Patent Application
20090056403
This invention relates to the process and systems of hot stamping metal parts. In particular, this invention relates to a process of hot stamping and joining metal parts.
Metal parts are often formed from sheet metal. Sheet metal is cut, bent and pressed in to the shape of the desired metal parts. After the metal part is formed, it can then be welded or otherwise attached to other metal parts created by the same process or by other means.
Hot stamping is a process of forming metal parts from sheet metal stock that involves heating a portion of the sheet metal material to a high temperature for a period of time and then forming the heated material using a die.
Ovens are often used to heat the pieces to the high temperatures needed. In a manufacturing facility, pieces may be continuously moved through the oven so the parts are consistently heated to the desired temperature for the desired length of time. Ovens are generally an expensive element of the manufacturing facility, in terms of both capital and operating costs, and the throughput of the oven a limiting factor in the hot stamping process.
The part may then be stamped to form the metal part into the desired shape. Stamping is the forming of metal by using a die and a punch that resembles the shape of the part. By heating the piece, the metal becomes more ductile and easier to form by pressing within the die.
After being pressed in the die, the formed piece may be quenched by rapidly cooling the part, often using water. Quenching of the metal generally improves certain properties in the metal such as hardness and strength that would not otherwise be present if cooled gradually.
After the part is cooled, it may be welded or otherwise attached to other parts to create a composite metal component. As often multiple different parts must be welded together, multiple dies must be used to form each of the parts before they can be welded together, and each of the parts must be separately heated in the oven before stamping.
Hot stamping facilities may hot stamp a first part for a period of time by cutting, heating and stamping the first part. After a suitable quantity of the first part has been created, a second part may be hot stamped by cutting, heating and stamping the second part. Only after the second part is formed, may the first and second parts be welded together. This process requires that a suitable quantity of the first part be stored pending the hot stamping of the second part. Alternatively, a manufacturer must run multiple ovens at the same time in order to heat the first and second parts in parallel, with attendant additional cost and space usage.
Moreover, it is conventionally considered that the integrity of a weld between parts that are welded together before the parts are heated to a sufficiently hot temperature for hot stamping is suspect, in contrast to welds effected after the hot stamping process.
In drawings which illustrate by way of example only a preferred embodiment of the invention,
The present invention relates to a method of producing a stamped composite part, the method comprising the steps of cutting at least two metal component parts into a desired shape; welding the at least two metal component parts to each other to hold the at least two metal component parts together in a selected position as a composite blank; heating the composite blank for stamping; and stamping the composite blank to form the composite blank into a desired shape, thereby creating a stamped composite part.
The method may further comprise the step of further welding the at least two metal component parts to each other in the composite part.
With reference to
In the two-component embodiment of the invention described and illustrated by way of example only, as shown at 1 and 2 each of the two metal component parts is cut from sheet metal stock. The sheet metal stock may be cut to form the metal parts using any suitable technique, for example without limitation, punching, laser cutting, trimming, or shearing, to create blanks.
At block 5, the two component parts are arranged together in a selected position and held in the selected position with one or more welds, for example spot welds as indicated. The spot welds retain the two parts in the selected position during the heating step 10 and the stamping step 20. The retaining spot welds may be effected manually or by a machine designed to position and spot weld the parts. In one preferred embodiment the component parts 100, 105 are further welded together after stamping to augment the strength of the composite part 115.
As shown in
At block 10, the two component parts are heated, by a heating apparatus, for example a furnace or oven. As mentioned, the two component parts are held together by the retaining spot welds completed at block 5, creating a composite blank 112. The two parts 100, 105 are heated in the heating apparatus preferably to a sufficiently high temperature to prepare the composite blank 112 for the stamping step 20, for example by rendering the composite blank 112 ductile. After heating the composite blank 112, the composite blank 112 is removed from the heating apparatus as indicated at block 15. The heating apparatus may be a walk through oven such as used in conventional hot stamping processes. Alternatively, the heating apparatus may be an oven with one or more compartments suitable for placing a part. The composite blank may be heated to 920 degrees Centigrade for between 4 to 10 minutes. Heating the composite blank 112 for an undue lengthy period of time may cause damage to any coating on the surface of the two parts 100, 105.
At block 20, the heated composite blank 112 is placed in a die and pressed using a hot stamping press. The die forms both of the component parts 100, 105 while the component parts are sufficiently ductile from the heating process 10, the retaining spot welds from step 5 being sufficient to maintain the two component parts 100, 105 in position relative to one another during the stamping stage 20.
At block 25, the heated and formed composite part 115 is quenched by rapid cooling, as is conventional. Quenching may be done using water or gas or any other suitable technique. In one embodiment, the die and punch are cooled by water flowing through ducts integrated with the die and punch so that quenching occurs substantially simultaneously with the stamping process. After being hot stamped, the composite part 115 may be need to be cleaned to remove scale from the heating and forming steps.
After the composite part 115 has been hot stamped, the component parts 100, 105 may be further welded together to augment the strength or integrity of the composite part 115, as indicated at block 30, more fully integrating the two component parts 100, 105 with the shape and number of welds desired. An example of a completed composite part 115 prepared according to the invention is shown in
By positioning the two component parts 100, 105 prior to heating the composite blank 112 in the oven, the throughput of the overall process may be increased.
The integrity of the retaining spot welds is maintained through the heating and stamping parts of the process.
The process of hot stamping as described above may involve other steps such as quality assurance and dimensional checking as part of the manufacturing process.
In a composite part 115 produced according to the method of the invention the integrity of the retaining welds between the component parts 100, 105 is retained despite heating the component parts to a sufficiently hot temperature for hot stamping.
