Specifications

Chemical composition and mechanical properties

Nickel includes cobalt. Limits as given in ASTM B160, B161 and B162.

Values for hot-rolled annealed plate; other forms and conditions as given in each standard.

Actual values for each heat are reported on the mill test certificate.

Why Nickel 200 / 201

Nickel 200 / 201 is commercially pure nickel with at least 99% nickel, with Nickel 201 the low-carbon grade for service above about 315 °C. It is chosen for caustic soda and caustic potash at high concentrations and temperatures, food products, distilled water, dry chlorine and hydrogen chloride at moderate temperatures. Compared with stainless steels, nickel resists hot concentrated caustic without stress corrosion cracking; Nickel 201 is chosen over Nickel 200 above about 315 °C to avoid graphitisation; it is not suitable for oxidising acids.

Nickel 200 or 201 pipe?

Nickel 200 pipe is used up to about 315 °C. Above that temperature, use Nickel 201, whose low carbon prevents graphite forming at the grain boundaries during long service, which would make Nickel 200 brittle. For caustic evaporators and other hot equipment, Nickel 201 is therefore the usual specification. Annealed pipe and tube is used where bending, flaring or expanding into tube sheets is required; stress-relieved material has higher strength for straight runs.

Caustic evaporator tubing

Caustic soda produced in membrane chlor-alkali cells is concentrated in multiple-effect evaporators, where the tubes see hot, concentrated caustic. Nickel tubes corrode at very low rates in this service, while stainless steels suffer caustic stress corrosion cracking. Tubes to ASTM B163 are supplied straight or U-bent in the sizes the evaporator design requires, eddy-current or hydrostatically tested.

Welding and fabrication

Nickel 200 / 201 is welded by TIG, MIG and manual arc processes with ERNi-1 filler metal, on clean joints free of oil, paint, marking crayon, sulphur and lead, using low heat input and controlled interpass temperatures. Heat tint is removed and welds are pickled where corrosion resistance at the weld matters. Fabrication areas should be kept separate from carbon steel, and dedicated tools used to avoid iron contamination.

Testing and ordering

Common supplementary requirements are positive material identification, ultrasonic or eddy-current testing and third-party inspection by the buyer's nominated agency. Please give the grade and specification, product type, size, schedule or class, quantity and any testing or inspection requirement with your enquiry. Each piece is marked with grade, specification, size and heat number, packed in wooden boxes or on pallets, and traceable to its mill test certificate.

Sizes, supply and packing

Pipes are supplied in random lengths, typically about 6 metres, or cut to length, with plain or bevelled ends and plastic end caps. Tubes are supplied in straight lengths to order, or U-bent for heat exchangers. Every length is marked with grade, specification, size, heat number and seamless or welded construction. For heat-exchanger tubes, please give the outside diameter, minimum or average wall thickness, length and bend schedule with the enquiry.

Certification and traceability

Nickel 200 and 201 differ only in carbon content, which cannot be checked by a portable analyser, so traceability to the mill test certificate is essential. Every piece carries its grade and heat number, and the certificate reports nickel, carbon and other elements and the mechanical properties. Please state whether Nickel 200 or Nickel 201 is required, or whether dual-certified material is acceptable, with the enquiry.

Applications and related products

Nickel pipes and tubes are used in caustic evaporators and concentrators, chlor-alkali plants, synthetic fibre production, food processing, and chemical equipment handling alkalis and dry chlorine. Matching products include nickel alloy sheets and plates and nickel alloy round bars. Background on the alloy is on the Nickel 200 page. Other materials are on the seamless pipes and tubes page.