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Application of stainless steel materials

Update:12-07-2019
Summary:

The exact composition varies for martensitic stainless […]

The exact composition varies for martensitic stainless steel grades. But typically  stainless steel will contain Carbon. It may also have small amounts of silicon, molybdenum, and phosphorous. Brearley’s initial samples of stainless steel were martensitic. These alloys are magnetic and are usually formed in the annealed condition, and heat treated afterwards.Chromium is the main alloying element of martensitic  stainless steel, carrying moderate corrosion resistance to a material with inherently high strength and hardness.

Normally, nickel concentrations of  are added as a stabilizing element to make sure that a martensitic steel keeps its toughness properties during heat treatment, which allows the fabrication of a number of component types.Martensitic stainless steels are often forgotten, maybe because compared to austenitic and ferritic grades, they are not in high demand. Though, they often play a huge and often unseen role in modern infrastructure. The strength which is gained by heat treatment depends on the carbon content of the alloy. Increasing the carbon content increases the potential hardness and strength but decreases toughness and ductility.The higher carbon grades are capable of being heat treated to a hardness up to 60 HRC.

In the heat-treated, hardened and tempered condition optimum corrosion resistance is achieved. Other martensitic grades have been created with nickel and nitrogen additions but possessing lower carbon levels than the traditional grades. These steels have improved weldability, toughness, and corrosion resistance.artensitic stainless steels are similar to a lot of low alloy steels where carbon is the main element. Usually, steels transform from the ferrite to the austenite state when they are heated. The steel reverts to ferrite upon slow-cooling. Yet, the carbon atoms become trapped in a somewhat distorted atomic matrix with fast cooling through quenching in water or oil. This is known as body-centered tetragonal.

he distortion of the atomic matrix results in the hard-martensitic structure. Adolf Martens first observed the body-centered tetragonal martensite microstructure in 1890. The higher the carbon level the harder the martensite is. Martensitic steels are virtually useless in the as-quenched and un-tempered condition, as they do not have enough impact toughness, they are brittle and unsuitable for engineering applications.The most common treatment after quenching is tempering  quench-and-temper heat treatment. This requires heating the steel to a temperature between . The temperature and length of time at temperature determines the final properties of the steel. Tempering imparts a combination of resilience and strength. Martensitic stainless steel can also be non-destructively tested using the magnetic particle inspection method, unlike austenitic stainless steel.

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