Welding material selection of nickel base alloy

1. nickel-based alloy classification and grade (seven categories) :

◆ Industrial pure nickel (P41) : containing 99.5% nickel. Such as Ni200, Ni201.

◆Ni-Cu alloy (P42) :

Such as: Monel 400 (Monel, Ni66Cu32) etc.

◆Ni-Cr alloy (P43) :

Such as: 0Cr30Ni70

Corronel230 (Coro Nickel, Cr35Ni65)

Inconel671 (Inconel, Cr50Ni50)

◆Ni-Cr-Fe alloy (P43) :

Such as: Inconel600 (Inconel, Cr76Ni15Fe8)

Inconel625 (Cr61Ni21Mo9Fe3)

◆Ni-Mo alloy (P44) :

E.g. Hastelloy A (Hastelloy A, Ni60Mo19Fe20)

Hastelloy B (0Ni65Cr28Fe5V)

Hastelloy B-2 (00Ni70Mo28)

◆Ni-Cr-Mo alloy (P44) :

Such as: Hastelloy C (Ni60Cr16Mo16W4)

Hastelloy C-276 (000Ni60Cr16Mo16W4)

Hastelloy C-4 (000Ni60Cr16Mo16Ti).

◆Ni-Fe-Cr alloy (P45) :

E.g. Incoloy 800 (Inconroy, Ni32Fe46Cr21)

Incoloy 825 (Ni42Fe30Cr21)

2. nickel-based alloy welding characteristics:

Nickel-based alloy welding has similar problems with austenitic stainless steel welding:

(1) Welding hot crack

(2) Porosity: Compared with low carbon steel and low alloy steel, porosity tends to be larger, especially for unclean bevelings and Welding Wires.

(3) Corrosion resistance: most nickel-based corrosion resistant alloys do not have much impact on corrosion resistance after welding. But for Ni-Cr, Ni-Mo, Ni-Cr-Mo series of some alloys near the heat affected zone will occur chromium deficiency phenomenon, resulting in some medium in the intergranular corrosion, stress corrosion performance decline.

(4) Process characteristics: the fluidity of liquid weld metal is poor; Weld metal melting depth.

3. welding process points:

(1) Correct selection of welding materials

(2) Connector type: the joint type with large groove Angle and small pure edge

(3) Cleaning near the groove and welding wire: the characteristics are important to prevent hot cracks and pores.

(4) Preheating before welding: generally do not need to preheat before welding, the interlayer temperature should be controlled below 100 ℃. However, when the temperature of the base material is lower than 15 ° C, it should be heated to 15-20 ° C to avoid condensation of moisture.

(5) Welding process:

◇ Limit the heat input, use small line amount and maintain the stability of arc voltage, and use the operation method of short arc without swing or small swing.

◇ For the small diameter pipe welding process should take forced cooling measures to reduce the high temperature residence time of the weld, increase the cooling speed of the weld.

◇ Timely cleaning of slag and splash on the weld surface after welding to prevent impurities such as S in the slag from causing embrittlement of the weld or decreasing anti-corrosion performance.

(6) Post-welding heat treatment: generally not recommended post-welding heat treatment. But sometimes in order to ensure that no intergranular corrosion or stress corrosion occurs in use, heat treatment is required.

4. Classification and model of Welding Rod:

★GB/T13814-92 "Nickel and nickel alloy electrode" standard equivalent to the United States ANSI/AWS A5.11-89 "Nickel and nickel alloy coated electrode regulations" : (five types)

◆ Industrial pure nickel electrode: ENi-0, ENi-1

◆Ni-Cu electrode: ENiCu-7

Ni-Cr-Fe electrode: ENiCrFe-0 to ENiCrFe-4

Ni-Mo welding rod: ENiMo-1, ENiMo-3, ENiMo-7

◆Ni-Cr-Mo electrode: EnICRMI-0 to EnICRMI-9

★ Coating type: Titanium-calcium type (03), alkaline (15, 16)

5. welding wire classification and model:

★ According to GB/T15620-1995 "Nickel and nickel alloy welding wire" :

◆ Industrial pure nickel wire:

Ni-Cu welding wire: ERNiCu-7

◆Ni-Cr welding wire: ERNiCr-3

Ni-Cr-Fe welding wire: ERNiCrFe-5, ERNiCrFe-6

Ni-Fe-Cr welding wire: ERNiFeCr-1, ERNiFeCr-2

Ni-Mo welding wire: ErnifECR-1, ERNiMo-2, ERNiMo-3, ERNiMo-7

◆Ni-Cr-Mo welding wire: ErnicrMIo-1 to ErnicRMIO-4, ErnicRMIO-7 to ErnicRMIO-9

6. nickel-based alloy Welding Material selection principle:

(1) Welding material selection of the same nickel material:

◇ Should be selected and base metal alloy series of the same welding material

◇ If there is no corrosion resistance requirement, the welding material different from the base metal alloy system can be selected, but the joint should be guaranteed to have the performance required by the design.

■ Examples:

Monel 400: electrode ENiCu-7; Welding wire ERNiCu-7

Inconel600: Welding rod ENiCrFe-1; Welding wire ERNiCrFe-5

Incoloy 800H: Electrode ENiCrFe-2; Welding wire ERNiCr-3

Hastelloy C-276: Electrode ENiCrMo-4; Welding wire ernicrmio-4

(2) The welding between dissimilar nickel materials and nickel materials and austenitic stainless steel should consider the following factors:

(7) ◇ The strength of the weld (including high temperature lasting strength), corrosion resistance to meet the design;

(END)

The article is excerpted from Chinese Version (Selection of Nickel based Alloy Welding Materials) by Tang Feng