What is a continuous mesh belt sintering furnace

Continuous mesh belt sintering furnace

        The compact passes through the hearth of the preheating section, high temperature section and cooling section of the furnace at a certain speed. This kind of furnace has the advantages of large production volume, uniform product quality, high thermal efficiency, convenient operation, low cost of furnace materials and heating elements, long life, low peak power, and saving sintering costs. In the production of powder metallurgy machinery parts, the commonly used continuous sintering furnaces include mesh belt furnaces, walking beam furnaces and push rod furnaces.

Mesh belt furnace

1) Features of mesh belt furnace

(1) Under normal conditions, there is no need to use a burning boat, and the sintered parts are heated uniformly and have little deformation.

(2) Simple operation and high degree of automation.

(3) The rapid burning off (RBO) mechanism can be used to accelerate the burning off of the lubricant, and carbon compensation can ensure the carbon potential in the furnace.

(4) With driving and transmission devices, the feeding and discharging are carried out stably and continuously. The speed of the conveyor belt can be adjusted between 1.4~14m/h to meet the different requirements of various green compacts sintering time.

(5) There are various safety devices. To ensure operational safety, all applicable alarm systems and corresponding measures are adopted. Such as gas low pressure alarm, cooling water cut-off alarm, temperature abnormal alarm, etc.

(6) With auxiliary parts. There are automatic control devices for the temperature of each sintering heating zone and the temperature of the slow cooling zone, as well as a device for automatically recording the purity of the sintering atmosphere, and an automatic control device for gas pressure and flow.

The structure of the mesh belt furnace

The mesh belt furnace is composed of driving device, burning zone, sintering zone, cooling zone (water jacket cooling type), feeding and unloading device, heating device, various piping and electrical and testing devices.

(1) Burn-in area.

In order to smoothly remove the evaporated lubricant from the furnace, an air flow system is added to facilitate the removal of part of the lubricant slag that cannot be discharged. A collection port is provided at the bottom of the furnace, which is easy to clean from the furnace.

Both the furnace cover of the pre-burning zone and the flange connection with the sintering zone use bolts, so the inspection is simple.

(2) Sintering zone.

The furnace tube in the sintering zone adopts the muffle furnace tube made of heat-resistant cast steel, and the furnace tube has a sufficient length, which can stabilize the protective atmosphere and ensure that the lateral temperature difference on the conveyor belt is controlled within ±2°C.

In order to prevent the protective gas that was contaminated during the delubrication in the pre-burning zone from flowing into the sintering zone, a baffle is provided between the pre-burning zone and the sintering zone to prevent this part of the gas from flowing in.

In addition to bearing the gravity of the furnace tube, the heat insulation material of the furnace tube is all made of ceramic fiber, so the heat economy is good, and the heat insulation effect is good, so that the surface temperature of the furnace body is controlled below 60 ℃.

Indirect heating with SiC heating element. It can be replaced from the outside. In addition, each terminal of the heater is made of heat-resistant material.

(3) Slow cooling zone.

The slow cooling zone adopts natural air cooling. Equipped with sufficient length, heat preservation with heat insulation material, has the effect of restoring carbon content. This zone and the sintering zone are integrally processed from the same heat-resistant cast steel.

(4) Cooling zone.

The cooling is divided into three stages. The bottom of the first section is processed into a boat shape. This design is to speed up the flow of water. To prevent the adhesion of scale and other blocking water flow, resulting in high temperature at the bottom and cracking of sintered parts. In order to facilitate the cleaning of scale, etc., cleaning ports are provided in each area.

3) Precautions for use

(1) The operating temperature must be strictly limited, within the range of 1120～1150℃, otherwise the life of the mesh belt will be greatly shortened.

(2) The main forms of mesh belt failure are: deformation and elongation exceeding the allowable elongation range of 10% to 20%; the material of the mesh belt wire is reduced in cross section due to oxidation, carburization and fatigue, resulting in fatigue cracks or even fracture. The service life of the mesh belt is short (about 6-9 months), and the cost of the mesh belt is high.

(3) The furnace door is always open, leaving a gap to allow the green compact to just pass through. This kind of furnace needs a lot of protective atmosphere.