Monel alloy is a metallurgy term published in 2019. Monel 400 is a corrosion-resistant alloy with the largest usage, widest range of applications, and excellent comprehensive performance. This alloy exhibits excellent corrosion resistance in hydrofluoric acid and fluorine gas media, as well as excellent corrosion resistance to hot concentrated alkaline solution. At the same time, it is also resistant to corrosion from neutral solutions, water, seawater, atmosphere, organic compounds, etc. An important feature of this alloy is that it generally does not produce stress corrosion cracks and has good cutting performance.

-- Monel 400 similar brands

UK: EN 2.4360 Germany: W.r.2.4360 US: UNS N04400 Japan: NW4400 ISO: Ni68Cu28Fe

-- Monel 400 Chemical Composition

-- Monel 400 Physical Performance

-- Minimum mechanical properties of Monel 400 alloy at room temperature

-- Mechanical behavior

Room temperature mechanical properties Inconel 400 annealed

Inconel 400 Annealed Hot Rolled Plate

Inconel 400 Annealed Cold Rolled Sheet

Work hardening characteristics

The work hardening property of UNS N04400 is far lower than that of SUS 301 and SUS 304, so it can be easily bent.

-- Monel 400 Features

Moenl 400 is a corrosion-resistant alloy with the largest amount, widest use, and excellent comprehensive performance. This alloy has excellent corrosion resistance in the medium of hydrochloric acid and fluorine gas, and also has excellent corrosion resistance to hot concentrated alkaline solution. At the same time, it is also resistant to corrosion from neutral solutions, water, seawater, atmosphere, organic compounds, etc. An important feature of this alloy is that it generally does not produce stress corrosion cracks and has good cutting performance.

-- Metallographic structure of Monel 400

The alloy is a single-phase solid solution with high strength Monel 400

-- Alloy corrosion resistance:

Monel's corrosion resistance is generally superior to nickel copper. It is more resistant to corrosion in reducing media and oxidizing media than pure nickel, and has excellent corrosion resistance to sulfuric acid, phosphoric acid, and carbon. Especially resistant to the corrosion of hydrochloric acid, it also has excellent corrosion resistance to hot concentrated alkali. Monel400 alloy has excellent corrosion resistance in fluorine gas, hydrochloric acid, sulfuric acid, hydrofluoric acid, and their derivatives.

At the same time, Monel400 is more corrosion resistant than copper based alloy in seawater. Monel400 is a deformable nickel copper based alloy, which has good seawater corrosion resistance and chemical corrosion resistance, and has strong chloride stress corrosion cracking resistance. This alloy is one of the few alloys that can be used in fluoride. It has good resistance to oxide stress fission corrosion in hydrofluoric acid and fluorine gas media, such as in seawater and saline environments. Monel 400 also exhibits excellent corrosion resistance in medium concentrations of alkaline and salt solutions. In colder alkaline environments, this alloy is used in weak acid environments such as sulfur and hydrogen fluoride.

-- Acid medium

Monel400 is corrosion-resistant in sulfuric acid with a concentration of less than 85%. Monel400 is one of the few important materials that can withstand hydrofluoric acid.

aqueous corrosion

Monel400 alloy not only has excellent corrosion resistance under most water corrosion conditions, but also rarely finds pitting corrosion, stress corrosion, etc. The corrosion rate is less than 0.025mm/a.

High-temperature corrosion

The maximum temperature for continuous operation of Monel400 in air is generally around 600 ℃, and in high-temperature steam, the corrosion rate is less than 0.026mm/a. Ammonia: Due to the high nickel content of Monel400 alloy, it can withstand corrosion under anhydrous ammonia and ammonification conditions below 585 ℃.

-- Monel400 processing and welding

Monel400 hot working is easy to form. The temperature is 927~1177, and slight deformation can be achieved at 649 degrees. Monel400 alloy is very easy to form. The heat treatment temperature is generally 871-982 degrees, but for the sake of performance and fine grain size, the solution temperature should not be too high. Solution annealing is generally chosen between 871 and 982. Monel400 alloy has good welding performance, and different welding methods require different welding wires. Generally, Monel60 and 190 welding wires are chosen.

Preparation before welding of Monel400

(1) Selection of protective gas: The function of protective gas is to prevent oxidation of the weld bead and ensure the formation of the weld bead. When using GTAW welding, the shielding gas is Ar with a purity of 99.99%. Before welding, use Ar as welding back protection inside the pipe until the thickness of the weld metal reaches 6.4 mm, to ensure that the weld metal is not oxidized to the maximum extent. The back Ar protection needs to be sealed at both ends, and welding operations can only be carried out when the oxygen content of the internal gas is measured to be below 0.5%.

(2) Cleaning work: there is a refractory oxide film on the surface of Monel 400 alloy, which is easy to generate inclusions in the weld during welding, causing welding defect. Before welding, a stainless steel brush that has not been used on carbon steel should be used to clean the inside and outside of both sides of the weld seam within a range of at least 25 mm to prevent harmful effects of paint, grease, rust, dirt, and oxides on the weld seam. During the welding process, stainless steel grinding wheels that have not been used on carbon steel should be used for grinding between each layer and each pass to avoid slag inclusion; After the weld bead is welded, it should be wiped with anhydrous ethanol. The protrusion inside the root weld bead shall not exceed 2 mm, and the root weld bead shall form a smooth curve. Only the groove surface and surrounding areas require solvent cleaning, and interlayer welds can be polished with resin alumina or silicon carbide grinding wheels.

Monel400 welding process

(1) Manual tungsten argon arc welding is widely used for the welding of Monel alloy, especially suitable for welding thin parts, small sections, and structural parts that do not allow residual slag after welding. Monel alloy can absorb a large amount of gas in the molten state, so it is prone to generate dense pores during welding. Therefore, under the conditions of corrosion resistance, the general practice is to use tungsten argon arc welding as the penetration backing weld for the root.

(2) Welding rod arc welding is also a common welding method in the welding of Monel 400. When the workpiece thickness is large, if only argon arc welding is used, the heat input will increase, which will have a negative impact on the performance of the base metal, and will increase the crack tendency of the weld; In addition, production efficiency is low and the labor intensity of welders is high. Therefore, arc welding with welding rod is the best filling method for welding thicker materials. However, the disadvantage of electrode arc welding in Monel 400 welding is the poor fluidity of the weld, and the change of welding parameters must be strictly controlled in the welding process. Especially at the end of the arc crater, cracks are prone to occur.

-- Monel 400 matching welding materials

Monel Monel400 welding rod (ENiCu-7), Monel400 welding wire (ERNiCu-7)

-- Monel 400 application areas

1. Seamless water and steam pipes in power plants

2. Seawater exchanger and evaporator

3. Sulfuric acid and hydrochloric acid environment

4. Crude oil distillation

5. Pump shafts and propellers for equipment used in seawater

6. Equipment for manufacturing uranium refining and isotope separation in the nuclear industry

7. Pumps and valves used in the manufacturing and production of hydrochloric acid equipment