Methodical ovens used for heating the blanks before rolling of sheet metal mills, are most prevalent in metallurgical production.
Usually in this type of furnaces heated harvesting 60-400 mm in thickness, width 60-1850 mm and a lenght of 1000 to 12000 mm and mass of 50 to 40000 kg. A main feature is a methodical furnaces movement of gases and metal.
Heated metal move is into pushed water cooled pipes. Fuel is burned whith burners located above and below the surface of metal. Products of combustion two streams - the upper and lower are move along the furnace working space in the opposite direction to the movement of metal, ie counter flow.The combustion products boron are removed through the smoke channels and from the recuperator and through the chimney into the atmosphere. Hot metal through the window falls on role extradition table and along it to the roller.
The heat and temperature regimes of methodical work stoves is constant over time. However, the temperature in the methodical furnaces changies significantly along the length of the furnace. The nature of changes in temperature, depending on the desired timetable for heating the metal, defines both the number of zones and the purpose of a furnace and heat treatment in each of them. Cold metal enters the zone of the lowest temperatures ahd moving toward the flue gases the temperatures of which are rises all the time, gradually (metodically) is heated
The first (in the process of metal) zone has changing in length temperature and is called metodicfl zone. Fuel combustion in this zone doesn't take place. Metal is gradually heated until of high temperatures (welding zone) enter the heated zone.
To avoid excessive heat stress it is necessary to heat of massive bodies in the temperature range from 0 to 500 ° C. The gradual heating of the metal in such a methodical zone provides heating rate at which there is no unacceptable temperature changes on along the cross - section of a blank.
The second (in the process of metal) zone is called the zone of high temperatures or welding zone. The aim of the zone - the rapid heating of the surface of harvesting to final temperature of 1150 - 1250 ° C. For the intensive heating of the metal surface to these temperatures in the welding area the temperature should be on 150 - 250 ° C above.
The third (in the process of metal) soaking zone (zone excerpts) serves to equalize the temperature on the plane of metal and eliminate cold spots on the bottom of the blanks. In the welding area only the surface of metal is heated to high temperatures; the temperature of medium layers of metal, of course, is far less then the surface temperatures, that creates a temperature range of metal plane, prohibited by technological requirements. Metal in soaking zone comes with this temperature range in thickness. The temperature in the area of soaking zone is supported by only 50 - 70 ° C above the required temperature ultimate of metal heating. Therefore, the metal surface temperature in soaking zone virtually does not change and is maintained at the achieved level in the welding area; alignment occurs only in temperature on the thickness of the metal in a uniformly distributed radiation treatment of external heat.