Hot and cold

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The benefits of hot rolled and drawn material

Do you like to sweat? The highest temperature ever recorded on our planet dates back to 1913. The air in Death Valley in the USA reached a value of 56.7°C at that time. At the Einsal we can only smile wearily about that. When we talk about 'warm' we mean temperatures of over 1,000°C.

Because with this heat, one of two possible steel processing methods takes place in our factories. The so-called hot rolling. His congenial partner is drawing, in which we leave our systems at room temperature.

Both methods have their own advantages. However, we wouldn't be Walzwerke Einsal if we didn't go a little further and, with a lot of know-how and the use of state-of-the-art machines, manufacture materials that clearly stand out from imported standard goods in terms of quality and flexibility.

We would like to bring you closer to the advantages of both processes and explain what sets our steel apart from so many of its competitors on the market.

Cold drawn material

Hot rolled material

Hot as magma: hot rolled steel

Hot rolling refers to a forming process above the recrystallization temperature of a material. In the case of steel, this is between 600 and 700°C; our plant works with forming temperatures of more than 1,000°C in order to keep the rolling forces as low as possible. Almost all metallic materials and steel qualities can be hot formed; we use the process to manufacture our steel bars.

The great advantage of hot rolling is that our rolled stock is easier to form (but not liquid!) at these high temperatures. In theory, this means that degrees of deformation of up to 25 can be achieved - this means that the geometric relationships between the inlet and outlet cross-sections of a rolled material can be changed by a factor of 25.

Hot rolling therefore allows the production of the most varied of gauge blocks for bar steel. But that doesn't mean we have reached the end of the benefits of our hot-rolled steel. Because we:

  • Can achieve surface roughness from Ra 5.0 μm with our systems. We achieve this quality by cyclically over-rotating the roller surfaces in use.
  • Continuously deliver all dimension combinations between 24.0 x 5.0 and 160 x 60mm, or with a square cross-section from 23.0 to 125.0. Rods close to final measurements and the fulfillment of customer-specific requests are therefore easily possible for us.
  • Are also flexible in terms of rod lengths. From rolling lengths of 3, 4 or 6m as standard to 13m long steel bars, everything is possible.
  • Are able to set mechanical-technological values ​​such as notched impact strength, elongation, strength or hardness thermomechanically directly during rolling or through subsequent heat treatment processes. For example, we achieve different strengths - from high for blades to very ductile as an input material for cold-formed parts.
  • Guarantee, on request, the straight-rolling design, up to a minimum straightness deviation of 0.5 mm/m.
  • Also fulfill the smallest batch sizes. We manufacture and deliver from quantities of 500kg.

Recrystallization refers to the removal of lattice defects through the formation of a new structure due to nucleation and grain growth. What does that mean? If a metallic material is deformed at low temperatures, defects, so-called dislocations, form in its crystalline lattice structure. Initially, these can still run freely through the material, but as the deformation progresses, more and more dislocations form, which mutually hinder each other's movement. The material solidifies, so it becomes harder and less and less ductile. If too many dislocations have accumulated, the material breaks with further deformation. Recrystallization is now a method to eliminate these lattice defects. From a certain temperature - around 600 to 700°C for steel - new crystal nuclei form in the metal, also known as nuclei in metallurgy. These begin to grow and thereby attract dislocations in order to incorporate them into their crystal structure. This reduces the number of lattice errors. The remaining dislocations can run freely through the material again, it becomes flexible and malleable again.

Precision work: cold drawn steel

Did you know that drawn steel is also called bright steel?
The main advantages of bright steel include the high dimensional accuracy of the end product over the entire length of the bar and the high surface quality. In contrast to hot rolling, drawing takes place below the recrystallization temperature. The work hardening enables high strengths to be achieved. With increasing work hardening, the deformability decreases, which can, however, be restored by a subsequent heat treatment.

With our materials such as 1.4441 or 1.4472, we achieve yield strengths of up to 1200N/mm2 with simultaneous elongation at break of at least 10 percent and even with classics such as 1.4301 or 1.4404, yield strengths of up to 1000N/mm2 are possible with sufficient residual ductility.

Our customers benefit from these special strengths which, with a weight-optimized design, enable smaller cross-sections with constant component strength. But that's not all, because:

  • We cold-draw bright steel in drawing dies with wear-resistant hard metal cores or in drawing boxes with continuously adjustable drawing jaws to achieve geometries close to net dimensions. For our customers, this means less material loss and less reworking - and thus significantly lower costs.
  • We can produce chamfers and edge radii in closed tools and thus set very tight tolerances according to customer requirements.
  • Our drawing process generates the highest quality in surface finishes. In the standard we achieve a roughness of Ra max. 3.2 μm and Rz max. 20 μm. Ground surfaces with grain 120 Ra, grain 240 Ra and grain 320 Ra as well as subsequent processing of the rods with Scotch tapes are also possible.
  • Finally, our bars are straightened on a fully automatic roller straightener. We achieve a maximum straightness deviation of 0.5mm/m and a maximum twist of 1°/m with consistent quality, and can guarantee a homogeneous state of tension. Individual marking of the individual bars is also possible by means of laser marking. On request, we can record the straightness and twist for each straightened rod.
  • The standard lengths are between 2500 and 6000mm. Short pieces from 10mm with a length tolerance of +/- 0.1mm begin below this. Maximum lengths of 7000mm are possible.
  • We saw our bright steel exclusively with carbide-tipped circular saw blades or saw bands and thus ensure a right-angled, burr-free saw cut without tarnishing or thermal influence on the cut surface.

Cold or warm: a question of where it is used

Whether hot-rolled bar steel or cold-drawn bright steel is the right choice for you, ultimately the intended use decides.

Due to its high dimensional accuracy, bright steel is suitable for visible parts and parts that should only be machined to a minimum.

Bar steel, on the other hand, is suitable for components that require extensive mechanical processing.

So if you have any questions about our production processes and would like further advice or would you like to place your order right away, just contact us. We are looking forward to your contact.

Contact us!