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 hardening, with cooling
in oil or gases under high pressure, which ensures lower deformation and,
consequently, allows to reduce the grinding allowance.
Cooling
takes place in the highest purity expanded nitrogen from cryogenic form, under
a maximum pressure of 8 bar in single-chamber vacuum furnaces.
The use of
FINECARB® technology allows to obtain optimal parameters of the surface layer
as a result 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 hardening processes take place in the same chamber, as
well as 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 with 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.
After the
carburizing stage, we can quench in vacuum oil or nitrogen under high pressure.
It is a variant
of the low-pressure carburizing process, intended mainly for thicker layers.
Thanks to its technological solutions, it 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 hardening 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 in order 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 in order to
obtain structures close to the equilibrium state.
We
distinguish between recrystallization annealing, homogenization, stress relief,
complete, isothermal and spheroidizing annealing.
We carry
out orders from a wide range of services in the field of annealing.
It is the
most modern technology in terms of reliability, cleanliness and durability.
The process
of joining materials by means of high-temperature soldiering 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.