50Mn18Cr4WN

50Mn18Cr4WN is a type of ring steel

50MN18CR4WN Non-Magnetic Steel, also known as 50MN steel, is a medium carbon non-magnetic structural steel, which is a typical and widely used manganese-chromium series non-magnetic austenitic shrouding steel. This steel features low permeability (μ<1.1H/m), high strength, and good machinability. Through quenching and tempering processes, different tempering temperatures affect the steel's microstructure, resulting in varying combinations of strength, ductility, and toughness. The as-fabricated hardness of 50MN18CR4WN non-magnetic steel is 23HRC, and its hardness after solution aging treatment can reach approximately 35HRC. It can meet the requirements for non-magnetic molds in general electronics industries.

Introduction

50Mn18Cr4WN is a non-magnetic austenitic retaining ring steel of the manganese-chromium series, obtained by adding tungsten and nitrogen to 50Mn18Cr4. Tungsten slows down the precipitation of carbides in the steel, while nitrogen expands and stabilizes the austenite, further strengthening the steel. After solution heat treatment, it undergoes semi-hot or cold deformation strengthening to meet different strength requirements. 50Mn18Cr4WN is used for non-magnetic turbine generator retaining ring forgings and other components requiring non-magnetism.

Chemical Composition

Carbon C: 0.40-0.60

Silicon (Si): 0.30 ~ 0.80

Manganese (Mn): 17.00～19.00

Sulfur (S): ≤0.025

Phosphorus (P): ≤0.080

Chromium (Cr): 3.00～5.00

Nitrogen (N): 0.08~0.12

Tungsten W: 0.70～1.20

Mechanical properties

Tensile Strength σb (MPa): Grade I, ≥895

Condition Yield Strength σ0.2 (MPa): Grade I, ≥760

δ5 elongation (%): Grade I, ≥25

Section shrinkage rate ψ (%): Grade I, ≥35

Heat Treatment Specifications

Heat Treatment Specifications: 1) Before hot forming and deformation strengthening: solution treatment; 2) After deformation strengthening: heat at a rate of ≤40℃/h to 320-350℃, hold for 8-12 hours, then cool down slowly at a rate of ≤40℃/h to below 100℃ to relieve residual stress.

Non-magnetic steel

Introduction

Non-magnetic steel, also known as non-magnetic steel and non-magnetic material, actually refers to steel that lacks ferromagnetism and cannot be magnetized.

Features

Non-magnetic steel belongs to the Austenitic series of Fe-Mn-Al-C, with its chemical composition determining its electromagnetic properties. It features stable microstructure, excellent mechanical properties, low permeability, and high electrical resistance, resulting in minimal eddy current losses in a magnetic field. At a magnetic field strength of 16,000 A/m (200 Oe), the permeability of the non-magnetic steel μ ≤ 1.319×10-6 H/m (1.05 Gs/Oe), while the permeability of 1.339×10-6 H/m (1.1 Gs/Oe) is for stainless steel. Austenitic stainless steel, after cold working, exhibits slight magnetism [1].

Content Elements

Dragon magnet steel typically contains a large amount of alloy elements such as nickel, manganese, chromium, and copper in the steel, lowering the Austenite transformation point A3 below room temperature.

Principle of Operation

Steels with Austenitic (non-magnetic) microstructure at room temperature are employed in high-magnetic field technologies due to the advancement of superconductivity, including superconducting coil energy storage, superconducting power generation, magnetohydrodynamic power generation, magnetic levitation linear motors, and nuclear fusion. In such high magnetic fields, the presence of easily magnetizable materials can disrupt magnetic field distribution and induce eddy currents within the material. This not only causes the material to heat up, leading to energy loss, but may also compromise the entire structure. Consequently, non-magnetic steels with a permeability less than 1.5 (typically around 150 for ordinary steel) that are unaffected by magnetic fields have been developed [2].

Elemental Content Parameters

Typical non-magnetic steels include 25% Ni steel, high manganese non-magnetic steel containing 12-18% Mn, such as the 14Mn, 18Mn, and 25Mn series, as well as 18Cr-8Ni austenitic stainless steel and Ni-C; Cr-Mn austenitic steel, etc. High manganese austenitic steel, as a new type of non-magnetic steel, boasts excellent properties.