JPS5856733B2 - Method for manufacturing circular workpieces - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for manufacturing a circular workpiece.

More particularly, the present invention relates to a method for producing circular workpieces from hypereutectoid steel produced after quenching of martensite with a low carbon content having a transition detail structure.

Centrifugal casting, ie the casting of metal in a high speed rotating ingot mold of a centrifugal casting apparatus with a vertical or horizontal rotation axis, is often used as a modern casting method.

Therefore, the rotation speed is determined by the type of metal and the cooling rate, whether using a temporary sand mold or a permanent mold.

This method is used for the production of solid rolling shapes, tubular, sleeve-like, annular products and small articles produced in mass quantities from special steel.

The use of molten metal is very good as there are no shrinkage pores and there is little formation of segregations brought to the surface of the molten metal by centrifugal force.

This advantage has over steel, especially from an economical point of view.

This method has been investigated in detail for various fields of application.

To produce hollow circular workpieces from centrifugally cast tubes, the part is first cut to a width corresponding to the width of the final product, and then this part is formed by casting or rolling into the desired shape. Ru.

The semi-finished product of the anti-friction bearing ring is produced immediately after being removed from the casting in a centrifugal casting machine at a temperature of 1050-900°C.

Hollow circular workpieces are formed from rotating centrifugally cast hollow solids, for example ingots or objects of different shapes, from which tubes are formed that are cut into smaller parts.

These smaller parts are then processed by rolling, forging or swaging; after machining they are heat treated and finished to optimum hardness.

All these methods are to some extent effective manufacturing methods since they allow direct casting of semi-finished products by centrifugal casting and by reducing intermediate semi-finished products with relatively high savings in material.

However, these have the general drawback that the heat supplied to the manufacturing process during casting, molding and further heat treatment is not fully utilized.

At the same time, the additional heat must be supplied to the product being processed into processing steps that are accomplished at temperatures higher than ambient temperature.

It is therefore an object of the present invention to provide a method for the production of solid, rotating-shaped articles by centrifugal casting, in which the heat originally supplied to the molten steel is utilized to a high degree, without having the disadvantages of methods known in practice. It is useful and advantageous to try.

It is therefore an object of the present invention to produce circular workpieces, e.g. An object of the present invention is to provide a method for manufacturing an anti-friction bearing ring from a ring that has been cleaned from impurities.

According to the invention, the ring obtained by centrifugal casting or by cutting a centrifugally cast hollow ingot is cooled to a temperature that is at most 100°C lower than the casting temperature by the eutectoid transformation temperature of the steel, and then Up to 10 above the transformation temperature
After heating to a temperature 0°C higher and reaching a spherical pearlite structure, it is usually heated to 850-950°C at a maximum of 11
The temperature is raised to 50'C, and the semi-finished product is then shaped, for example by rolling, quenched from above the temperature of eutectoid transformation, and tempered for about 1 to 3 hours at a temperature of about 150 to 250C. (See Figure 1).

To this end, the surface of the ring is cleaned, for example from surface sag due to machining or other impurities, before cooling from the casting temperature to a temperature at most 100° C. below the eutectoid transformation temperature of the steel.

Before forming, especially before rolling, this ring usually has a temperature of 850-9
50° C. to a maximum of 1150° C. and then cooled to a temperature within the range between the eutectic temperature and the martensite generation temperature at a cooling rate of at least 50° C./sec (second
(see figure).

Compared to known methods, the present invention makes it possible to fully utilize the centrifugal structure and the heat required for the subsequent forming and heat treatment as well, so that solid rotating shapes, such as large-sized bearing rings for rolling bearings, can be This is based on the fact that when manufacturing certain large articles, the heat once supplied is sufficient for the entire manufacturing process.

The manufacture of bearings of small dimensions requires only a small additional heating of the material relative to the level of processing temperatures.

When manufacturing a product according to the invention, the method typically includes:
For example, by melting under vacuum or under sludge or otherwise, the rotating ingots, for example cylinders, are centrifugally cast from previously cleaned steel.

The temperature of the eutectoid transformation of the steel used or perhaps up to 1
While partially cooling these to temperatures as low as 00°C,
The ingot is divided into rings and all slag layers or other impurities are removed from it. After cooling this ring to the eutectoid transformation temperature or up to 100 °C below it, the ring is heated to a temperature higher than the temperature, thereby spheroidized, and usually
After being heated again to a temperature of 50 DEG to 950 DEG C. and up to 1150 DEG C., they are shaped in a suitable manner, for example by rolling.

According to another processing method, a ring heated to a maximum of 1150°C, usually 850-950'0°C, is cooled to a temperature between the temperature of eutectoid transformation of steel and the temperature of martensite generation, and then formed. , quenched, and about 150-250℃
tempered at a temperature of

This method of producing products with a circular rotating shape from centrifugal casting semi-finished products is useful not only for the production of bearing rings, but also for the production of rings for steam engine rotors, wheels for rail vehicles, such as wheels for railway vehicles, gear rims, etc. It has the advantage that it can be applied in the same way.

The advantages of this solution become even clearer from the examples below, which explain the features of the invention even more clearly and do not limit the scope of the invention in any way.

Examples 0.7-0.8% by weight carbon, 2% by weight manganese, 2
A steel having a chemical composition of % silicon, 1% chromium, less than 0.03% phosphorous and sulfur, and the balance substantially iron was produced by a steelmaking process in an electric arc furnace.

This steel was cast in a rotating ingot mold that was rotated around a horizontal axis of rotation at a rate of 800 revolutions per minute and allowed to crystallize.

The weight of the product obtained in this way was approximately 3 tons, and the outer diameter was 380 mm.
A hollow ingot of mm1 length 4,400 mm was removed from the mold while still hot and cut into 24 rings with a rotary saw.

This ring is cooled below the temperature of the eutectoid transformation and again
The mixture was heated to 60° C., whereby granulation of perlitic cementite progressed.

The granulated part is heated again to 820°C and rolled with a mandrel between a mandrel and a rolling disk.
A product was molded whose shape approximately corresponded to the inner and outer rings of a 3080 type bearing.

Immediately after rolling, the finished material was quenched in an oil bath at a temperature of 800°C.

After quenching, this material was tempered at a temperature of 170°C for 3 hours,
The product was finished by machining, including grinding.

According to the method of the present invention mentioned in the example, the processing time is substantially shorter than the methods currently used because rough rolling of the ingot is not required as well as dividing, swaging, punching, ring forging, etc. This saves about 12 hours.

The machining time is likewise reduced by 205 minutes.

The total time savings is therefore approximately 15 hours per bearing.

Furthermore, approximately 50% by weight of liquid ingot steel is saved.

The properties of the produced ingot were improved by about 15%, calculated according to the state of the art.

[Brief explanation of drawings]

The attached drawing is a graph showing the temperature change of the workpiece over time during the treatment process from casting to tempering when the method of the present invention is applied. FIG. 2 shows the temperature process when forming progresses, and FIG. 2 shows the temperature process when forming proceeds below the eutectoid transformation temperature of the steel after quenching.

Claims (1)

[Claims] 1. Casting a ring-shaped semi-finished product by centrifugal casting, cleaning the semi-finished product from a layer of slag and other impurities, and converting the ring-shaped semi-finished product from the casting temperature to the eutectoid transformation temperature of the steel structure. cooled to a temperature that is at most 100°C lower, and heated again to a temperature that is at most 100°C higher than the eutectoid transformation temperature,
After obtaining a spherical pearlite structure, the temperature is increased to 1150 ℃.
℃ to austenitize the structure, molding the product at a temperature higher than the eutectoid transformation temperature, then quenching from the molding temperature, and tempering to a temperature range of 150 to 250°C. A method for manufacturing a circular workpiece from hypereutectoid steel produced after quenching low carbon content martensite having a transition detail structure. 2 Producing a ring-shaped semi-finished product by centrifugal casting, cleaning the semi-finished product from a layer of slag and other impurities, and heating the ring-shaped semi-finished product from a casting temperature of up to 100 °C below the eutectoid transformation temperature of the steel structure. temperature, then heated again to a temperature that is at most 100°C higher than the eutectoid transformation temperature,
After obtaining a spherical pearlite structure, the temperature is increased to 1150 ℃.
°C to austenitize the structure, then cooling at a cooling rate of at least 50 °C/sec to a temperature in the range between the eutectoid transformation temperature and the martensite generation temperature, and forming the article at this temperature; Quenched from the molding temperature and 15
A method for producing a circular workpiece from a hypereutectoid steel produced after quenching a martensite with a low carbon content having a transition detail structure, characterized by tempering to a temperature range of 0 to 250°C. .