How To Weld Stainless Steel with Spot Welding
Stainless steel is a widely used material known for its excellent corrosion resistance and mechanical properties. Medium frequency inverter spot welding offers unique advantages in terms of precision, control, spot welding is one welding process of resistance welding, and welding quality for stainless steel. In this article, we will explore the process and considerations for resistance spot welding stainless steel.
Material Selection and Preparation: Choosing the right stainless steel based on specific application requirements is crucial before starting the welding process. Stainless steel contains various alloy elements such as chromium, nickel, and molybdenum, which contribute to its corrosion resistance and weldability. Additionally, the workpiece surface should be properly cleaned and free of contaminants to ensure optimal welding quality.
Electrode Selection: The choice of electrode is critical when welding stainless steel. It is recommended to use electrodes made from materials compatible with stainless steel, such as chromium zirconium copper or copper alloys. These electrodes offer good electrical conductivity and thermal stability, ensuring effective energy transfer and prolonged electrode life.
Welding Parameters: To successfully weld stainless steel, it is crucial to precisely control the welding parameters. Factors such as welding current, time, and pressure need to be optimized based on the grade and thickness of the stainless steel. Generally, a lower welding current is preferred to minimize heat input and prevent deformation while ensuring proper fusion of the material. Different thicknesses of stainless steel plates may require different welding currents and times. Therefore, you need to know the appropriate welding parameters for each thickness of stainless steel. Below is a table of welding parameters for spot welding stainless steel.
| Thickness/mm | Electrode tip diameter/mm | Welding current/A | Welding time/s | Electrode pressure/N |
| 0.3 | 3.0 | 3000~4000 | 0.04~0.06 | 800~1200 |
| 0.5 | 4.0 | 3500~4500 | 0.06 ~0.08 | 1500 ~2000 |
| 0.8 | 5.0 | 5000~6500 | 0.10 ~0.14 | 2400~3600 |
| 1.0 | 5.0 | 5800 ~6500 | 0.12 ~0.16 | 3600~4200 |
| 1.2 | 6.0 | 6500 ~7000 | 0.14 ~0.18 | 4000 ~4500 |
| 1.5 | 5.5~6.5 | 6500~8000 | 0.18 ~0.24 | 5000~5600 |
| 2.0 | 7.0 | 8000 ~10000 | 0.22 ~0.26 | 7500 ~8500 |
| 2.5 | 7.5 ~8.0 | 8000~11000 | 0.24~0.32 | 8000 ~10000 |
Shielding Gas: Welding stainless steel typically requires the use of shielding gas to protect the weld area from oxidation and contamination. A common choice is a mixture of argon and helium, which provides a stable arc and effectively protects the molten metal. The flow rate of the shielding gas should be adjusted to ensure adequate coverage and protection during the welding process.
Welding Technique: When using spot welder for stainless steel, the correct welding technique is crucial. It is recommended to use a series of short welding pulses instead of continuous welding to minimize heat input and control the weld pool. Additionally, maintaining consistent pressure throughout the welding process helps achieve strong and uniform weld joints.
Post-Weld Treatment: After completing the welding process, it is important to perform post-weld treatment to ensure the stainless steel meets the required performance standards. This may include processes such as passivation, pickling, or annealing, depending on the specific stainless steel grade and application requirements. These treatments help restore corrosion resistance and eliminate any potential sensitization issues caused by the welding process.
Post-Weld Testing: To verify the weld strength meets the required standards, destructive testing or tensile testing is typically performed after welding. Destructive testing visually inspects whether the weld joint has fully penetrated the workpiece. If the joint is easily broken, the weld is unsuccessful. A successful weld will tear the base metal without breaking the joint. Tensile testing measures the maximum tensile strength the weld joint can withstand, providing a professional assessment to determine if it meets the required specifications based on the needed tensile strength of the workpiece.
Medium frequency inverter spot welding offers an effective method for welding stainless steel, providing precise control, minimal heat input, and excellent weld quality. By considering factors such as material selection, electrode choice, welding parameters, shielding gas, welding technique, and post-weld treatment, manufacturers can achieve reliable and durable welds in stainless steel applications. With its inherent advantages, medium frequency spot welding machines are valuable tools in industries like automotive, construction, and food processing, where corrosion resistance and mechanical integrity are crucial.
When you use a spot welder for stainless steel welding, the above insights should be helpful. Additionally, choosing a high-quality stainless steel spot welder is also an important factor.