The physical and mechanical properties of
the metal powder can be obtained by sintering. For multicomponent liquid phase
sintering, the sintering temperature is generally lower than that of refractory
metals, but higher than that of fusible metals.
1. Powder metallurgy sintering
process
After the powder forming process, sintering and
post-treatment (such as finishing) are required. Sintering and finishing are
generally done separately. That is, sintering finished, and then put on the press
finishing. For multicomponent liquid phase sintering, this separate process
makes the quality of products difficult to be guaranteed. The sintering
temperature is low, the fusible metal is not melted, and the bonding
enhancement effect is not obtained. High sintering temperature, fusible metal
melting, and easy loss and re-accumulation, will also affect the quality of
products. The ideal method is to press in the furnace immediately when the
sintering temperature is reached. The following describes the structural
principles of some pressurized and sintered integrated equipment used in
aviation powder metallurgy for high temperature sealing materials of copper or
steel in the range of 500 ~ 900 ℃, pressing in the range of 50 ~ 2 000 kg and controlling accuracy of
±1.5% of the set value.
In order to achieve pressure sintering of powder
metallurgy, the following problems need to be solved in the equipment:
(1) when the products are heated in
the reducing atmosphere, the sealing of the furnace cover and the furnace tank
must be ensured first, and the gas cannot be leaked. When the furnace tank is
expanded by heat, when the tank body extends, there should be expansion and
contraction space, can not be gored;
(2) pressurization is carried out
in the 900 ℃ high temperature furnace tank, and the extrusion mechanism is set
in the furnace tank. Firstly, the high temperature strength of metal materials
should be considered, and secondly, the sealing of sports pairs should be
considered. They cannot produce creep, cannot be bitten to death, and the
friction resistance should not be too large;
(3) the melting point of copper
alloy is generally more than 750 ℃. Once the sintering temperature reaches, the pressure should be followed
up immediately, and the pressure should be given as much as it is set, followed
up dynamically, and the pressure should be kept stable.
(4) the heating process and
pressurizing process are controlled by PLC (programmable control) to ensure the
repeatability of sintering process.
2. Equipment structure features
The invention relates to a steel - based product with
copper alloy powder as adhesive, pressurized and sintering furnace.
In this furnace, there is a fixed pressure head of metal
embedded in the furnace body, furnace frame, elevator, furnace cover trolley,
furnace tank and pressure cover. The upper end of the fixed pressure head is
connected with the beam of the furnace body, and only the pressure plane inside
the furnace is exposed. The furnace body, furnace frame, beam and fixed
pressure head are rigidly connected. When the bottom plate of the furnace frame
is welded with the ground embedded iron, a rigid frame member is formed. The
vertical distance between the bearing plane of the upper constant pressure head
and the ground is fixed.
The elevator is set in the pit below the furnace. The upper
plane of the elevator is welded with two tracks, flush with the ground track,
to facilitate the access of the furnace cover trolley. The surrounding plane of
the furnace cover trolley is equipped with two sealing grooves, the inner ring
is sand seal, and the outer ring is liquid seal (emulsion).There are N pressure
springs in the liquid seal tank, which can carry the weight of the furnace.
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