Advanced Materials - 230321

Question 1

Sequence of operations

Answer 1

schneiden from the coil, tiefziehen, schneiden, schneiden und lochen (piercing), trennen, calibration (adjust the shape to the final shape)
Process chain

Question 2

What is method planning?

Answer 2

Develop the process chain, from the CAD until the manufacturing process itself.

Question 3

How is the assembly of sheet metal parts divided?

Answer 3

three assembly lines:
1: Base components are mounted.
2: Side panels are mounted, framing station, roof.
3: Hang on parts, doors, trunk lid, hoods.

Question 4

What is hemming?

Answer 4

Die Hammming, folds the borders of two sheet metal parts and this join the metals.
Roller Hemming, it is done by using a roller on the edges and this joins the sheets.

Question 5

When forming a material what happens in the microscopic level?

Answer 5

Lattice structure.
Movement of the dislocations across the material. Tiny worms like structures

Question 6

How can you influence the strength of the materials?

Answer 6

• Mild steel: dislocations have a very big mobility, elongation at fracture (A80) is very high, strength low. High ductility, low strength.
• High hindrance of the mobility of dislocations:

Question 7

Strategies for strengthening the material:

Answer 7

strain hardening: no alloy added, just the material. Forming the metallic material, change the shape, increase the strength, dislocations blockk each other, like this little worms)
Thermal treatment: too expensive, but effective.
Alloys: Solid solution hardening, adding some other atoms (substitutional atoms, deflection of structure, increase on the resistance of dislocations), instertitial atoms.
Grain boundaries: small grain materials, have a greater strength than big grain ones. Fine grain materials. Grain boundary: obstacle for dislocation movement.
Precipitations hardening: the size and disttribution of dislocations, will locally block the motion of the lattice.

Question 8

Grain variation

Answer 8

Fine gray, cooling temperature when you cool the steel.

Question 9

How are sheet coils produced?

Answer 9

Hot and cold rolling will produce the sheet metals.

Question 10

How are sheet coils produced?

Answer 10

1. Slab. Initial thickness of the material. A rectangular block.
2. Hot rolling: decrease the formability of the structure. Increase the temperature in order to avoid the strain hardening. 1250 degrees. Just one rolling station, reversal rolling, forward and backward, the thickness gets reduced gradually.
3. Pickling: cleaning of the product.
   OPTION 1: end the process here, hot rolled strip.
4. Cold rolling: The reversal rolling is not possible, since the length grows very quickly. The sheet is so cold and so thin, that you can coil it.

Question 11

What are the disadvantages of the purely cold rolled sheet metal?

Answer 11

Strain hardening: Elongation at fracture at around 2% and anisotropy

Question 12

What is annealing?

Answer 12

Bell type annealing: coils are stacked, then a protective cover of nitrogen is put on top of it, then a heater and then a cooler.
Disadvantage: the coil is not heated uniformally, the inside is cooler than the outside.
Continuous annealing: a line, first abwickel, then degreasing, entfettung, then a furnace section where it gets hot, ofenteil, schlafenturm (ein echter turm ) and then aufwickel
This is done at the sheet metal factory.

Question 13

What is skin pass rolling?

Answer 13

a further reduction of the thickness,