The purpose
of hardening is to obtain a hard martensitic or sometimes bainitic structure.
It includes austenitization, rapid cooling and tempering.
Depending
on the type of material, the shape and cross-section of details as well as the
operational requirements, we perform vacuum volumetric quenching, with cooling
in oil or gases under high pressure. It ensures lower deformation and,
consequently, allows to reduce the grinding allowance.
In
single-chamber vacuum furnaces, the cooling takes place in nitrogen, which is
expanded from cryogenic form, of the highest purity, at a maximum pressure of
13 bar.
The use of
FINECARB® technology allows to obtain optimal parameters of the surface layer because
of the elimination of internal oxidation and uncontrolled, unfavourable precipitation.
An additional effect is the reduction of deformation of elements during their
heat treatment.
We offer
the implementation of processes in single-chamber vacuum furnaces, in which
both the carburizing and quenching processes take place in the same chamber.
Also, we perform the process in two-chamber vacuum furnaces, where the
carburizing process is carried out in one chamber, the so-called "Heating
chamber", and the hardening process in the second chamber, the so-called
"Cooling chamber", connected to a quenching bath.
Low-pressure
carburizing of steel with the FineCarb® technology guarantees the achievement
of the assumed thickness of the surface layers in a much shorter time compared
to gas carburizing, as well as full control and repeatability of the processes.
It is a
variant of the low-pressure carburizing process, intended mainly for thicker
layers, which, thanks to its technological solutions, allows the process to be
carried out at higher temperatures without the phenomenon of grain growth.
The use of
the PreNitLPC® high-temperature technology is justified both in economic and
functional terms.
We
implement this technology in single-chamber HPGQ VPT furnaces, in two-chamber
furnaces with cooling in quenching oil and in process chambers of modular
systems for vacuum carburizing.
Steels with
austenitic structure, as well as other alloys - mainly non-ferrous metals -
which do not show allotropic changes but are characterized by variable
solubility of one of the components in a solid solution, can be subjected to
precipitation hardening.
We offer
processes that are combined technological operations:
• supersaturation
• aging
Supersaturation
It involves
heating the alloy to a temperature higher by approx. 30 ÷ 50°C than the limit
of solubility to dissolve the separated component (in steels, most often
tertiary cementite) in a solid solution, heating at this temperature and then
cooling rapidly. As a result of supersaturation, the alloy obtains a
single-phase structure.
In the case
of austenitic steels, the structure is austenite supersaturated with carbon.
The strength properties of steel after supersaturation are slightly reduced,
but plastic properties increase.
Aging
It involves
heating the previously supersaturated alloy to a temperature below the limit of
solubility, heating at this temperature and cooling it down. During the aging
process, the excess component in the supersaturated solid solution is released
in the form of highly dispersed phases.
In some
cases, the aging involves intermediate phases and Guinier-Preston zones, which
are complexes in which they segregate atoms dissolved in the solvent.
Aging
causes strengthening, manifested by an increase in strength properties and a
decrease in plastic properties.
The aging
effect occurs when the temperature is too high, consisting in coagulation of
the precipitates and the loss of their coherence, which does not increase the
hardness in relation to the supersaturated state, but on the contrary - reduces
it.
Sometimes
aging occurs at room temperature, then it is called spontaneous aging.
Aging can
also be an undesirable process, e.g., in deep drawing sheets and in boiler
steels, as it reduces plastic properties and increases brittleness.
A method of
heat treatment of the material, which usually involves heating the steel to a
specific temperature, heating it at this temperature and cooling it to obtain
structures close to the equilibrium state.
We
distinguish between recrystallization annealing, homogenization, stress relief,
complete, isothermal and spheroidizing annealing.
In the
field of annealing, we carry out orders from a wide range of services.
After
hardening, all steels show reduced plastic properties and unfavourable
stresses.
A heat
treatment procedure is carried out to eliminate them, which involves heating
the previously hardened material, heating and cooling it in order to obtain the
optimal structure and properties.
We offer
low, medium and high tempering in the temperature range of 180-650°C. It is
possible to carry out the processes in the presence of shielding gas, and in
the case of highly personalized requirements for the highest purity, the
implementation of the vacuum tempering process.
It is the
most modern technology in terms of reliability, cleanliness and durability.
The process
of joining materials by means of high temperature soldering in vacuum furnaces,
complementing welding techniques, has been developing as an important and stand-alone
technology.
Vacuum
brazing is a flux-free process, with the removal of air, e.g., in a vacuum,
using soldering materials for which the liquidus temperature is above 900°C.