Method of heat treatment of tram bandages

 

(57) Abstract:

The invention relates to heat treatment of ferrous metals and can be used in the manufacture of wheel rims made of carbon steel for tramway rolling stock. The technical result is the provision of modes protivogololednoy processing tram bands in unheated wells, as well as narrowing of the temperature interval between rolling and marking tires. The method includes rolling and marking tires in a hot state, isothermal aging in unheated wells, slow air cooling. What's new is that between rolling and marking the temperature of the metal bands stand in the range of 840 - 880oWith, and the process is isothermal aging is carried out for 0,8 - 1,1 h at 500 - 650oWith subsequent slow cooling to 250oC.

The invention relates to heat treatment of ferrous metals and can be used in the manufacture of wheel rims made of carbon steel for tramway rolling stock.

Tram bandages, and rings made of medium-carbon steel, is made by rolling in a hot state upset and stitched the Ute small (compared to car tires) dimensions - the diameter of 700 mm, width and wall thickness in the range of 90 and 60 mm, weight up to 100 kg, the technology used to manufacture locomotive tyres for railway transport (diameter greater than 1000 mm, width: 145 mm, thickness 90 mm, weight about 450 kg) leads to increased culling platinum and large gradient properties of the metal in various parties.

As a prototype adopted a method of heat treatment of bandages [3] , which involves the following process steps: heating of the billets to a temperature of 1250oC, upsetting the smooth plates, and justify the firmware of the center hole, rolling at a temperature of 850 - 1050oC, branding on the lateral surface at a metal temperature of 800 - 1000oC, a collection of bandages on the feet of 20 pieces and installing them in an unheated wells at a temperature of 300 - 400oC for slow cooling. Such technology in the manufacture of small tram bandages minor mass leads to the analysis of the properties of the metal - temporary resistance from 75 to 95 kgf/mm2the relative elongation of 8 to 14%, the hardness of 230 - 250 HB, and requirements of the consumer properties similar to higher limits specified values. Therefore, up to 15% Bandarenka the absence of isothermal processing results, despite the small cross section of the brace to the culling of up to 2.5% platinum.

Thus, the use of known technology of heat treatment of tram bandages leads to great financial losses in the form of increased marriage on the properties and platinum and low resistance tyres in operation.

The objective of the proposed method of heat treatment of tram tires is providing modes protivogololednoy processing tram bands in unheated wells, as well as narrowing of the temperature interval between rolling and marking tires.

The problem is solved due to the fact that in the method of heat treatment of tram bands, including the rolling and marking in a hot state, isothermal aging in unheated wells, slow cooling in the wells and air cooling between rolling and marking the temperature of the metal bands stand in the range of 840 - 880oC, and the process is isothermal aging is carried out for 0.8 to 1.1 hours at a temperature of 500 to 650oC followed by slow cooling.

The proposed new technology of heat treatment tram bandageoC, the sediment at the press force 3200 ie, smooth plates, justify and firmware of the Central hole in the workpiece, rolling and marking bands on the lateral surface, the temperature of the tyres between rolling and marking is maintained in the range of 840 - 880oC. Here are significant as the selected range, and place in the technological chain of control: the temperature of the end of the hot deformation has a significant impact on the size distribution and its properties, while the lower chapel (840oC) associated with the possible formation of microcracks in the places of drawing marks (minimum allowable temperature for this reason), and the upper limit (880oC) ensures virtually 100% yield tires on the mechanical properties of the metal. The selected location of the temperature control between the rolling and the stigma associated with the ability to regulate this temperature bandage-rolling mill and between the rolling mill and lamiales. Then the bands gather at the foot of 20-25 pieces and placed in cold, but warmed up to a temperature of about 400oC wells. The temperature in the wells with the footsteps of bands with temperature 700oC is aligned to a temperature of 600 - 650oC and within 0.8 to 1.1 Cassia hydrogen range 650 - 500oC. As shown by the experiments, this time isothermal exposure for section 60x90 mm medium carbon steel is enough to reduce scrap tires on platinum from 2.5 to 0.6%. The lower range of the exposure time (0.8 hour) corresponds to the banding steel with a carbon content of 0.6% or less, and the upper (1.1 hours) - for steel, carbon 0.7% and more. Subsequent cooling of the stop bands together with the well to a temperature of 250oC provides the minimum distortion profile tires.

Thus, the use of the proposed method of heat treatment of tram bandages provides a mode protivogololednoy processing in unheated wells with the exception of marriage platinum, and the narrowing of the temperature range and its control between rolling and marking it helps to enhance the mechanical properties of metal bands.

Example. In the manufacture of tram bands of steel with a carbon content of 0.7%, an outer diameter of 716 mm, a width of 88 mm, an inner diameter of 594 mm and a weight of 97 kg initial workpiece weight 125 kg was heated in a methodical and chamber furnaces to a temperature of 1250oC, two systems smooth plates on the press 3200 ie, and at the same press after RA is Ali the temperature of the metal, which regulate the supply of cooling water. The final temperature level bands 840 - 880oC regulated before marking with air baths. After marking the bands gathered at the foot of 20 pieces and metal temperature of about 700oC was placed in an unheated wells that previously using the gas nozzle was heated to a temperature of 400oC. Exposure bands in the wells was carried out at a controlled temperature of 650 - 500oC for 0.8 hours. With decreasing temperature below 500oC until the expiration of the specified time the well is heated by a gas burner. Then the bandages slowly cooled together with the well to a temperature of 250oC. the party into 240 pieces of experimental - industrial batch of tram bandages on platinum marriage was not, in the interim resistance rejected 2 of the bandage.

Literature

1. Shifrin, M. Y., Solomonic M. I. Production of solid-rolled wheels and tires. - M.: metallurgy, 1954, S. 474-484.

2. USSR author's certificate N 619265, 1978.

3. The production of tires and tracks. Technological instruction JSC "NTMK" TI 102 - P. SP - 41. - S. 54-66.

Method of heat treatment of tram bandages, including procate in wells and air cooling, characterized in that between rolling and marking the temperature of the metal bands stand in the interval 840-880oC, and the process is isothermal aging is carried out for 0,8-1,1 h at 500-650oC followed by slow cooling to 250oC.

 

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