TRIP steel

TRIP steels (English TRansformation Induced Plasticity, dt: " umwandlungsbewirkte plasticity " ) are modern, especially high-strength steel alloys.

Use

TRIP steels have, compared to conventional steels, a higher strength in combination with good ductility. This feature allows for the production of lighter components at a given required strength and ductility. These properties makes TRIP steels particularly for the automotive industry to interesting materials in which they are increasingly being used today.

TRIP effect

The TRIP effect is the particular martensite during forming. The stress-induced martensite formation of the deformation induced martensite formation is to be distinguished because the latter uses only the TRIP effect. This causes a simultaneous increase in hardness and formability of plastic strain in the product manufacture or use. The extent of the effect is mainly influenced by the low-cost alloying elements of aluminum and silicon. In addition, while much more expensive alloying elements such as nickel may be substituted.

The material- own yield strength is higher than comparable steels, since the alloyed silicon enables a solid-solution strengthening. Once the plastic range is reached at a strain or deformation, the metastable carbon-rich austenite to martensite induced by deformation begins to transform. Wherein the TRIP steel is hardened selectively by means of the plastic deformation.

Alloy constituents

TRIP steel is mainly composed of a plurality of phases of iron -carbon alloys; essentially of ferrite, bainite and karbidfreiem 5-10% metastable carbon-rich austenite, the deformation- induced transforms into martensite. Skip typical alloying additions for austenitic steels, the so-called austenite nickel, chromium ( at low levels ), cobalt, carbon, manganese and nitrogen are common. The special feature of TRIP steels are higher alloying additions of silicon and aluminum, whose admixture affects the so-called TRIP effect and makes controllable.

Production

The desired steel alloy is first brought to the recrystallization temperature and left there for a certain time in order to remove any lattice defects through the formation of new seeds and grain growth. There are in the structure of ferrite and austenite. Then the annealed structure is quenched to the temperature TB (B = bainite ), i.e., the cooling rate must be above the critical to avoid diffusional phase transformations. It formed in the microstructure of the following components:

• Ferrite
• Karbidfreier bainite (which is why silicon alloys are used which prevent carbide formation )
• Carbon-rich austenite.

To smoothen the fabric is a time held at the temperature TB, and is subsequently quenched to room temperature. This forms the following structures from:

• Ferrite
• Karbidfreier bainite
• Metastable carbon-rich austenite.

It forms at room temperature martensite, because the martensite is a high carbon content in the austenite under this.