The high carbon steel wires are heated in the patenting furnace according to their carbon content (0.2 – 0.9%C) to about 850 – 950°C and are quenched in a lead bath (usually ~480 – 520°C) immediately after exiting the furnace. By variation of these temperatures the tensile strengths of the wire may be influenced slightly, but the rule is:
the higher the C-content, the higher are the obtainable tensile strengths.
In the past, conventional patenting furnaces were very long, with many burners and zones of regulation. Compared to the output, such a furnace was of very costly maintenance. OFENBAU FRITZ has therefore introduced a new type of patenting furnace, whose design is comparable to our BECKER-FRITZ continuous wire annealing furnace. The whole furnace (length 12 to 26m) is heated by a light-weight heating cover with 1 – 4 burners (depending on the furnace size and output), which is placed on the muffle. The wires pass the furnace in a closed muffle, against the heat current; the regulation is very easy.
The length of the lead bath furnace is 4 – 10m, according to the type and speeds of the wires to be patented. Most lead baths require only 1 to 2 burners for heating up and keeping the bath at temperature in idle; with full production the wires coming from the patenting furnace bring in so much heat that it is even necessary to cool the lead bath, in order to not exceed the working temperature.
● extremely low consumption compared to the previous design
● easy regulation (only 1 – 4 burners in the heating cover)
● reduced dimensions = less heat losses
● maximum use of the waste gases
● easy maintenance of the muffle: just lift the light-weight cover (by crane), and you get to the muffle plates