Lightweight construction has top priority also in the press shop in Münchsmünster; Audi has installed two large furnaces here for the production of parts made of hot-pressed steel. With hot pressing, controlled temperature increases are used to obtain a so-called martensitic structure with extremely high tensile strength; the thin material thicknesses this allows result in lower weight.
Today, the hot-pressed steel parts used to reinforce the bodywork of many Audi models are mainly produced in Ingolstadt in continuous furnaces. With the transfer of production to Münchsmünster, a new, more energy-efficient process is being used.
The new, multilayer chamber furnaces fired by natural gas together accommodate about 40 sheet-metal blanks. The feeder places the blanks into the chambers, where they are heated to a temperature of over 800 degrees Celsius in five to six minutes. After that, they are transported out of the chambers in insulated boxes to maintain their high temperatures. With some sheet-metal blanks – for the B-columns for example – the box is heated less in certain zones; the tensile strength of the component is then slightly lower there, which is advantageous in the case of a crash.
Two presses fitted with water-cooled tools shape the sheet-metal blanks at about 600 degrees Celsius; they are also responsible for cutting, punching and stamping with the utmost precision. Robots remove the finished parts and deposit them in a buffer. Some processing still has to be done on some of the components; this is performed fully automatically by a fast-operating laser system consisting of eight units.
In the coming months, Audi will also install a conventional car-body press in Münchsmünster; it will cold-press high-strength parts for the body structure. With dimensions of 33 meters long, eight meters wide and eleven meters high, the so-called TS 32 middle press is the biggest individual stage of the new facility; its head unit alone weighs 280 tons. With a closing pressure of up to 3,200 tons, the transfer press can perform a maximum of 30 strokes per minute. When it goes into operation in 2014, it will perform more than five million strokes each year, producing eight million components.
The strip-cutting machine, which will be installed in 2015, feeds the presses by cutting out the sheet-metal blanks from the large rolls of sheet steel delivered by suppliers. It is designed also to work with the hard aluminum silicon coatings required for hot pressing. Offcuts, just like scrap from the presses, are collected in the hall’s 7,000 square-meter basement and recycled.
Under the basement of the press shop there is a floor slab with an average thickness of 1.5 meters. This slab is supported by 13 bored piles, five meters long and 90 centimeters in diameter. 80 additional piles between eight and ten meters in length make sure that the foundations stand firm.