18/11/2009
The heat of an oven and the weight of a dinosaur – no problem for CERATIZIT tools
Marcegaglia relies on carbide tools from CERATIZIT for the cold drawing of tubes |
 |
The largest Marcegaglia company producing cold-drawn tubes is located in Boltiere (Bergamo, Italy). The Marcegaglia company there produces welded and seamless cold-drawn tubes for automotive, hydraulic and mechanical applications. The drawing mandrels and dies that Marcegaglia Boltiere needs are ordered at CERATIZIT Alserio, Italy, which specializes in the development, manufacture and maintenance of high-quality carbide tools.
50 tons at a temperature of 200 degrees (Centigrade) – that’s what the CERATIZIT tools must withstand
Antonello Valsecchi, application engineer at CERATIZIT Alserio explains: “Cold drawing of tubes is a typical area where carbide, thanks to its properties, is the best choice for tools. Dies and mandrels are loaded with very high pressure during drawing. Just imagine that for instance a tube with a diameter of 100 millimetres is pushed inside the die at a speed of 25m/min with a tensile force of 50 tons.” This was also the weight of the largest dinosaur in Europe.
Furthermore mandrels and dies have to guarantee very high wear resistance. “The drawing process is performed at room temperature, but the friction between tube, die and mandrel increases the local temperature to over 200°C,” Valsecchi adds. Heat equivalent to the heat in a domestic oven, which of course cannot harm the CERATIZIT tool. The most frequently used carbide grades for this application are CTF30, CTM30 and CTM40.
Cold drawing of steel tubes - four steps to achieve the perfect tube
Tube drawing is an industrial process for reducing and calibrating both internal and external diameters of a tube. Cold drawing guarantees a very good surface finish and increases the mechanical properties of the tubes.
Step 1:: The raw tubes (8 to 12 m long, 10 to 210mm in diameter) are heat-treated in order to make the material ‘malleable’.
Step 2: The raw tubes are cold formed to reduce their diameter on one side. This step is called pointing and is necessary to form the tubes so that they can be drawn inside the die.
Step 3: The raw tubes are chemically treated whereby their surfaces are cleaned with an acid. The tube may now be inserted into the drawing tool.
Step 4: The tubes are drawn on drawing benches with drawing dies and mandrels.
The part CERATIZIT dies play in the cold drawing process
The CERATIZIT dies are brought into play in steps 2 and 4.
Step 2: The tube is inserted into a CERATIZIT carbide die to a depth of 20 to 30 cm. The conical surface of the die reduces the diameter of the tube; the tube is then pulled out from the same side of the die. This reduction of the tube is usually effected by means of 2 to 4 dies: the tube is pushed in and pulled out in sequence from the largest to the smallest die.
Step 4: For drawing Marcegaglia applies drawing dies and mandrels from CERATIZIT. The tube is placed inside the die and the mandrel is placed inside the tube. Then the tip of the tube is clamped on the drawing bench by the grippers and pulled inside the die along its full length.
---------------------------------------------------------------------------------------------------------------------
Interview with Luciano Giol, Plant & Sales Manager, Marcegaglia Boltiere: “Some of our carbide tools are already 25 years old and can still be used”
What is the production capacity at the Boltiere site and where do the tubes go to?
Giol: ""The site in Boltiere produces 100,000 tons of cold drawn precision tubes per year, of which 70% are applied in the hydraulic sector: telescopic tubes, cylinder tubes suitable for skiving and rollerburnishing, skived and rollerburnished tubes and ready-to-use cylinder tubes. The remaining 30% are produced for the automotive industry."
What is typical for the cold drawing process of tubes and what does that mean for the carbide?
Giol: "The utilization of carbide tools in the production process is absolutely essential. In the manufacturing of precision tubes, it is vital to achieve overall good quality. In order to guarantee constant precision, carbide tools must be used in the production process."
Are there alternatives to carbide tools? If so, which ones? And what are the advantages and / or disadvantages
Giol: "The alternative to carbide tools are carbon steel tools. The main benefit is the initial price, which is much lower than that of carbide tools. On the other hand, this kind of tooling has a shorter life, as it wears faster than its carbide equivalent. Carbon steel tools may be about 2 or 3 times cheaper, but the cost-benefit ratio is on the carbide side. Carbide tools maintain a good surface for finishing and guarantee good precision of the hole dimensions for longer periods of time. Carbide tools guarantee fewer machine downtimes, lower setup costs and the quality of the output tubes is constantly high for the whole life of the drawing tool. All in all, we save hours of production and money, thanks to carbide tools."
Why did Marcegaglia opt for CERATIZIT products?
Giol: "CERATIZIT products were chosen by Marcegaglia mainly because of the longer tool life, but also for their overall quality and service performance. As an example, a carbon steel tool must be reworked (‘revamped’) after 1,000 metres of production, while we are still using carbide tools that are 25 years old."
How would you describe the cooperation between Marcegaglia and CERATIZIT?
Giol: "I would describe the cooperation as very good. The cooperation with CERATIZIT is based on continuous close support of our internal staff. CERATIZIT guarantees high-level technical assistance in the maintenance of the existing tools and in the development of new kinds of tooling."
|
Specials
