N6 nickel plate selection full solution| Class 4 status + Class 7 medium + Domestic import price +5 steps to avoid pits

Published by Engineering Team, Shaanxi Qianyi Tuoda Technology Co., Ltd on 2026-07-30

Evaporation process of a 300,000 ton/year caustic soda plant, The drawing requires the selection of N6 nickel plate annealed M state material, There have been instances where suppliers have replaced supplied rolled hard R status N6 nickel plates.The two plates have the same material grade., But the material properties vary greatly., R hard nickel plate operates for 3 to 6 months at 80% sodium hydroxide concentration, stress corrosion cracking occursM annealed nickel plate under the same operating conditions, stable operation for 8 years without abnormal.In this paper, four kinds of material states of N6 nickel plate are systematically disassembled, Seven types of media adaptation scheme, Comparison of domestic and imported nickel plate market, Sort out the five steps to avoid pit points of procurement, Chemical Equipment Procurement, Process engineers recommend collections.

Core conclusion: N6 nickel plate selection can not only look at pure nickel brand, material state selection error is equivalent to selection failure.T Four types of state adaptation conditions are different, Improper selection of plate cracking failure within months, Reasonable selection can achieve stable use for more than 15 years.

Why nickel plate is the core material of caustic soda and salt making equipment

N6 nickel plate has three core advantages, alkali corrosion resistance, It has irreplaceable performance in 80% NaOH high temperature concentration condition.Resistant to reducing acid, adapt to dilute sulfuric acid, dilute hydrochloric acid and other reducing acid corrosion environment;Clean material, medicine, food, electronic scene use will not precipitate metal ions cause pollution. In caustic soda production scenarios, the problem with most nickel plate failure is not corrosion of that plate body, It is the wrong choice of material state that causes stress corrosion cracking.R hard nickel plate has high stress corrosion susceptibility in concentrated alkali environment, M annealed nickel plate has better stress corrosion resistance.Stainless steel is prone to pitting corrosion in concentrated sodium hydroxide environment, stress corrosion problem, Titanium material has alkali brittleness risk under concentrated alkali condition, Pure nickel material is the best material in concentrated alkali condition, This is chlor-alkali., sodium carbonate, caustic soda, The main reason why N6 nickel plate is widely used in PTA project.

Detailed explanation of N6 nickel plate state of Class II and IV

R hard state is rolled state, Hot rolled and cold rolled, No annealing, Hardness range 180-220HV, Mostly used in non-corrosive environment equipment structural partsM annealing state is also called soft state, Annealed to relieve internal stress, Hardness 110-140HV, Suitable concentrated alkali, reducing acid condition, is that most common type selection for chlor-alkali projectY solid solution state, Adopt high temperature solid solution and water quenching process, Hardness 120-150HV, High temperature environment and material strengthT aging state, Aging strengthening after solution treatment, Hardness 150-180HV, Suitable for working conditions requiring both high strength and corrosion resistance.

Comparison of M Annealed State and R Hard State, M Annealed hardness 110-140HV, Tensile strength 380-450MPa, The elongation is not less than 40%, Strong alkali stress corrosion resistance, Good bending and welding processing performanceR hard hardness 180-220HV, tensile strength 550-700MPa, elongation only 15%-25%, weak stress corrosion resistance under concentrated alkali conditions, need to anneal in advance before welding bending processing, purchase price is slightly lower than M annealing about 5%.

Three, seven types of media selection reference

30%-80% concentration of sodium hydroxide, temperature ≤400℃ working conditions, preferably N6 nickel plate M annealed state, plate thickness can be selected from 1mm to 20mm;Dilute reducing acid with concentration less than 10%, N6M annealed state, thickness range 1mm to 10mm;molten sodium hydroxide, potassium hydroxide, Temperature is greater than 400℃ conditions, Select N6Y solid solution state, Sheet thickness 5mm to 20mmSeawater, neutral brine containing chloride ions, R hard state or M annealed state N6 nickel plate, thickness 1mm to 15mm;High temperature fatty acid, organic acid conditions, N6M annealing state adaptation, plate thickness 2mm to 10mm;High-purity N200 nickel plate, M annealed state, meeting GMP specifications, thickness 1mm to 8mm;Electroplating anode, R hard N6 nickel plate, thickness 3mm to 20 mm.

IV. Field application cases

Case 1: N6 nickel plate for evaporator of 300,000 tons/year caustic soda plant, specification δ8mm×1500mm×3000mm, N6M annealed state.The medium was 80% NaOH concentrate at 320℃.Early use of R hard plate, 3-6 Stress corrosion cracking occurred in months, After replacing M annealed N6 nickel plate, Stable operation for 8 years, The purchase cost of the whole set of plates is 120,000 - 180,000 yuan. Case 2: PTA oxidation reactor lined with N6 nickel plate, specification δ6mm×2000mm×4000mm, medium containing bromoacetic acid, temperature 120℃.Pitting and perforation occurred in the original 316L stainless steel liner after 3 - 5 years, Replace N6 nickel plate lining, 6 years of continuous operation in good condition, The total price of the plate is 150,000 - 220,000 yuan. Case 3: 600,000 tons salt project evaporation chamber N6 nickel plate, specification δ10mm×2500mm×5000mm, medium saturated sodium chloride with 30% NaOH, temperature 90℃.Multilayer delamination occurs in the original stainless steel clad plate within one year, Replacement of pure N6 nickel plate evaporation chamber, Stable operation for 5 yearsExplosive welding process, Ti-Ni composite structure, 2mm titanium with 8mm nickel, The whole set of plates cost 250,000 - 350,000 yuan.

V. Manufacturing process and key control parameters

N6 nickel plate production process: electrolytic nickel raw material incoming inspection, verification furnace batch number and mechanical properties;hot roll step, controlling temperature at 850-1100 DEG C, and multi-pass press forming;Cold rolling is processed according to the target thickness, and the single reduction is 10%-30%.intermediate anneal 700-800 deg. c for 1 h to eliminate cold hardening;final annealing is carried out after finishing rolling to a specified thickness, and softening is finished by keeping the temperature at 700-800 DEG C for 1-2 hours;pickling passivation treatment, wherein the ratio of nitric acid and hydrofluoric acid is 3:1, and the treatment time is 30-60 minutes;NC shearing plate trimming, size tolerance control ±0.5mm;100% ultrasonic UT test of the plate, re-inspection of mechanical properties, M-state tensile strength not less than 380MPa, yield ≥100MPa, elongation ≥40%;Surface roughness Ra≤0.8μm, moisture-proof packing wooden case lined with PE film. Production control points: strictly control the hot rolling temperature to prevent over-burning grain coarsening;Annealing process parameters must be up to standard, to ensure that M state hardness ≤140HV;Acid pickling passivation forms stable passivation film;The size tolerance shall be strictly controlled to avoid leakage caused by excessive welding seam.

VI. Implementation Standard Reference

GB/T 2054-2013 is the basic standard for nickel and nickel alloy plates;GB/T 5235 - 2021 Specification for machined nickel alloy grades Chemical composition;YS/T 301-2019 is the nickel strip standard for the colored industry.American standard ASTM B162-2019 is often adopted for export projects, and ASME BPVC Section III is additionally added for nuclear power projects.N6, Ni200 and UNS N02200 belong to the same material, but the different standard system names are different.

VII. Domestic and import price quotation (2026 Q2)

δ3mm N6M annealed nickel plate, domestic unit price 180-220 yuan per kilogram, imported 280-340 yuan per kilogram;δ6mm N6M annealing domestic 175-215 yuan per kg, imported 270-325 yuan per kg;δ10mm N6M annealing domestic 170-210 yuan per kg, imported 260-310 yuan per kg;δ 5mm N6R hard state domestic 160-200 yuan per kg, imported 250-300 yuan per kg;δ6mm high purity N200 domestic 220-260 yuan per kg, imported 340-400 yuan per kg;δ8mm ultra-low carbon Ni201 domestic 260-320 yuan per kg, imported 400-480 yuan per kg.The price of imported nickel plate is generally about 50% higher than that of domestic nickel plate.Purchasing reference: M annealed N6 nickel plate thickness 3-20mm, unit price range 170-220 yuan per kg;R hard N6 nickel plate thickness 1-10mm, unit price 160-200 yuan per kilogram;High purity N200 plate thickness 1-8mm, unit price 220-260 yuan per kilogram.Single purchase of one ton or more, unit price can be reduced by 8%-12%.

VIII. Points for avoiding pits during processing

first, Vigilance for Material Status Replacement, M annealing state must be selected for concentrated alkali working condition, Hardness controlled within 140HV, R hard plate is not suitable for concentrated alkali environment, short-term crackingsecond, Nickel plate welding both sides should be filled with argon protection, The purity of argon shall not be less than 99.99%, Inadequate protection weld oxidation, Buried corrosion failure hidden dangerthirdly, 700-800℃ annealing treatment for 1 hour after welding is completed, Unannealed welds are prone to stress corrosion cracking under concentrated alkali conditionsFourth, the pressure equipment strictly controls the thickness of the plate, and the thickness tolerance exceeds ±0.3mm, which will reduce the strength of the equipment;Fifth, the plate must be 100% UT ultrasonic inspection, check the plate delamination defects, and implement GB/T2054 standards. Material verification method: check the furnace batch number, standard number, material status code and mechanical index in the quality assurance document;M Annealed plate field hardness re-inspection, hardness is not higher than 140HV;XRF detection of nickel content;Verify complete UT ultrasonic test report.

IX. Procurement risk warning

Procurement five risks: suppliers with R hard state pretending to M annealing state;Ordinary N6 plate as high purity N200, medical and food projects cause metal ions to exceed bid;the intergranular corrosion occur under high temperature condition when that ultra-low carbon Ni201 is replaced by the common N 6;The thickness of the plate is reduced and the pressure bearing capacity is insufficient;Lack of NDT report, internal defects of sheet cannot be detected.Purchase contract must be clear brand, material state, thickness tolerance, surface treatment methods, UT Test Requirements, Missing any item, All are prone to equipment failure.

X. Frequently Asked Questions

Q: How to select N6 nickel plate and stainless steel plate? A: 30%-80% concentrated alkali, dilute reducing acid, molten alkali working condition priority N6 nickel plate;Stainless steel is suitable for neutral medium, low chloride ion normal temperature scene.The purchase cost of N6 nickel plate is 3-5 times that of stainless steel, but the service life can be increased by 5-10 times. Q: N6, N200, Ni201 selection difference? A: N6 industrial pure nickel nickel content ≥99.0%, chemical general;N200 high purity nickel, nickel content ≥99.5%, pharmaceutical food GMP scene;Ni201 belongs to ultra-low carbon nickel, carbon content ≤0.02%, suitable for high temperature conditions above 300℃.

XI. Industry development trend

The domestic nickel plate market continues to grow, and the industry growth rate is stable.Thick specification nickel plate in nuclear power, large chlor-alkali evaporator demand rise;Titanium nickel composite plate application popularization, bimetal structure can reduce project cost;High-end nuclear power and electronic projects continue to improve the purity and processing accuracy of nickel plates.

written in the end

Nickel plate seems simple, selection details determine equipment life.The core equipment of caustic soda, soda ash and PTA plant, such as evaporator, reactor and storage tank, uses N6 nickel plate in large quantities.If the material state is wrong, the whole equipment will be scrapped within months.Type selection locking brand, state, thickness, medium, concentration of five indicators;Process control annealing temperature, weld protection, size tolerance, UT detection, pickling passivation;Equipment acceptance check sheet surface, section, weld, identification, quality assurance data.

Shaanxi thousand billion Tuoda Technology Co., Ltd. is located in Baoji China titanium valley, deep ploughing nickel material,Titanium non-standard equipmentFor many years, we can provide N6 nickel plate selection, customization and supporting technical services.

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disclaimer, the proces parameters herein, price range, Field cases are for technical reference only, Does not constitute a technical commitment and commercial offer.Shaanxi Qianyi Tuoda Technology Co., Ltd. reserves the right of final interpretation of this article.Technical consultation: 15909236031 / 0917-3557966.