1.6368 (WB36 / 15NiCuMoNb5-6-4) open-die forgings
Forged bars, seamless rolled rings, flanges, discs, hollow bars and valve bodies in 1.6368 power-plant alloy steel, made to drawing by Jiangyin Jiangnan Metal Co., Ltd.
- EN chemical name
- 15NiCuMoNb5-6-4
- Common trade name
- WB36
- Also known as
- DIWA 373
- ASTM forging grade
- A182 F36
- ASTM pipe grade
- A335 P36
- Steel type
- Ni-Cu-Mo-Nb alloy
1.6368 is the EN material number for 15NiCuMoNb5-6-4, a nickel-copper-molybdenum-niobium alloy steel. In the power industry it is usually called WB36, the Mannesmann trade name. The grade was developed for feedwater piping, headers and pressure components in high-parameter thermal and nuclear plants. Niobium keeps the grain fine and copper gives precipitation strengthening during tempering, so the steel holds a higher yield strength than carbon-manganese steel at the same service temperature. Designers use that to cut wall thickness, which lowers component weight and eases thermal fatigue when a unit cycles.
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory in Jiangyin, Jiangsu Province, China. We forge 1.6368 / WB36 to customer drawings: round and flat bars, seamless rolled rings, flanges, discs, sleeves, hollow bars, tees and valve bodies. Send a drawing to sales@steelforgepieces.com or call +86 189 2135 9659.
What is 1.6368 steel?
1.6368 is a low-carbon alloy steel for pressure service at elevated temperature. The EN chemical designation 15NiCuMoNb5-6-4 reads straight off the analysis: about 0.15 % carbon, with nickel, copper and molybdenum as the main alloy additions and a small niobium addition.
The grade is listed in EN 10216-2 for seamless tubes, EN 10028-2 for plate and ISO 9328-2 for pressure-vessel flat products. American practice covers the same chemistry as A335 P36 for seamless pipe and A182 F36 for forgings, which is the specification that normally applies to forged parts.
Niobium forms fine carbonitrides that pin the austenite grain boundaries during hot working, so the grain stays small. Copper at 0.50 to 0.80 % precipitates during tempering and adds strength without the loss of creep ductility that other strengthening routes bring. Minimum yield strength is 460 MPa in thin sections, and the steel still welds.
1.6368 equivalent grades and standards
1.6368 goes under several names, depending on the standard and the region. They all describe the same base chemistry. Confirm the product form and the governing standard on the order.
| Designation | System or standard | Product form |
|---|---|---|
| 1.6368 | EN material number | All forms |
| 15NiCuMoNb5-6-4 | EN chemical designation | All forms |
| WB36 | Mannesmann trade name | All forms |
| DIWA 373 | Dillinger trade name | Plate |
| A182 F36 / SA-182 F36 | ASTM / ASME | Forged flanges, fittings, valve parts |
| A335 P36 / SA-335 P36 | ASTM / ASME | Seamless pipe |
| T36 | ASTM tube grade | Seamless tube |
| 15NiCuMoNb5 | Short form, DIN practice | All forms |
Related standards: EN 10216-2 (seamless tubes for pressure purposes), EN 10028-2 (flat products for pressure purposes), EN 10222-2 (steel forgings for pressure purposes), ISO 9328-2, VdTÜV Werkstoffblatt 377.
1.6368 chemical composition
Chemical composition of 1.6368 (15NiCuMoNb5-6-4) in mass percent, to EN 10028-2. Copper and niobium are what separate this grade from an ordinary carbon-manganese pressure steel.
| Element | C | Si | Mn | Ni | P | S | Cr | Mo | N | Nb | Al | Cu |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Mass % | ≤ 0.17 | 0.25–0.50 | 0.80–1.20 | 1.00–1.30 | ≤ 0.025 | ≤ 0.010 | ≤ 0.30 | 0.25–0.50 | ≤ 0.020 | 0.015–0.045 | ≤ 0.015 | 0.50–0.80 |
Balance iron. The figures are the specified analysis range. The actual heat analysis is stated on the EN 10204 mill certificate that ships with the order.
1.6368 mechanical properties
Room-temperature properties in the normalised and tempered condition, by nominal thickness. Both yield and tensile strength drop as the section gets thicker, which matters on heavy forged parts.
| Nominal thickness | to 40 mm | 40–60 mm | 60–100 mm | 100–150 mm | 150–200 mm |
|---|---|---|---|---|---|
| ReH, min. yield strength (MPa) | 460 | 440 | 430 | 420 | 410 |
| Rm, tensile strength (MPa) | 610–780 | 610–780 | 600–760 | 590–740 | 580–740 |
Tensile strength is specified as one band for thickness up to 60 mm.
Impact energy and elongation
| Property | −20 °C | 0 °C | +20 °C |
|---|---|---|---|
| KV, impact energy, transverse (J) | 27 | 34 | 27–40 |
| A, min. elongation at fracture (%) | 16–19 | ||
Impact values are transverse minima. Longitudinal values run higher. State the test direction and temperature you need on the enquiry.
Heat treatment and welding of 1.6368
Delivery condition
1.6368 is supplied normalised and tempered, or quenched and tempered. After final heat treatment the structure is bainite with ferrite and sorbite, or bainite with a little ferrite. Tempering is what develops the copper precipitation strengthening, so the cycle should not be cut short.
Welding
1.6368 welds by manual arc and TIG. It is sensitive to cold cracking, so preheat to 150–200 °C and apply post-weld heat treatment. Set the stress-relief temperature about 30 °C below the actual tempering temperature of the parent material. Going above it disturbs the tempered condition of the forging.
Consumables in general use are an E11016-G class electrode for manual welding and an ER110S class wire for TIG. Check the consumable against the fabrication code that governs your project.
Forging
We forge in the hot working range with a controlled finishing temperature, then normalise and temper. Reduction ratio is agreed on the order so the grain flow follows the part geometry.
What is 1.6368 used for?
1.6368 / WB36 is a power-generation steel. The higher yield strength lets designers reduce wall thickness against carbon steel. That cuts component mass and improves resistance to thermal fatigue when a unit cycles.
- Feedwater piping, headers and manifolds in high-parameter thermal power plants
- Pressure components in nuclear power generating units
- High-pressure boiler tubes, superheater and heat-exchanger tubing
- Forged valve bodies, bonnets, seats and stems for high-temperature service
- Forged flanges and pipe fittings for elevated-temperature pressure systems
- Pressure-vessel shells, nozzles and forged transition pieces
1.6368 forgings we supply
Everything below is open-die forged to your drawing in 1.6368 / WB36 / 15NiCuMoNb5-6-4. We do not carry catalogue sizes. Send the drawing or the dimensions and we quote against them.
Forged bars
Round, square, rectangular, flat and hexagonal bar in 1.6368.
Seamless rolled rings
Forged and seamless rolled steel rings in 1.6368, rough or finish machined.
Flanges, discs and blocks
Forged 1.6368 flanges, discs, plates and rectangular blocks.
Hollow bars and sleeves
Bored 1.6368 hollow bar, sleeves, bushes, cylinders, shells and housings.
Valve components
Forged 1.6368 valve bodies, bonnets, seats, seat rings and stems.
Tees and wyes
Equal, eccentric and lateral tees, Y-pieces and piggable wyes in 1.6368.
Manufacturing capability and testing
| Forging process | Open-die (free) forging, ring rolling |
|---|---|
| Melting route | EAF + LF + VD; ESR on request |
| Heat treatment | Annealing, normalising, normalising + tempering, quenching + tempering |
| Delivery condition | As forged, rough turned, black after Q&T, or machined to drawing |
| Non-destructive testing | UT, MT, PT, RT |
| Destructive testing | Chemical analysis, tensile, impact, hardness, grain size, metallography |
| Certification | EN 10204 3.1 mill certificate; 3.2 with third-party witness on request |
| Third-party inspection | SGS, BV, TÜV, Lloyd’s and customer inspectors welcome |
Checks run through the whole route: ingot melting, forging, heat treatment and machining. Each shipment goes out with the material certificate, the heat-treatment chart, the dimensional report and the UT report.
Frequently asked questions about 1.6368
What is 1.6368 steel?
1.6368 is the EN material number for 15NiCuMoNb5-6-4, a nickel-copper-molybdenum-niobium alloy steel for pressure service at elevated temperature. It is usually called WB36. Its main use is feedwater piping and pressure components in thermal and nuclear power plants.
What is the ASTM equivalent of 1.6368?
For forged products the ASTM equivalent of 1.6368 is A182 F36 (ASME SA-182 F36). For seamless pipe it is A335 P36, and for tube, T36. All share the 15NiCuMoNb5-6-4 base chemistry.
What is the yield strength of 1.6368 / WB36?
Minimum yield strength of 1.6368 is 460 MPa for sections up to 40 mm. It falls to 440 MPa at 40–60 mm, 430 MPa at 60–100 mm, 420 MPa at 100–150 mm and 410 MPa at 150–200 mm. Tensile strength is 610–780 MPa up to 60 mm.
Is 1.6368 weldable?
Yes. 1.6368 welds well but is sensitive to cold cracking. Preheat to 150–200 °C and apply post-weld heat treatment. Set the stress-relief temperature about 30 °C below the actual tempering temperature of the parent forging.
Why does WB36 contain copper?
Copper at 0.50–0.80 % precipitates during tempering and raises the strength of the steel without reducing creep ductility. Together with niobium grain refinement, that is why 1.6368 carries a higher yield strength than carbon-manganese steel at the same service temperature.
In what condition is 1.6368 supplied?
Normally normalised and tempered, or quenched and tempered. The resulting structure is bainite with ferrite and sorbite, or bainite with a little ferrite.
Who manufactures 1.6368 forgings?
Jiangyin Jiangnan Metal Co., Ltd., an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, forges 1.6368 / WB36 parts to customer drawings, including bars, seamless rolled rings, flanges, discs, hollow bars, tees and valve bodies. Contact sales@steelforgepieces.com or +86 189 2135 9659.
What sizes and shapes of 1.6368 forgings can be made?
Parts are forged to drawing rather than to a fixed catalogue. The range covers round and flat bars, seamless rolled rings, flanges, discs, blocks, hollow bars, sleeves, tees, wyes and valve bodies. Send the drawing with the standard, the heat-treatment condition and the testing scope you need.
What certificates come with 1.6368 forgings?
Every order ships with an EN 10204 3.1 mill certificate covering chemical composition and mechanical properties, plus the heat-treatment chart, the dimensional report and the ultrasonic test report. EN 10204 3.2 certification with third-party witness is available on request.
Request a quotation for 1.6368 forgings
Send the drawing of the 1.6368 / WB36 / 15NiCuMoNb5-6-4 part you need, with the governing standard, the heat-treatment condition and the testing scope. We come back with a price and a lead time.
- Manufacturer
- Jiangyin Jiangnan Metal Co., Ltd.
- Factory address
- No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
- Telephone
- +86 189 2135 9659