Stainless steel is a material with a wide range of applications in industry, construction and production, valued for its corrosion resistance, durability and aesthetics. It is used in structures exposed to moisture, chemicals and extreme temperatures, such as in the food, pharmaceutical, chemical and shipbuilding industries. The key feature of stainless steel is the passive oxide layer, which protects it from corrosion. However, improper welding of stainless steel can lead to damage to this layer, weakening the material and the formation of intergranular corrosion.
Welding in difficult conditions – in places with high humidity, large temperature fluctuations or the presence of pollution – is an additional challenge. Incorrect steel welding technology can lead to cracks, deformation or weakening of welds. In such conditions, the use of appropriate methods is crucial, such as TIG welding, MIG welding, consumable electrode welding or welding in an inert gas shield, which ensure high quality welds and minimize the risk of corrosion.
Stainless steel – properties and challenges in welding
Stainless steel is distinguished by its high corrosion resistance, which makes it an ideal material for applications in the food, chemical, medical and construction industries. Its key feature is the passive oxide layer, which protects the surface from the effects of moisture, chemicals and oxygen. However, this layer can be damaged during welding of stainless steel, leading to an increased risk of intergranular corrosion.
Another challenge is the effect of high temperature on the structure of the steel – improper welding of stainless steel can cause local overheating, leading to deformation and weakening of the mechanical properties of the material.
Types of stainless steel
Stainless steels are divided into several types, which differ in structure and properties:
- Austenitic steel – most commonly used, characterized by high corrosion resistance and good weldability (e.g. 304, 316 steel).
- Ferritic steel – resistant to oxidation, but more difficult to weld due to its tendency to crack.
- Martensitic steel – hard and durable, but susceptible to brittleness after welding.
- Austenitic-ferritic steel (Duplex) – combines the features of austenitic and ferritic steel, has high strength and good corrosion resistance.
Problems When Joining Stainless Steel
Different problems can occur when welding stainless steel:
- Intergranular corrosion – damage to the passive layer, leading to a weakening of the structure.
- Thermal deformations – resulting from thermal expansion, especially in thin sheets.
- The impact of inappropriate welding methods – e.g. use of the wrong shielding gas or too high a temperature, which can cause cracks and structural changes.
Which welding methods work best in difficult conditions?
Welding stainless steel in difficult conditions requires the use of methods that provide high-quality welds and corrosion resistance. The choice of the right technology depends on the thickness of the material, the environmental conditions and the requirements for the durability of the connections.
TIG welding – a precise method for thin elements
TIG welding (Tungsten Inert Gas) is one of the most precise methods used to join stainless steel, especially in thin-walled structures.
- It uses a tungsten electrode, which allows for high quality and cleanliness of the weld.
- A shield of inert gases (usually argon or an argon mixture) protects the molten metal from oxidation.
- A method used to join stainless steel in the food, pharmaceutical and aerospace industries.
- It requires high precision and experience of the welder, and the welding speed is lower than in other methods.
MIG and MAG welding – effective stainless steel welding with a mig machine
MIG (Metal Inert Gas) and MAG (Metal Active Gas) welding are fast and efficient methods that work well in stainless steel welding with a mig machine.
- Welding with a consumable electrode allows for effective joining of thick and medium materials.
- The shielding gas in the MIG method (argon) provides protection against oxidation, while MAG uses active gases (e.g. CO₂).
- Popular in welding stainless steel in the heavy, construction and automotive industries.
- Higher risk of spatter formation and the need for appropriate surface preparation.
Electrode welding (MMA) – resistance to difficult conditions
The MMA (Manual Metal Arc) method, or welding with a coated electrode, is used in field conditions and where other methods are difficult to use.
- Electrodes for stainless steel provide good weld quality in outdoor conditions.
- Reliable in places exposed to moisture, variable temperatures and strong gusts of wind.
- Slower than MIG/MAG methods and requires more post-processing.
Orbital Welding – Ideal for Joining Pipes and Structural Components
Orbital welding is an automated method used to precisely join stainless steel pipes.
- Ensures repeatability of welds and minimizes the risk of welding errors.
- Used in pharmaceutical, food and chemical installations, where high quality welding is required.
- Requires specialist equipment and precise calibration.
Laser welding – modern technology limiting the impact of temperature
Laser welding is a modern method used where it is crucial to limit the impact of temperature on the material.
- Allows to connect thin sheets and decorative elements without the risk of deformation.
- Ensures high precision and durability of welds.
- Ideal for automation and robotic welding in industry.
- Expensive and requiring advanced equipment.
How to ensure corrosion resistance during welding?
When welding stainless steel, one of the most important challenges is to maintain its corrosion resistance. Inappropriate working conditions, errors in material preparation or the use of incorrect parameters can lead to damage of the protective layer and increased susceptibility to intergranular corrosion. To avoid this, several key rules must be followed.
Preparing the surface for welding
A thorough cleaning and removal of contamination is the first step in ensuring high-quality welds.
- Removal of grease, oil and chemical contamination.
- Use of stainless steel brushes to clean welds – avoid contact with other metals that may cause rust.
- Degreasing of surfaces with chemicals to prevent non-metallic inclusions.
Selecting the right shielding gases
Inert gas welding protects the molten metal from reacting with oxygen.
- Argon – ensures high weld purity and minimizes oxidation.
- Argon and CO₂ mixture – improves arc stability and penetration depth in the MIG/MAG method.
- Helium in the shielding gas mixture – improves thermal conductivity and ensures better weld quality.
Controlling the welding temperature and speed
Overheating the material can lead to loss of the passive oxide layer and deformation.
- Avoiding excessive heat input so as not to weaken the metal structure.
- Appropriate welding speed – welding too slowly causes overheating, and too fast can result in insufficient weld penetration.
- Interpass cooling – reduces the risk of oxidation and improves the quality of the joint.
Types of welding wires
Choosing the right welding wires affects the durability and resistance of the joints.
- 308 LSi welding wires – designed for austenitic steels, providing good corrosion resistance.
- 316 LSi welding wires – used in aggressive environments, e.g. in the chemical and food industries.
Passive oxide layer protection
The passive oxide layer is a key element that protects stainless steel from corrosion.
- Avoiding mechanical damage – any scratch can weaken the protective layer.
- Treating the surface with chemical passivation – restoring resistance after welding.
- Minimizing exposure to high temperature – prevents the formation of weakened zones around the weld.
What are the challenges of welding stainless steel in industrial conditions?
Welding stainless steel in industrial conditions involves a number of challenges that can affect the quality and durability of joints. Factors such as weather conditions, material thickness, weld aesthetics and process automation require the use of appropriate methods and technologies.
Welding in outdoor conditions – the influence of humidity and temperature
Welding in the open, e.g. on construction sites or in industrial installations, requires taking into account the influence of humidity, temperature and wind.
- Humidity can lead to weld contamination and increased risk of corrosion.
- Low temperatures can cause cracks in the structure of stainless steel, so controlled heating is necessary.
- Proper shielding of inert gases (argon, argon and CO₂ mixture) minimizes metal oxidation.
- Spawanie grubych materiałów – jak zapewnić optymalną jakość przy dużych przekrojach?
Thicker cross-sections require precise control of welding parameters to avoid incomplete fusion and internal stresses.
- MIG/MAG and TIG welding methods are most commonly used for welding thick materials.
- Preheating and controlled cooling prevent deformation and cracks.
- Multi-layer welding helps to obtain a solid and durable joint.
Welding decorative elements – how to avoid discolouration and maintain aesthetics?
In the furniture and architectural industry, the aesthetics of welds and stainless steel surfaces are important.
- Avoid overheating – too high a temperature causes discolouration, which requires additional processing.
- Thorough cleaning and passivation restore the natural appearance of the steel.
- TIG welding ensures smooth and precise welds, minimising the need for grinding.
Robotic welding – automation of welding processes in industry
In modern industry, robotic welding is increasingly used, which ensures repeatability and efficiency.
- Precise process control eliminates human errors and increases the quality of welds.
- Possibility of welding in difficult conditions – robots can work at high temperatures and with chemically aggressive substances.
- Lower production costs thanks to reduced material consumption and waste minimization.
How to weld stainless steel?
Welding stainless steel in difficult conditions requires a precise approach, appropriate methods and process control to ensure high quality joints and corrosion protection. Surface preparation for welding, selection of the right shielding gases and temperature control are crucial to avoid overheating and damage to the passive oxide layer.
In difficult conditions, such as welding in the field, with variable temperature and humidity, MIG/MAG, TIG and electrode welding (MMA) are particularly important, which ensure durability of welds and resistance to atmospheric factors. In the case of industrial applications, robotic welding is increasingly used, which guarantees repeatability and efficiency of the process.
If you are looking for professional stainless steel welding services, contact Deffor. Our team of specialists offers high-quality welding in all conditions, taking care of the durability and resistance of welds. Regardless of the scale of the project, we ensure precise execution and compliance with industry standards.
Contact us today! See how we can help you implement your project – professional stainless steel welding services available at Deffor.
