How to Weld WC4, WC5 and WC6 alloy casting


WC4, WC5 & WC6 Material

WC4, 5 & 6 are low alloy casting as per ASTM Specification ASTM A217. The main alloying are Chromium and Molybdenum along with Nickel (WC6 without Nickel). The material is suitable for high temperature applications and used in valve, flange & fitting casting parts for oil & gas, petrochemical and powerplant.

ASME P No. & Group No. for WC4, WC5 and WC6: P No. 4, Group No. 1

Material Specification & UNS No.

  1. Material specification for WC4, WC5 & WC 6: ASTM A 217
  2. UNS No. WC4: 12082
  3. UNS No. WC5: J22000
  4. UNS No. WC6: 12072

Chemical and mechanical properties of WC4, WC5 & WC6

ElementWC4WC5WC6
Carbon 0.05- 0.2 0.05- 0.2 0.05- 0.2
Manganese 0.5- 0.8 0.5 – 0.70.5- 0.8
Silicon 0.6 0.60.6
Chromium0.50-0.800.5 – 0.91- 1.50
Molybdenum0.45-0.650.9 – 1.20.45-0.65
Copper 0.5 0.50.5
Nickel0.7- 1.100.6 -1.00.5
Tungsten 0.1 0.10.1
Phosphorus 0.045 0.045 0.045
Sulfur 0.045 0.045 0.045
Single values are the maximum permitted

Mechanical properties of Grade WC4, WC5 & WC6 is given in the below table:

  1. Tensile Strength: 70 Ksi [485 MPa to 95 Ksi [655 Mpa]
  2. Yield Strength: 40 Ksi [275 MPa]
  3. Elongation: 20%

Welding rod/ filler wire for WC4, WC5 & WC6

Stick Welding or SMAW (Shielded metal arc welding) of Grade WC4, WC5 & WC6 is carried out using E8018-B2 type low hydrogen electrodes. Before the welding, electrode must be baked as per manufacturer recommendation or guidelines listed here.

TIG welding or MIG Welding of Grade WC4, WC5 & WC6 is carried out using ER80S-B2 type filler wire. Welding is also carried out using ER80S-B3 filler wire. Pure argon gas is used for shielding in TIG welding. Due to low amount of chromium, purging is not required for welding of Grade WC4, WC5 & WC6.

Preheat & Interpass temperature

A preheat temperature of 350-450°F (175-230°C) is applied before the welding of Grade WC4, WC5 & WC6 and preheat shall be maintained during the welding. Maximum interpass temperature of 600 °F (315 °C) is applicable for welding of Grade WC4, WC5 & WC6 or other 1.25Cr-0.5 Mo materials.

PWHT or Post weld heat treatment is carried out at 650 °C to 705 °C (1,200 °F to 1,300 °F). The holding time for PWHT is 1 hour per 25 mm or 1 inch but minimum shall be15 min as per ASME B31.3 PWHT guidelines.

Use below calculator to calculate preheat temperature for any materials.

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