Material of stock headers and x-pipe: Incoloy 800.
#1
Material of stock headers and x-pipe: Incoloy 800.
This came up because I wanted to adapt my x-over to fit my new turbo. This first post has been updated to include the information I have gathered:
Ok So I went and got the headers tested and this is the composition of the pipes and flanges.
Exhaust port flanges: ss304
Other flanges: Mild steel.
Heat shields: ss304
Tubes and collectors, crossover Incalloy 800 group.
The main chemical composition is
Cr (Cromium): 19.05
Fe (iron): 45.75
Ni (Nickel): 30
Monell: 0.029
Zn (Zinc): 3.79
This comes up as Incoloy 800 series alloy according to this table http://www.painc.com/chemical_composition.htm.
No wonder people have trouble repairing these once they crack They are surely assuming it is a lesser alloy and using inadeqaute cleaning and the wrong filler materials:
To make matters worse it is diffucult to work with aged components:
These are the recommended filler materials:
Perhaps this should be made a sticky?
Ok So I went and got the headers tested and this is the composition of the pipes and flanges.
Exhaust port flanges: ss304
Other flanges: Mild steel.
Heat shields: ss304
Tubes and collectors, crossover Incalloy 800 group.
The main chemical composition is
Cr (Cromium): 19.05
Fe (iron): 45.75
Ni (Nickel): 30
Monell: 0.029
Zn (Zinc): 3.79
This comes up as Incoloy 800 series alloy according to this table http://www.painc.com/chemical_composition.htm.
No wonder people have trouble repairing these once they crack They are surely assuming it is a lesser alloy and using inadeqaute cleaning and the wrong filler materials:
From TWI.co.uk http://www.twi.co.uk/technical-knowl...alloys-part-1/
The most serious cracking problem with nickel alloys is hot cracking in either the weld metal or close to the fusion line in the HAZ (heat affected zone) with the latter being the more frequent. Both weld metal and HAZ cracking are generally the result of contamination by grease, oil, dirt, etc left behind following inadequate cleaning;. [...] .Machining or vigorous stainless steel wire brushing followed by thorough degreasing with a suitable solvent is necessary prior to welding, with the welding taking place within about eight hours to reduce the risk of contamination. Any heat treatment must be carried out using sulphur-free fuel or by using electric furnaces. Components that have been in service and require weld repair may need to be ground or machined prior to degreasing to remove any contaminants that have become embedded in the surface in or adjacent to the weld repair area. Remember that if mechanical wire brushing is carried out AFTER the degreasing operation or during welding the compressed air from air powered tools contains both moisture and oil and the cleaned surfaces may be therefore be re-contaminated.
Porosity can be a problem with the nickel alloys, the main culprit being nitrogen. As little as 0.025% nitrogen will form pores in the solidifying weld metal. Quite light draughts are capable of disrupting the gas shield and atmospheric contamination will occur resulting in porosity. Care must be taken to ensure that the weld area is sufficiently protected and this is particularly relevant in site welding applications. [...G]as purity and the efficiency of the gas shield must be as good as possible. It goes without saying that gas purging of the root is essential when depositing a TIG root pass. [...] A small amount of hydrogen (up to 10%) added to the argon shield gas has been found to reduce the problem.
The most serious cracking problem with nickel alloys is hot cracking in either the weld metal or close to the fusion line in the HAZ (heat affected zone) with the latter being the more frequent. Both weld metal and HAZ cracking are generally the result of contamination by grease, oil, dirt, etc left behind following inadequate cleaning;. [...] .Machining or vigorous stainless steel wire brushing followed by thorough degreasing with a suitable solvent is necessary prior to welding, with the welding taking place within about eight hours to reduce the risk of contamination. Any heat treatment must be carried out using sulphur-free fuel or by using electric furnaces. Components that have been in service and require weld repair may need to be ground or machined prior to degreasing to remove any contaminants that have become embedded in the surface in or adjacent to the weld repair area. Remember that if mechanical wire brushing is carried out AFTER the degreasing operation or during welding the compressed air from air powered tools contains both moisture and oil and the cleaned surfaces may be therefore be re-contaminated.
Porosity can be a problem with the nickel alloys, the main culprit being nitrogen. As little as 0.025% nitrogen will form pores in the solidifying weld metal. Quite light draughts are capable of disrupting the gas shield and atmospheric contamination will occur resulting in porosity. Care must be taken to ensure that the weld area is sufficiently protected and this is particularly relevant in site welding applications. [...G]as purity and the efficiency of the gas shield must be as good as possible. It goes without saying that gas purging of the root is essential when depositing a TIG root pass. [...] A small amount of hydrogen (up to 10%) added to the argon shield gas has been found to reduce the problem.
The sensitivity of the age hardened alloy to cracking causes problems when attempts are made to repair items, particularly when these have been in high temperature service and additional precipitation on the grain boundaries has occurred.
Little can be done to overcome this problem apart from a full solution heat treatment but this is often not possible with a fully fabricated component. If repair is to be attempted, small weld beads and controlled low heat input welds are recommended.
Little can be done to overcome this problem apart from a full solution heat treatment but this is often not possible with a fully fabricated component. If repair is to be attempted, small weld beads and controlled low heat input welds are recommended.
INCOLOY alloy 800 has good weldability by all welding processes. Material to be welded must be thoroughly clean, and the proper joint designs must be used. [...]
For (TIG) gas-tungsten-arc, gas-metal-arc, and submerged-arc welding, INCONEL Filler Metal 82 is recommended. Alloy 625 has been extensively used for welding dissimilar joints in austenitic and duplex steels. Use of this filler metal has caused problems and has been discontinued. Alloy 59 or C22 filler metals has replaced Alloy 625 as the filler of choice.
For additional information, refer to the Special Metals publication “Joining” on the Special Metals website at www.specialmetals.com
Click the image to open in full size.
For (TIG) gas-tungsten-arc, gas-metal-arc, and submerged-arc welding, INCONEL Filler Metal 82 is recommended. Alloy 625 has been extensively used for welding dissimilar joints in austenitic and duplex steels. Use of this filler metal has caused problems and has been discontinued. Alloy 59 or C22 filler metals has replaced Alloy 625 as the filler of choice.
For additional information, refer to the Special Metals publication “Joining” on the Special Metals website at www.specialmetals.com
Click the image to open in full size.
Last edited by bebbetufs; 04-03-2013 at 07:21 AM. Reason: New important information added.
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#8
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Inconel 625: 8.03 g/cc
Stainless Steel 304: 8.44 g/cc
Titanium (for reference): 4.51 g/cc
As you can see there is a slight difference but not much. It is the perfect choice for those who want the best of the best, well they could also pony up for Hastelloy C-276, but that is heavier at 8.89 g/cc.
#9
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Patick:
Love the new avatar, simply stunning eye candy. If I continue to keep my job the whole year, I might waste a ton of money and put that dry sump system on my garage queen just for the look!!!
Love the new avatar, simply stunning eye candy. If I continue to keep my job the whole year, I might waste a ton of money and put that dry sump system on my garage queen just for the look!!!
Last edited by URG8RB8; 04-03-2013 at 12:14 AM.
#10
Sorry guys, I'm not making anything in inconel, only adapting the x-pipe to fit my new turbo using SS.
I have been assurered on several occasions that the stock headers are inconel, hence why they're so hard to repair once they crack. I need to know if the x-pipe really is inconel, or if this is just heresay, so I can choose the right filler rod for the job.
I have been assurered on several occasions that the stock headers are inconel, hence why they're so hard to repair once they crack. I need to know if the x-pipe really is inconel, or if this is just heresay, so I can choose the right filler rod for the job.
#13
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From: Bangkok, Thailand, Milpitas, CA & Weeki Wachee, FL
If they truly are Inconel, ideally you would not want to use a SS filler rod, but that doesn't mean it won't work. It would not be that unbelievable that Porsche would have selected this alloy as it is one of the best options for headers, albeit at a considerable difference in price. Some notes from the web:
Use Inconel 625 filler metal for welding Inconel where possible. This is generally the most weldable Inconel alloy and is effective in welding two Inconel pieces together. Inconel 625 can also weld other dissimilar metals, such as stainless steel.
Expect a poorly defined weld pool. Inconel filler metals produce a weld pool with a "skin" on the surface that can appear dirty to welders accustomed to steel. This is normal for Inconel. These welds should be strong and highly resistant to corrosion when they are properly made.
Use Inconel 625 filler metal for welding Inconel where possible. This is generally the most weldable Inconel alloy and is effective in welding two Inconel pieces together. Inconel 625 can also weld other dissimilar metals, such as stainless steel.
Expect a poorly defined weld pool. Inconel filler metals produce a weld pool with a "skin" on the surface that can appear dirty to welders accustomed to steel. This is normal for Inconel. These welds should be strong and highly resistant to corrosion when they are properly made.