Forming process

Forming is the generic term for all manufacturing processes in which metals or thermoplastics like PTFE are brought vividly targeted in a different form. Depending on the school is also spoken by forming more slowly shaping. Here is a urgeformtes (eg cast ) starting material ( a strand of the continuous casting or a block from the block casting) in a semi-finished reshaped (first stage processing ) or workpieces from the semifinished product produced (second stage processing ). The material retains its mass and its cohesion during deformation. Transform differs from deformation, characterized in that the change in shape is deliberately introduced. Deformation is an untargeted plastic deformation (eg in the crash of an automobile ).

In the classification of the manufacturing method according to DIN 8580 forming is the term of the second main group and stands next to manufacturing processes such as archetypes, cutting, joining, coating and material property change.

After the original forms the major part of the materials by forming into semi -finished products ( sheets, wires and other profiles ( for example, rods, billets ) ) is further processed. For the production of mass products, the further transformation of the semi-finished products is usually the most economical method.

Basics

Metals are composed of crystallites whose orientation is isotropic or anisotropic. Plastic deformations of metallic materials carried by flowing on preferred crystallographic slip planes and slip directions in preferred within the crystallites. Slip planes and directions are dependent on the structure of metals and their lattice structures. There are body-centered cubic, face-centered cubic or hexagonal distinguish lattice structures. The forming of metals occurs by migration of dislocations ( translation) or by so-called twinning. Hiking begins when an applied shear stress exceeds a critical value ( the so-called critical shear stress ). In the hexagonal structure of the metals the lattice work from one position to another position ( twinning ).

A distinction is made between cold forming, warm forming and hot forming. During hot-forming, the workpiece is heated to a temperature above the recrystallization temperature of the material before forming. This results in periodically for recrystallization during the deformation which counteracts the solidification of the material. Cold forming as a conversion is referred to, in which the workpiece is in the cold state - is fed to the forming process, - at room temperature. When it comes to their solidification in reduced toughness of the material. The warm forming covers theoretically from the deformation region between room and recrystallization. However, here below is often understood only the temperature range between 700 and 950 ° C. Recently, the notion of Lauwarmumformung is introduced. The workpiece temperature is input here between 200 and 500 ° C.

If due to the forming process, the effective stresses in the material, the shear strength or cohesion strength exceed unintentionally, there is Schiebungs or separation breakthroughs that make the work useless. Can you Entgegengewirken this material failure by a more adapted transformation, ie an amended stages transition or an increase in temperature of the material.

Today is a big area of ​​research in metal forming, as in other fields, the simulation. With the help of various programs (mostly based on the finite element method, for example, AutoShape or LS -Dyna ) are modeled forming process, calculate and display the calculation results visually. This enables more accurate fault prediction in the production of the components and the optimization of material consumption and process design.

Forming

The forming method according to DIN 8582 is divided by the stresses which cause the deformation mainly.

We distinguish between the following groups:

Pressure forming to DIN 8583

Forming at the prevailing compressive stress; Subgroups:

Tensile compressive forming to DIN 8584

Forming with simultaneous loading by train and pressure loads of different effective direction; Subgroups:

Tensile forming to DIN 8585

Forming at the prevailing tensile stress; Subgroups:

Bending deformation according to DIN 8586

Forming at prevailing bending stress; Subgroups:

Shear deformation according to DIN 8587

Forming at the prevailing shear stress; Subgroups:

Other methods

• Hexagonal structure
• Guerin process