Among the several metalworking processes for industrial production, cold rolling is a fundamental step to manufacture wire, strips and metallic profiles. The main goal of metal rolling is to reduce the thickness or diameter of the material while simultaneously improving its mechanical features.
Although the cold rolling process is fairly recent, nowadays it is an intermediate production stage for many industrial components in multiple sectors: automotive, welding, electronic, medical, building and more.
The machine used for this kind of process is the cold rolling mill, or tandem rolling mill, able to perform various applications on metals resulting in perfect dimensions: indeed, metal rolling machines on the market provide numerous features and customizations.
Let’s check out the different types of tandem rolling mills on the market, and what’s most important to know in order to choose the most suitable cold rolling mill for industry.
Starting from the basics: what is cold rolling?
Let’s start with a brief insight into the metal rolling process, in order to understand how important using the most suitable rolling mill is for industrial production.
Cold rolling involves a metallic material (usually steel, brass, aluminum or other alloys) placed between coupled rolls close to each other. These rolls rotate in opposite directions at constant speed, compressing the material into a new diameter, thickness or shape.
Through the cold roIling process, the metal hardens without over-crystallizing (becoming too thick) too quickly: the metal is thus enhanced and strengthened with a special finishing and a perfect precision. Indeed, from a metal plate with a thickness of a few millimeters, it’s possible to obtain thin wires and stripes with a thickness of a few tenths of a millimeter.
Types of cold rolling mills for industrial applications
A cold rolling mill is a machine for metalworking consisting of a series of rolls, supported by parallel steel profiles, through which the metallic material passes. We are referring to:
- Rolling stands: the system composed of parallel steel profiles and rolls;
- Tandem mills: the set of stands that operate on the rolling machine.
Based on the cylinders’ number in a stand, it is possible to define a “duo”, “quarto” or “sesto” rolling mill, meaning a machine with 2, 4 or 6 rolls; whereas based on the stands’ number, it is possible to define a single rolling mill, if there’s only one stand, or a tandem rolling mill if there are 2 or more stands.
Moreover, cold rolling machines can also be:
- Reversible: the metal can be rolled in both directions and in more consecutive passages, according to the reduction that is needed in the milling process.
- One-way: the rolling process is only in one direction, often in a system of tandem mills, where each machinery contributes to reducing the metal’s dimensions.
Depending on the thickness needed, industrial rolling mills can be:
- Intermediate: for materials that come from a hot rolling process, like steel or aluminum, from an initial thickness of 10-20 mm to 0.5 mm up to 0.2-0.1 mm;
- Finishing: designed to operate an additional rolling following the intermediate one, it is possible to roll metallic materials from a thickness of 0.6 mm up to 0.05 mm.
Tandem rolling mills: guidelines and specifications
In order to reduce wires’ diameter and plates’ thickness in the most controlled and compliant way, it is important to know and verify the main guidelines and specifications of a tandem rolling mill. The key elements of choosing a cold rolling mill are:
- Type of metallic material: copper, brass, steel alloys, special alloys, bimetallic materials, or precious materials like gold, silver and platinum.
- Number of stands: it is possible to choose between a multi-stand machinery with 8, 10, 12 or more stands operating in single drive mode, according to production need.
- Material shape and dimension: cold rolling mills can work on different profiles, like oval, square, round or flat, with final dimensions often smaller than 1 millimeter.
- Rolling speed: can be set from a range of 10 m/min to 150 m/min, and should be monitored constantly depending on the different applications.
- Metal speed and tension: it is fundamental to adjust the speed and the tensile strength of the material inside the wire rolling mill, at both input and output.
- Flatness and central thickness: in every stage of metal strip rolling, the material’s thickness must be constant and the surface must be plain and smooth.
- Lubrication and cooling systems: tandem rolling mills are often automated,thus ensuring that the metallic material doesn’t overheat and doesn’t get damaged.
- Auxiliary devices: such as winding and unwinding tools to collect the wire in reels, calender or cutting machines for shearing the cold rolled profiles.
The experience of Invimec, manufacturers of cold rolling mills for almost 60 years, makes it possible to develop customized rolling mills for the most specific industrial applications.
Combined machines for rolling and profiling, tandem rolling mills with independent heads and technology for Industry 4.0, machines and production lines for welding wires, ribbed tubes or seamed profiles: contact us to develop your new industrial cold rolling mill!
