Thermal Insulation Material and Structure Design of Annealing Furnace

Ⅰ. Thermal insulation material of the annealing furnace

The types of annealing furnaces are divided into trolley-type annealing furnaces, pit-type annealing furnaces, box-type annealing furnaces and bell-type annealing furnaces, which are all very common annealing furnaces. The annealing furnace is an energy-saving periodic operation furnace with a super energy-saving structure, using ceramic fiber and aluminum silicate fiber as the thermal insulation structure, which can save more than 60% of energy.

The structure of trolley-type annealing furnace, pit-type annealing furnace and bell-type annealing furnace is relatively similar, so the same ceramic fiber and aluminum silicate fiber can be used as the thermal insulation structure. Since the temperature of the annealing furnace is below 1200 degrees, it is recommended to combine ceramic fiber modules and ceramic fiber blankets with high-temperature-resistant metal anchors to make the wall lining insulation layer of annealing furnace.

The box-type annealing furnace is also called annealing line. The furnace is small but very long. According to the temperature, it is composed of preheating zone, high temperature zone, heat preservation zone and cooling zone. Due to the low temperature at both ends, standard ceramic fiber modules and ceramic fiber blankets can be selected for the thermal insulation at preheating zone and cooling zone. And it is better to use high-purity ceramic fiber modules and ceramic fiber blankets for the thermal insulation at the high temperature zone and the heat preservation zone.

Ⅱ. Annealing principle and structure design of the annealing furnace

The annealing furnace is mainly used for hypereutectoid carbon steel and alloy tool steel (such as the steel used in the manufacture of cutting tools, measuring tools, and molds). Its main purpose is to reduce hardness, improve machinability, and prepare for subsequent quenching. This technology is conducive to plastic working and cutting, and also improves mechanical toughness. Especially for steel grades such as bearing steel and tool steel, if spheroidizing annealing is performed before quenching, the following effects can be achieved:

(1) Bearing steel: the quenching effect is uniform; reduce quenching deformation; improve quenching hardness; improve cutting performance of workpiece; improve bearing performance such as wear resistance and corrosion resistance.

(2) Tool steel: the quenching effect is uniform; the phenomenon of quenching cracking and quenching bending is suppressed; the wear resistance, the sharpness of the blade and the service life are improved.

(3) General spheroidizing annealing: heat the steel to between Ac1 and Ac3, and after sufficient heat preservation, slowly cool to 500 to 600 °C for cooling. General purpose of spheroidizing annealing: used for pre-heat treatment of bearing parts, tools, cold molds, etc.

The annealing furnace adopts an energy-saving structure, a full-fiber furnace structure, and uses clean energy gas as the energy source. The trolley-type annealing and heat treatment furnace is pulled by a winch, the furnace is built with refractory bricks, and the trolley is used as the movable bottom of the furnace. This kind of furnace has great heat preservation effect, can heat up fast, and is conducive to improving the thermal efficiency, with no smoke, reduced labor intensity, and greatly improved working environment. Trolley-type annealing furnaces are widely used in: steel mills, special steel, machining, chemical machinery, heavy industry, smelting, casting, forging, flange rings, steel components, wire drawing, environmental protection equipment, mechanical supporting equipment, loaders, diesel engines, and also used for heating in heat treatment workshops of other industries.