AN EXCLUSIVE CHROMIUM PLATING PROCESS
The STELMI process can easily meet the most severe environmental control requirements. The conventional plating processes require complex and expensive control equipment and offer limited security even if operated
with the best attention.
Pollution in the environment
Stelmi’s chromium baths are closed loop and work slightly under the atmospheric pressure: the vapours are continuously collected and treated with both dry and wet scrubbers, recycling the condensation into the baths.
The impact on the environment is practically reduced to nothing, inside and outside the workshop. There is no risk of leaks of liquid solution.
The only solid wastes resulting from the process is the mud generated from the physical and chemical treatment of the waters: its volume is reduced to about 5% of those generated treating the waters of
an equivalent conventional plating plant.
Chromium bath volume
Stelmi’s continuous chromium plating technology requires a bath volume which is about one tenth the what is required for conventional plating equipment offering the same production capacity.
A continuous and automatic monitoring of the characteristics of the chromium bath guarantees a chromium layer that is completely homogeneous.
Less power installed
The Stelmi process helps to save energy. The Stelmi process demands far less electrical power than conventional plating.
It also offers safety advantages for the operators in the shop. The equipment is designed according to the
highest safety criterion; automation is used everywhere possible. There are no pits, racks, below ground tanks or confined spaces.
The STELMI hard chromium plating process is a continuous horizontal operation: The bars advance and rotate, driven one by one through the chromium plating machine using a hydraulic system which also transfers the required electric contact to each bar. The ground and polished bars enter the machine from one side and exit, fully plated, from the other. The bars are fully plated up to the ends, contrary to the conventional processes.
1) waiting bars
2) loading bench
4) cathode contacts
6) chromium plating unit
7) unloading bench
COMPARISON BETWEEN CONTINUOUS AND CONVENTIONAL PROCESS
In the conventional plating methods, the chromium plating operation takes place on stationary bars; the dipping rack carrying the bars is submerged in the bath, horizontally or vertically, for a period of time. The bars are mechanically and electrically fixed to the rack which is connected to the cathode. The anodes are placed on the long side of
the tank; there is no way to create an electric field concentric to the bars and this leads to thickness variations in the
chromium overlay. In the Stelmi process the chromium plating is done with a circular anode, and the bar
advances and rotates through the anode, so that a completely homogeneous chrome layer is guaranteed.
STELMI CHROMIUM PLATED BARS : ADVANTAGES
Unique, continuous chromium plating process which ensures:
Completely homogeneous chromium layer.
Bars chromium plated up to the ends: no scraps.
A chromium layer characterised by a peculiar micrographic structure, different from all the others, unique in the world and always identifiable.
CONVENTIONAL APPLICATIONS HIPERCHROMIUM® 200
GATES AND AUTOMATIC DOORS
MACHINES FOR AGRICULTURE
HEAVY DUTY APPLICATIONS HIPERCHROMIUM® 500/1000
SLUICE GATES FOR DAMS
EXTREME APPLICATIONS HIPERCHROMIUM® 200
HEAVY DUTY CYLINDERS
EARTH MOVING MACHINES
CABIN LIFTS, SKI LIFTS
MARINE AND COASTAL
STEEL BARS : STEEL GRADES IN USE
UNI EN 10083/1 2 C 45 similar to DIN Ck45 – BS 080M46 NF XC 48 -SAE 1045. Normalized carbon steel, available also induction hardened.
UNI EN 10083/1 2 C 50 similar to DIN Ck50 – BS 080M50 -SAE 1050. Carbon steel in use to obtain the highest hardness values by induction hardening.
20MnV6 / 18MnV5 Vanadium microalloyed steel grade with an higher yield point, good weldability and impact strength.
45MnV1 Vanadium microalloyed steel grade, with high yield point (> 520 Mpa), suitable for induction hardening.
UNI EN 10083/1 42 CrMo 4 similar to BS 708M40 – NF 42CD4 – SAE 4140 – Medium-alloyed steel grade, quenched and tempered, used whenever higher mechanical characteristics are requested.
QUALITY OF A CHROMIUM PLATED SURFACE
The quality of a chromium plated surface is essential for the gaskets life, the seal and the coupling accuracy; the corrosion resistance and the quality of lubrication depend on this factor as well. The values Ra Rt (or Rmax), Rz and the bearing ratio Tp are commonly in use to define its technical characteristics.
SURFACE ROUGHNESS RaIt is given by the arithmetical average, extended to the measuring length lm, of the absolute values of the distances of the roughness profile R from the centre line. A good chromium plated surface must have Ra
values below 0.2 ?m; the best average values is around 0.1 ?m.
MANUFACTURING PROGRAMM(Stelmi Productin Range)
The standard manufacturing program is given hereafter. Stelmi production range goes today from 16 mm up to 140 mm; sizes outside this range are traded.
Ck45 and 20MnV6 are available in the whole range listed. All the other grades are available from 20 up to 140 mm included. The only exception is 45MnV1 which is available from 25 mm up to 90 mm.