SU1399360A2 - Method of heat treatment of rails - Google Patents

Abstract

The invention relates to the heat treatment of steel and can be used in the manufacture of railway rails. The invention is an improvement of the method of heat treatment of rails by auth.St. ,; No. 1239170. The purpose of the invention is to increase the operational durability of rails by increasing the uniformity of structure and properties over the sole section. In the known method, which involves volumetric heating of the rails, cooling the head and the sole with subsequent self-tempering (tempering), cooling the sole takes place with a decrease in the supply of coolant as it moves away from the central axial zone of the sole to the peripheral portions, and the cooling of the axial zone is wide 0.3-0.4 widths of the sole produced by supplying 50-70% of the chiller, which comes in to cool the entire surface of the sole. 1 tab. S C /

Description

H: .u ifipcTPHHp RELATES TO THERMAL (lOfafioTKe steel, can be used - P (1.g1uvans1 in the manufacture of railroad rails and is a refinement; P1enstvo (1 understanding of the method of heat treatment: rails according to the bus. No. 1239170. I increasing the operational durability of the rails by increasing the homogeneity of the structure and properties over the sole section.

In the method, which provides for a volume of heating up to the austenitization temperature, cooling the head and the bottom of the rail with a specific cooling rate of the bodies on the sole equal to 0.6-0.8 specific consumption per head at the appropriate time, cooling the soles are produced with a decrease in the flow of the cooler as the soles move away from the central og.v. zone to the peripheral areas in proportion to the thickness of the base layer pen, while cooling the axial zone with the width P, 3-0,. -70% cooler supplied to hlazhdenie entire sole surface.

I Chilling the sole JC by reducing the coolant supply from the central axial zone to the peripheral sections ensures the cooling rates of different sections of the rail base, taking into account the temperature gradient in them and the volume of the cooled metal, simultaneous passage of structural transformations and obtaining uniform structures and properties over the sole section, i Cooling with the supply of a larger amount of cooler to the central Isev zone of the sole provides the required cooling rate of the most recent m an assessed and high temperature section of the rail foot.

The choice of the nature of the distribution of the flow rate of the cooler across the width of the sole is determined by the following considerations.

In the general case, the cooling rate is determined by the ratio of the area of the body surface to be cooled to its volume. When the specific cooling areas are equal, the cooling rate largely depends on the specific thickness of the cooled layer under other equal conditions (for example, temperature, the influence of adjacent layers). etc.) Determine the rate of cooling in various vylennye-elementary sections

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5 0 5

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They have the bottom of the rail with the same surface area to be cooled, and also take into account the real change in temperature conditions in these sections due to the different degree of heat transfer to the air from the inner (lower) air. the base of the base, the distribution of cooling rates over the width of the sole is established - an increase in the cooling rate occurs in proportion to the decrease in the thickness of the sole. Therefore, in order to equalize the cooling rates across the width of the sole, it is necessary to reduce the coolant supply towards the edges of the sole, and the reduction should be proportional to the decrease in the thickness of the sole.

The restriction of the central zone of the sole, subjected to the greatest cooling, at an interval of 0.3-0.4, the width of the sole, is determined by the structural shape of the profile of different types of rails (thickness of the neck, size of the radius of the conjugation of the neck and the sole) and the degree of influence on the cooling process of the sections adjacent to the sole necks.

The flow rate of the coolant supplied to the central part of the sole, which is 50-70% of the total surface cooling charge, is due to the achievement of the necessary cooling rate of the most massive part of the sole, which also has a significant thermal effect from the rail neck. The width of the specified range is due to the different distribution of metal over the cross section of the base of various types of rails. For example, for rails P43, having a thicker sole with a small width, the equal cooling rates across the width of the sole is achieved by applying 50% of the cooler to the central zone, and for rails P50, P65 with a wider and thinner sole, 60-70%.

Going beyond the limits of the coolant consumption range leads to an unequal cooling rate across the width of the sole and the formation of heterogeneity of structures and properties over the cross-section of the sole.

Differentiated by the width of the sole, cooling is achieved in various ways depending on the type of cooling device used. For example, during spray cooling

the soles reduce the diameter of the holes towards the peripheral areas of the sole; when cooled with sprayed water (nozzles), spray nozzles with the highest density in the center and gradually decreasing towards the edges are used.

The proposed method can be implemented by heat treatment of the rails by a known method, for example on a roller, type. After volumetric heating in the furnace up to the austenitization temperature, the rails are individually supplied to the unit, where, during the forward movement of the rail, its head and sole are cooled with a smaller amount of coolant supplied to the sole (0.6-0.8 of the flow per head in this section) , while cooling the soles begin 2-10 seconds after the start of cooling of the head. In order to obtain a homogeneous structure and properties over the cross section of the sole, the latter is cooled by producing a differentiated supply of cooler to the width of the sole. Depending on the type of rail being processed, the amount (supplied within the specified range) of the cooler supplied to the central part of the sole is set and the degree of decrease in the flow rate of the cooler towards the peripheral parts of the sole is determined in proportion to the decrease in the thickness of the sole.

Example, The proposed method has been tested in industrial conditions during heat treatment of P50 rails made of converter steel. Heating to austenization temperature (820-840 C) was carried out in a continuous heating furnace. After turning the heated rails into the head-down position, the roller-type rail and rail assembly (RZA) was set, where the head and the sole of the rail moving at a certain speed were cooled using cooling devices installed between the transport rollers. Cooling of the head was made by jets of water through sprayers, cooling of the sole by sprayed water using nozzles. The mode of cooling of the head and the sole was set in accordance with known modes. Gap-type nozzles were used to provide a cooling width differentiated sole. By changing the main

the geometric dimensions of the nozzle (radius of the rounding of the bottom of the inlet channel, the angle of the flame of the torch, the size of the outlet, and others) controlled the density of irrigation of various sections along the width of the bottom.

Testing the proposed method gave the results shown in the table.

When cooling with differentiated by the width of the sole supply of the cooler, the heterogeneity of the MexaHmiecKHx properties over the cross section is reduced by 70-100%

soles as compared to cooling by a known method, and when cooling the central axial zone of the sole with the coolant supply in the interval for the specified values (50-70% of the flow rate for

cooling the entire surface of the sole) the non-uniformity of the properties across the width is practically eliminated (does not exceed 5% with 63% coolant applied to the central part of the sole).

The use of the proposed method of heat treatment of rails with cooling differentiated by the width of the bottom provides a reduction of 70-100% compared with the known method

heterogeneity of structures and mechanical properties of the metal over the cross section of the sole, reduction of the level of residual stresses in the feathers of the sole and alignment of their values along the width of the sole, which makes it possible to increase operational durability. rails by 3% due to a decrease in the removal of rails from the track due to pokes, soles, leading to rail fracture.

Claims (1)

Invention Formula The method of heat treatment of rails by ed. Sat No. 1239170, characterized in that, in order to increase the operational durability of rails by increasing the uniformity of structure and properties over the sole section, the sole cooling is performed with decreasing the coolant supply as the central axial zone is removed from the peripheral areas, the thickness is reduced the sole of the sole, while cooling the axial zone with a width of 0, 3-0, and the width of the sole, is supplied by supplying 50-70% of the coolant supplied to cool the entire pinholeness of the sole.