Technical ceramics for forming technology

The unique mechanical, tribological and thermal properties of high-performance ceramic materials make it possible to increase the productivity of forming tools. Used correctly, ceramics have a longer service life than conventional materials and represent an economical and technological alternative to tool steels and carbides.

The tool, as an interface between machine and workpiece, is subjected to particular stresses. The energetic transformation of a movement into a change in form takes place at this interface. Ceramic tools guarantee constant operating conditions, ensuring that the tool performs its function in the transformation process.

This requires a high stability of form on the part of the tool as well as a uniform (low) friction. A balanced energy balance also prevents the system from heating up.

The main argument in favour of using technical ceramics is their high resistance to wear and the much longer service life. Secondary reasons arise from an evaluation of the system as a whole. A better service life leads to an increase in productivity due to fewer interruptions to production as well as reduced costs for maintenance, re-tooling and reworking and lubrication of the tool.

  • On the one hand, forming tools are subject to abrasive wear. This involves the abrasion which occurs in the case of a tangential movement of the surfaces between tool and workpiece. Here, due to their hardness ceramic tools offer a good resistance to wear.
  • However, in addition, contact wear occurs in the form of fatigue and crack formation in the case of contact loads applied perpendicular to the surface. This is where the high compressive strength of ceramics scores highly. However, the resulting Hertzian contact stresses demand that the material should also possesses good tensile strength, in particular under impact loads.
  • Ceramic functional surfaces reduce the friction within the tool and reduce the amount of forming energy required. This permits a higher degree of deformation and an improvement of the workpiece surface.
  • Ceramic materials exhibit a low tendency towards adhesion and in comparison with steel tools make possible operation with a minimal amount of cooling lubricant and with longer cleaning intervals.

Ceramic materials

  • Aluminium oxide is an extremely hard material which is however characterised by a high resistance to wear resulting from sliding friction.
  • Zirconium oxide, as a high-strength technical ceramic, is highly suitable for use in applications subject to tensile stresses. The elastic modulus of this material indicates a favourable behaviour under contact loads (Hertzian contact stresses).
  • Silicon nitride – in addition to its resistance to wear, silicon nitride makes possible electrical insulation and working with reduced lubrication.

Cold forging – forming takes place at ambient temperature. At this temperature, the workpiece possesses its normal strength. The forming has to take place in different stages. Rolling (wire rod, pipes and strips)

Hot forging – forming takes place while the workpiece is heated, its reduced strength permitting a higher degree of deformation. Ceramic tools retain their strength and hardness even at higher temperatures and do not exhibit any annealing effects under the influence of temperature. Silicon nitride withstands temperature shock without any problem.

Sheet metal working – in the field of sheet metal forming, for economic and technological reasons, high-performance ceramics offer an interesting alternative to tool steels and carbides.

Pipe end shaping, i.e. the widening or narrowing of pipe ends. For this purpose, a sphere is drawn through the pipe, or a mandrel is pressed into the pipe end. A dishing tool is used to narrow the pipe end through compression.

Manufacturers of containers which subsequently come into contact with foodstuffs or drinking water use ceramic tools, since these can be operated without lubricants. This saves the otherwise necessary lubricant cleaning process.

Seaming rollers are in continuous use in the sealing of canned drinks and foods. In comparison with coated rollers, ceramics have a longer service life and are less susceptible to friction deposits than metallic rollers. Food cans are processed using CVT GreyCer forming rolls, since vinegar can cause wear on stainless steel.

Welding rollers made of silicon nitride are used in plants for the production of pipes made from coil in order to join the seam flanks during the longitudinal welding. They are non-magnetic and electrically insulating and do not influence the welding process with induction and electric arc welding.

  • Ceramic guide bars provide a low-wear guide for the seam flanks.
  • Straightening jaws made of ceramics, in particular silicon nitride, used in straightening machines for wire straightening are distinguished by an outstanding surface quality. Straightening units for wire clamping

Rolls are used in order to manufacture thin sheets and foils made of metal. A distinction is made between forming rolls and feed rolls. Whereas the latter are only responsible for transporting the sheet, the actual forming roll acts as a tool by means of which high pressure is applied to the material being rolled. Constant operating conditions in a continuous process are crucial here.

Dies for forging (extrusion)

Drawing dies are required in wire production. Drawing cones for drawing wire.