1. Ներածություն
Welding stainless steels is routine in industry, բայց how matters: every stainless group (ավստենիտիկ, ֆերիիտիկ, կրկնակի, պատերազմական, precipitation-hardening, and high-alloy grades) brings distinct metallurgical behaviours that determine process choice, filler alloy, heat input, pre/post-treatment, and inspection regimes.
With correct process selection and controls—shielding gas, heat input, filler match, interpass temperature and appropriate post-weld cleaning—most grades can be welded to deliver reliable strength and corrosion resistance.
Misapplied practices, սակայն, lead to hot cracking, զգայունացում, embrittlement or unacceptable corrosion performance.
2. Why Weldability Matters for Stainless Steels
Չժանգոտվող պողպատ’s value lies in its unique dual promise: Կոռոզիոն դիմադրություն (from its chromium-rich oxide layer) and structural reliability (from its tailored mechanical properties).
In industries such as oil & գազ, Էլեկտրաէներգիայի սերունդ, Քիմիական մշակում, շինարարություն, and food equipment, the majority of stainless components require welding during fabrication, տեղադրում, or repair.
Weldability is not merely a “manufacturing convenience”—it is the linchpin that ensures this promise holds true in welded components.
Poor weldability undermines stainless steel’s core functions, leading to catastrophic failures, excessive costs, and non-compliance with industry standards.
3. Key Metallurgical Foundations of Stainless Steel Weldability
The weldability of stainless steel is fundamentally controlled by their Քիմիական կազմ մի քանազոր crystal structure.
Alloying elements not only define corrosion resistance but also govern how stainless steels behave under the thermal cycles of welding.
Influence of Alloying Elements
| Alloying Element | Role in Base Metal | Impact on Weldability |
| Քրոմ (Խուզարկու, 10.5–30%) | Forms passive Cr₂O₃ film for corrosion resistance. | High Cr increases hot cracking risk; Cr carbide (Cr₂₃C₆) precipitation causes sensitization if C > 0.03%. |
| Նիկել (Մեջ, 0–25%) | Կայունացնում է օստենիտը (Բարելավում է ճկունությունը, կոշտություն). | High Ni (>20%, Է.Գ., 310Ծուռ) increases hot cracking risk; low Ni in ferritics reduces ductility in the HAZ. |
| Մոլիբդեն (Ժամանակ, 0–6%) | Enhances pitting resistance (raises PREN values). | No direct weldability issues; maintains corrosion resistance if heat input is controlled. |
| Ածխածնային (Գ, 0.01–1.2%) | Strengthens martensitic steels; affects sensitization. | >0.03% in austenitic → carbide precipitation and intergranular corrosion; >0.1% in martensitic → cold cracking risk. |
| Տիտղոս (Է) / Niobium (Նբ) | Forms stable TiC/NbC instead of Cr₂₃C₆, preventing sensitization. | Improves weldability of stabilized grades (Է.Գ., 321, 347); reduces HAZ degradation. |
| Ազոտ (Ն, 0.01–0.25%) | Strengthens austenite and duplex phases; increases pitting resistance. | Helps control ferrite balance in duplex welds; excess N (>0.25%) may cause porosity. |
Crystal Structures and Their Influence
- Austenite (FCC): High toughness, Լավ ճկունություն, եւ գերազանց զոդում. Սակայն, fully austenitic compositions are prone to տաք ճեղքվածք due to their low solidification range.
- Ֆերիտ (Բեկոր): Good resistance to hot cracking but limited ductility and toughness in the heat-affected zone (ՀԱԶ). Grain growth during welding can embrittle ferritic steels.
- Martensite (BCT): Very hard and brittle, especially if high carbon is present. Welding tends to create cracks unless preheating and post-weld heat treatments are applied.
- Կրկնակի (mixed FCC + Բեկոր): The combination of ferrite and austenite offers both strength and corrosion resistance, but precise heat input control is critical to maintain the ~50/50 phase balance.
4. Weldability of Austenitic Stainless Steels (300 Series)
Austenitic stainless steels—especially the 300 series (304, 304Լակոտ, 316, 316Լակոտ, 321, 347)—are the most widely used stainless steels due to their Գերազանց կոռոզիոն դիմադրություն, առաձգականություն, և կարծրություն.
They are generally the most weldable stainless family, explaining their widespread use in սննդի վերամշակում, Քիմիական բույսեր, յուղել & գազ, ծովային, և կրիոգեն կիրառություններ.
Սակայն, their fully austenitic crystal structure մի քանազոր high thermal expansion bring specific welding challenges that require careful control.
Key Weldability Challenges
| Մարտահրավեր | Explanation | Mitigation Strategies |
| Hot Cracking | Fully austenitic solidification (A-mode) creates susceptibility to solidification cracking in weld metal. | Use filler metals with small ferrite content (ER308L, ER316L); control weld pool solidification rate. |
| Զգայունացում (Կարբիդի տեղումներ) | Cr₂₃C₆ forms at grain boundaries between 450–850 °C if carbon >0.03%, Կոռոզիոն դիմադրության նվազեցում. | Use low-carbon grades (304Լակոտ, 316Լակոտ) or stabilized grades (321, 347); limit interpass temperature ≤150–200 °C. |
| Distortion & Residual Stress | Austenitic steels expand ~50% more than carbon steels; low thermal conductivity concentrates heat. | Balanced welding sequences, proper fixturing, ցածր ջերմության մուտքագրում. |
| Ծակոտկենություն | Nitrogen absorption or contamination in the weld pool may form gas pockets. | High-purity shielding gases (Ար, Ար + O₂); prevent N₂ contamination. |
Welding Consumables & Filler Selection
- Common filler metals: ER308L (for 304/304L), ER316L (for 316/316L), ER347 (համար 321/347).
- Ferrite balance: Ideal FN (ferrite number) in weld metal: 3–10 to reduce hot cracking.
- Shielding gases: Argon, or Ar + 1–2% O₂; Ար + He blends improve penetration in thicker sections.
Welding Process Suitability
| Ընթացք | Suitability | Նշումներ |
| Շրթնային (Տեգ) | Գերազանց | Ճշգրիտ հսկողություն; ideal for thin walls or critical joints. |
| Ծնոց (Ես) | Շատ լավ | Higher productivity; requires good shielding control. |
| SMAW (Stick) | Լավ | Բազմակողմանի; use low-hydrogen electrodes. |
| FCAW | Լավ | Productive for thick sections; requires careful slag removal. |
| Laser/EB | Գերազանց | Low distortion, բարձր ճշգրտություն; used in advanced industries. |
5. Weldability of Ferritic Stainless Steels (400 Series)
Ferritic stainless steels, primarily 400 series grades ինչպիսիք են 409, 430, մի քանազոր 446, are characterized by a Մարմնի կենտրոնացած խորանարդ (Բեկոր) crystal structure.
They are widely used in automotive exhaust systems, decorative architectural components, և արդյունաբերական սարքավորումներ due to their չափավոր կոռոզիոն դիմադրություն, magnetic properties, and lower cost compared to austenitic grades.
While ferritic stainless steels can be welded, their weldability is more limited compared to austenitic grades.
The combination of Low ածր ճկունություն, high thermal expansion, and coarse grain growth in the heat-affected zone (ՀԱԶ) introduces specific challenges.
Key Weldability Challenges
| Մարտահրավեր | Explanation | Mitigation Strategies |
| Brittleness / Low Toughness | Ferritic steels are inherently less ductile; HAZ can become brittle due to grain growth. | Limit heat input, use thin sections or intermittent welding; avoid rapid cooling. |
| Distortion / Thermal Stress | Coefficient of thermal expansion ~10–12 µm/m·°C; lower than austenitic but still significant. | Pre-bend, proper fixturing, and controlled weld sequence. |
| Cracking (Cold / Hydrogen-assisted) | Martensite-like structures may form in some high-C ferritics; hydrogen from moisture can induce cracking. | Preheat (150–200 °C) for thicker sections; use dry electrodes and proper shielding gases. |
| Reduced Corrosion Resistance in HAZ | Grain coarsening and depletion of alloying elements can locally reduce corrosion resistance. | Minimize heat input and avoid post-weld exposure to sensitization temperature ranges (450–850 °C). |
Welding Consumables & Filler Selection
- Common filler metals: ER409L for 409, ER430L for 430.
- Filler selection: Match the base metal to avoid excessive ferrite or intermetallic formation in welds.
- Shielding gases: Argon or Ar + 2% O₂ for gas tungsten arc welding (Շրթնային) or gas metal arc welding (Ծնոց).
Welding Process Suitability
| Ընթացք | Suitability | Նշումներ |
| Շրթնային (Տեգ) | Շատ լավ | Precise heat control, ideal for thin sections. |
| Ծնոց (Ես) | Լավ | Suitable for production; requires shielding gas optimization. |
| SMAW (Stick) | Չափավոր | Use low-hydrogen electrodes; risk of HAZ embrittlement. |
| FCAW / Laser | Սահմանափակ | May require preheating; risk of cracking in thicker sections. |
6. Weldability of Martensitic Stainless Steels (400 Series)
Martensitic stainless steels, commonly 410, 420, 431, են բարձր ուժ, hardenable alloys characterized by high carbon content and a body-centered tetragonal (BCT) martensitic structure.
These steels are widely used in Տուրբինային շեղբեր, պոմպի լիսեռներ, cutlery, valve components, and aerospace parts, where strength and wear resistance are critical.
Martensitic stainless steels are considered challenging to weld due to their tendency to form hard, brittle microstructures in the heat-affected zone (ՀԱԶ), which increases the risk of cold cracking and reduced toughness.
Key Weldability Challenges
| Մարտահրավեր | Explanation | Mitigation Strategies |
| Cold Cracking / Hydrogen-Assisted Cracking | Hard martensite forms in HAZ, susceptible to cracking if hydrogen is present. | Preheat 150–300 °C; use low-hydrogen electrodes; control interpass temperature. |
| Hardness in HAZ | Rapid cooling produces high hardness (Վեր > 400), leading to brittleness. | Post-weld tempering at 550–650 °C to restore ductility and reduce hardness. |
| Distortion & Residual Stress | High thermal expansion and rapid phase transformation generate residual stress. | Proper fixturing, balanced welding sequences, and controlled heat input. |
| Corrosion Sensitivity | HAZ may experience reduced corrosion resistance, especially in wet or chloride-containing environments. | Select corrosion-resistant martensitic grades; avoid sensitization temperature range. |
Welding Consumables & Filler Selection
- Common filler metals: ER410, ER420, ER431, matched to base metal grade.
- Preheat and interpass: 150–300 °C depending on thickness and carbon content.
- Shielding gases: Argon or Ar + 2% He for GTAW; չոր, low-hydrogen electrodes for SMAW.
Welding Process Suitability
| Ընթացք | Suitability | Նշումներ |
| Շրթնային (Տեգ) | Շատ լավ | Ճշգրիտ հսկողություն; recommended for critical or thin-section components. |
| Ծնոց (Ես) | Չափավոր | Requires low heat input; may need preheating on thicker sections. |
| SMAW (Stick) | Չափավոր | Use low-hydrogen electrodes; maintain preheat. |
| Laser / EB Welding | Գերազանց | Localized heating reduces HAZ size and cracking risk. |
Post-Weld Performance Considerations
| Performance Aspect | Observations After Proper Welding | Գործնական հետևանքներ |
| Մեխանիկական ուժ | Welds can match base metal tensile strength after post-weld tempering; as-welded HAZ may have hardness >400 Վեր. | Components achieve required strength and wear resistance post-tempering; avoid loading immediately after welding. |
| Առաձգականություն & Կոշտություն | Slightly reduced in as-welded HAZ; restored after tempering. | Critical for impact-prone parts like pump shafts and valves. |
| Կոռոզիոն դիմադրություն | Reduced locally in HAZ if not properly tempered; generally moderate for martensitic grades. | Suitable for low-to-moderate corrosion environments; use protective coatings if needed. |
| Service Life & Ամրություն | Post-weld tempering ensures long-term stability; untempered welds may crack under stress or cyclic loading. | Post-weld heat treatment is mandatory for safety-critical components. |
7. Weldability of Duplex Stainless Steels (2000 Series)
Duplex stainless steels (DSS), commonly referred to as 2000 series (Է.Գ., 2205, 2507), են dual-phase alloys containing approximately 50% austenite and 50% ֆերիտ.
This combination provides Բարձր ուժ, Գերազանց կոռոզիոն դիմադրություն, և լավ ամրություն, դարձնելով դրանք իդեալական Քիմիական մշակում, offshore oil & գազ, Desalination բույսեր, and marine applications.
While duplex steels offer significant advantages over austenitic or ferritic grades, their weldability is more sensitive due to the need to maintain a balanced ferrite-austenite ratio and avoid the formation of intermetallic phases (sigma, chi, or chromium nitrides).
Key Weldability Challenges
| Մարտահրավեր | Explanation | Mitigation Strategies |
| Ferrite–Austenite Imbalance | Excess ferrite reduces toughness; excess austenite reduces corrosion resistance. | Control heat input and interpass temperature; select appropriate filler metal with matching duplex composition. |
| Intermetallic Phase Formation | Sigma or chi phases may form at 600–1000 °C, causing embrittlement and reduced corrosion resistance. | Minimize heat input and cooling times; avoid multiple reheats; rapid post-weld cooling. |
| Hot Cracking in Weld Metal | Duplex steels solidify primarily as ferrite; small amounts of austenite required to prevent cracking. | Use filler metals designed for duplex welding (ERNiCrMo-3 or similar); maintain ferrite number (FN) 30-50. |
| Distortion & Residual Stress | Moderate thermal expansion; low conductivity concentrates heat in the weld zone. | Proper fixturing and balanced welding sequence; interpass temperature ≤150–250 °C. |
Welding Consumables & Filler Selection
- Common filler metals: ER2209, ER2594, or duplex-matched fillers.
- Ferrite number (FN) հսկողություն: FN 30–50 in weld metal for optimal toughness and corrosion resistance.
- Shielding gases: Pure argon for GTAW; Ար + small additions of N₂ (0.1–0.2%) may be used to stabilize austenite.
Welding Process Suitability
| Ընթացք | Suitability | Նշումներ |
| Շրթնային (Տեգ) | Գերազանց | High control over heat input and phase balance; preferred for critical piping and vessels. |
| Ծնոց (Ես) | Շատ լավ | Suitable for production; control welding speed and interpass temperature carefully. |
| SMAW (Stick) | Չափավոր | Low productivity; requires duplex-compatible low-hydrogen electrodes. |
| Laser / EB Welding | Գերազանց | Localized heating minimizes HAZ; preserves ferrite-austenite balance. |
Post-Weld Performance Considerations
| Performance Aspect | Observations After Proper Welding | Գործնական հետևանքներ |
| Մեխանիկական ուժ | Weld metal tensile strength typically 620–720 MPa; HAZ slightly lower but within 90–95% of base metal. | Allows use in high-pressure piping and structural applications; retains superior strength over austenitic steels. |
| Առաձգականություն & Կոշտություն | Լավ, Ազդեցության կոշտություն >100 J at room temperature if ferrite content controlled. | Suitable for offshore and chemical plant environments; avoids brittle failure in HAZ. |
| Կոռոզիոն դիմադրություն | Pitting and crevice corrosion resistance comparable to base metal (PREN 35–40 for 2205, 2507). | Reliable in chloride-rich and acidic environments; ensures long-term service life. |
| Service Life & Ամրություն | Properly welded duplex joints resist intergranular corrosion and stress corrosion cracking. | High reliability for critical offshore, քիմիական, and desalination applications. |
8. Weldability of Precipitation-Hardening (PH) Չժանգոտվող պողպատներ
Precipitation-hardening stainless steels, ինչպիսիք են 17-4 PH, 15-5 PH, մի քանազոր 13-8 Ժամանակ, են martensitic or semi-austenitic alloys strengthened through controlled precipitation of secondary phases (Է.Գ., պղնձ, նիբիում, or titanium compounds).
They combine Բարձր ուժ, չափավոր կոռոզիոն դիմադրություն, եւ գերազանց կոշտություն, դարձնելով դրանք իդեալական օդատիենտ, defense, քիմիական, and high-performance mechanical applications.
Welding PH stainless steels presents unique challenges, as the precipitation-hardening mechanism is disturbed by the thermal cycle, potentially leading to softening in the heat-affected zone (ՀԱԶ) կամ loss of strength in weld metal.
Key Weldability Challenges
| Մարտահրավեր | Explanation | Mitigation Strategies |
| HAZ Softening | Նստվածքներ (Է.Գ., Մգոհել, Նբ) dissolve during welding, reducing hardness and strength locally. | Post-weld heat treatment (solution + aging) to restore mechanical properties. |
| Cold Cracking | Martensitic structure in HAZ may be hard and brittle; residual stresses from welding exacerbate cracking. | Preheat 150–250 °C; low-hydrogen electrodes; controlled interpass temperature. |
| Distortion & Residual Stress | Moderate thermal expansion; thermal cycles can induce warping and residual stress in thin sections. | Proper fixturing, ցածր ջերմության մուտքագրում, balanced weld sequence. |
| Corrosion Resistance Reduction | Local softening and altered precipitation may reduce corrosion resistance, particularly in aged or overaged zones. | Use solution treatment post-weld; control welding heat input. |
Welding Consumables & Filler Selection
- Լրացուցիչ մետաղներ: Matched to base metal (Է.Գ., ER630 for 17-4 PH).
- Preheat and interpass temperature: 150–250 °C depending on thickness and grade.
- Shielding gases: Argon or Ar + He blends for GTAW; չոր, low-hydrogen electrodes for SMAW.
Welding Process Suitability
| Ընթացք | Suitability | Նշումներ |
| Շրթնային (Տեգ) | Գերազանց | Precise heat control; ideal for thin-section, critical, or aerospace components. |
| Ծնոց (Ես) | Շատ լավ | Higher productivity; careful heat input management required. |
| SMAW (Stick) | Չափավոր | Requires low-hydrogen electrodes; limited for thin sections. |
| Laser / EB Welding | Գերազանց | Minimizes HAZ width and thermal impact; preserves base metal microstructure. |
Example Post-Weld Data:
| Դասարան | Weld Process | Առաձգական ուժ (MPA) | Կարծրություն (ԲՈՀ) | Նշումներ |
| 17-4 PH | Շրթնային | 1150 (base: 1180) | 30-32 | Post-weld aging mandatory; HAZ softening restored. |
| 15-5 PH | Ծնոց | 1120 (base: 1150) | 28–31 | High toughness and corrosion resistance maintained after aging. |
| 13-8 Ժամանակ | Շրթնային | 1200 (base: 1220) | 32–34 | High-strength aerospace components; controlled welding critical. |
9. Comparative Weldability Summary
| Ասպեկտ | Օստենիտիկ (300 Series) | Ֆերիտիկ (400 Series) | Մարտենզիտիկ (400 Series) | Կրկնակի (2000 Series) | Տեղումներ-Կարծրացում (PH) |
| Representative Grades | 304, 304Լակոտ, 316, 316Լակոտ, 321, 347 | 409, 430, 446 | 410, 420, 431 | 2205, 2507 | 17-4 PH, 15-5 PH, 13-8 Ժամանակ |
| Mechanical Weldability | Գերազանց; HAZ retains ductility | Չափավոր; lower ductility, HAZ can be brittle | Չափավոր; high risk of cold cracking | Լավ; strength typically maintained | Moderate to challenging; HAZ softening |
| Corrosion Resistance Post-Weld | Գերազանց; low-carbon/stabilized grades prevent sensitization | Լավ; may be locally reduced if heat input excessive | Չափավոր; may be locally reduced in HAZ | Գերազանց; maintain ferrite–austenite balance | Չափավոր; restored after post-weld heat treatment |
| Weldability Challenges | Hot cracking, աղավաղում, ծակոտկենություն | Grain coarsening, cracking, HAZ brittleness | Hard martensitic HAZ, cold cracking | Ferrite/austenite imbalance, intermetallic phase formation | HAZ softening, residual stress, կրճատված կոշտություն |
| Typical Post-Weld Considerations | Minimal preheat; low interpass temperature; optional solution annealing | Preheat for thick sections; controlled heat input | Preheat and low-hydrogen electrodes; mandatory post-weld tempering | Heat input control; interpass ≤150–250 °C; filler metal selection | Preheat, low-hydrogen electrodes, mandatory post-weld solution + aging |
| Ծրագրեր | Սնունդ, ֆարմա, Քիմիական բույսեր, ծովային, cryogenics | Automotive exhausts, ճարտարապետական վահանակներ, high-temp industrial components | Փականի բաղադրիչներ, լիսեռներ, Պոմպային մասեր, օդատիենտ | Օֆշորային, Քիմիական բույսեր, անկարգություն, ծովային | Օդատիենտ, defense, high-performance pumps, վիրաբուժական գործիքներ |
Key Observations:
- Austenitic չժանգոտվող պողպատներ are the most forgiving, առաջարկ excellent weldability with minimal precautions.
- Ferritic grades are more sensitive to brittleness and grain growth, requiring careful heat input management.
- Martensitic steels need preheating and post-weld tempering to prevent cold cracking and restore toughness.
- Duplex steels պահանջել precise phase control to avoid ferrite-rich or brittle welds while maintaining corrosion resistance.
- PH stainless steels must undergo post-weld solution treatment and aging to restore strength and hardness.
10. Եզրափակում
The weldability of stainless steel spans a spectrum—from highly weldable austenitic grades to challenging martensitic and PH steels.
Մինչդեռ most grades can be welded successfully, success hinges on understanding the metallurgical behavior, applying appropriate welding procedures, and performing necessary pre- or post-weld heat treatments.
For engineers and fabricators, weldability is not just about joining—it is about preserving corrosion resistance, ուժ, and service life.
Careful filler selection, heat input management, and adherence to codes ensure stainless steel components meet both design and lifecycle expectations.
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Why is 316L more weldable than 316 չժանգոտվող պողպատ?
316L has a lower carbon content (C ≤0.03% vs. C ≤0.08% for 316), which drastically reduces sensitization risk.
During welding, 316’s higher carbon forms Cr₂₃C₆ carbides at grain boundaries (depleting Cr), leading to intergranular corrosion.
316L’s low carbon prevents this, with a 95% pass rate in ASTM A262 IGC testing vs. 50% համար 316.
Do ferritic stainless steels require preheating?
No—ferritic stainless steels (409, 430) have low carbon content, so preheating is not needed to prevent cold cracking.
Սակայն, post-weld annealing (700–800°C) is recommended to recrystallize large HAZ grains, restoring ductility and toughness (increases impact energy by 40–50%).
Can 17-4 PH stainless steel be welded without post-weld heat treatment?
Technically yes, but the HAZ will be significantly softened (tensile strength drops from 1,150 MPa to 750 MPa for H900 temper).
For load-bearing applications (Է.Գ., aerospace brackets), post-weld solution annealing (1,050° C) + re-aging (480° C) is mandatory to reform copper precipitates, restoring 95% of the base metal’s strength.
Which welding process is best for thin austenitic stainless steel (1–3 mm)?
Շրթնային (Տեգ) is ideal—its low heat input (0.5–1.5 kJ/mm) minimizes HAZ size and sensitization risk, while its precise arc control produces high-quality, low-porosity welds.
Use a 1–2 mm tungsten electrode, argon shielding gas (99.99% pure), and travel speed 100–150 mm/min for optimal results.
