Monel Alloy

Today I will tell you about monel alloy. It is a kind of corrosion-resistant alloy metal, let’s take a look at it!

The earliest application of corrosion-resistant nickel alloy. The composition of the Monel alloy produced is Ni-30Cu. Monel alloys produced in various countries today also contain a small amount of iron, manganese and other elements. The corresponding brand in China is 28-2.5-1.5 nickel-copper alloy (code name is NCu28-2.5-1.5. Its main components are: copper 27.00% ~ 29.00%, iron 2.00% ~ 3.00%, manganese 1.20% ~ 1.50%, the balance It is nickel. Monel type alloys include K Monel (Monel K 500), cast Monel and S Monel, etc. Since K Monel contains 3% aluminum, it can form a strengthening phase NiAl, which can be aging strengthened Its strength is higher than that of ordinary Monel, so it is called high-strength Monel. Cast Monel and S Monel are alloys used to produce castings. Although the composition of the two is different, they both contain higher silicon (2 %～5%) to improve its castability and wear resistance.

Monel alloy has good corrosion resistance in a variety of media. It is stable in air, soil, fresh water and sea water. The corrosion rate in the soil is not more than 0.0003mm/a; the corrosion rate in seawater is 0.03mm/a. Monel also has good corrosion resistance in non-oxidizing acids (sulfuric acid, hydrochloric acid, phosphoric acid, hydrofluoric acid), salt solutions and organic acids. But in the presence of aeration medium or oxidant, the corrosion resistance is significantly reduced. At room temperature, the corrosion rate is less than 0.5mm/a in sulfuric acid with a concentration of less than 80% and hydrochloric acid with a concentration of 20%. In medium-concentration phosphoric acid and hydrofluoric acid, the temperature remains stable up to the boiling point, second only to platinum and silver. But it is sensitive to stress corrosion, stress relief treatment should be carried out before use.

In addition to good corrosion resistance, Monel alloy also has good mechanical properties and processing properties, and can still maintain its room temperature strength at 400°C. The tensile strength in the cold rolled state can reach 600-700MPa. The strength of K Monel is higher, and the tensile strength in the cold rolled state can reach 980～1120MPa.

Monel alloy is suitable as a structural material for chemical equipment that works in corrosive media such as sulfuric acid, hydrochloric acid, acetic acid or phosphoric acid with low concentration. K Monel is used to make components with higher strength requirements, such as marine propeller shafts, impellers and pump shafts. Cast Monel and S Monel are used for components that require corrosion resistance and wear resistance, such as valve seats and friction parts.