Welder Red Seal · Question
A welder is fabricating a tank from 304L stainless steel sheet. After welding several sections, the welder notices a series of small, dark spots forming adjacent to the weld seams. Subsequent testing confirms a reduction in localized corrosion resistance in these areas. What is the most probable cause for this issue?
The formation of dark spots and reduced corrosion resistance in 304L stainless steel adjacent to welds is a classic sign of sensitization, which occurs when exc
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Question: A welder is fabricating a tank from 304L stainless steel sheet. After welding several sections, the welder notices a series of small, dark spots forming adjacent to the weld seams. Subsequent testing confirms a reduction in localized corrosion resistance in these areas. What is the most probable cause for this issue?
Answer options: ✅ Excessive heat input leading to carbide precipitation.
- Insufficient post-weld cleaning, leaving behind slag.
- Using a filler metal with insufficient chromium content.
- A too-slow travel speed causing weld metal dilution.
Correct answer: Excessive heat input leading to carbide precipitation.
Explanation: The formation of dark spots and reduced corrosion resistance in 304L stainless steel adjacent to welds is a classic sign of sensitization, which occurs when excessive heat input causes chromium carbides to precipitate at grain boundaries. This depletes the surrounding areas of chromium, making them susceptible to intergranular corrosion. This is a common issue with stainless steel welding.
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