The classification of stainless steel welding consumables is a crucial and practical topic. The choice of welding consumables directly impacts weld quality, corrosion resistance, and mechanical properties. There are various ways to categorize stainless steel welding consumables, primarily based on material form, matching principles, and functional characteristics. Below, I will provide a detailed and systematic overview.
一. Classification by Welding Consumable Product Form
1. Welding Electrodes (Covered Electrodes / MMAW Electrodes)
● Description: A consumable electrode coated with a flux used for manual metal arc welding (SMAW). The flux generates gas and slag during welding, protects the weld pool, and adds alloying elements.
● Model Identification: Typically designated EXXX (e.g., E308L-16).
● E indicates the electrode.
● XXX indicates the chemical composition of the deposited metal (e.g., 308, 316).
● L indicates low carbon (e.g., 308L).
● -16 indicates the coating type and applicable current (e.g., 16 indicates a basic coating suitable for both AC and DC applications).
● Advantages: Flexible, suitable for various locations and complex working conditions, simple equipment.
● Disadvantages: Lower efficiency, slag that needs to be cleaned.
2. Solid Wires (GMAW Wires)
● Description: Bright, coiled metal wire used for gas shielded welding (MIG/MAG) or tungsten inert gas welding (TIG as a filler wire).
● Model Identification: Usually indicated by ERXXX (e.g., ER308LSi).
● ER indicates electrode rod or filler wire.
● XXX indicates chemical composition (same as electrode).
● L indicates low carbon.
● Si indicates a high silicon content, which improves wettability and weld bead formation.
● Advantages: Continuous wire feed, high efficiency, and no slag.
● Disadvantages: Requires an external shielding gas (e.g., an Ar+CO₂ mixture) and poor wind resistance.
3. Flux-Cored Wires (FCAW Wires)
● Description: Tubular welding wire filled with flux powder. Available in gas-shielded (requires external gas) and self-shielded (does not require external gas).
● Model Identification: Typically designated EXXXT-X (e.g., E308LT1-4).
● E designates the wire type.
● XXX designates the chemical composition.
● T designates flux-cored wire.
● The final digit indicates the shield type, welding position, and performance characteristics.
● Advantages: High deposition efficiency, minimal spatter, good weld formation, and suitable for outdoor windy environments (self-shielded).
● Disadvantages: Generates fumes and is generally more expensive than solid wire.
4. Strip & Flux (SAW)
● Description: Used for submerged arc welding (SAW). The strip is a wide, thin metal strip, and the flux is a granular material that covers the arc to provide shielding.
● Advantages: Deep penetration, extremely high efficiency, high-quality and stable welds, and no spatter.
● Disadvantages: Limited to flat and horizontal welding positions, requiring bulky equipment.
二. Classification by Weld Metal Alloy Type (Matching Principle)
1. Austenitic Stainless Steel Welding Consumables
● Features: Contains high levels of Cr and Ni, generally non-magnetic, with excellent corrosion resistance and ductility.
● Common Grades:
E/ER308(L): For welding 304/304L stainless steel.
E/ER309(L): For welding dissimilar metals, such as stainless steel to carbon steel.
E/ER316(L): For welding 316/316L stainless steel. Contains Mo for improved pitting resistance.
E/ER347: Contains Nb and is used for welding stabilized stainless steels containing Ti or Nb, such as 321/347, to resist intergranular corrosion.
2. Martensitic Stainless Steel Welding Consumables
● Features: High strength, high hardness, and heat treatability, but poor weldability, prone to cold cracking, and requiring preheating and postheating.
● Common Grade: E410 (used for welding martensitic steels such as 410 and 420). Austenitic welding consumables (such as 309) are often chosen to avoid cracking, but this sacrifices weld strength.
3. Ferritic Stainless Steel Welding Consumables
● Features: Contains Cr but no Ni, is magnetic, and easily coarsens grains during welding, resulting in decreased toughness and corrosion resistance.
● Common Grade: E430 (used for welding ferritic steels such as 430). Austenitic welding consumables (such as 309) are also often used to improve performance.
4. Duplex Stainless Steel Welding Consumables
● Features: The weld metal consists of a dual-phase structure of austenite and ferrite, resulting in very high strength and excellent resistance to stress corrosion and pitting corrosion.
● Common grades:
E/ER2209: For welding standard duplex steel 2205 (S31803).
E/ER2594: For welding super duplex steels such as 2507 (S32750).
5. Precipitation-hardening stainless steel welding consumables
● Features: Strengthened by precipitation during heat treatment, it achieves ultra-high strength while maintaining good corrosion resistance. The welding process is complex.
● Common grades: Specialized welding consumables that match the base metal composition, such as those matching 17-4PH.
三. Classification by Special Functional Properties
1. Low Carbon Grade and Extra-Low Carbon Grade (L/EL Grade)
● Designation: The grade contains L (e.g., 308L). Extra-low carbon grades may be designated as EL.
● Purpose: Strictly control the carbon content (C ≤ 0.03%) to minimize chromium carbide precipitation and thus resist intergranular corrosion. It is the most common choice for welding austenitic stainless steel.
2. Nitrogen Grade (N Grade)
● Purpose: Adds nitrogen to duplex steel or super-austenitic steel welding consumables to stabilize the austenite phase and improve strength and corrosion resistance.
3. High Silicon Grade (Si Grade)
● Identification: Contains Si in the grade (e.g., 308LSi).
● Purpose: Increases the silicon content to improve weld pool fluidity, resulting in smoother, more aesthetically pleasing welds and improved wettability (especially for fillet welds).
Summary and Material Selection Principles
When selecting stainless steel welding consumables, the following core steps should be followed:
● Determine the base material composition and type: This is the foundation (is it 304, 316, or 2205?).
● Identify the service environment: This determines the corrosion resistance requirements (is it general corrosion, pitting corrosion, or stress corrosion? Is a low-carbon grade required?).
● Consider the welding method and working conditions: This determines the type of welding consumables (is it manual welding, argon arc welding, or gas shielded welding? Will it be used in a workshop or outdoors?).
● Refer to the principles of equal strength and composition: Generally, the weld metal’s performance must be no less than that of the base material.
● Consider special requirements, such as color matching (important in the decorative industry) and welding dissimilar steels.
We hope this detailed classification will help you better understand and select stainless steel welding materials.