4.3　Silicon Strip Horizontal Annealing Furnace

4.3.1　Furnace type and thermal source shall be selected as per the following provisions:

1　Continuous decarburizing annealing of oriented silicon strips and non-oriented silicon strips should better be processed in horizontal roller hearth furnaces.

2　Gas fired radiant tubes should be adopted for silicon strip horizontal annealing furnace as thermal source of heating section，and electric heater as thermal source of soaking section.

4.3.2　The T.O.P.parameters of public media of the furnace shall conform to the following requirements.

1　Technical parameters of coke-oven gas as thermal source of silicon strip horizontal annealing furnace shall be in conformity with the Table 4.3.2.

2　Technical indexes of furnace controllable atmosphere should be determined as per the Table 4.2.1-4 of this Specification.

3　Technical requirements for recirculating water shall conform to the No.3 stipulation of the item 4.2.26.

4.3.3　For silicon strip horizontal annealing furnace with scale-free heating section，gas with steady calorific value，rather than gas with unstable calorific value shall be applied for the scale-free heating section.

4.3.4　Long-flame type characteristics of low NOx generation and even temperature distribution along flame center axis shall be selected for radiant burner.For radiant tube used in controlled hydrogen atmosphere annealing furnace，its internal pressure is negative.The recuperator within it can be used to preheat combustion air.

4.3.5　Light refractory materials with ferric oxide content lower or equal to 1% should be applied for furnace lining，except for particular positions.

4.3.6　Strip entry seal consists of baffle，nitrogen seal and sealing rollers.

4.3.7　The exit sealing chamber shall be set at the location where strip will come out，and sealing units consist of baffle，nitrogen seal and sealing rollers.

4.3.8　Furnace throat shall be set between soaking section and cooling section.

4.3.9　The spacing of furnace rollers cannot be too large，and should better be 1.5-3.0m.

4.3.10　Circulating gas blowing-cooling device should be equipped for the cooling section，and water quenching-cooling device will be installed on low temperature cooling section when strip speed exceeds 150m/min.

4.3.11　Annealing furnace should be equipped with an big enough emergency nitrogen tank.

4.3.12　Mechanical seal could be set between furnace bottom rollers neck and furnace body.The combination of mechanical seals and nitrogen seals shall be applied when high demand is made on the cooling section.The same is true of axle neck of circulating fan.

4.3.13　In the exit sealing chamber，there should be ignition device like glow heater，and pressure releasing device must be installed for the purpose of directional decompression in case of explosion.

4.3.14　Pressure releasing device and glow heater should be set in cooling section.

4.3.15　In the entry sealing chamber of radiant tube heating furnace or electric heat treatment furnace，the blow off valve should be set for controlled atmosphere.One ignition burner should be mounted at the outlet of the valve on condition that the level of hydrogen in furnace controlled atmosphere is greater than 10%.