Welding Nickel base alloy to Stainless steel Dissimilar weld
Welding Inconel (or) Incoloy to Stainless steel
UNS No ALLOY Ni C Mn Fe S Si Cu Cr Al Ti Nb OTHER
N06600 600(Inconel 600) 76.0 0.08 0.5 8.0 0.008 0.25 0.25 15.5 . . . . . . . . . . . .
N08800 800 (Incoloy800) 32.5 0.05 0.5 39.5 0.008 0.50 0.50 21.0 0.40 0.40
Important points to be noted during welding of dissimilar welds by GTAW.
N06600 600(Inconel 600) 76.0 0.08 0.5 8.0 0.008 0.25 0.25 15.5 . . . . . . . . . . . .
N08800 800 (Incoloy800) 32.5 0.05 0.5 39.5 0.008 0.50 0.50 21.0 0.40 0.40
Important points to be noted during welding of dissimilar welds by GTAW.
- For dissimilar welds the weld joint Edge preparation angle should be larger,
- The welding job should be cleaned and welded in clean environment.
- Because the welding area should be screened to avoid drafts, because disruption of the shielding atmosphere and drawing in of air can cause porosity in the weld metal.
- Welding gas purity and dryness of the welding gas are important, welding-grade shielding gas should be used.
- During welding, the hot end of the wire must remain under the shielding gas to avoid oxidation.
- A short arc length should be maintained to ensure that deoxidizing elements transfer to the weld pool.
- The speed of welding affects penetration, weld width, and weld soundness, especially when no filler metal is added.
- Speeds outside this range,either faster or slower, can result in increased porosity.
- When
welding thinner-gage material, the required heat input is considerably
lower. This contributes to increased porosity, which is due to the
increased solidification rate of the molten
weld pool. - This metal has such a high thermal conductivity
- The largest gas nozzle size applicable to the job should be used for GTAW weld, and a minimum practical distance between the nozzle and the work should be maintained.
How to weld Inconel to SS butt joint using Inconel filler wire?
Whether we have to weld from
A) Inconel base metal to SS base metal or
B) SS base metal to Inconel Base metal.
Answer is "A"
What will happen is SS is welded over Inconel?
Fissure will be developed.
SS's are typically Cr based.
Inconels are Ni based materials.
Inconel weld has a tendency to hot crack or delay crack even upto 72 hrs after reaching ambient temperature
Inconel is much more sluggish than welding everyday stainless steel!
As per ASM handbook
Hot shortness of welds
1. Can result from contamination by - low-melting-point elements like sulfur, phosphorous,zinc etc
Weld metal cracking also can be caused by
a. heat input that is too high,
b. high welding current and
c. low welding speed
d. cracking may result from undue restraint
e. convex beads are virtually immune - to center-line splitting,
f. concave beads are particularly susceptible to center-line cracking.
h. If Dilution is higher on the dissimilar side eg. low alloy steel or SS (other side of the nickel alloy)
i. The width to depth ratio of bead to be smaller.ie smaller bead size,
When join nickel and nickel alloys to dissimilar metals.
1.When depositing the first bead, the arc should be directed toward the member from which dilution of the weld metal will be least detrimental.
2. The welding current should be maintained near the middle of the recommended range.
3.Dilution usually can be kept below 25% by manipulating the electrode to dissipate the arc force on already-deposited weld metal.
Welding procedures that reduce the amount of penetration, which can cause or reduces dilution of the weld metal by the base metal, will increase the probability of securing a good weld.
Refer:
1. ASM handbook vol 6. Welding of Nickel Alloys E.B. Hinshaw, Inco Alloys International, Inc
2. Liquation cracking during the welding of austenitic stainless steel and nickel alloys
by J.B. Robinson and A.H Scott, phil.trans.R.Soc.Londen A 295 105-117 (1980)
The welding institute , Abington Hall, Cambridge
Whether we have to weld from
A) Inconel base metal to SS base metal or
B) SS base metal to Inconel Base metal.
Answer is "A"
What will happen is SS is welded over Inconel?
Fissure will be developed.
SS's are typically Cr based.
Inconels are Ni based materials.
Inconel weld has a tendency to hot crack or delay crack even upto 72 hrs after reaching ambient temperature
Inconel is much more sluggish than welding everyday stainless steel!
As per ASM handbook
Hot shortness of welds
1. Can result from contamination by - low-melting-point elements like sulfur, phosphorous,zinc etc
Weld metal cracking also can be caused by
a. heat input that is too high,
b. high welding current and
c. low welding speed
d. cracking may result from undue restraint
e. convex beads are virtually immune - to center-line splitting,
f. concave beads are particularly susceptible to center-line cracking.
h. If Dilution is higher on the dissimilar side eg. low alloy steel or SS (other side of the nickel alloy)
i. The width to depth ratio of bead to be smaller.ie smaller bead size,
When join nickel and nickel alloys to dissimilar metals.
- Direction of arc flow during welding
- Current range
- Dilution shall be controlled as given below.
1.When depositing the first bead, the arc should be directed toward the member from which dilution of the weld metal will be least detrimental.
2. The welding current should be maintained near the middle of the recommended range.
3.Dilution usually can be kept below 25% by manipulating the electrode to dissipate the arc force on already-deposited weld metal.
Welding procedures that reduce the amount of penetration, which can cause or reduces dilution of the weld metal by the base metal, will increase the probability of securing a good weld.
Refer:
1. ASM handbook vol 6. Welding of Nickel Alloys E.B. Hinshaw, Inco Alloys International, Inc
2. Liquation cracking during the welding of austenitic stainless steel and nickel alloys
by J.B. Robinson and A.H Scott, phil.trans.R.Soc.Londen A 295 105-117 (1980)
The welding institute , Abington Hall, Cambridge