RU2405638C1 - Method of rolling p50 rails - Google Patents

Abstract

FIELD: process engineering. ^ SUBSTANCE: proposed method comprises calibration of rolls, adjustment of stands, rolling and process control. In rolling, finishing stand rolls are used, their surface being hardened by electric-arc hardening to micro hardness of 7500-8000 MPa. Control of geometrical sixes of rail profile is performed using gages. Note here that in finishing pass rolling is started using the gages with departure from rated values within negative tolerances: rail height - 0.5 mm, web height - 0.5 mm, head width - 0.5 mm, foot width -1.0 mm, web thickness - 0.5 mm, blade height - 0.5 mm. Note that rolling is terminated on reaching geometrical parametres of rail profile corresponding to gages with departure within positive tolerances: rail height - 0.8 mm, web height - 0.3 mm, head width - 0.5 mm, foot width - 1.0 mm, web thickness - 0.8 mm, blade height - 1.0 mm. ^ EFFECT: longer life, stable geometrical sizes of produced rails. ^ 6 dwg

Description

The invention relates to ferrous metallurgy, in particular to rolling production, and can be used in rolling railway rails.

There is a known method of rolling rails, including rolling the rough profile in two-roll T-bars and two-roll or universal rail gauges, rolling the pre-finishing profile in the universal three-roll gauge, and the finishing one in the four-roll universal gauge, characterized in that the sole width is controlled in the pre-finishing caliber, and the neck and sole are crimped in the two-roll section, head compression - in the three-roll section of the caliber using the vertical brook profile stream and the connectors between the collars of the vertical roll and the ends of the horizontal rolls at the places of curvature of the side surfaces of the head with a small radius from the side of the sinus, and in the fine four-roll caliber, the connector from the side of the rail head between the shoulders of the vertical roll and the ends of the horizontal rolls is carried out at the junctions of the rolling surface with the side surfaces of the rail head [1 ].

A significant disadvantage of this method is the insufficient use of the resource of the fine caliber.

There is also a known method of rolling railway rails using only two roll calibers in the rolling scheme [2].

Significant disadvantages of this method are the unstable execution of the finished rail profile, as well as the insufficient operational stability of the rolls.

There is also known a prototype method of rolling rails of type P50, including calibrating rolls, adjusting stands, rolling in rough and finish calibers and controlling the process using templates [3].

Significant disadvantages of this method are:

- unstable obtaining the required geometric dimensions of the rail profile;

- high weight per linear meter of rails;

- insufficient operational stability of the rolls;

- high consumption of rolls for hire;

- high consumption of time for transshipment.

The desired technical results of the invention are:

- obtaining the required geometric dimensions of the rail profile;

- weight reduction per meter of rails;

- increase the operational stability of the rolls;

- reduction in the consumption of rolls for hire;

- reduction in the duration of transhipments.

For this purpose, a method for rolling rails of type P50 is proposed, including calibration of rolls, setting up stands, rolling and process control, in which when rolling the finishing stand rolls are used with a surface hardened by electric arc hardening with a microhardness of 7500-8000 MPa, the geometric dimensions of the rail profile are controlled using templates, and the beginning of the process of rolling the rail profile in the finishing gauge is carried out by templates with deviations from the nominal values at minus tolerances: that rail - 0.5 mm, neck height - 0.5 mm, head width - 0.5 mm, sole width - 1.0 mm, neck thickness - 0.5 mm, feather height - 0.5 mm, and termination rolling of the rail profile with templates with deviations from the nominal value on plus tolerances: rail height - 0.8 mm, neck height - 0.3 mm, head width - 0.5 mm, sole width - 1.0 mm, neck thickness - 0, 8 mm, pen height 1.0 mm.

The claimed parameters are selected experimentally based on the following premises. The absence of electric arc hardening leads to an increase in the consumption of rolls of the finishing stand per ton of rolled products, as well as a decrease in their operational stability. In the case of conducting electric arc hardening until a microhardness of more than 8000 MPa is obtained on the surface of the finishing roll, the likelihood of brittleness and chipping of the hardened layer increases, less than 75000 MPa the required caliber strength is not achieved. The strengthening of the calibers of the rolls of the finishing stand 850 along a helix provides a continuous hardened layer.

The provision of the rolling process of the rail profile using templates with deviations from the nominal values for the declared minus tolerances allows to achieve high accuracy of the geometric dimensions of the finished rail profile, as well as reduce the running meter weight to theoretical values. Otherwise, the accuracy of the finished profile is not achieved, and the metal consumption of the process increases.

The termination of the rolling process of the rail profile by controlling it with templates with deviations from the nominal values for the declared plus tolerances allows to reduce the time for transshipment, as well as to reduce the consumption of rolls per ton of rolled metal. Otherwise, the consumption of rolls increases significantly.

The inventive method of rolling rails of type P50 was implemented in a rail and beam workshop.

In rolling the following work stands were used:

- crimping stand 900 duo reversible;

- roughing stand 800-1 trio irreversible;

- final stand 800-2 trio irreversible;

- finishing stand 850 duo irreversible.

A continuously cast billet with a section of 300 × 340 mm was rolled on a crimp stand for 7 passes until a trapezoidal shape was obtained. Further rolling was carried out according to the following scheme:

Crate 800-1 lower horizon

upper horizon

90 ° tilt

lower horizon

upper horizon

Crate 800-2 lower horizon

upper horizon

lower horizon

Crate 850 rolling in fine hardened caliber.

Measurement of the geometric dimensions of the profile was carried out on templates cut off from the roll after the finishing stand and chilled in water and in air.

When obtaining the results of measuring the head width, neck thickness and width of the sole of the rail corresponding to the minimum tolerance, the gaps between the rolls of the finishing stand 850 and the gaps in the lower horizon of the stand 800-2 were increased, with the results corresponding to the maximum tolerance, the gaps between the rolls of the finishing stand 850 and gaps in the lower horizon of stand 800-2. Upon receipt of the result of measuring the height of the rail corresponding to the minimum tolerance, the gaps in the lower horizon of the stand 800–2 were increased, while the maximum tolerance was reduced, the gaps were reduced. Upon receipt of the results of measuring the thickness of the flanges and the neck height corresponding to the maximum tolerance, the rolling transition was made to a new unworked caliber of stand 850.

The geometric dimensions of the profile were controlled by the following templates:

- rail height - a template with a minimum and maximum tolerance (figure 1);

- neck height - template with minimum and maximum tolerance (figure 2);

- the width of the head and the thickness of the neck - a template with a minimum and maximum tolerance (figure 3);

- the width of the sole is a template with a minimum and maximum tolerance (figure 4);

- pen height - templates with a minimum tolerance (figure 5), a template with a maximum tolerance (figure 6).

The inventive rolling method provided high accuracy of geometric dimensions that meet the requirements of GOST R 51685-2000 for category T1. The mass of linear measure approached the theoretical (51.80 kg) and amounted to 51.2-52.4 kg. At the same time, the roll resistance increased from 1000 tons to 1500 tons. The reduction in roll consumption per tonne of rolled products was 0.2 kg / t, and the time for transshipment was reduced by 1 hour per month.

Information sources

1. Patent RU 2241556 Russia, IPC ⁷ B21B 1/08 // B21B 1/08: 02. The method of rolling rails. / Pavlov V.V., Dorofeev V.V., Kravchenko E.L., Pyataykin E.M., Yunin G.N., Erastov V.V .; LLC “Rails of the Kuznetsk Metallurgical Plant” - No. 2003124405/02, declared 08/04/2003, publ. December 10, 2004; bull. Number 34.

2. Rolling rail R75 // Steel. 1983. No. 7. S.40-42.

3. Technological instruction TI 109-RB-057-2007 "Production of rolled products in the rail and beam shop."

Claims (1)

A method of rolling rails of type P50, including calibrating the rolls, adjusting the stands, rolling with a control of the geometric dimensions of the rail profile, characterized in that when rolling in the finishing stand, rolls with a hardened electric arc hardening surface are used, the microhardness of which is 7500-8000 MPa, control of the geometric dimensions of the rail the profile is carried out using templates, while in the rolls of the final caliber, the rolling process is started using templates with deviations from the nominal values by minus tolerances of a rail height of 0.5 mm, a neck height of 0.5 mm, a head width of 0.5 mm, a sole width of 1.0 mm, a neck thickness of 0.5 mm, a pen height of 0.5 mm, and complete upon reaching the geometric parameters of the obtained rail profile corresponding to patterns with deviations from the nominal values on plus tolerances of rail heights of 0.8 mm, neck heights of 0.3 mm, head width of 0.5 mm, sole width of 1.0 mm , neck thickness 0.8 mm, pen height 1.0 mm.

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