Overview: What Is 1.6368 Steel and Why Does It Exist?
In the late 1960s and early 1970s, European power plant engineers faced a specific unsolved problem: as boiler operating pressures climbed above 18 MPa and feedwater pipeline temperatures pushed toward 400–450 °C, none of the available low-alloy steels — grades such as 15Mo3 or 13CrMo4-5 — delivered an optimal simultaneous combination of high yield strength at temperature, adequate low-temperature toughness, and weldability without mandatory preheat. A new alloy was needed.
The solution was 15NiCuMoNb5-6-4, assigned European material number 1.6368 and known in the German power industry as WB36 (Werkstoff Bainit, originally rated at 36 kgf/mm² minimum yield — now confirmed as ≥ 440 MPa). Its defining innovation was the deliberate addition of copper (0.50–0.80 wt%) and niobium (0.015–0.045 wt%) to a Ni-Mo matrix — a combination that produces copper precipitation hardening and fine-grained bainite through air cooling alone, eliminating the distortion risks of oil quenching in large forged components.
According to published nuclear engineering research (Rieth et al., 2001, Nuclear Engineering and Design), 1.6368 / WB36 was selected as piping and vessel material in boiling water reactor (BWR) and pressurized water reactor (PWR) nuclear power plants in Germany specifically because of its "improved 0.2% yield strength at elevated temperatures" combined with the microstructural advantage that bainite with high bainite content — without any pearlite — results from air cooling after austenitizing. This makes thick-section heat treatment practical, economical, and distortion-free.
Designation, Standard Numbers & International Equivalents
1.6368 carries multiple designations across different national standard systems. The complete cross-reference matrix as used in Jiangsu Liangyi's production documentation and customer qualification packages:
| Standard System | Grade / Designation | Product Forms | Notes |
|---|---|---|---|
| EN (European) | 1.6368 / 15NiCuMoNb5-6-4 | All forms | Primary standard reference |
| EN 10028-2:2003 | 15NiCuMoNb5-6-4 | Flat products, plates, sheets | Most referenced for composition |
| EN 10216-2 | 15NiCuMoNb5-6-4 | Seamless steel tubes for pressure | Pipe/tube procurement standard |
| DIN 17755 (legacy) | WB 36 / 15NiCuMoNb5 | Boiler-grade forgings & tubes | German nuclear industry origin |
| ASTM A335 | Grade P36 | Seamless ferritic alloy steel pipe | US pipe equivalent |
| ASTM A213 | Grade T36 | Boiler, superheater, heat-exchanger tubes | US tube equivalent |
| ASME SA-335 | P36 | Pressure-certified piping | ASME code equivalent |
| ASME SA-213 | T36 | Pressure boiler tubes | ASME code equivalent |
| Trade name | WB36 | All forms | Legacy commercial designation only |
| Always specify the EN or ASTM grade number in procurement documents. "WB36" is a trade/legacy designation, not a live standard — it lacks full traceability on its own. | |||
For forged components specifically, Jiangsu Liangyi manufactures 1.6368 forgings in compliance with EN 10250-1/3 (open steel die forgings for general engineering purposes) and supplies material with EN 10204:2004 Type 3.1 Mill Test Certificates as standard. Type 3.2 (third-party counter-signed) is available on request. TPI by SGS, Bureau Veritas, TÜV SÜD, or any buyer-nominated inspector is accommodated on request at buyer's cost.
Chemical Composition of 1.6368 per EN 10028-2:2003
| Element | Symbol | Min (wt%) | Max (wt%) | Primary Metallurgical Function |
|---|---|---|---|---|
| Carbon | C | — | 0.17 | Bainite matrix strength; tightly capped for weldability without mandatory preheat |
| Silicon | Si | 0.25 | 0.50 | Deoxidation during steelmaking; moderate solid-solution strengthening |
| Manganese | Mn | 0.80 | 1.20 | Hardenability increase; supports bainite transformation; toughness matrix |
| Phosphorus | P | — | 0.025 | Controlled impurity — limits grain-boundary segregation and temper embrittlement |
| Sulfur | S | — | 0.010 | Ultra-low impurity ceiling — prevents MnS bands that nucleate HIC in feedwater |
| Chromium | Cr | — | 0.30 | Residual element only — low cap prevents unwanted carbide networks |
| Molybdenum | Mo | 0.25 | 0.50 | Hardenability; bainite TTT curve suppression; Mo₂C creep resistance at temperature |
| Nickel | Ni | 1.00 | 1.30 | Low-temperature CVN toughness; DBTT reduction; austenite field stabilisation |
| Copper | Cu | 0.50 | 0.80 | ε-Cu precipitation hardening (+60–90 MPa); thermally stable to 400 °C |
| Niobium | Nb | 0.015 | 0.045 | NbC/NbN grain boundary pinning; ASTM 8–10 grain size; precipitation strengthening |
| Nitrogen | N | — | 0.020 | Controlled for Nb effectiveness (N:Nb ratio); limits excess nitride formation |
| Aluminium | Al | — | 0.015 | Deoxidation; combined with Nb for grain size control during normalising |
| Highlighted rows (Cu, Nb) are the two defining elements that differentiate 1.6368 from standard Ni-Mo boiler steels. Source: EN 10028-2:2003. Jiangsu Liangyi verifies every incoming heat against these limits; full composition is included in the EN 10204 3.1 MTC supplied with every order. | ||||
The Role of Each Alloying Element: Deep Metallurgical Analysis
Standard datasheets list composition ranges without explaining why each element is present at those specific levels. Understanding the metallurgical rationale is essential for engineers specifying, qualifying, or troubleshooting 1.6368 forgings.
Carbon (C ≤ 0.17 wt%) — The Strength–Weldability Trade-off
Carbon is capped at 0.17 wt% — the practical upper limit where the steel can be welded without mandatory preheat in sections up to 30 mm, avoiding cold cracking in heat-affected zones. Below this ceiling, carbon contributes to bainite lath hardness while keeping the carbon equivalent (CE per IIW formula) below approximately 0.45 for the lower end of the composition range. The required strength is delivered by microstructural mechanisms (Cu precipitation, Nb grain refinement, bainite lath strengthening) rather than carbon content, which is the fundamental innovation of 1.6368 versus earlier boiler steels.
Nickel (Ni: 1.00–1.30 wt%) — Low-Temperature Toughness
Nickel at 1.00–1.30 wt% lowers the ductile-to-brittle transition temperature (DBTT) by approximately 20–25 °C per 1 wt% Ni addition, enabling 1.6368 to pass Charpy CVN ≥ 47 J at –20 °C. This is critical for pipelines in cold-climate power plants and for nuclear safety system components that must function at ambient temperature after long service. Ni also widens the austenite phase field during hot working, suppressing premature ferritic transformation and extending the practical forging temperature window below 950 °C without surface quality penalty.
Copper (Cu: 0.50–0.80 wt%) — The Grade's Defining Innovation
Copper is what makes 1.6368 different from all predecessor Ni-Mo steels. At 0.50–0.80 wt%, copper remains fully dissolved in austenite at normalising temperature (≥ 880 °C) but precipitates as fine ε-Cu particles (body-centred cubic copper clusters, 2–5 nm diameter) during cooling and tempering. This copper precipitation hardening mechanism contributes approximately 60–90 MPa to yield strength without increasing the carbon equivalent or reducing weldability. Critically, Cu precipitates are thermally stable up to approximately 400 °C — unlike conventional carbide precipitation hardening mechanisms (e.g., Mo₂C, V₄C₃) that coarsen rapidly above 450–500 °C. This thermal stability is the direct reason for WB36's superior elevated-temperature yield strength retention compared with 15Mo3 and 13CrMo4-5 at 300–400 °C service temperatures.
Molybdenum (Mo: 0.25–0.50 wt%) — Bainite Promoter & Creep Resistance
Molybdenum serves two independent functions. First, it shifts the pearlite and bainite nose on the TTT (Time-Temperature-Transformation) diagram far enough to the right that air cooling of sections up to 150 mm produces a predominantly bainitic microstructure without oil quenching. Without Mo, sections above approximately 50 mm would transform partially to soft pearlite with inadequate strength. Second, Mo forms fine Mo₂C carbides during tempering at 580–660 °C, which pin dislocations at elevated temperatures and provide measurable creep resistance in components operating continuously above 300 °C.
Niobium (Nb: 0.015–0.045 wt%) — Grain Refinement Champion
Despite its low absolute concentration — the lowest of any intentionally added element in 1.6368 — niobium has the largest per-kilogram impact on the final mechanical properties. Nb dissolves fully in austenite above approximately 1050 °C during normalising and then precipitates as fine NbC and NbN particles as temperature falls through the finish-forging range (950–1020 °C). These 5–20 nm precipitates pin austenite grain boundaries, preventing grain coarsening during the last forging passes and producing the fine austenite grain size (ASTM 8–10) that translates into superior low-temperature CVN toughness after normalising. Without Nb, the Ni-Cu-Mo combination would provide adequate strength but inferior toughness in sections above 50 mm — a critical shortcoming for thick-walled boiler drum forgings.
Microstructure: Fine-Grained Bainite
The combined effect of Ni and Mo suppresses the bainite nose on the TTT diagram far enough to the right that air cooling of forgings up to 150 mm section diameter produces > 90% bainite microstructure. For sections between 150–400 mm, accelerated cooling (forced air or water mist) is applied after normalising to maintain sufficient cooling rate through the bainite transformation range. For sections exceeding 400 mm, core hardenability calculations must be performed against the specific heat chemistry before committing to N+T treatment.
Mechanical Properties of 1.6368 Steel at Room Temperature
All mechanical properties below apply to the Normalised + Tempered (N+T) delivery condition. Engineers sourcing material can review available product forms — forged bars, seamless rings, discs, and heavy-section blanks — on our 1.6368 forged parts catalogue, where dimensional ranges and lead times are listed for each form.
| Property | Symbol | Unit | Value / Range | Test Standard |
|---|---|---|---|---|
| 0.2% Proof Stress | Rp0.2 | MPa | ≥ 440 | EN ISO 6892-1 |
| Tensile Strength | Rm | MPa | 610 – 760 | EN ISO 6892-1 |
| Elongation at fracture | A5 | % | ≥ 19 | EN ISO 6892-1 |
| Reduction of Area | Z | % | ≥ 50 | EN ISO 6892-1 |
| Charpy CVN Impact at –20 °C | KV | J | ≥ 47 (average of 3); ≥ 34 (individual) | EN ISO 148-1 |
| Hardness (Brinell) | HB | HBW | 180 – 250 | EN ISO 6506-1 |
| Elastic Modulus at RT | E | GPa | ~210 | EN 13445 / Literature |
| Elastic Modulus at 400 °C | E | GPa | ~190 | EN 13445 / Literature |
| Density | ρ | g/cm³ | 7.84 | Calculated |
| Specific Heat Capacity at RT | cp | J/(kg·K) | ~480 | Literature |
| Thermal Conductivity at RT | λ | W/(m·K) | ~42 | Literature |
| Mean CTE (20–400 °C) | α | 10⁻⁶/K | ~12.5 | Literature |
| Values are reference minimums per EN 10028-2 for N+T (Normalised + Tempered) delivery condition. Jiangsu Liangyi's production values typically exceed minimums by 5–15% on yield strength and 15–30% on CVN impact. Certified test results are included in the EN 10204 3.1 MTC supplied with every forging order. | ||||
Elevated-Temperature Mechanical Properties of 1.6368 Steel
The principal engineering reason for selecting 1.6368 over competing grades is its superior yield strength retention at service temperatures. The table below documents the temperature-dependent mechanical behaviour of 1.6368, referenced against published nuclear engineering data (Rieth et al., 2001) and EN standard minimums:
| Temperature (°C) | Rp0.2 Min. (MPa) | Rm Range (MPa) | Engineering Significance |
|---|---|---|---|
| 20 (RT) | ≥ 440 | 610 – 760 | Base reference — all property minimums apply |
| 100 | ≥ 420 | ~590 – 740 | Minor softening; Cu precipitates fully stable |
| 200 | ≥ 395 | ~560 – 710 | Dynamic strain aging may produce slight hardening peak |
| 300 | ≥ 375 | ~535 – 685 | Cu ε-phase precipitates fully stable; Mo₂C creep resistance active |
| 350 | ≥ 353 | ~520 – 660 | Typical BWR/PWR nuclear plant operating window |
| 400 | ≥ 330 | ~500 – 640 | Fossil plant continuous operation maximum (typical) |
| 450 | ≥ 295 | ~470 – 610 | Upper service limit; creep becomes design-controlling; Cu over-aging onset |
| 500 | Not specified | — | Above recommended service temperature; Cu coarsening degrades strength |
| Note: Above 450 °C, Cu precipitate coarsening (over-aging) progressively reduces the copper precipitation hardening contribution. 1.6368 is NOT recommended for continuous service above 450 °C. For 450–560 °C service, use 13CrMo4-5 (1.7335). For above 560 °C, use P91 (X10CrMoVNb9-1). | |||
Forging Characteristics & Process Requirements for 1.6368 Steel
Forging Temperature Parameters
| Stage | Temperature Range | Metallurgical Purpose |
|---|---|---|
| Ingot heating / soaking | 1180 – 1220 °C | Full austenitisation; NbC/NbN dissolution above Nb solvus (~1050 °C); homogenise Cu in solid solution; eliminate ingot segregation segregation bands |
| Initial breakdown (cogging / upsetting) | 1100 – 1180 °C | Destroy as-cast dendritic structure; close solidification porosity; achieve billet-grade internal soundness; first forging ratio increment |
| Intermediate forging passes | 1000 – 1100 °C | Progressive shape development; controlled partial Nb reprecipitation begins; austenite grain boundaries remain pinned |
| Finishing passes | 950 – 1020 °C | Maximum Nb grain boundary pinning effectiveness; final grain size established; this is the most critical temperature window for achieving fine ASTM 8–10 grain size |
| Minimum forging stop temperature | ≥ 900 °C | Below 900 °C, Ar₃ is approached; proeutectoid ferrite forms at austenite grain boundaries; surface cracking risk; non-uniform microstructure |
| All temperatures measured by calibrated contact pyrometer at forging surface. Sections > 300 mm diameter: furnace soak at soaking temperature ≥ 1 hr per 100 mm cross-section before forging commences to ensure temperature homogeneity through the section. | ||
Recommended Forging Ratio
A minimum forging ratio of 4:1 (total reduction from ingot to finished forging cross-section) is required for standard industrial-grade 1.6368 forgings. This ensures complete breakdown of ingot segregation banding and achieves homogeneous microstructure through the full cross-section. For ultrasonic-critical components — boiler drum shells, nuclear pressure boundary nozzle forgings, valve bodies for high-integrity service — Jiangsu Liangyi targets a forging ratio of 6:1 to 8:1, which produces the maximum UT cleanliness and minimum segregation depth achievable from ingot route material.
Step-by-Step Production Process at Jiangsu Liangyi
Raw Material Inspection
PMI (positive material identification), chemical composition verification against EN 10028-2 limits, radioactivity test, visual and dimensional surface inspection of incoming ingots or billets. Heat number and chemical composition confirm traceability before any processing begins.
Ingot Heating & Soaking
Charge to furnace at ≤ 600 °C (to avoid thermal shock cracking in large-section ingots), controlled ramp to 1180–1220 °C at ≤ 80 °C/hr for sections > 500 mm, soak for ≥ 1 hr per 100 mm of cross-section. Ensures full NbC/NbN dissolution above the Nb solvus and homogeneous Cu in solid solution.
Initial Breakdown (Cogging / Upsetting)
First forging passes at 1100–1180 °C on hydraulic press (2,000T – 6,300T capacity). Cumulative forging ratio tracked against target on each heat. Objective: destroy dendritic cast structure, close solidification shrinkage porosity, and establish billet-grade internal soundness.
Intermediate & Finishing Passes
Progressive shape development at 950–1100 °C. Reheating cycles as required to maintain metal temperature above 950 °C. Finishing passes in the 950–1020 °C range are critical: this is where Nb pinning of austenite grain growth is most effective and where final grain size is established. For rings: seamless ring rolling on our 1-meter and 5-meter ring mills.
Post-Forging Cooling
Sections ≤ 150 mm: controlled air cooling in still air — Ni + Mo combination ensures predominantly bainitic transformation without oil quench. Sections 150–400 mm: forced-air or water-mist cooling to maintain cooling rate above 2 °C/min through the 550–350 °C bainite transformation range and prevent core pearlite formation.
Normalising + Tempering (N+T)
Final heat treatment cycle per Jiangsu Liangyi's qualified procedure (see Section 09 below). Computer-controlled furnaces maintain ±5 °C temperature uniformity. Full furnace chart record forms part of the MTC documentation package.
Inspection, Testing & Certification
100% volumetric UT per EN 10228-3 (or ASTM A388, ASTM A745 on request); surface inspection by MT (EN ISO 10228-1) or PT (EN ISO 10228-2); dimensional inspection to drawing; mechanical testing (tensile, CVN impact, hardness) from test prolongations; chemical composition verification; hardness traverse; EN 10204 3.1 MTC compilation and sign-off.
Heat Treatment of 1.6368 Forgings
| Stage | Temperature | Atmosphere | Soak Time | Cooling |
|---|---|---|---|---|
| Normalising (austenitising) | 880 – 940 °C | Air atmosphere furnace | ≥ 1 hr / 25 mm section (min. 2 hr) | Air cool for sections ≤ 150 mm; forced-air or water mist for heavy sections |
| Tempering | 580 – 660 °C | Air atmosphere furnace | ≥ 1.5 hr / 25 mm section (min. 3 hr) | Furnace cool at ≤ 50 °C/hr to ≤ 300 °C, then air cool to ambient |
| Stress Relief (post-weld, optional) | 550 – 600 °C | Air atmosphere furnace | ≥ 1 hr / 25 mm weld section thickness | Furnace cool at ≤ 30 °C/hr to ≤ 300 °C, then air cool |
| Jiangsu Liangyi's 10 computer-controlled continuous furnaces maintain ±5 °C temperature uniformity throughout every tempering cycle, verified by calibrated thermocouples at multiple section positions. Full furnace time-temperature charts are supplied as part of the MTC package. | ||||
Do NOT temper 1.6368 steel at temperatures between 450–560 °C under any circumstances. At these temperatures, fine Cu precipitates migrate to and coarsen preferentially at austenite grain boundaries rather than remaining uniformly distributed within the bainite laths. This grain-boundary copper embrittlement phenomenon reduces CVN impact energy by 25–40% at –20 °C and can cause forgings to fail Charpy impact tests even when hardness and tensile properties appear within specification — because hardness and tensile strength are insensitive to this microstructural change.
If a 1.6368 forging has been inadvertently tempered in this temperature range: do NOT re-temper at the correct temperature and assume the problem is corrected. The grain-boundary embrittlement is not reversible by re-tempering alone. The correct corrective action is: full re-normalise from fresh austenitising temperature (880–940 °C), then re-temper at 580–660 °C to re-dissolve and re-precipitate the copper in its correct intragranular morphology.
For engineers specifying N+T certified components — boiler drum forgings, pressure vessel tube sheets, valve bodies, and flanged nozzles — all product forms available from Jiangsu Liangyi in 1.6368 are listed with dimensions and lead times on our 1.6368 forged pressure vessel components and valve body page. Every shipment is supplied in the correct N+T condition with full furnace time-temperature records included in the MTC.
Weldability of 1.6368 Steel
| Section Thickness | Preheat Requirement | Post-Weld Heat Treatment (PWHT) | Note |
|---|---|---|---|
| ≤ 25 mm | None (if CE ≤ 0.45) | Optional stress relief at 550–600 °C | Verify CE of specific heat MTC before waiving preheat |
| 25 – 60 mm | 75 – 100 °C recommended | Stress relief at 550–600 °C recommended | Preheat is precautionary; CE 0.45–0.48 zone |
| > 60 mm | 100 – 150 °C required | PWHT at 580–620 °C mandatory | HAZ hydrogen cracking risk in high-constraint joints |
| CRITICAL: Maximum PWHT temperature = 640 °C. Above this limit, incipient Cu over-aging in the HAZ reduces local yield strength below design minimums. Always verify base metal CE from the MTC before setting preheat. CE = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15 (IIW formula). | |||
The carbon equivalent advantage of 1.6368 over alternative high-strength grades is significant: P91 (X10CrMoVNb9-1), which offers higher elevated-temperature strength, requires mandatory preheat of 200–250 °C on all weld joints regardless of section thickness and mandatory PWHT after all welding. The additional fabrication cost and schedule impact of P91 welding requirements is a significant factor in selecting 1.6368 for service temperatures up to 450 °C, where WB36 provides adequate performance without these constraints.
Industrial Applications of 1.6368 Forged Parts
The combination of high yield strength at service temperature, adequate low-temperature CVN toughness, good weldability, and long-term microstructural stability targets a defined set of industries where no cheaper grade provides equivalent performance. 1.6368 is not a commodity-substitute material — it is an application-specific grade selected where its triple performance advantage justifies a modest cost premium over simpler boiler steels.
Fossil Power Generation
Boiler drums, high-pressure feedwater heater shells and tube sheets, main steam valve bodies, collector rings, and flange forgings for feedwater pipelines at up to 450 °C and 22 MPa design pressure.
Nuclear Power (BWR / PWR)
Primary circuit piping components, evaporator nozzle forgings, reactor pressure vessel nozzle forgings, and Emergency Core Cooling System (ECCS) line components. Widely used in German KKW-era nuclear plants per SIEMENS/KWU qualification data from the 1970s–1990s.
Pressure Vessel Fabrication
Thick-walled pressure vessel shells per EN 13445, forged flanged nozzles, manway covers and manway flanges, vessel heads (domed, hemispherical), and tube sheet forgings for high-pressure shell-and-tube heat exchangers.
Petrochemical & Chemical Processing
Reactor vessel bodies, high-pressure separator drums, hydrocracker and hydrotreater pressure components, fired heater coil supports, and regenerator vessels operating in the 250–400 °C temperature range.
Steam System Valve Bodies
Gate valve bodies, globe valve bodies, check valve disc forgings, and valve bonnet forgings for main steam isolation valves, feedwater control valves, drain valves, and bypass service valves in fossil and nuclear power plants.
Water Treatment & Desalination
High-pressure pump casings, impeller rings, and pressure vessel components for seawater desalination multi-effect distillation (MED) and multi-stage flash (MSF) plants where both mechanical strength and mild corrosion resistance to brackish water are required.
1.6368 vs Alternative Grades: Engineering Selection Guide
The table below compares 1.6368 against the four most commonly considered alternative grades for elevated-temperature pressure vessel and piping service. Values are reference minimums from respective EN standards.
| Grade | Yield at RT (MPa) | Yield at 350 °C (MPa) | CVN at –20 °C | Weldability | Max. Service Temp. | Key Trade-off |
|---|---|---|---|---|---|---|
| 1.6368 (WB36) | ≥ 440 | ≥ 353 | ≥ 47 J | Good — no preheat ≤ 30mm | 450 °C | Best 350–450 °C combination |
| 1.5415 (15Mo3) | ≥ 265 | ≥ 175 | ≥ 27 J | Very good — lower CE | 500 °C | Simpler but 60% lower yield at temp |
| 1.7335 (13CrMo4-5) | ≥ 295 | ≥ 215 | ≥ 27 J | Good — preheat required | 560 °C | Higher temp range; lower strength |
| 1.7380 (10CrMo9-10) | ≥ 280 | ≥ 215 | ≥ 40 J | Moderate — preheat required; PWHT rec. | 580 °C | Higher temp range; complex welding |
| P91 (X10CrMoVNb9-1) | ≥ 450 | ≥ 390 | ≥ 40 J | Complex — mandatory preheat 200–250 °C; PWHT required always | 620 °C | Best >500 °C; high fabrication cost |
| Grade selection guide: Use 1.6368 when service temperature is 350–450 °C and maximising yield strength combined with easiest weldability is the priority. Use P91 when temperature exceeds 450 °C. Use 13CrMo4-5 when temperature is 400–560 °C and cost is the primary constraint. Contact Jiangsu Liangyi for material selection support specific to your project. | ||||||
The table makes the selection rationale clear: no other grade in the 350–450 °C service window simultaneously delivers ≥ 440 MPa yield strength and weldability without mandatory preheat on sections ≤ 30 mm. At 350 °C, 1.6368 provides 101% more yield strength than 15Mo3 and 64% more than 13CrMo4-5 — advantages that directly translate into reduced wall thickness, reduced vessel weight, and reduced installation cost in large boiler and pressure vessel fabrication projects.
Frequently Asked Questions about 1.6368 Steel
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Jiangsu Liangyi manufactures 1.6368 (WB36) open-die forgings, seamless rolled rings, valve bodies, tube sheets, flanges, and custom components from 30 kg to 30,000 kg. ISO 9001:2015 certified. EN 10204 3.1 Mill Test Certificate supplied with every order. Global delivery to 50+ countries. Our engineering team provides free material selection support.