Keywords: furnace, repair, maintenance, Resistance furnace, temperature, furnace body, various furnace, heating, brick furnace, Brick furnace,

Resistance furnace daily repair and maintenance experience

　　ordinary heat treatment resistance furnace processing technology is mostly concentrated at the temperature of 650~1700 ℃, the furnace temperature changes greatly, the furnace body is ablated by high temperature, and the chemical erosion of various furnace gas, molten liquid and slag, etc. Therefore, its daily repair characteristics are: avoid hot repair with accident nature, take cold repair as the main method, and repair times are many, more on-site repairs.

Repair of 1. around furnace body

　　 Common failures of brick furnaces are mainly local repairs of heating bodies and masonry bodies. salt bath furnace common failures are salt leakage and electrode corrosion; Common failures of vacuum furnaces are heating body damage and furnace body leakage. In view of the common failure phenomena and causes, attention should be paid to the method, structure and material selection of masonry furnace body.

1. Overall furnace building

　　When the ordinary heat treatment resistance furnace is built as a whole, the original brick laying heating body of the brick laying furnace shall be left with a brick laying slot at the high aluminum brick laying size. The daily repair is mainly to change the furnace wire brick and furnace wire.

　　For salt bath furnace fault-salt leakage and electrode corrosion, pouring method is adopted to solve the salt leakage of the furnace body; In view of the easy corrosion of the motor, the furnace body is poured into two bodies, I .e. the electrodes are poured separately into a stepped block. After the electrodes are corroded, remove only the part of the electrode to be replaced.

2. Brick furnace method

　　(1) Take targeted repairs. Pay attention to the rear wall, side wall, furnace door arch, furnace vault, etc. of the larger brick furnace not to bite each other and crush each other, so that the above parts can be repaired separately without heavy laying bricks or stones in case of local damage.

& nbsp;& nbsp;& nbsp; For example, the arch of the furnace does not have to be supported on the side wall, but can be supported on the arch beam of the steel structure on both sides of the furnace, so that the furnace wall is not subject to the force of the arch, which is good for both the furnace wall and the arch. However, considering the thermal expansion of the arch foot beam, there should be a gap. When building the arch roof bricks, they shall be built symmetrically from the arch feet on both sides to the center at the same time. The vault locking bricks shall not be cut, and shall be accurately distributed according to the center line of the vault.

　　(2) For the exposed parts of the furnace body, which have sharp temperature changes and activities, such as furnace doors and furnace door arches, the following methods should be adopted: when building the furnace, add high modulus sodium silicate to increase the integrity of the furnace doors and furnace openings after sintering, and in its external leakage part with high temperature adhesive paste refractory fiber felt strip (according to the influence of the furnace atmosphere and the working temperature of the furnace to choose the type of adhesive and refractory fiber). When building the furnace door, lay the furnace door flat on the ground, build bricks from both ends to the middle, and the last layer of bricks & ldquo; Squeeze & rdquo; Go in.

　　If the furnace wall is built with two or more kinds of bricks, when each 1 kind of bricks of the wall is built separately, it is like a 1 group of single walls. After many times of heating and cooling, the furnace wall of different kinds of brick is easy to separate. In order to maintain the integrity and stability of the furnace wall, take every 5~8 layers, in the same height of the bricklaying layer overlap place, the internal and external walls pull each other solid masonry method, that is, half of the refractory brick is inserted into the other 1 brick layer, or fixed with metal anchor.

　　When designing the furnace lining, the bricks of each layer of furnace wire of the furnace lining shall be & ldquo; embedded & rdquo; in the furnace lining wall, and shall not be crushed to death. When the brick is broken, the brick can be replaced. The bottom of the furnace wire high aluminum brick bottom directly into a whole, not hanging.

　　 (3) Masonry requires staggered joint masonry, full mud, horizontal and vertical, and no internal and external collusion of gas after masonry is built. Bricklaying must follow the alignment, as the saying goes & ldquo; The upper and lower follow the line, the lower and the stare blankly, the left and right follow the flat & rdquo;, do not & ldquo; Swim the top and walk the seam & rdquo;. Bricks built on the wall must be laid flat, and the joints of the bricks must not be inclined while thick. Half-brick thick walls are completely built with smooth bricks. 1 thick brick walls are built with jacking bricks. Half-thick walls with 1 bricks are built with 1 rows of bricks and 1 rows of bricks. The two-brick wall is built with one layer consisting of two rows of bricks and 1 rows of top bricks between them, and the other layer is built with two rows of top bricks. In the process of masonry, the level of the masonry layer should be checked frequently, and the vertical and flat of the masonry wall should be comprehensively checked.

　　 (4) Brick joint is the weakest place of masonry, and its position should avoid the stressed parts of masonry, thermal insulation brick layer and furnace framework.Brick joints shall be filled with refractory slurry and dry masonry shall be filled with refractory powder to make the refractory masonry as a whole. The expansion joint shall not penetrate through the masonry, and there shall be no fire, air leakage, etc., and shall be staggered up and down, left and right. Plug refractory fiber and asbestos products at the expansion joint, and do not fall into mud, broken bricks and other sundries. When there are metal components in the masonry, expansion joints shall be set aside between the metal components and the masonry.

　　 (5) the refractory tube for the lead-out rod must be aligned with the hole on the positive furnace shell. if the center height of the hole is not right, the lower part of the clay brick supporting the furnace wire brick can be appropriately ground. The furnace wire brick is made of high alumina material, and the high alumina brick Fe2O3 & lt;1.5%. Iron oxide in 450~550 ℃, is to promote the atmosphere of carbon monoxide precipitation carbon black reaction catalyst. Carbon black deposits in the brick swell its volume, resulting in a decline in the strength of the masonry and early failure.

　　 The use temperature of light refractory bricks should be lower than the sintering temperature of the bricks by 70~100 ℃, so as to avoid large re-burning shrinkage and cause cracks in the bricks and cracks of the bricks. Fire-resistant clay bricks shall be used for the parts bearing heavy load such as furnace bottom and arch foundation. The brick at the door of the box furnace is easily damaged due to the entry and exit of the workpiece, and the bottom brick can be heavy high alumina brick.

3. Other precautions when laying furnace

　　(1) The ambient temperature shall be in strict accordance with the relevant requirements of the Code for Construction and Acceptance of Industrial Furnace Masonry Engineering. The key points can be pre-built, test the technical parameters, and then formally build after the appropriate.

　　(2) When carrying out targeted repairs on local parts, the demolition shall ensure that the unrepaired parts of the masonry are complete and not loose, so as to eliminate the possibility of masonry collapse or individual brick falling.

　　When watering the demolition and repair part of the furnace, fine water can be used to splash, so as to avoid water accumulation in the furnace and flowing to parts that need no repair. The retained old masonry should be leveled and leveled. If there is a stepped boss, carefully clean it up. Pay attention to the combination between the old and new masonry. When the old mud is firmly bonded, it is not easy to remove, thin mud must be used when biting stepped bricks; for low-lying and uneven places, thick mud with broken bricks can be used.

　　 When pulling out the broken brick, do not directly pull out the broken brick. First, pull out the intact brick near the broken brick, shake it left and right, gently take it out, and finally take out the broken brick. Do not knock hard with hard objects to avoid cracks in the furnace lining. When repairing and replacing the refractory pipe, first remove the insulator, take away the lead-out rod, then gently knock the pipe with a special hook to loosen it, insert it into the end of the pipe, and hook it out. Be careful not to break the diatomaceous earth bricks.

　　In the process of wall building, if there is a stop or temporary barrier in bricklaying, do not leave a vertical socket, but build the masonry layer into a stepped back platform or a staggered platform. The built wall cannot be adjusted by smashing bricks. If there is a large deviation in the wall, it should be removed and re-built. The bricks shall be cut neatly and accurately, and the mud shall be mixed with use.

　　(3) Pay attention to the selection of bricks. The bricks to be laid on the same floor shall be selected, and the bricks with the same external dimensions shall be selected as far as possible (the national standard stipulates that the quality requirements for the first-class bricks allow the size deviation of the bricks to be & plusmn;2mm). To check the brick surface, observe the shape and color, check the dimensional tolerance, distortion, missing angle, missing edge, melting hole, slag erosion and crack, etc., the surface must be smooth, there should be no cracks, slag erosion and vitrification, no missing edge off angle, the broken and uniform structure must be uniform, there should be no large impurities, no pores, cracks and layered structure, and the clinker particles should not fall off and crack, and should not be affected with moisture. Put the well-sintered and defect-free bricks on the forehand end face and lay the bricks in the furnace. The brick surface with missing edges and corners or after processing shall not be laid on the place where the furnace directly contacts with flame, molten steel or slag (it shall not face the furnace or contact with furnace gas), and the part bearing gravity.

Daily repair of 2. heating elements

　　Damage to the heating element

　　 General heat treatment resistance furnace non-vacuum furnace heating elements are mainly iron-chromium-aluminum (such as OCr25Al7Mo2) and nickel-chromium alloy (such as Cr20Ni80), vacuum furnace is mainly molybdenum heating elements.

& nbsp;& nbsp;& nbsp; (1) When the molybdenum heating element of the vacuum furnace is damaged, replace the partially damaged part of the molybdenum heating belt. Cut off the damaged part, take the 1 section and the same size molybdenum sheet, clamp it on both sides with 2~3mm thick molybdenum sheet, match the screw hole, and tighten it with molybdenum screw.

　　 When the molybdenum sheet is found to be deformed, falling, lodging, etc. during daily inspection, it can be baked with a blowtorch to soften it, restore its proper shape and relevant size with external force, and then hang it up and bind it with molybdenum wire.

　　(2) The normal damage of the alloy is mainly due to oxidation, thinning and embrittlement, overlapping short circuit, over-burning or erosion by the medium. Nickel chromium alloy than iron chromium aluminum alloy long service life, ribbon is longer than the filamentous, continuous work is longer than the intermittent work.

　　Nickel-chromium alloy has good plasticity, easy drawing and winding, and is not easy to embrittle when heated at high temperature, which is convenient for repair and welding. Iron-chromium aluminum alloy has a large resistivity and a small temperature coefficient of resistance. Compared with nickel-chromium alloy, it can save materials, has stable power and high heat resistance. It has strong resistance to carburization, sulfur resistance and various hydrocarbon gas resistance, but its processing performance is slightly poor, and it is difficult to draw and wind. It is properly adjusted outside the furnace during installation. The necessary bending and compression should be used for gas welding and baking; the thermal expansion coefficient is large (low high temperature strength and large creep elongation), so there should be room for installation; the welding time should be shortened as much as possible to shorten the length of the heat affected zone

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