Treatment equipment and furnaces
Agibi: a thorough study on heat treatment of springs
The thermal treatment is often considered as a cost and not as an essential part in the production process of springs. All machinery involved in the production, such as coilers, benders, grinders, control instrumentations, have experienced improvements in the last decades, but what about furnaces?
Prompted by some important Italian and German customers, which in recent years were asked to produce springs with increasingly high performances, AGIBI Progetti equipped itself with modern instrumentations to perform tests on furnaces.
The treatment specifications are provided by steelworks, but the furnaces must be certificated according to the most recent rules, such as the CQI9 norm, used in the automotive industry, and the AMS2750E norm, used in the aerospace branch.
AGIBI Progetti performed field tests on furnaces with different backgrounds, which indicated that most of them had problems in meeting the requirements of the norms (see pictures 2-4-5).
Therefore AGIBI decided to commission a computerized fluid dynamics center to search a technical solution, which would allow to reach widely acceptable results. Based on the results of this research, the company modified the air circulation system and the thermal insulation of the furnaces and performed the tests again.
Results on chamber furnaces
As required by the AMS2750E rules, to perform the tests, AGIBI inserted into the furnace a frame with 15 probes, placed as shown in picture 1.
The graphic of picture 2 shows the test report of a furnace before the changes, while in the picture 3 we can see the difference after the modifications.
According to AMS2750E rules, the furnace tested in the first case can’t be classified even in the 5th class (± 14°C); While the second chart shows that AGIBI's furnace has reached the 1st class (± 3°C).
Please note that, to meet the CQI9 requirement, the furnace have to be classified at least in the 4th class (± 10°C).
Thanks to these experiences, the company had developed a new generation of furnaces, which are characterized by excellent temperature uniformity (an important requirement to get a certification of the treatment according to the strictest norms). Moreover, thanks to the special insulation materials, used also in the aerospace industry, they allow an energy saving of more than 40% compared with traditional ovens.
On the right, picture 1.
Picture 2 below:
Picture 3:
Results on belt conveyor furnaces
In this case, the goal was to improve the characteristics of a belt conveyor furnace, in order to satisfy the requirements of a customer who produces springs for the medical industry.
To perform the tests, AGIBI Progetti used 3 flexible probes, placed at a high of 20 mm from the conveyor belt, one in the center and the others on the sides. The treatment time was 30 minutes (average duration of the treatment required by the customers), and the set point was set to a temperature of 250°C (a customer asked also for a test at 450°C).
The pictures 4 and 5 show the results on an old generation furnace, while picture 6 presents the results on a furnace that was modified after the research of the fluid dynamics center.
From the analysis of these charts we can observe that, excepted the oscillations due to the control instrumentation, in furnaces with an insufficient air circulation and with inadequate insulation (pictures 4 and 5) the material to be treated remains at the set temperature for less than 30% of the required treatment time, while in furnace of new generation this percentage rises up to 80%.
Moreover, also in this case we can save more than 40% of energy.
Picture 4:
Picture 5:
Picture 6:
by A. Bortolazzi
Agibi Progetti srl
Via C. Battisti 278/D
37057 S. Giovanni Lupatoto, Italy
Tel.: +39 045 9230443
[email protected]
www.agibiprogetti.it
