Core points of welding after stainless steel casting processing: scientific prevention of cracks and intergranular corrosion

existStainless steel casting processingDuring the process, welding is a key follow-up process, but improper operation can easily causecrackandintergranular corrosion, directly affects the performance of the workpiece. This article starts from technical principles and provides practical solutions.

1. Causes and prevention methods of welding cracks

1. Heat affected zone embrittlement problem
   High temperature during welding will cause local carbide precipitation in stainless steel castings. It is recommended to take the following measures:

• SelectLow carbon stainless steel welding consumables(such as ER308L)

• Control the interlayer temperature to be less than or equal to 150 degrees Celsius

• Use small current and fast welding to reduce heat input

2. Residual stress induces cold cracks
   There is internal stress in the casting itself, and welding may aggravate the stress concentration. It can be improved in the following ways:

• Before weldingstress relief annealing(600-650 degrees Celsius heat preservation and slow cooling)

• Avoid cross welds and use segmented jump welding technology

2. Targeted protection against intergranular corrosion

Intergranular corrosion is common in austenitic stainless steels (such as 304, 316). The combination of chromium and carbon results in chromium deficiency at the grain boundaries. Solutions include:

• Material optimization:

• Use stabilized welding consumables containing titanium\/niobium (such as ER347)

• For harsh environments, it is recommended to use ultra-low carbon steel such as 316L

• process improvement:

• Rapidly cool to below 500 degrees Celsius after welding

• on sensitized workpiecesSolution treatment(Water quenching at 1050-1100 degrees Celsius)

3. Practical guide for welding operations

1. Preparation before welding:

• Remove scale and oil stains (acetone cleaning is highly recommended)

• The appropriate bevel angle is 60 degrees ±5 degrees.

2. Parameter suggestions:

   Welding consumable type	Current(A)	Voltage(V)	protective gas
   ER308L	90-120	20-24	Ar plus 2 percent O₂
   ER316L	85-110	18-22	Pure Ar

3. Post weld inspection:

• Penetrant testing(PT) Detect surface defects

• Salt spray test to verify corrosion resistance

4. Analysis of typical cases

A valve factory developed cracks when welding a CF8M stainless steel valve body. After analysis, it was found that:

• Direct welding without preheating causes cold cracks

• Misuse of ordinary 308 welding wire (308L is not selected)
  Improvement plan: preheating at 200 degrees Celsius and adding ER308L welding wire before welding will significantly reduce the problem.