INOX STEEL INDIA is a recognised manufacturer and global supplier of Chrome-Moly Alloy Steel Welded Tubes, engineered for high-temperature, high-pressure, creep-resistant, and critical service environments.
These tubes are manufactured as welded equivalents of seamless ASTM A335 tubes, using high-alloy chrome-moly plates/strips and advanced welding technologies such as TIG Welding, SAW – Submerged Arc Welding, and HFIW / ERW.
Alloy Steel Welded Tubes form the backbone of power plants, boilers, refinery heaters, petrochemical furnaces, and steam distribution networks, delivering superior durability and stability under extreme conditions.
Alloy Steel Welded Tubes are formed by welding chrome-moly alloy steel plates or strips to produce tubes capable of withstanding:
Because these alloys contain Chromium, Molybdenum, Vanadium and Niobium (grade dependent), they offer exceptional strength, high thermal stability, corrosion resistance and long service life.
Also known as Chrome-Moly Welded Tubes, ASTM A691 Welded Tubes, High-Temperature Alloy Tubes, Alloy Pressure Tubes and P-Grade Welded Tubes.
| Weld Method | Usage |
| ERW / HFIW | Small OD welded tubes |
| TIG Welding | Thin-wall precision tubes |
| SAW Welding | Medium to thick wall tubes |
| Manual GTAW | Special joints & fabrication |
INOX ensures full weld penetration and uniform seam quality.
All alloy steel welded tubes undergo PWHT at 720–780°C depending on grade to restore grain structure, remove residual stress and improve creep resistance.
| Feature | Welded Alloy (ASTM A691) | Seamless Alloy (ASTM A335) |
| Cost | Lower | Higher |
| Availability | Faster | Longer lead time |
| Sizes | Excellent for large OD | Limited to small OD |
| Weld Strength | Very High (SAW/TIG) | No weld |
| Temperature & Pressure | High | Very High |
| Fabrication | More flexible | Less flexible |
| OD (mm) | WT (mm) | Length |
| 19 – 60 | 2.0 – 6.0 | Up to 12 m |
| 60 – 168 | 2.5 – 12.0 | Up to 12 m |
| 168 – 323.9 | 3.0 – 18.0 | Up to 12 m |
| 323.9 – 508 | 4.0 – 20.0 | Up to 12 m |
| Temperature | Pressure | Recommended Grade | Reason |
| 300–400°C | Medium | P1 | Cost-effective |
| 400–500°C | High | P11 | Creep strength |
| 500–580°C | Very High | P22 | Thermal fatigue resistance |
| 580–620°C | Extreme | P5 / P9 | Oxidation resistance |
| 600°C+ | Ultra-critical | P91 | Highest creep strength |
| Grade | Type | INR/Kg | USD/Kg |
| P1 | Black | ₹145 – ₹185 | $1.80 – $2.30 |
| P5 / P9 | Black | ₹210 – ₹280 | $2.50 – $3.40 |
| P11 | PWHT | ₹180 – ₹240 | $2.20 – $3.00 |
| P22 | PWHT | ₹210 – ₹300 | $2.60 – $3.60 |
| P91 | N&T | ₹380 – ₹550 | $4.50 – $7.00 |
Q1. What are alloy steel welded tubes used for?
Boilers, power plants, refineries and steam lines.
Q2. Are PWHT and NDT mandatory?
Yes.
Q3. Which grades are available?
P1, P5, P9, P11, P22, P91.