P5 Buttweld Pipe Fittings
5Cr-½Mo / EN 1.7362 (X12CrMo5) — the standard CrMo grade for high-temperature sulfidic corrosion service in petroleum refining. Higher chromium content than P22 gives significantly better resistance to sulfidic attack (H₂S + hydrocarbon service per McConomy curves) and oxidation up to 600°C. ASME B16.9 and EN 10253-3 Type B.
½″–48″
Size Range
600°C
Max Service Temp
420 MPa
Min Tensile (EN)
EN 10204
3.1 Std / 3.2 On Req.
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P5 Grade Equivalents
| ASTM | EN W.Nr. | EN Name | DIN | UNS | ASME P-No. |
|---|---|---|---|---|---|
| A234 WP5 | 1.7362 | X12CrMo5 | X12CrMo5 | K41545 | 5B, Gr 1 |
| A182 F5 (forged) | 1.7362 | X12CrMo5 | — | — | 5B |
| A335 P5 (pipe) | 1.7362 | X12CrMo5 | — | — | 5B |
Chemical Composition — P5 / 1.7362
| Standard | C | Cr | Mo | Mn | Si | P max | S max |
|---|---|---|---|---|---|---|---|
| ASTM A234 WP5 | ≤0.15 | 4.00–6.00 | 0.44–0.65 | 0.30–0.60 | ≤0.50 | 0.030 | 0.030 |
| EN 1.7362 (EN 10253-3) | 0.08–0.15 | 4.00–6.00 | 0.45–0.65 | 0.30–0.60 | ≤0.50 | 0.025 | 0.010 |
Mechanical Properties — P5 / 1.7362
| Standard | Min. UTS (MPa) | Min. YS (MPa) | Elongation (%) | Max. Hardness | HT Condition |
|---|---|---|---|---|---|
| ASTM A234 WP5 | 415 | 205 | ≥22% | 241 HBW | A or N+T |
| EN 1.7362 (EN 10253-3) | 420–600 | ≥220 | ≥20% | 241 HBW | N+T |
Sulfidic Corrosion Resistance — Why P5?
McConomy Curves — Grade Selection for H₂S + Hydrocarbon Service
The McConomy curves (API RP 939-C) define sulfidic corrosion rates as a function of temperature and sulfur content. P5 (5Cr) offers approximately 4× lower corrosion rate than carbon steel and ~2× lower than P11/P22 at temperatures above 260°C in H₂S-bearing streams.
| Grade | Cr% | Sulfidic Resistance vs CS | Typical Refinery Use |
|---|---|---|---|
| Carbon Steel (WPB) | — | Baseline | Low-temp, low-sulfur streams |
| P11 / 1.7335 | 1.25 | ~2× better | Steam headers, moderate H₂ service |
| P22 / 1.7380 | 2.25 | ~3× better | Hydroprocessing, reformers |
| P5 / 1.7362 | 5.0 | ~4–5× better | Crude distillation, cat reformers, cokers |
| P9 / 1.7386 | 9.0 | ~5–6× better | Highest-temp refinery sulfidic service |
Welding & PWHT Requirements
⚠ PWHT Mandatory — High Preheat Required
P5 has high hardenability. Welds cool to martensite if preheat is not maintained. PWHT at 720–760°C is mandatory; un-PWHTed P5 welds are extremely hard and brittle. Do not weld P5 with carbon steel or P11/P22 filler — always use the matching CrMo consumable.
Preheat Temperature
200–250°C minimum. Higher preheat than P22 required due to higher hardenability.
Inter-pass Temperature
Maximum 350°C.
Filler Metal
ER80S-B6 (GTAW) or E8018-Cr3 (SMAW) — 5Cr-½Mo matching composition.
PWHT Temperature
720–760°C. Minimum hold: 1 hour per 25mm wall.
Cooling
Furnace cool to 300°C, then air cool. Chart-recorded temperature cycles required.
Post-PWHT Hardness
Weld and HAZ ≤241 HBW after PWHT.
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