What should be paid attention to in the routine repair process of the heating element of resistance furnace?
In our daily use of large equipment resistance furnace, usually there will be some small parts damage or failure problems, now China electric heater network has a coup, teach you easy to solve the trouble.
Damage of 1. heating element
The ordinary heat treatment resistance furnace non vacuum furnace heating element mainly adopts the FeCrAI (such as OCr25Al7Mo2) and Ni Cr alloy (such as Cr20Ni80), vacuum furnace is mainly molybdenum heating element.
(1) when the molybdenum heating element in the vacuum furnace is damaged, replace the part damaged by the molybdenum and the tropical part. The damaged part is cut off, and a piece of molybdenum sheet with the same size as the original size is taken and clamped on both sides of the molybdenum sheet with 2 to 3mm thickness. The screw hole is matched with the screw, and then screwed with molybdenum screw.
In the daily inspection found molybdenum sheet deformation, straining, lodging and other phenomena, can the torch bake to soften, restore its shape and size with external force, and then lift the fixed bundle of molybdenum wire.
(2) the normal damage of the alloy is mainly caused by oxidation, thinning, embrittlement, lap short circuit, over burning or erosion by medium. Ratio of Fe Cr Ni Cr alloy Aluminum Alloy long life, a long strip of filamentous, continuous work than continuous work for long.
Nickel chromium alloy has good plasticity, easy drawing and winding, and it is not easy to be brittle after heating at high temperature, so it is easy to repair and weld. Fe Cr Aluminum Alloy resistance coefficient, low temperature coefficient of resistance, compared with Ni Cr alloy material can be saved, and the power stability, high heat resistance, strong anti carburizing and sulfur resistance, resistance to various hydrocarbon gases, but the processing performance is poor, drawing and winding difficult, when installed in the furnace to adjust right, bending and compression by welding the necessary roast school; thermal expansion coefficient (high temperature strength and low creep elongation), installation leeway; welding to try to shorten the time to shorten the length of the heat affected zone.
When the heating body works for a long time, it will appear soft, swelling, falling, lodging, overlapping, post fusing (melting) and so on. In order to make the furnace wire have a certain strength at high temperature, and prevent softening, collapse or sagging, the size of the furnace wire must be designed, such as spiral resistance wire, attention should be paid to the diameter, pitch and spiral diameter of the alloy element. The heating body should be installed close to the furnace lining, put flat on the brick, and keep its expansion space properly. A small position to the right, a general 400 ~ 600mm, and can prevent the hook down firmly. In addition, in order to prevent contact between the furnace wires, it is necessary to pad. It can be made of 95 porcelain and other high temperature resistant materials to prevent the lap joint. Especially for conversion between the furnace brick layer and layer (in place of furnace brick, put between brick and the front end wall left in general 50mm space, resistance wire for turning and installation), advance pad tiles, or a porcelain tube furnace wire (porcelain tube to the top end). High temperature furnace can not use diatomite tiles saw in the middle of the furnace plate, because the diatom soil brick heat resistance is poor, can only be used below 900 degrees Celsius, easy to dissolve in high temperature furnace metamorphism.
The furnace wire lodging trend, check whether the furnace wire hooks play a role (hook ribbon resistance furnace must be cemented, pressed, plugged, not loose), and can be used welding torch bake furnace wire or make it become soft, and then restored to its original shape and size, and wear in the porcelain furnace wire tube (porcelain tube wear mandrel) etc.. If two porcelain pipes are used simultaneously, the head of porcelain pipe must be close to each other.
The heating body welding of head can, for the collapse of serious, not straight, local burning part of the serious damage, the general can be used for repairing method of a, not because of the local failure will be set for retirement, should pay attention to the resistance wire welding material, diameter, length and pitch must comply with the technical requirements of the original, not the new resistance wire fill crack, rust and other defects, to uniform spacing. When using the old resistance wire, the resistance wire can not have obvious uneven thickness, oxidation corrosion, crack deformation and aging brittle phenomenon. The old rod can not have serious oxidation and corrosion phenomenon.