martensite start temperature

The martensite start temperature of such steels is important during fabrication, and can not be estimated using conventional empirical methods.

The transformation is essentially time-independent with the phase fraction depending only the degree of cooling below the critical martensite start temperature.

The steel is quenched to a much lower temperature than is used for austempering; to just above the martensite start temperature.

In the martempering process, austenitized metal part is immersed in a bath at a temperature just above the martensite start temperature (Ms).

The martensite transformation being a diffusionless shear transformation is represented by a straight line to signify the martensite start temperature.

The martensitic reaction begins during cooling when the austenite reaches the martensite start temperature (M) and the parent austenite becomes mechanically unstable.

A further distinction is often made between so-called lower-bainite, which forms at temperatures closer to the martensite start temperature, and upper-bainite which forms at higher temperatures.

It is a form of isothermal heat treatment applied after an initial quench of typically in a molten salt bath at a temperature right above the "martensite start temperature".

This is possible provided the cooling rate is such that the cooling curve intersects the martensite start temperature or the bainite start curve before intersecting the Pcurve.

Most alloying elements (solutes) have the benefit of not only increasing hardness, but also lowering both the martensite start temperature and the temperature at which austenite transforms into ferrite and cementite.

Other methods of tempering consist of quenching to a specific temperature, which is above the martensite start temperature, and then holding it there until pure bainite can form or internal stresses can be relieved.

Bain and Davenport also noted the existence of two distinct forms: 'upper-range' bainite which formed at higher temperatures and 'lower-range' bainite which formed near the martensite start temperature (these forms are now known as upper- and lower-bainite respectively).