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St35.8, St45.8, 17Mn4, and 19Mn5 are widely used seamless steel tube grades manufactured for applications involving elevated temperatures. These steels are known for their high mechanical strength, excellent heat resistance, and good weldability, making them ideal for boiler tubes, heat exchangers, and pressure vessels in industries such as power generation, petrochemicals, and thermal processing.
This article provides a technical overview of these steel grades, highlighting their material properties, specifications, chemical and mechanical characteristics, and applicability in high-temperature environments.
These grades are part of the DIN 17175 standard, which specifies seamless steel tubes used in high-temperature service. They are non-alloy or low-alloy heat-resistant steels, produced through hot rolling or hot extrusion, and often undergo normalizing or annealing treatments to improve mechanical properties and heat resistance.
St35.8: Non-alloy steel for average pressure applications.
St45.8: Similar to St35.8 but with higher tensile strength.
17Mn4 & 19Mn5: Low-alloy steels with added manganese for enhanced strength and oxidation resistance at elevated temperatures.
Standard: DIN 17175
Manufacturing Process: Seamless (hot-rolled or cold-drawn)
Delivery Conditions: +N (Normalized), +A (Annealed)
Outer Diameter (OD): 10.2 mm – 711 mm
Wall Thickness (WT): 1.6 mm – 100 mm
Length: 6 – 12 meters or custom
End Types: Plain, beveled, or threaded
Surface Condition: Black (bare), varnished, or oiled
✅ Excellent High-Temperature Strength
✅ Reliable Creep Resistance
✅ Good Weldability
✅ High Pressure Resistance
✅ Consistent Microstructure due to Seamless Construction
✅ Dimensional Accuracy with Tight Tolerances
| Grade | C (%) | Si (%) | Mn (%) | P (max. %) | S (max. %) |
|---|---|---|---|---|---|
| St35.8 | 0.17 max | 0.10 – 0.35 | 0.40 – 0.80 | 0.035 | 0.035 |
| St45.8 | 0.21 max | 0.10 – 0.35 | 0.40 – 1.20 | 0.035 | 0.035 |
| 17Mn4 | 0.17 max | 0.10 – 0.35 | 1.00 – 1.50 | 0.035 | 0.035 |
| 19Mn5 | 0.20 max | 0.10 – 0.35 | 1.30 – 1.80 | 0.030 | 0.030 |
| Property | St35.8 | St45.8 | 17Mn4 | 19Mn5 |
|---|---|---|---|---|
| Yield Strength (MPa) | ≥ 235 | ≥ 255 | ≥ 275 | ≥ 295 |
| Tensile Strength (MPa) | 360 – 480 | 440 – 570 | 450 – 600 | 480 – 630 |
| Elongation (%) | ≥ 25 | ≥ 22 | ≥ 22 | ≥ 21 |
| Impact Toughness (J) | ≥ 27 (at RT) | ≥ 27 (at RT) | ≥ 27 (at RT) | ≥ 27 (at RT) |
| Hardness (Brinell HB) | ≤ 180 | ≤ 200 | ≤ 210 | ≤ 220 |
St35.8: For moderate temperature and pressure, offering basic strength and weldability.
St45.8: Enhanced strength, used in higher pressure conditions than St35.8.
17Mn4: Manganese-alloyed for improved mechanical properties at elevated temperatures.
19Mn5: Higher Mn content for improved heat resistance and creep performance.
These steel grades are widely used in:
Boiler Tubes
Heat Exchangers
Superheaters
Steam Pipelines
High-Temperature Pressure Vessels
Chemical and Thermal Processing Plants
Power Generation Systems
Depending on the service condition, alternatives may include:
| Alternative Grade | Standard | Note |
|---|---|---|
| ASTM A106 Gr. B | ASTM (USA) | Seamless carbon steel pipe for high-temperature service |
| P235GH, P265GH | EN 10216-2 | Non-alloy pressure vessel steel |
| 13CrMo4-5, 10CrMo9-10 | DIN/EN | For higher temperature and creep resistance |
| SA 210 A1/C | ASME | Boiler tubes with high-temperature strength |
A: manufacturer,also can do trading.
A: Generally speaking,it is 10-15 days if the goods are in stock,or it is 30-40 days if the goods are not in stock, it is according to quantity.
A: Yes, we could offer the sample for free charge but need pay the cost of freight.
A: Payment<=2000USD, 100% in advance. Payment>=2000USD, 30% T/T in advance ,balance before shippment.
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