Low-temperature carbon steel pipe is a specialised product class where the selection criterion is not just tensile strength but Charpy V-notch toughness at sub-zero service temperatures. Standard carbon steel grades such as ASTM A106 Grade B or API 5L Grade B lose ductility rapidly below about -20°C and can fracture in a brittle manner under impact loading — a failure mode that is catastrophic in pressurised gas systems. ASTM A333 Grade 6 is the standard solution for this problem: a carbon-manganese steel pipe manufactured and impact-tested for service down to -45°C (-50°F), widely specified for natural gas processing, LNG, offshore cold-climate piping, and refrigeration systems.
ZC Steel Pipe supplies seamless ASTM A333 Grade 6 pipe in sizes from 2 inches to 24 inches NPS, to EN 10204 3.1/3.2 mill test certificates with full Charpy V-notch impact records, for EPC projects in the Middle East, West Africa, Southeast Asia, and South America.
What we have seen on West Africa NGL projects: On an NGL processing plant in West Africa, a supplier quoted ASTM A333 Grade 6 seamless pipe and delivered ASTM A106 Grade B. Both materials have identical OD, wall thickness, and common schedule markings. The A106 MTC showed tensile and bend tests only — no Charpy data. The receiving inspector checked the dimensional conformance but did not review the MTC specification designation line or verify the absence of impact test data. The pipe was installed in a -45°C design temperature piping system. Four months into operation, a brittle fracture at a girth weld in the cold section caused emergency shutdown. Verifying the Charpy test temperature and all three specimen values on the MTC — not just the tensile numbers — takes 2 minutes per heat and prevents this failure entirely.
What Is ASTM A333?
ASTM A333, titled Standard Specification for Seamless and Welded Steel Pipe for Low-Temperature Service and Other Applications with Required Notch Toughness, covers steel pipe that must retain adequate Charpy V-notch toughness at specified test temperatures. The specification defines multiple grades differentiated by alloy content and minimum service temperature:
| Grade | Key alloy | Min. test temp | Typical application |
|---|---|---|---|
| 1 | Carbon-Mn | -45°C (-50°F) | General LT service (lower strength) |
| 6 | Carbon-Mn | -45°C (-50°F) | Most common grade; gas processing |
| 3 | Ni 3.5% | -100°C (-150°F) | Ethylene, LPG at very low temps |
| 9 | Ni 2.0–2.5% | -73°C (-100°F) | NGL, propane, LPG plants |
| 8 | Ni 9% | -196°C (-320°F) | LNG, liquid nitrogen, LOX |
Grade 6 is the most widely produced grade. It covers both seamless and welded pipe (ERW, DSAW), whereas Grade 8 is seamless only. Grade 6 is interchangeable with ASME SA-333 Grade 6 — SA-333 is the ASME Boiler and Pressure Vessel Code adoption of the ASTM standard, used wherever ASME stamp is required.
Mechanical Properties
ASTM A333 Grade 6 mechanical requirements are modest compared to high-strength grades, reflecting its role as a low-temperature ductile material rather than a high-strength one:
| Property | SI (MPa) | US customary (ksi) |
|---|---|---|
| Tensile strength, min | 415 MPa | 60 ksi |
| Yield strength, min (0.2% offset) | 240 MPa | 35 ksi |
| Elongation in 50 mm (2 in), min | 35% | 35% |
These are minimum values; actual mill test results typically exceed minimums by 10–20% for commercial quality pipe. The elongation of 35% is substantially higher than high-strength grades (which run 15–22%), reflecting the importance of ductile behaviour at low temperatures. Crucially, the identical tensile and yield minimums shared with ASTM A106 Grade B (415 MPa / 60 ksi tensile, 240 MPa / 35 ksi yield) are the root cause of the most common substitution error in low-temperature piping — the numbers on the MTC look the same, but the Charpy test is either present or absent.
For the complete pipe schedule dimensions and weight tables, see the ASME pipe specification tables →
Charpy V-Notch Impact Requirements
The defining requirement for A333 Grade 6 is the Charpy V-notch (CVN) impact test performed at -45°C (-50°F). Tests are conducted on specimens machined from the pipe body — transverse specimens are the controlling requirement for pipe:
| Specimen orientation | Average of 3 specimens (min) | Lowest individual (min) |
|---|---|---|
| Transverse | 20 J (15 ft·lbf) | 13 J (10 ft·lbf) |
| Longitudinal | 27 J (20 ft·lbf) | 20 J (15 ft·lbf) |
Each heat of pipe must be impact-tested. The MTC must report the actual absorbed energy for each specimen in the set. Both the average and the individual minimum must be verified independently — a three-specimen set can pass on all individuals yet fail the average. For critical service (offshore risers, pressure vessels, or when specified by project MDMT requirements), procurement specifications often add a supplementary requirement for 100% of specimens to exceed the minimum individual value.
Reading a Charpy V-Notch MTC: Pass/Fail Examples
ASTM A333 Grade 6 requires two independent criteria: transverse average ≥ 20 J, and lowest individual ≥ 13 J. Both must be met. A set that satisfies one criterion does not automatically satisfy the other.
Scenario A — Passing heat (adequate margin): Specimens: 24 J, 22 J, 19 J (all transverse at -45°C) Average = (24 + 22 + 19) / 3 = 21.7 J — passes (≥ 20 J required) Lowest individual = 19 J — passes (≥ 13 J required) Margin on average: 21.7 / 20.0 = 1.08 (8% margin — acceptable but modest; a marginal mill may not clear this with every heat)
Scenario B — Failing heat (fails average despite all individuals above the individual minimum): Specimens: 21 J, 20 J, 14 J (all transverse at -45°C) Average = (21 + 20 + 14) / 3 = 18.3 J — FAILS (< 20 J average required) Lowest individual = 14 J — passes (≥ 13 J required) Result: REJECT entire heat — even though all three individual specimens exceed the 13 J minimum
Scenario B is the critical case. A QC inspector who only checks "are all specimens above 13 J?" and assumes the average is acceptable will miss this failure. The MTC tabulation always lists three individual values; the average must be calculated and verified independently, not accepted as given from the supplier's summary line. We have seen supplier-prepared MTC summaries round the average up — always recalculate from the three raw values.
Chemical Composition
ASTM A333 Grade 6 is a carbon-manganese steel. The specification intentionally keeps the chemistry simple — no alloy additions — and relies on controlled rolling and fine-grain practice to achieve toughness:
| Element | Requirement |
|---|---|
| Carbon (C) | 0.30% max |
| Manganese (Mn) | 0.29–1.06% |
| Phosphorus (P) | 0.025% max |
| Sulfur (S) | 0.025% max |
| Silicon (Si) | 0.10% min (when required for fine-grain practice) |
The key to low-temperature toughness in Grade 6 is the combination of controlled carbon (lower C improves toughness), adequate Mn (raises the ductile-to-brittle transition temperature DBTT), and fine austenite grain size. Supplementary fine-grain practice using Al or Nb additions is not explicitly mandated by the base specification but is widely used by mills to consistently pass the -45°C Charpy test with margin.
The carbon equivalent (CE = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15) for Grade 6 typically runs 0.38–0.43, making the material readily weldable with standard procedures.
The ductile-to-brittle transition temperature (DBTT) for ASTM A106 Grade B can vary between -10°C and -30°C depending on the specific heat chemistry and cooling rate — this range is uncontrolled by the A106 standard. Some A106 heats will accidentally pass a -45°C Charpy test; others will fail at -20°C. This is precisely why A333 Grade 6 exists: it controls the DBTT not by fixing the chemistry but by requiring a Charpy V-notch impact test at -45°C on every heat. The impact test is the only reliable screening criterion for low-temperature service — not chemistry, not dimensional conformance, and not the tensile test. Substitute materials that are "the same chemistry" are not the same product if the impact test was not performed.
Standard Sizes
ASTM A333 Grade 6 is available as both seamless and welded pipe. Size availability and typical wall schedules:
| NPS | OD (mm) | SCH 40 WT (mm) | SCH 80 WT (mm) |
|---|---|---|---|
| 2 | 60.3 | 3.91 | 5.54 |
| 4 | 114.3 | 6.02 | 8.56 |
| 6 | 168.3 | 7.11 | 10.97 |
| 8 | 219.1 | 8.18 | 12.70 |
| 12 | 323.9 | 9.53 | 12.70 |
| 16 | 406.4 | 9.53 | 12.70 |
| 20 | 508.0 | 9.53 | 12.70 |
| 24 | 609.6 | 9.53 | 12.70 |
Wall thicknesses follow ASME B36.10M schedules. For LT service piping systems, SCH 40 and SCH 80 cover the majority of process plant requirements. Heavier schedules (SCH 120, 160, XXS) are available in smaller NPS ranges (½" to 10") for high-pressure low-temperature applications. Lead times for Grade 6 are typically 2–4 weeks longer than equivalent A106 schedules because Grade 6 requires heat-by-heat Charpy testing; factor this into project procurement schedules for cold-section pipe.
For a unit conversion tool for OD, wall thickness, and weight: Unit Converter →
Low-Temperature Service — Design Considerations
Ductile-to-Brittle Transition
Carbon steel undergoes a transition from ductile to brittle fracture mode as temperature decreases. The ductile-to-brittle transition temperature (DBTT) varies with chemical composition, grain size, and heat treatment. For A333 Grade 6, the manufacturing controls are designed to ensure the DBTT lies below -45°C with margin. Field failures occur when substitutions are made — e.g., using A106 Grade B (no impact test requirement) in a system rated for LT service. An A106 pipe may show adequate tensile properties at room temperature but shatter at the design low temperature.
Thermal Cycling and Fatigue
LNG and gas processing facilities experience repeated thermal cycles as equipment is commissioned, shut down, and brought back into service. Each cycle imposes thermal stresses in flanges, elbows, and branch connections. For systems that cycle frequently, specify minimum bend radius per ASME B31.3, use forged fittings (ASTM A420 WPL6 — the low-temperature fittings companion to A333 Gr. 6), and verify that all flanges and valves in the system are rated for the minimum design metal temperature (MDMT).
Companion Materials
For complete low-temperature piping systems, all materials must be impact-tested to match the pipe:
- Fittings: ASTM A420 WPL6 (seamless and welded buttweld fittings, LT service)
- Flanges: ASTM A350 LF2 (carbon steel flanges for LT — not A105)
- Valves: API 6D or ASME B16.34 with Charpy-certified body and bonnet
Mixing un-tested carbon steel fittings or flanges into an A333 Grade 6 piping system is a code violation and a safety risk. The failure mode — brittle fracture at the fitting while the pipe body remains intact — produces a distinctive fracture surface signature that points directly to a companion material mismatch.
ASTM A333 Grade 6 vs ASTM A106 Grade B
Both are seamless carbon steel pipe, but their service temperature ratings are fundamentally different:
| Property | A333 Grade 6 | A106 Grade B |
|---|---|---|
| Tensile strength min | 415 MPa (60 ksi) | 415 MPa (60 ksi) |
| Yield strength min | 240 MPa (35 ksi) | 240 MPa (35 ksi) |
| Elongation min | 35% | 30% |
| Impact tested? | Yes — at -45°C | No |
| Min design temp (ASME B31.3) | -45°C | -29°C |
| Below -29°C without impact testing? | Permitted | Not permitted |
The tensile and yield numbers are identical — substituting A106 for A333 is easy to miss on a dimensional review but creates a latent failure risk at operating temperature. The elongation difference (35% vs 30%) is the only mechanical property distinction visible in a standard tensile test, and most inspectors do not flag it as a disqualifier on its own. This substitution is one of the most common procurement errors in LT piping systems, particularly when a project uses the same NPS and schedule for both ambient and cold sections.
When NOT to Use ASTM A333 Grade 6
| Condition | Correct specification | Reason |
|---|---|---|
| Design temperature below -45°C | A333 Grade 9 (Ni, to -73°C) or Grade 8 (9Ni, to -196°C) | Grade 6 is not impact-qualified below -45°C |
| Above-ground ambient-temperature piping | ASTM A106 Grade B | No low-temperature requirement; A106 is more available and economical |
| High-pressure steam piping at elevated temperature | A335 P11 or P22 (alloy steel) | Grade 6 yield (240 MPa) is insufficient for high-temperature creep applications |
| Buried gas gathering at design temp -29°C or warmer | API 5L Grade B PSL1 | A333 Gr.6 unnecessary; adds cost for no service benefit |
| LNG carrier piping below -165°C | 9% Ni steel (A333 Gr.8) or austenitic stainless | Grade 6 DBTT far above LNG operating temperature |
This table is not a complete substitute for a piping material selection study, but it identifies the five conditions where Grade 6 is commonly over-specified (adding cost) or under-specified (adding risk). The first and last rows represent safety risks; the middle three represent unnecessary cost.
Low-Temperature Pipe Failure Modes to Specify Against
Failure Mode 1 — A106 Substitution in Low-Temperature Service
Mechanism: A106 Grade B pipe installed in a -45°C NGL or LNG system because the physical appearance is identical to A333 Grade 6 and the MTC tensile values meet Grade 6 minimums. At the design minimum temperature, the A106 pipe encounters a thermal or pressure shock. The steel is in the brittle fracture regime — the DBTT of this heat is -15°C, as controlled by its specific chemistry. The pipe fractures in a brittle manner at a stress level well below yield.
Diagnostic: MTC review at goods receipt — A106 MTC shows tensile, bend, and flattening tests only; no Charpy data. A333 Grade 6 MTC must show three transverse Charpy specimen values at -45°C. If Charpy data is absent on the MTC, the pipe is not A333 Grade 6 regardless of what is printed on the pipe. The pipe stencil is not the acceptance criterion — the MTC is.
Fix: Make MTC Charpy data verification a mandatory hold point at goods receipt, before the pipe enters the warehouse. A333 Grade 6 cannot be accepted without three documented Charpy values at -45°C. This check requires 2 minutes per heat number and costs nothing.
Failure Mode 2 — PWHT Above 620°C Reducing Low-Temperature Toughness
Mechanism: An A333 Grade 6 piping system undergoes post-weld heat treatment at 650°C (within the normal PWHT range for carbon steel per ASME B31.3 — 595–680°C range allowed). At 650°C, PWHT coarsens the ferrite grain structure that provides low-temperature toughness in Grade 6. The PWHT is technically compliant with ASME code but reduces the absorbed energy at -45°C from the original 21 J average to approximately 17–18 J — below the required 20 J. The pipe passes PWHT hardness surveys and visual inspection; the toughness degradation is not visible.
Diagnostic: Post-PWHT Charpy test on a welded test coupon from the same heat shows impact values below the Grade 6 minimum. This is discovered during mandatory weld test coupon qualification, if the WPS requires post-PWHT impact testing. If the WPS only requires pre-PWHT pipe qualification (using the original MTC), this failure mode is invisible until in-service conditions expose it.
Fix: Specify maximum PWHT temperature of 620°C for A333 Grade 6 piping on the Welding Procedure Specification and on the purchase order. The ASTM A333 standard implicitly protects against this by requiring impact testing after any heat treatment — specify that impact test results must be provided post-PWHT, not just pre-PWHT. This is a one-line addition to the WPS that prevents the failure entirely.
Failure Mode 3 — Companion Fitting Out of Low-Temperature Specification
Mechanism: A333 Grade 6 pipe connected with ASTM A234 WPB buttweld fittings — standard carbon steel fittings, no impact test, minimum design temperature -29°C. The elbow in a 90-degree bend sees the same -45°C operating temperature as the adjacent pipe. The fitting fails in brittle fracture while the pipe body does not, because the fitting material has a higher DBTT than the impact-tested pipe.
Diagnostic: Failure at a fitting-to-pipe girth weld zone with no visible corrosion or mechanical damage. Fracture surface shows cleavage (brittle) fracture on the fitting side, dimple (ductile) fracture on the A333 Gr.6 pipe side — a clear material mismatch signature. Materials laboratory analysis confirms the fitting is WPB, not WPL6.
Fix: Specify ASTM A420 WPL6 for all buttweld fittings, ASTM A350 LF2 for all flanges, and confirm valve body and bonnet Charpy qualification at -45°C for every LT piping system. List the companion fitting specification on the same purchase order as the pipe, not as a separate order where the low-temperature requirement could be lost in the reorder process.
Purchase Order Guidance
Required PO Line Items
When specifying ASTM A333 Grade 6 pipe, a complete purchase order should include:
- Specification: ASTM A333 / ASME SA-333, Grade 6
- Product form: seamless or welded (state preferred)
- NPS and schedule (or OD × wall thickness)
- Heat treatment: normalised (standard for Grade 6); specify if quench-and-tempered is required
- Test temperature for CVN: -45°C (standard); state if a lower test temperature is required
- NDE: hydrostatic test per the standard; add UT or EMI if required by project specification
- Mill documentation: EN 10204 Type 3.1 MTC
- Third-party inspection: state inspection level (witness, review, or release note)
Procurement Trap 1 — A106 Substituted for A333 Grade 6
Wrong PO: "SA-333 Grade 6, 6-inch SCH 40, seamless pipe."
What ships: Supplier short of A333 stock substitutes A106 Grade B — same OD, wall, schedule, and appearance. MTC shows tensile and bend test (A106 format). Supplier assumes "carbon steel, seamless, same schedule" is an acceptable substitution without explicit restriction on the PO. The MTC is issued without Charpy data because A106 does not require it. This substitution is compliant under A106 and the supplier considers themselves clear.
Correct PO: "ASTM A333 / ASME SA-333, Grade 6 only — no A106 or equivalent substitution permitted; EN 10204 3.1 MTC must include Charpy V-notch test results at -45°C showing all three transverse specimen values and the average; test must be conducted per ASTM A333 requirements, not as a supplementary test to A106."
Procurement Trap 2 — Companion Fitting Material Mismatch
Wrong PO for fittings: "A234 WPB buttweld fittings to match A333 Gr.6 pipe."
What ships: Standard A234 WPB fittings with no impact test — suitable to -29°C only. The fittings are installed in a -45°C system alongside A333 Gr.6 pipe that was correctly specified. The pipe is impact-qualified; the fittings are not. This is fully compliant with a PO that only says "WPB" — the supplier did exactly what was ordered.
Correct PO: "ASTM A420 WPL6 buttweld fittings — the low-temperature companion fitting grade to A333 Grade 6. For flanges, specify A350 LF2, not A105." List the low-temperature fitting specification on every purchase order that includes A333 Gr.6 pipe — even if the fittings are procured on a separate line. The low-temperature requirement must follow every component into a -45°C system.
The Low-Temperature Substitution Trap — Field Verification
The most common procurement error is substituting ASTM A106 Grade B for A333 Grade 6 when a supplier is short of stock. The two grades have the same tensile and yield minimums and the same common schedules. The critical difference — the Charpy impact test at -45°C — does not appear on a cursory dimensional check. Always verify that the MTC lists the Charpy test results and that the test temperature is -45°C or lower. If the MTC shows only tensile and bend test results (the A106 format), the pipe is A106, not A333, regardless of what is stamped on the pipe.
MTR Verification Checklist
Before accepting a consignment of A333 Grade 6 pipe:
- Confirm the heat number on the pipe marking matches the MTC heat number
- Verify the Charpy V-notch test temperature is -45°C (not -29°C or -18°C)
- Confirm all three transverse specimen values: recalculate the average from raw data — average ≥20 J, minimum individual ≥13 J
- Confirm yield and tensile meet minimums; check elongation ≥35%
- Confirm the manufacturing process (seamless or welded) matches the purchase order
- Verify P and S chemistry limits — A333 limits (P ≤0.025%, S ≤0.025%) are tighter than A106
- Verify the MTC specification designation line reads "ASTM A333" or "ASME SA-333" — an A106 designation with Charpy data added as a supplementary test does not make the pipe A333 Grade 6
For complete ASME pipe dimension tables and schedule lookup, see the ASME pipe specification tables →
Use the Unit Converter → to convert between imperial and metric pipe dimensions and wall thicknesses.
Frequently Asked Questions
What is ASTM A333 Grade 6 pipe used for?
ASTM A333 Grade 6 is used for piping systems that operate at low temperatures, typically down to -45°C (-50°F). Common applications include natural gas processing plants, LNG and NGL facilities, offshore topsides in cold climates, refrigeration and cryogenic process piping, and low-temperature storage and transfer systems where carbon steel must retain ductility and impact toughness below -29°C.
What is the minimum design temperature for ASTM A333 Grade 6?
ASTM A333 Grade 6 is impact-tested at -45°C (-50°F) and is therefore suitable for design down to -45°C under ASME B31.3 Process Piping and ASME B31.8 Gas Transmission without additional impact qualification. Some engineers use it down to -50°C with a small design margin, but any service below -45°C should be verified by Charpy impact testing at the actual design temperature per the applicable code.
What Charpy impact values does ASTM A333 Grade 6 require?
ASTM A333 Grade 6 requires Charpy V-notch impact testing at -45°C (-50°F). The minimum average energy for a set of three transverse specimens is 20 J (15 ft·lbf). The minimum individual value for any single specimen is 13 J (10 ft·lbf). For longitudinal specimens, the minimums are 27 J (20 ft·lbf) average and 20 J (15 ft·lbf) individual. These values must appear on the mill test certificate and be confirmed against the heat number.
What is the difference between ASTM A333 Grade 6 and Grade 8 or Grade 9?
Grade 6 is a carbon-manganese steel for service down to -45°C. Grade 3 and Grade 9 incorporate nickel (2.0–2.5% Ni) and are rated to -90°C and -73°C respectively. Grade 8 is a 9% nickel steel (ASTM A333 Gr. 8) qualified to -196°C (-320°F) for LNG and liquid nitrogen service. Grade 6 is the most economical and widely available grade; nickel grades are specified only when design temperatures fall below -45°C or when code requirements demand the higher absorbed energy of Ni-steel.
Can ASTM A333 Grade 6 be welded, and what preheat is required?
Yes — Grade 6 is fully weldable by SMAW, GMAW, FCAW, and SAW using procedures qualified to ASME Section IX. Preheat is generally not required for wall thicknesses below 25 mm when the carbon equivalent (CE) is ≤0.43%. For heavier walls, a preheat of 50–100°C is recommended to prevent hydrogen cracking. PWHT is not mandatory unless specified by code (e.g. ASME B31.3 for high-pressure or corrosive service), but when performed, it should not exceed 620°C to avoid reducing the low-temperature impact properties.
How does ASTM A333 differ from ASTM A106 for low-temperature service?
ASTM A106 Grade B is not impact-tested and is not code-permitted below -29°C (-20°F) without supplementary impact testing (SA-333 Gr. 6 supplementary requirements or EN 10216-3 equivalent). ASTM A333 Grade 6 is specifically manufactured and tested for low-temperature service and is the correct material for systems below -29°C. Specifying A106 for low-temperature LNG or NGL service is a common and dangerous procurement error; the pipe may meet tensile requirements but fail a drop-weight or Charpy test at operating temperature.
What pipe schedules are available in ASTM A333 Grade 6?
ASTM A333 Grade 6 is available in nominal pipe sizes (NPS) from ½ inch to 24 inches and in standard wall schedules including SCH 40, SCH 80, SCH 120, and SCH 160, as well as XS (extra strong) and XXS (double extra strong). Availability is best in the 2-inch to 16-inch range and in SCH 40 and SCH 80. Heavy walls (SCH 120 and above) and large diameters above 20 inches may have longer mill lead times, particularly in low-temperature grade.
What documentation should be required when purchasing ASTM A333 Grade 6 pipe?
Require an EN 10204 Type 3.1 mill test certificate (MTC) showing heat number, chemical analysis, tensile test results, and the Charpy V-notch impact test results at -45°C. Verify that the impact values meet the minimums for both average and individual specimens. For critical service, specify hydrostatic testing per the ASTM standard and nondestructive examination (NDE). Confirm the pipe manufacturer is approved under your project's vendor qualification and that the MTC heat number matches the pipe heat stamp.
What companion fittings and flanges are required for A333 Grade 6 piping?
All companion materials must be impact-qualified to the same design temperature. Specify ASTM A420 WPL6 for buttweld fittings — it is the designated low-temperature companion fitting grade to A333 Grade 6. For flanges, specify ASTM A350 LF2 rather than standard A105. For valves, confirm body and bonnet Charpy qualification at -45°C per the valve data sheet. Installing standard A234 WPB fittings or A105 flanges in a -45°C system alongside correctly specified A333 Gr.6 pipe creates an unqualified joint — the fitting will be in brittle fracture territory even though the pipe is not.
What PWHT temperature limit applies to A333 Grade 6 piping?
Post-weld heat treatment for A333 Grade 6 piping should not exceed 620°C. The ASME B31.3 allowable PWHT range for carbon steel extends to 680°C, but temperatures above 620°C coarsen the ferrite grain structure that provides low-temperature toughness in Grade 6. At 650°C, PWHT can reduce the Charpy absorbed energy at -45°C below the 20 J average minimum. Specify a maximum PWHT temperature of 620°C on the Welding Procedure Specification and on the purchase order, and require post-PWHT Charpy impact results on weld test coupons.