Heat treatment is a metal hot working process in which the material is heated, kept warm and cooled in solid state to obtain the expected structure and properties.
Heat treatment fixture is designed and manufactured mainly based on the adaptability of furnace type, and suitable for the heat treatment of commonly used large quantities of workpieces.Its role is to clamp and load the workpieces,from entering into the furnace and heating, cooling process to reduce the workpiece heat treatment deformation, complete the whole heat treatment process.
Since the shapes and sizes of the workpieces are different, and the furnace types of heat treatment are various, the fixture used for heat treatment is also diverse. We should reasonably design and make convenient and flexible fixture according to the actual working conditions of the workpieces they handle.
- Design of Heat Treatment Fixture
Before design,we should make better understanding on the specific heat treatment equipments and process, the specific situation of the product to be processed, the selected specific alloy performance, especially the thermal performance.The corresponding 3D computer software and the corresponding stress analysis software will be very helpful during our design work.
Attention in fixture design should be paid:
(1)We should make a specific analysis of the workpiece structure and working condition to meet the technical requirements to the greatest extent.
(2) It ensures that the fixture can safely and reliably carry the workpieces to complete the heat treatment process, and has a long service life.
(3) It ensures that the workpiece loaded on the fixture is uniformly heated, carburized, carbonitriding, and evenly cooled.
(4) It loads as many workpieces as possible to improve heat treatment production efficiency and reduce energy consumption.
(5) It gives consideration to the universality of fixture as far as possible, reduce fixture types, simplify fixture management and reduce costs.
(6) It minimizes fixture materials and manufacturing costs.
- Material of Heat Treatment Fixture
Functions of contained elements are as below:
(1) Cr: oxidation resistance, corrosion resistance;
(2) W,Mo,Co,Cr.V: solid solution strengthening;
(3) Al,Ti,Nb,Ta: precipitation strengthening;
(4) B,Zr,Mg,Rare earth element : grain boundary strengthening.
- Types of Heat Treatment Fixture
(1) Heat-Treatment Tray Series
(4) Well Type Furnace Fixture Series
(5) Fixture Application
Common Jig for Pallet Type and Box Type Heat Treatment Furnace
In order to make the furnace gas unobstructed, heating uniform, and make the workpiece stable, we can design special heating chassis, pad, used for workpiece normalizing, annealing, quenching, tempering and so on.
FIG (a) is a heating chassis made of cast steel. Its size and shape depend on the size of the trolley. The structure can be designed as a grid or a strip.
FIG (b) is the pad block,which is used to support the workpiece;
FIG (c) is a pad block,which is used to support circular workpieces such as impeller;
FIG (d) is a v-shaped pad block,which is used to support axial workpieces.
Fixture for Salt Bath Furnace
Small and medium-sized workpieces after salt bath furnace heat treatment have different shapes. According to the shape of the workpiece, there are many special tools and fixtures designed for quenching heating, cooling and tempering. The commonly used ones are shown in FIG 4-7.
FIG (a), (d) and (f) are used to suspend various small workpieces for quenching;
FIG (b), (e) and (I) are used for quenching and tempering smaller cylindrical workpieces;
FIG (b), (c) shape of the fixture and the fixture bit, reamer and other parts requiring local quenching.Quenching with the above fixture ensures the dimensional consistency of the workpiece heating parts;
FIG (g), (h), (j) can be used for all kinds of small workpieces, such as bolts, bolts, nuts, etc. Tempering;
FIG (a), (d), (f) and (k) can be used to suspend various workpieces for tempering.
Jig for well type furnace, carburizing furnace and nitriding furnace
The workpiece processed by this kind of equipment is mainly slender, and the design of fixture must ensure the vertical heating, quenching and tempering of the workpiece.For the treatment of small and medium carburized parts and nitrided parts, the corresponding fixture can also be designed.
The Hanging Form of the Workpiece of Vertical Hanging Shaft
FIG (a) is used for banding all kinds of slender pieces for annealing and tempering;
FIG (b)(c) is used for vertical hanging all kinds of slender pieces for quenching, tempering, carburizing, nitriding treatment;
FIG(d) for small and medium-sized parts carburizing, nitriding treatment;
FIG (e) is used for binding or hanging slender pieces for carburizing and nitriding treatment.
- Basic requirements for heat treatment fixturemanufacturing
(1) Good Heat Resistance
Generally high temperature load workpiece fixture is required to have better heat resistance and a certain corrosion resistance, in order to prevent serious oxidation of workpiece. Some also require anti-carburization.In order to meet these requirements, the selection of materials is generally considered.
(2) A Certain High-temperature Strength
High-temperature strength refers to that the workpiece loading fixture can bear the weight of the workpiece being heated at high temperature for a long time, and the fixture does not suffer from serious deformation or even disassembly.The high temperature strength of the fixture is guaranteed by the material and the structure of the fixture.But if the structure is too strong, the weight is too large, absorbing too much heat, so that the unit energy consumption of the workpiece increases, heating time, resulting in the rise in production costs.
(3) Cost-effective Alloy Materials
Heat treatment fixture is a kind of vulnerable parts, the main form of failure is high temperature oxidation thinning, strength seriously decreasing.The process of investment casting and welding are often used to make fixture.Controlling fixture material and fixture cost is an important aspect of controlling heat treatment production cost.
Eternal Bliss Alloy Casting & Forging Co, Ltd.
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