RU2365637C1 - Method of refrigeration of rails after rolling and cutting - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to ferrous metallurgy, in particular to the heat treatment of rails. After being cut with the saws, 25 m long rails of type R65 are delivered sidelong to the cooling device with the temperature of 900-1000°C, then they are put opposite the cooling device with the ends of the rails projecting by 1 m over the cooling device. Compressed air blows on the surface of the rail head with the rate of 10-35 m³/min and the pressure of 3-5 atm and the temperature of 10-30°C or water is sprinkled with the rate of 1-5 l/min and the temperature of 10-30°C for 1.5-2.5 min.

EFFECT: reduced horizontal and vertical rail curvature as well as residual stress.

2 tbl

Description

The invention relates to ferrous metallurgy, in particular to methods for cooling hot-rolled railway rails.

There is a method of cooling the rails after rolling on the refrigerators in the "on the side" position until the magnetic properties appear in them, after which the rails are transferred to the delayed cooling wells using magnetic taps [1]. A significant disadvantage of this method is the significant curvature of the ends of the rails in the horizontal and vertical plane, as a result of which there is a need for cold straightening of the rails, which adversely affects the magnitude of the residual stresses.

There is also a known method of cooling rails after rolling, in which, during cooling, compressed air, water, or a steam-air mixture, or another soft cooler [2] is supplied to the upper lateral surfaces of the ends of the rails up to 1 m in the temperature range 800-600 ° C.

Significant disadvantages of this method are:

1. The lack of straightness of the rails in the vertical plane due to the uneven cooling of all elements of the rail profile.

2. The need for cold dressing in the vertical plane to ensure the straightness of the rails.

3. The probability of formation of quenching structures from the rail surface increases.

The desired technical results of the invention are: reducing the curvature of the rails in the horizontal and vertical planes, minimizing forces during cold dressing and ensuring minimal residual stresses.

To this end, a method is proposed for cooling the rails after rolling and cutting, including cooling on the refrigerators in the “on the side” position, characterized in that compressed air is supplied to the rolling surface of the rail head, excluding their ends 1 m long, in the temperature range 900-1000 ° C. with a flow rate of 10-35 m ³ / min at a pressure of 3-5 atm and a temperature of 10-30 ° C or water with a flow rate of 1-5 l / min and a temperature of 10-30 ° C for 1.5-2.5 minutes.

The claimed limits are selected experimentally based on the requirements for straightness, microstructure and residual stresses of rails made of carbon steel.

The method was implemented in an industrial environment in a rail and beam workshop on P65 type rails 25 m long. Laminated rails after cutting on saws are fed in the “on the side” position to the cooling device. The cooling device includes 5 sections 4 m long. Each section consists of perforated boxes that are connected to the water supply regulators. By adjusting the volumes of water or air supply, the necessary cooling conditions are created, providing a minimum temperature gradient between the head and the bottom of the rail.

The rail is set in the cooling device at a temperature of 900-1000 ° C. Each rail is positioned opposite the cooling device, with the ends of the rail projecting behind the cooling device to a length of 1 m. Then, a cooler is supplied to the rail head for 1.5 to 2.5 minutes, while the neck and sole of the rail are protected from the cooler by a screen. Due to the short-term intensive cooling of the surface of the head, the temperature of the head is aligned with the temperature of the sole. After stopping the supply of cooler, further cooling is carried out in conditions of natural air convection.

After cooling, the microstructure of the metal was investigated, and the deflection arrow and residual stresses were determined.

The technological parameters of the cooling of the rails are shown in table 1. The results of measurements of the deflection arrows and residual stresses, as well as studies of the microstructure are presented in table 2.

The proposed cooling method has improved the straightness of the rails, to obtain low residual stresses with a satisfactory pearlite structure.

Information sources

1. V.V. Polyakov, A.V. Velikanov. The basics of rail technology. - M.: Metallurgy, 1990.416 s.

2. AS of the USSR No. 227357, class C21D 9/04.

Table 1 Technological parameters of rail head cooling in a cooling unit Rail number Rail temperature, ° С Rail head cooling mode Cooling time, min Water consumption, l / min one 1000 1,5 thirty 2 980 1.8 thirty 3 950 2 25 four 940 2.1 twenty 5 930 2,3 twenty 6 920 2.5 fifteen 7 900 2.5 fifteen

table 2 Test results Rail number Rail deflection arrow, mm Groove divergence, mm Rail microstructure one 10 1,2 Perlite 2 10 1,5 Perlite 3 5 1,0 Perlite four 6 1,0 Perlite 5 10 1,2 Perlite 6 5 1,0 Perlite 7 10 0.9 Perlite

Claims (1)

A method of cooling rails after rolling and cutting, including cooling the rail in refrigerators in the side position, characterized in that the rolling surface of the rail head is cooled from a temperature of 900-1000 ° C for a length of 1 m from their ends by supplying compressed air with a flow rate of 10- 35 m ³ / min at a pressure of 3-5 atm and a temperature of 10-30 ° C or water with a flow rate of 1-5 l / min and a temperature of 10-30 ° C for 1.5-2.5 minutes.