At Montanstahl we use different technologies to find the best way to meet our customers’ needs. Among the cold working technologies we rely on cold rolling and cold drawing, which allow us to produce profiles with complex geometries, but clearly with different objectives:
- Cold rolling is a very efficient production process, developed mainly for small profiles and offering certain advantages such as an excellent surface finish and the possibility of producing very small batches (500 kg).
- Cold drawing, on the other hand, is a cost-effective production technology that can reach very tight tolerances and a very good surfaces finish for medium and large profiles.
How steel is processed using cold-working technology
Cold rolling is used for thinner thicknesses and allows a better surface finishes and greater dimensional accuracy of the product. In fact, cold rolling entails rather important changes in the mechanical characteristics. This is referred to as work hardening, i.e. when irreversible sliding of the metal fibres within the sheet takes place, hardening of the material occurs and it becomes harder.
This process involves reducing the thickness and consequent elongation of the bar by passing it through a series of rollers held at a distance less than the thickness of the material, which, with their pressure action cause important changes: a very pronounced elongation, a medium-small widening and a very small reduction in thickness. To achieve the final desired material thickness it may be necessary to perform the process several times by proceeding by successive reductions.
Profiles can be supplied as bars in fixed lengths up to 6,000 mm or be coiled, and bundles can be cut to size with a tolerance of +/- 10 mm.
Cold drawing from a process point of view, involves the deformation of steel, which is transformed into bars or coils by means of machines that draw the blanks through matrices called dies.
Dies are characterised by the presence of a series of holes of progressively smaller diameter. From this it can be understood that the drawing process takes place in several stages, as the steel gradually passes through the dies with increasingly smaller dimensions, until the desired size and tollerances are obtained.
After this first stage of shaping, the next stage, which aims to achieve greater precision of the product through the use of mechanical means or heat treatment, is carried on. At the end of this second stage, the steel piece is cut to size according to the customer’s requirements.
The special feature of cold drawing is that, in addition to the size, it is possible to change the structure and mechanical properties of the steel to suit the specific purpose for which it will be used.
Cold-worked steel and its uses
Cold worked steel is a versatile and reliable choice that is widely used in a variety of applications, including medical, automotive, aerospace industries, transportation & railways, manufacturing, nuclear, shipbuilding, pulp & paper, interior design and more.
High strength and resistance to wear and fatigue make cold-worked steel bars ideal for the production of fasteners, screws and other small parts that require high performance and precision.
Another advantage of cold worked steel profiles is its improved surface finish, which is achieved through the manufacturing process. This surface finish is smoother and more uniform than others, making it more aesthetically pleasing and easier to polish or brush. In addition to its strength and durability, cold worked steel is also highly customizable.
A clear example of the complexity we are able to produce with these manufacturing technologies, is the profile requested by one of our customers, used as hair trimmer blades for electric razors.
For this type of profile, the challenges are manifold. Firstly, a steel grade with a high carbon content that allows hardening at high temperatures and superior consistency is required; these are the so-called martensitic steels for stainless steel and bearing and Q+T steels for its counterpart in carbon steel, which are employed for the same reasons.
Martensitic steels are composed of chromium (11.5-18%) and minimal amounts of molybdenum (0.2%-1.5%), nickel (no more than 2.5%) and carbon (0.08%-1.20%). This type of steel can also be hardened when subjected to appropriate heat treatment, has a high surface hardness and good resistance to wear and fatigue stress. One of the best-known martensitic steels is AISI 410, which is used where high machinability is required for cold and hot deformation, typically for the construction of self-tapping screws, scissors, knives and more.
The carbon steel alternatives, used for our industrial customers, are two different types of carbon steel, 100Cr6 and 42CrMo4. These types of steel have a high carbon content to allow hardening at high temperatures and superior constancy.
The blade profiles that we produce must be able to be machined and processed as needed. They are manufactured with very tight tolerances, down to even ±0.03mm generally, as well as having a tip, which must remain in a range between 0.57 and 0.63mm to allow the end customer to mill it to mill it, without having a lot of scrap, but at the same time having enough material in place to obtain the desired sharpness on the edges of the blades.
The customer requested us to supply the product both in bars with a maximum length of 5 meters and in coils. The latter guaranteeing savings up to 5% on cutting waste, because -unlike bars that have to be clamped on two sides, thus losing a considerable amount of material- coils are only clamped on the unwound side.