” designation indicates the electrode’s suitability for high-temperature applications.
  2. Gas Tungsten Arc Welding (GTAW):
    • Process: GTAW (TIG Welding)
    • Recommended Consumable: ER80S-B6
    • Description: ER80S-B6 is a solid filler wire suitable for GTAW welding of chromium-molybdenum alloy steels, including P5 and P9 materials. It offers good strength, high-temperature creep resistance, and excellent weldability. The “B6” designation signifies its compatibility with high-temperature applications.
  3. Gas Metal Arc Welding (GMAW):
    • Process: GMAW (MIG/MAG Welding)
    • Recommended Consumable: ER80S-B6
    • Description: ER80S-B6 solid wire is also recommended for GMAW welding of P5 and P9 materials. It provides similar characteristics as in GTAW, including high-temperature strength, creep resistance, and good weldability.
  4. Submerged Arc Welding (SAW):
    • Process: SAW (Submerged Arc Welding)
    • Recommended Consumable: F8PZ-EB6-B6
    • Description: F8PZ-EB6-B6 is a flux-cored wire designed for SAW welding of chromium-molybdenum alloy steels like P5 and P9. It offers high-strength welds with good resistance to high-temperature environments. The “EB6” designation indicates its suitability for elevated temperature applications.
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Welding Preheat for P5 Material

P5 Material (5Cr-0.5Mo) shall be preheated to a minimum temperature of 300-400 °F (150- 200°C). (Reference: ASME B31.3)

The interpass temperature shall be kept maximum of 600 °F (315 °C) during the welding of P5 or other Cr-Mo steel materials. (Reference: API 582).

PWHT for P5 Material

PWHT for P5 Material shall be carried out at a temperature of 1325 to 1375(°F). The hold time shall be kept a minimum of 2 Hours.


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