RU2527111C1 - Prevention of ring deformation at chemical-physical treatment and shaft furnace to this end - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: chemical-physical treatment of rings in shaft furnace comprises the placing of retort in heating chamber, placing of rings pile in said retort for it to be subjected to said treatment. Prior to said treatment piles of rings are hardened by top and bottom plates of gray iron. Said retort has flat bottom and is placed on heating chamber flat bottom. Note here that bottom plate of gray iron is fitted on return bottom for ring pile to be placed thereat. Then, said pile is hardened by placing top plate of gray iron thereon at aforesaid treatment. Said shaft furnace comprises heating chamber to accommodate said retort and cover accommodating saturated gas swirler to gas flows to be uniformly distributed over return height. Said retort has flat bottom and is placed on heating chamber flat bottom. Note here that bottom plate of gray iron is fitted on return bottom for ring pile to be placed thereat. Note here that said pile is hardened by placing top plate of gray iron thereon at aforesaid treatment.

EFFECT: higher surface quality.

6 cl, 2 dwg

Description

FIELD OF THE INVENTION

The invention relates to mechanical engineering, namely to chemical-thermal treatment, in particular to cementation, nitriding, nitrocarburizing of the surfaces of gears and rings from structural, tool and special steel grades to improve the quality and reduce production costs.

Previously, this type of ring bending method was not used during chemical-heat treatment in a shaft furnace; methods for spring biting were known:

1. Patent RU No. 2408737 "Method for the restoration of springs", the authors:

Tebenko Yuri Mikhailovich (RU), Zemlyanushnova Nadezhda Yuryevna (RU), Belkov Evgeny Grigoryevich (RU), Zemlyanushnov Nikita Andreevich (RU).

2. Patent RU No. 2424330 "Method for the restoration of springs", authors:

Tebenko Yuri Mikhailovich (RU), Zemlyanushnova Nadezhda Yuryevna (RU), Zemlyanushnov Nikita Andreevich (RU).

3. Patent RU No. 2296968 "Device for contact covering of springs", authors: Zemlyanushnova Nadezhda Yurievna (RU), Khalfin Marat Nurmukhamedovich (RU).

Characteristics of analogues:

4. Rustem S.L. "Equipment of thermal workshops", Moscow, "Engineering", 1971

5. Nikolaev E.N. "Heat treatment of metals and equipment of thermal shops", Moscow, "Higher School", 1980

6. USSR author's certificate No. 934163, authors: Sosonny A.A., Kucheruk G.E., Makarova N.V.

In all known methods, the shaft furnace (Fig. 1) consists of a metal body, lined with refractory material, item 2. Inside the heating chamber, a heat-resistant retort pos. 1 is placed, on top of the retort is closed by a lid pos. 3 with a fan pos. 4. Space is provided for thermal expansion between the bottom of the retort and the bottom of the heating chamber. The disadvantage of all the above methods of chemical-thermal treatment is the incomplete design of the retort used in shaft furnaces, which limits the use of skimming rings, including BZK.

The design of the shaft furnace is such that the retort located inside the furnace is suspended, which limits the mass of the load. The bottom of the retort is semicircular, which limits the use of slabs to maintain flatness.

Due to the fact that the retort does not have an even solid base, the shaft furnace's capabilities are limited by the mass of loading and preservation of flatness. At high temperature (950 ° C), the ductility of the metal increases by about 5 times. With a slight non-observance of the center of gravity when the mass is loaded into the furnace, there is a change in the flatness of the rings, including the BZK. And non-compliance with flatness over 0.5 mm with ⌀ 771 mm rings leads to marriage.

The closest prototype to the proposed device of a shaft furnace for implementing the method of overcoming ring deformation during chemical-thermal treatment is patent No. 2049296 "A shaft furnace for chemical-thermal treatment", authors: Cheerova A.V., Raskin I.G., Kocheshkov V. M.

The invention relates to furnaces for chemical-thermal treatment of metals. The shaft furnace for chemical-thermal treatment contains a heating chamber with a retort, a lid and a device installed on it to create vortex gas flows and evenly distribute them along the height of the retort. A device for creating vortex gas flows and uniformly distributing them along the height of the retort is made in the form of two vertical coaxial pipes of different diameters, while a pipe with a smaller diameter partially enters another pipe and is made with a blanked upper end and two diametrically located longitudinal slotted holes narrowing in direction to its inner surface, and the ratio of pipe diameters 3: 1.

The disadvantage of the prototype is also that the retort does not have an even solid base, the capabilities of the shaft furnace are limited by the mass of loading and preservation of flatness.

At high temperature (950 ° C), the ductility of the metal increases by about 5 times. With a slight non-observance of the center of gravity when the mass is loaded into the furnace, a change in the flatness of the rings occurs.

The imperfection of the retort design used in the shaft furnace limits the use of ring deflection.

The problem is solved in that the method of chemical-thermal treatment of rings in a shaft furnace involves installing a retort in a heating chamber, placing a stack of rings in a retort, followed by chemical-thermal treatment in it in a stream of saturating gas. Before chemical-thermal treatment, the pile of rings is laced with the upper and lower plates of gray cast iron. The retort is performed with a flat bottom and mounted on a flat bottom of the heating chamber. To prevent deformation of the rings, the lower plate of gray cast iron is installed on the bottom of the retort. A stack of rings is placed on the bottom plate and they are covered with a top plate of gray cast iron by placing it on the stack of rings during chemical-thermal treatment.

The problem is also solved by the fact that the shaft furnace for chemical-thermal treatment of rings contains a heating chamber configured to install a retort and a lid with a device installed therein to create vortex flows of saturating gas and uniformly distribute them along the height of the retort. The retort is made with a flat bottom for installing it on a flat bottom of the heating chamber and loading into it a stack of rings for chemical-thermal treatment. To prevent deformation of the processed rings, the bottom plate of gray cast iron with the possibility of placing a stack of rings on it is installed on the bottom of the retort, and the upper plate of gray cast iron is made with the possibility of installing on the stack of rings to seduce them during chemical-thermal treatment.

Overcoming the deformation of rings, including gears, during chemical-thermal treatment by covering with gray iron plates. The present invention can be used in the production of ball bearings, engineering, automotive and tractor industries, aircraft, space, defense and other industries.

The essence of the method: in the chemical-thermal treatment of rings in a shaft furnace, use plates of gray cast iron in order to cover the rings, including the BZK.

It is known that ring deformation during chemical-thermal treatment is influenced by internal stresses that occur during mechanical processing, phase transformations during the transition from perlite to austenite and vice versa with a change in the metal volume by 3.0-3.6%, uneven heating and cooling, the effect of gravity (since in the austenitic state, ductility increases by about 5 times) and other factors.

The use of a method of covering rings (including BZK) with plates of gray cast iron allows overcoming ring deformation and reducing rejects during chemical-thermal treatment.

Figure 2 shows a method of overcoming ring deformation during chemical-thermal treatment. The planes of the upper plate (pos. 6) and the lower cast iron plate (pos. 7) are straight and parallel to each other. The thickness of the plates (pos. 6; pos. 7) depends on the mass of a single loading of rings (pos. 5) into the shaft furnace for chemical-thermal treatment. The diameter of the plates (pos. 6; pos. 7) depends on the diameter of the ring (pos. 5).

For example: with a one-time maximum load of the BZK ⌀ 771 mm in the amount of 7 pcs. the top plate (pos. 6) and the bottom (pos. 7) should be ⌀ 800 mm and a non-flatness of 0.5 mm. Plane flatness is checked after 30 downloads.

Plates (pos.6, pos.7) are designed to maintain flatness along the diameter of the rings (pos.5).

Due to the mass, the upper plate (pos. 6) does not allow the rings to deform (pos. 5), which is possible due to internal stresses that arise during machining, phase transformations during the transition from perlite to austenite and vice versa with a change in the metal volume by 3, 0-3.6%, uneven heating and cooling, the effects of gravity (since in the austenitic state, ductility increases by about 5 times) and other factors.

With ionic cementation, the surface of the product (rings) is saturated with carbon. To do this, we supply hydrocarbons (kerosene, white spirit, benzene, synthine, etc.) to the retort, where decomposition occurs according to the reaction. The decomposition of hydrocarbons occurs due to pyrolysis at a temperature of 700-800 ° C and further decomposition by cracking at a temperature of 950 ° C.

Positive charged carbon ions are attracted to negatively charged ring steel by convective mixing of the carburizing atmosphere with a fan and settle on the surface of the ring steel for further diffusion into the ring steel. The use of gray cast iron for the manufacture of plates increases their service life compared to steel plates, because the carbon content in gray cast iron is more than 2%, so there is no local saturation of the plate with carbon, leading to a deviation of the flatness of the plate. The cost of gray cast iron is lower than the cost of heat resistant steel. Longer service life and lower cost lead to lower costs. The mass of the top plate is calculated based on the volume of the furnace load.

Achieving the result of the proposed method is carried out using a special device shaft furnace.

The essence of the design of the shaft furnace.

To increase the load mass of the products (rings) and to apply the method of looping the rings, it is necessary to apply a retort with a flat bottom, which is installed on a flat bottom in a shaft furnace, and the upper part of the retort remains in a free state for the possibility of thermal expansion (figure 2).

The rings fill the volume of the retort as much as possible, which leads to an increase in the payload of the shaft furnace, i.e. increase productivity and reduce costs.

The proposed device of the shaft furnace for implementing the method of overcoming ring deformation during chemical-thermal treatment differs from the prototype in that in order to increase the load mass of the rings (products) and to apply the ring bumping method, it is necessary to use a retort with a flat bottom, which is installed on a flat bottom in the shaft furnace, and the upper part of the retort remains in a free state for the possibility of thermal expansion (figure 2). The rings fill the volume of the retort as much as possible, which leads to an increase in the payload of the shaft furnace, i.e. increase productivity and reduce costs.

The invention is illustrated by drawings.

Figure 1 shows a General view of a shaft furnace in section with a retort located inside the furnace in a suspended state:

Pos. 1 - retort

pos.2 - case lined with refractory material

item 3 - cover

item 4 - fan

Figure 2 shows a General view of a shaft furnace in section, where:

Pos. 1 - retort

pos.2 - case lined with refractory material

item 3 - cover

item 4 - fan

pos.5 - ring (product)

pos.6 - top plate

pos.7 - bottom plate

pos.8 - heating chamber

The shaft furnace consists of a metal casing (pos. 2), lined with refractory material, inside of which there is a heating chamber (pos. 8), along the wall of which heating elements are laid. In a flat-bottom retort (item 1) made of a heat-resistant alloy and installed in the working chamber (item 8) so that the lower part of the retort is installed on a flat bottom in the shaft furnace, and the upper part of the retort remains in a free state for temperature extensions, place rings (product). At the bottom of the retort, the lower cast-iron plate (pos. 7) is laid, then a stack of rings is laid and pressed on top by the upper cast-iron plate (pos. 6) in order to reduce deformation.

The retort (pos. 1) is closed by a lid (pos. 3). The fan (item 4) is used to create vortex gas flows and their uniform distribution along the height of the retort.

Due to the mass, the upper plate (pos. 6) does not allow the rings to deform (pos. 5), which is possible due to internal stresses that arise during machining, phase transformations during the transition from perlite to austenite and vice versa with a change in the metal volume by 3, 0-3.6%, uneven heating and cooling, the effects of gravity (since in the austenitic state, ductility increases by about 5 times) and other factors.

With ionic cementation, the surface of the product (rings) is saturated with carbon. To do this, we supply hydrocarbons (kerosene, white spirit, benzene, synthine, etc.) to the retort, where decomposition occurs according to the reaction.

The decomposition of hydrocarbons occurs due to pyrolysis at a temperature of 700-800 ° C and further decomposition by cracking at a temperature of 950 ° C.

The positively charged carbon ions are attracted to the negatively charged steel (ring) with convective mixing of the carburizing atmosphere with a fan and settle on the surface of the steel (ring) for further diffusion into the steel.

Claims (6)

1. The method of chemical-thermal treatment of rings in a shaft furnace, comprising installing a retort in a heating chamber, placing a stack of rings in a retort, followed by chemical-thermal treatment in it in a stream of saturating gas, characterized in that before the chemical-thermal treatment, a pile of rings is lured the upper and lower plates of gray cast iron, the retort is performed with a flat bottom and installed on a smooth bottom of the heating chamber, while to prevent ring deformation, the lower plate of gray cast iron at tanavlivayut the bottom of the retort, which is placed on the stack of rings and carry them zanevolivanie top plate made of cast iron by placing it on a stack of rings with the chemical-thermal processing. 2. A shaft furnace for chemical-thermal treatment of rings, comprising a heating chamber configured to install a retort and a lid with a device installed therein for creating vortex flows of saturating gas and distributing them uniformly along the height of the retort, characterized in that the retort is made with a flat bottom for installing it in a heating chamber, made with a flat bottom, and loading into it a stack of rings for chemical-thermal treatment, while to prevent deformation of the processed rings is equipped with mounted on its bottom with a lower plate of gray cast iron to place a stack of rings on it and an upper plate of gray cast iron made with the possibility of installing on a stack of rings for mastication during chemical-thermal treatment. 3. The shaft furnace according to claim 2, characterized in that to ensure thermal expansion, the upper part of the retort is installed in a free state. 4. The shaft furnace according to claim 2, characterized in that the planes of the upper and lower plates are made rectilinear and are installed in the retort parallel to each other. 5. The shaft furnace according to claim 2, characterized in that the thickness of the plates is selected depending on the mass of a one-time loading of a stack of rings into the shaft furnace. 6. The shaft furnace according to claim 2, characterized in that the diameter of the plates is selected depending on the diameter of the ring.

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