Corrosion Resistance Copper Based Alloys Ni68Cu28Fe Monel400 N04400 For Pump / Valve

Corrosion Resistance Copper Based Alloys Ni68Cu28Fe Monel400 N04400 For Pump / Valve

Monel400 is the corrosion-resistant alloy with the largest amount, the most versatile and excellent comprehensive performance. The alloy has excellent corrosion resistance in hydrofluoric acid and fluorine gas media, and excellent corrosion resistance to hot concentrated alkali liquor. It is also resistant to corrosion by neutral solutions, water, sea water, atmosphere, organic compounds, etc. An important feature of this alloy is that stress corrosion cracking is generally not produced and the cutting performance is good.

Monel 400 Chemical composition

Monel 400 Physical properties

Monel 400 Alloy minimum mechanical properties in the room temperature

Mechanical character

Specification

Characteristic as below

1.Monel 400 Metallurgical structure

2.Monel 400 alloy is high-intensity single-phase solid solution.

3, chloride ion stress corrosion cracking is very insensitive;

4. Excellent mechanical performance from below zero to 550℃;

5. It can be used as pressure vessel under -10~425℃ as approved by ASME;

6. Good machining and welding performance

7.Good corrosion resistance in Marine and chemical environment;

Gas Corrosion:Monel 400 alloys have excellent corrosion resistance in fluorine, hydrochloric acid, sulfuric acid, hydrofluoric acid and their derivatives. At the same time, it is more resistant to corrosion in seawater than copper-based alloys.

Acid medium: Monel 400 is corrosion resistant in sulfuric acid with a concentration of less than 85%. Monel400 is one of the few materials that are resistant to hydrofluoric acid.

Water corrosion: Monel400 alloy has excellent corrosion resistance in most water corrosion conditions, and pitting corrosion and stress corrosion are rarely found. The corrosion rate is less than 0.025mm/a.

High temperature corrosion: The maximum temperature of Monel400 working continuously in air is generally around 600 °C. In high temperature steam, the corrosion rate is less than 0.026 mm/a.

Ammonia: Due to its high nickel content, Monel400 alloy can withstand corrosion under anhydrous ammonia and ammoniating conditions below 585 °C.

Monel 400 Application field
Monel 400 alloy is a multi-purpose material in many industrial applications:
1. Seamless water pipe in the power factory
2. Sea-water exchanger and evaporator
3. Sulfuric acid and hydrochloric acid environment
4. Crude distillation
5. Sea-water in the use of equipment and propeller shaft
6. Nuclear industry and used in the manufacture of uranium enrichment isotope separation equipment
7. Manufacturing hydrochloric acid equipment used in the production of pump and valve

Manufacturing and heat treatment

The monel 400 can be easily manufactured using traditional processes.

1. Heat

It is important to ensure that the surface of the monel 400 is clean before heat treatment. If there is S, p on the surface of the monel 400 during the heating process. The properties of alloys are likely to be weakened by contaminants such as pb or other low-melting metals. The main sources of contamination are marker marks, temperature indicating paint, grease and furnace gas.

• Hot working

The monel 400 can be hot-processed at 800~1200℃, but only slightly forged at 925℃. Thermal bending can be performed between 1025 and 1200℃. In order to carry out thermal processing, the furnace heat treatment is required, the furnace temperature should be first heated to 1200℃, and then the monel 400 materials into the heating. Materials should be heated according to a rule: 60 minutes per 100mm thick. As soon as the heating time arrives, the material shall be taken out for hot processing immediately. If the material temperature drops below the minimum hot processing temperature during the hot processing, it shall be reheated.

3.Cold working

Cold - processed monel 400 material must be annealed. Because it has a slightly higher work hardening rate than carbon steel, the forming equipment to make appropriate changes. Cold forming shall be annealed between processes. Cold deformation is sometimes used to improve mechanical properties. If the material is to be used in an environment where stress corrosion cracking is likely to occur, such as mercury, moist exposed hydrogen fluoride gas, it is recommended to conduct stress reduction heat treatment.

4.Heat treatment

Generally, the annealing temperature of monel 400 materials is 700~900℃, and the best effect is at 825℃. Fast air cooling after treatment can obtain good corrosion resistance. Annealing temperature and annealing time are directly related to the final grain size of materials, so annealing parameters should be carefully considered. And the sulfur content of the gas in the annealing furnace must be low to avoid brittle materials. Stress relief heat treatment is generally conducted at 300℃ for 1~3 hours. For pipes, the stress relief heat treatment temperature is generally controlled at 550~650℃. Cleaning of material surfaces prior to any heat treatment must be considered.

5.descaling

The oxides and stains near the weld seams of monel 400 materials are tighter than those of stainless steel materials, which can be polished by grinding wheel or pre-treated in salt bath before pickling in a mixture of nitric and hydrofluoric acids.

6, machining

The monel 400 material shall be machined in annealed condition. Cold forming and stress relief after the material is easier to process, this kind of material processing hardening to have enough understanding, for example: the surface cutting speed and carbon steel is smaller, the tool to continue to run, in order to avoid the surface hardening layer, the amount of feed to large. Machining tools should be nickel base alloy and high alloy stainless steel special tools, brush weld to use stainless steel brush. Measures should be taken to avoid contamination with iron impurities in manufacturing and processing machinery such as shears, presses and rolling machines. The processing site should be clean and separate from the carbon steel processing site.

7, welding

The welding groove of monel 400 material should be finished by mechanical processing method. If the groove is polished, the local overheating should be avoided. Due to the obvious physical properties of nickel alloy and high-alloy stainless steel compared with carbon steel, their thermal conductivity coefficient is low, and the thermal expansion coefficient is large, for this point welding method to use clamping, large foot (1-3mm) method to solve. Due to the poor fluidity of monel 400 material, a large groove Angle (60-70°) was designed to allow the wire to fill the weld seam. Cleaning groove and welding rod with acetone before welding, welding method with GTAW is ok, welding wire with ernicu-7. Monel 400 before welding does not need preheating, generally do not need post-welding heat treatment, because the processed material strength has been improved, for the future use of certain benefits.