Showing posts with label Reheating Furnace. Show all posts
Showing posts with label Reheating Furnace. Show all posts

November 8, 2008

Refractory Bricks, Mortar and Castable for Reheating Furnace Lining

Reheating Furnaces serve the purpose of heating various intermediate products of Steel like- ingots, blooms or billets before rolling to give them different shapes of angles, channels, bars, slabs, rods & wires etc (See detailed description of Reheating Furnace in another article). Area wise specifications of Refractory Bricks and Castables or Blocks which can be used for lining of reheating furnaces and the quality of Refractory Mortar which can be used for laying the bricks are given hereunder -



Furnace Hearth

  1. Dense high alumina bricks with low iron content. Alumina (Al2O3) 88-90%, Iron (Fe2O3) 1.8% (max), Bulk Density (BD) 3-3.2 gm/cc, Apparent Porosity (AP) 16-18%, CCS(kg/cm2) 800 (min), RUL(taOC) around 1550-1600, PLC at 1600OC/2hrs (+/-) 0.2% (max).

  1. Basic Magnesia, Mag-chrome bricks. MgO around 55-60%, Chrome (Cr2O3) around 12-15%, Silica (SiO2) 8% (max), AP 18-20%, CCS (kg/cm2) around 450-500, RUL (taOC) 1600 (min), PLC at 1600OC/2hrs (+/-) 0.5% (max).


Furnace Roof

Alumina (Al2O3) around 70%, Iron (Fe2O3) around 2.5-2.8%, BD 2.6-2.7 gm/cc, AP 21-23%, CCS (kg/cm2) 500 (min), RUL (taOC) around 1450-1500, PLC at 1500OC/2hrs (+/-) 2.5% (max).


Furnace Side-Wall and for General purpose

  1. Low porosity dense bricks. Alumina (Al2O3) 45%, Iron (Fe2O3) 1.6-1.8%, BD around 2.2 gm/cc, AP around 16%, CCS (kg/cm2) around 500, RUL (taOC) 1500 (min).
  2. Alumina (Al2O3) 40%, Iron (Fe2O3) 2.0-2.2%, BD 2.1 gm/cc (min), AP 22% (max), CCS (kg/cm2) around 350, RUL (taOC) 1400 (min).


Furnace Bottom, Blocks (Burner Block, Well Block, Seating Block, Seating Well Block) and Castables

  1. Medium purity Low Cement Castable (LCC). Alumina (Al2O3) around 90%, Iron (Fe2O3) 1.0-1.5%, BD 2.7-2.9 gm/cc, PCE 37 Orton (min), CCS (kg/cm2) at 110OC/24hrs 600 (min), at 1500OC/3hrs 550 (min), PLC at 1500OC/2hrs (+/-) 1.0% (max).
  2. Medium purity Castable conventional type. Alumina (Al2O3) around 60%, Iron (Fe2O3) 1.8% (max), BD 2.1 gm/cc (min), PCE 36 Orton (min), CCS (kg/cm2) at 110OC/24hrs 350 (min), at 1500OC/3hrs 450 (min), PLC at 1500OC/3hrs (+/-) 1.5% (max).



Furnace Door, Flue Stack, Heaters


Insulating Castables. Iron 1% (max), BD 1.0-1.2 gm/cc, CCS (kg/cm2) at 110OC/24hrs around 12-15.


Mortars


Have to be compatible with the laying brick quality (chemical spec).


All the data given above are tentative and should not be considered as ‘Typical Specification Data’. Methods of Installation and Furnace Heating Schedule may be provided by the refractory supplier however, in the coming posts we shall discuss on the same also.

November 6, 2008

Refractories for Reheating Furnace

Reheating Furnaces are used for heating the intermediate products of steel like- ingots, blooms or billets at temperatures around 1000 - 12000C before rolling to give them different shapes of angles, channels, bars, slabs, rods & wires etc. The furnace is a chamber having inside refractory lining to conserve heat and generally includes a mechanism for transporting products continuously from one end to the other end. Heat for the furnace is provided by natural gas or fuel oil.

Reheating Furnace which is considered an accessory to the rolling mill is a critical factor in the quality of end-product. In view of saving energy, requirement of Refractories with low thermal conductivity are required particularly for Door, Heaters, Flue-stack and further, for Hearths these criteria are corrosion, abrasion & spalling resistances with good strength. For these purposes, dense low-iron, high-alumina or chrome-magnesia bricks are best suited for Hearth. The side-wall and roof are lined with high-grog alumino-silicate bricks. Precast / Prefired (PCPF) blocks can be used for Burner-block, Seating Well Block, Well Block as well as for Furnace Bottom, made of low-iron high-alumina dense refractories having excellent spalling & abrasion resistances. The advantage of using PCPF blocks is that they can save time for both installation & for drying/preheating inducing more availability of the furnace. In the event of choosing Precast / Prefired (PCPF) blocks one has to take care of the design of these blocks which should be such that one person can handle them. How to select Refractories area wise for Reheating Furnace lining?