Welding of SS on CS

[Talha Aamir]

Why cannot weld SS 316L on CS directly? Why do we need to use the SS 309 welding rod on CS to provide a base to weld SS 316L?

[sridhar cn]

Dear Aamir,

  A 316L filler would yield a deposit that, when mixed with carbon steel, would be similar to a 410 a Martensitic stainless deposit.                     This would be a weld deposit that may be too brittle for the application.

 The recommended filler, in this case, would be 309L Mo (not 309L) since, when mixed with carbon steel, it yields a deposit similar 

 to a 316L (with Cr, Ni & Mo alloys) deposit. Carbon is close to chromium and under high heat for a long time, they combine for carbides. 

 

As a result, there is less free chromium to form the corrosion-resistant film, and rust can appear. Further, the affected metal becomes brittle and prone to cracking. This way, you keep the superior resistance of the stainless steel part and prevent hot-cracking defects.

To get a lower heat input (forming an undesirable bluish colour weld and HAZ),  

• set the lowest amperage that will melt the filler metal.
• set a faster travel speed.
• prefer stringer beads instead of weaving.
• use chill bars under or on the metals.
• prepare a symmetrical joint that needs the least amount of weld mental.
• point the arc towards the stainless part to get a good toe fusion. 

Sridhar.

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On Tue, 2 Jul 2024 at 09:58, Talha Aamir <aamirt...@gmail.com> wrote:

Why cannot weld SS 316L on CS directly? Why do we need to use the SS 309 welding rod on CS to provide a base to weld SS 316L?

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[Lubos Mraz]

You have to use SS309 filler metal in order to get austenitic weld metal of the joint. SS316L filler metal will provide you martensitic weld metal due to dilution with CS.

On Tue, Jul 2, 2024 at 6:28 AM Talha Aamir <aamirt...@gmail.com> wrote:

Why cannot weld SS 316L on CS directly? Why do we need to use the SS 309 welding rod on CS to provide a base to weld SS 316L?

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[Nguyễn Khắc Nhàn]

Hi,

1. If welding ss direct to cs lead to hydrogen or solidification cracking due to fully austenitic weld with impurities picked up from cs side. 

2. Type 309 allow the deposition of weld metal with delta ferrite  content, which reduce the sensitivity to hot cracking.

On Tue, 2 Jul 2024, 11:28 Talha Aamir, <aamirt...@gmail.com> wrote:

Why cannot weld SS 316L on CS directly? Why do we need to use the SS 309 welding rod on CS to provide a base to weld SS 316L?

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