The method of thermal hardening train bandages

 

(57) Abstract:

The invention relates to heat treatment of rolled rings and bands. The objective of the method is to increase the intensity of cooling of the outer layers of metal bands without changing the chemical composition of the steel, cooling water temperature and a radical change in technology. This is ensured by the fact that in the method of thermal hardening train bandages containing heat bandages feet in the oven ROWLOCK type to temperature austenitic, exposure at this temperature, rapid cooling of the foot bandages in the tank with water to the tempering temperature of the forced mixing of cooling water of the internal zone of bandages and vacation, additionally are mixing the cooling water of the outer areas of the foot tires with the addition of new portions of water, which impart a rotational movement around the feet of bandages, and the addition of new portions of the cooling water in the outer area passes through every 850-900 mm height of the foot. 2 Il.

The invention relates to heat treatment of rolled rings and bands and can be used in ferrous metallurgy in the manufacture of products such as bodies of rotation.

T is speyeria devices [1] and feet in water [2, the prototype]. The second method is more productive and more often used in practice. It involves the following process operations: heat bandages feet in furnaces ROWLOCK type to the temperature of austenitization, exposure at this temperature, rapid cooling of the foot in the tank with water to the tempering temperature of the forced mixing of cooling water of the internal areas of the foot bandages and leave. In this way stop the train tyres height of 3.6 m and a diameter of up to 1260 mm (foot 25-22 band), total weight 5-12,5 ton heat up in the oven ROWLOCK type to temperature 830-880oC. the Duration of heating of the feet of 1.5-2.0 and shutter speed of 1.5-2.0 hours, depending on the carbon content of the steel and the weight of the foot. After heating foot tires lowered into the quenching tank with water (Fig.1), where rapidly cooled to a temperature of holidays within 190-230 C. While the internal zone of the water is stirred by means of compressed air supplied from the bottom of the quenching tank. The water temperature in the quenching tank 40-50oC. Hardened foot bandages with a temperature of at least 300oC serves to vacation furnaces, where it is maintained at 480-520oC for 2.5-3.5 hours (heating+extract). The cooling shrouds the om method is the low level of acquired properties (tensile strength and hardness) external (working) layers of metal bands - accordingly to 95 kgf/mm2and up to 290 HB. When the hardness of the metal rails up to 450 HB and optimal from the point of view of durability in operation with respect to the hardness of the metal rails and tires, is equal to HBp/HBto=1,1, there is a need to raise the level of hardness of the metal bands to 350 HB. To reach this level by the use of known economic technologies of thermal hardening train bandages feet is very difficult.

The task of the claimed method of thermal hardening of shrouds is to increase the intensity of cooling of the outer layers of metal without changing the chemical composition of steel, water temperature and radical change in technology.

The problem is solved due to the fact that in the method of thermal hardening train bandages containing heat bandages feet in furnaces ROWLOCK type to the temperature of austenitization, exposure at this temperature, rapid cooling of the foot bandages in the tank with water to the tempering temperature of the forced mixing of cooling water of the internal zone of bandages and vacation, additionally are mixing the cooling water of the outer areas of the foot tires with the addition of new portway and the outer area passes through each 850-900 mm height of the foot.

In Fig. 1 is a diagram of the foot bandages in the water tank, where:

1 - bands in the foot,

2 - hardening tank of water,

3 - the internal area of the foot,

4 - pipe for compressed air,

5 - the outer area of the foot,

6 is a pipe for supplying water into the outer area of the foot.

In Fig. 2 shows graphs of the variation of hardness of the metal bands at the height of the foot on the well-known (curve 1) and proposed (curve 2) technology thermal hardening train bandages.

New technology, heat strengthening bands provides for heating of the foot tires in the oven until 830 - 880oC, holding at this temperature for 1.5-2.0 hours, after which the accelerated cooling bandages 1 in the tank 2 with water (Fig.1). When this cooling water in the inner zone 3 feet mixed with compressed air supplied through the pipe 4 under the pressure of 3 ATM. The temperature of the quenching water 40 - 50oC. Additionally lead the mixing of cooling water of the outer zone 5 with the addition of new portions. While cooling the outer zone 5 foot 1 water impart a rotational movement around the foot due to the supply of additional water along the tangent to the generatrix of the outer surface of the foot ban the experience). Adding new portions of the cooling water in the outer zone 5 is carried out every 850 - 900 mm height of the foot with the beginning of this interval from the bottom of the quenching tank 2. The size of this interval is due to the fact that the fall of the mechanical properties on existing technology observed at 7 to 8 bands in the foot from the bottom of quench tank (about 1000 mm from the bottom) at the location of pipelines in the inner zone of the bottom of the tank. Submission of additional portions of the cooling water in the outer area of the tank every 850 - 900 mm provides a more stable mechanical properties of metal bands (Fig. 2). As can be seen from the graphs, the overall level of properties (hardness) of the metal bands significantly higher with the use of new technology and more stable height of the foot. Time, heat strengthening of the stop bands is 150 to 220 C, and the addition of new portions of the cooling water in the outer zone allows you to keep constant cooling water temperature 50oC. heat-treated foot bandages placed in a vacation well, which is maintained at 480 - 520oC for 2.5 - 3.5 hours (heating + extract). Cooling bandages after a vacation exercise in the feet in still air to ambient temperature.

Therefore the intensive cooling of the metal with the higher level (about 17%) and more uniform distribution along the height of the foot properties. Experiments conducted in montageposition shop of JSC "NTMK" showed the adaptability of the method and its ability to implement without large capital expenditures.

Example. In the manufacture of railway tyres diameter, height, thickness, respectively 1060 x 140 x 98 mm (base band) according to GOST 398-81 for freight locomotives with a carbon content in the steel of 0.59 to 0.60% before heat strengthening them gathered in the foot by 22. Stack height 3.2 m (bandages in draft form). Stop bands were heated in the well to 830-880oC, held at this temperature for 2 h, then placed in a tank of water having a temperature of 40-50oC, where the stop bands rapidly cooled within 180 C. While the water in the inner zone of the foot was stirred by means of compressed air supplied from the bottom of the tank through a pipeline under pressure of 2 ATM. Additionally led the mixing of the cooling water of the outer zone with the addition of new portions under a pressure of 3 ATM for the three pipelines with a diameter of 35 mm, located at a distance of 850, 1700, 255 mm from the bottom of quench tank and at an angle of 45oto the plane passing through the inlet pipe and the axis of the foot. Heat-treated foot bandages passed in vacation wells, where videris the e in the pit.

Studies the hardness of the metal bands at the height of the foot showed that she was in the interval 315-335 HB.

The method of thermal hardening of the train bands, including heating of the tyres feet to the temperature of austenitization, exposure at this temperature, rapid cooling of the foot in the tank with water to the tempering temperature of the forced mixing of cooling water and leave, characterized in that the cooling of the outer area of the foot water impart a rotational movement around the feet of bandages with added throughout the cooling time of new portions of water every 850 - 900 mm of the foot.

 

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