RU2509615C1 - Method of rerolling of rails - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention serves to expand rolled-products range for increase in steel rolled stock cross-section and shaped sections by rerolling of used rails. Proposed method comprises heating of rails and subsequent multipass reduction at rolls with gages. Local decrease in rail steel resistance to deformation is ensured by heating the rails to 950-1150°C.Then, the rail is subjected to local heating to 1250-1290°C at joints between rail head and foot with web in pusher-type tunnel furnace with gas torches. Thereafter, rail is upset in height by 10-30% by rolling at 700-900 mm-dia rolls. Besides, web mid section is subjected to local heating to 1200-1250°C while rails are heated in noncorrosive atmosphere.

EFFECT: local reduction in rail steel deformation.

3 cl, 2 dwg, 1 tbl, 1 ex

Description

The invention relates to rolling production and can be used to obtain steel sections and shaped profiles by processing rolling railway rails decommissioned.

Known methods for the processing of steel railroad rails, including their heating and subsequent multi-pass rolling in rolls with calibres in long sections [1, 2].

The disadvantages of these methods are that during the rolling process, profiles such as “sunset”, “crease”, “lampas”, etc. are formed on the profiles. For this reason, the above methods did not find industrial application.

The closest analogue to the present invention is a method of rolling the rails into a strip-shaped profile, including heating them to a temperature of 2100 ° F (i.e., to 1149 ° C), and multi-pass compression in rolls with calibers in two stages, first by predominantly compressing the head and rail sole, and then with compression of the rail neck [3].

The disadvantage of this method is that multi-pass compression is performed with a sequential reduction in the cross-sectional area of the strip in each of the passages. This narrows the range of rolled profiles, since it does not allow to obtain profiles with an increased cross-sectional area.

The technical problem solved by the invention is to expand the range of profiles in the direction of increasing the cross-sectional area.

To solve the technical problem in the known method of rolling the rails, including heating and subsequent multi-pass reduction in rolls with calibers, according to the invention, the rail is first heated to a temperature of 950-1150 ° C, then subjected to local heating to a temperature of 1250-1290 ° C at the interface the heads and soles of a rail with a neck in a continuous tunnel furnace with gas burners, after which the rail is sedimented by 10-30% in height by rolling in rolls with a diameter of 700-900 mm.

The figure 1 presents the layout of the rail and burners in the continuous heating furnace; here 1 is a rail; 2 - drive conveyor rollers; 3 - gas burners for heating the joints of the neck with the head and sole of the rail; 4 - additional gas burners for heating the neck of the rail.

The figure 2 shows the sequence of changes in the cross section of the rail along the passages indicated by Roman numerals during its rolling.

The invention consists in the following. Additional local heating at the interface between the head and the sole (Fig. 1) with the neck of the rail 1 by the rows of burners 3 to a temperature of 1250-1290 ° C leads to a local decrease in the resistance to deformation of rail steel. Due to this, when the rail is upset by 10-30% in height by rolling in rolls with a diameter of 700-900 mm, local deformation occurs, concentrated mainly on the most heated sections of its cross section, which is accompanied by the formation of bulges at the junctions of the neck with the head and sole, as well as thickening of the neck, especially in the case of its additional heating by additional burners 4. Rail sediment produced in the rolls with the proposed gradient heating of its cross section eliminates buckling and bending eyki which would occur when the rail uniform heating by a known method [3].

Additional local heating of the middle part of the neck to a temperature of 1200-1250 ° C in the embodiment of the method helps to stabilize the rolling process, so you can further expand the range of rolled profiles in the direction of increasing their cross-sectional area by 5-10%.

It was experimentally established that upon initial uniform heating of the rail to a temperature below 950 ° C, the resistance of the metal to deformation increases, and also due to spontaneous cooling of the rail billet during the rolling process, the mass-average temperature required to obtain the desired mechanical properties of the end of the rolling of long sections is not provided. An increase in the heating temperature of the rail over 1150 ° C leads to a loss of neck stability during rail upsetting, the formation of folds of surfaces oxidized in air (“sunset” defect), which is unacceptable.

Local heating to a temperature below 1250 ° C does not exclude bending of the rail neck due to loss of stability and the formation of a defect in the form of folds. An increase in the heating temperature in excess of 1290 ° C leads to oxidation of the grain boundaries of the rail steel, their weakening, ruptures and discontinuities in the rolling process.

Sediment rail height less than 10% is ineffective, as it does not increase the cross-sectional area of long and shaped profiles. Precipitation in height of more than 30% leads to a loss of stability of the rail neck, its bending with the formation of folds and sunsets, which is unacceptable.

When using rolls with a diameter of less than 700 mm, the conditions for the capture of a railway rail with its draft by 10-30% are worsened. An increase in the diameter of the rolls of more than 900 mm leads to an increase in the length of the deformation zone and undermining of the contact surfaces of the rail, which leads to the formation of defects during rolling.

Method implementation examples

Decommissioned railroad wear type P65 rail with a height of H ₀ = 180 mm, neck thickness B ₀ = 18 mm (Figure 2) is loaded into a walking hearth furnace and heated to a temperature of T _a = 1000 ° C in an oxidizing atmosphere CO gas. After trimming the end sections with bolt holes, the heated rail 1 is fed into the tunnel-type continuous furnace (Figure 1). When transporting the rail 1 through the drive rollers 2, it is heated locally using two rows of gas burners 3 to a temperature of T _p = 1270 ° C at the interface between the head and the sole of the rail 1 and the neck. At the same time, using additional gas burners 4 (indicated by dashed lines in FIG. 1), also installed in a row, the middle part of the neck of rail 1 is heated to a temperature T _W = 1225 ° C.

After exiting the feed furnace, rail 1 (profile I in FIG. 2) is set into a vertical vertical cage duo with a diameter of roll barrels D ₁ = 800 mm, where precipitation is 36 mm in height, which is ε = 20% of its original height H ₀ = 180 mm, with the formation of profile II with a height of H ₁ . Due to the fact that the rail was previously heated with a temperature gradient over the cross section, its deformation is localized in areas with a higher temperature and lower strength. Therefore, after upsetting (profile II in figure 2), concavities of the mating neck with the sole and neck with the head are formed thickenings in the form of sagging metal.

In this case, the neck of the rail 1 heated by the additional burners 4 as a result of the upsetting becomes thicker and becomes convex of the side walls. The compression of the rail 1 during its upset occurs without changing the cross-sectional area.

After upsetting, the strip is crimped in the horizontal rolls of the section rolling mill (profile III in FIG. 2), then again in the horizontal rolls (profile IV), where the end bulges formed in the previous passes are compressed.

Finish rolling of the profiles is carried out using the standard oval-circle caliber system, partially shown in FIG. 2 (profiles V-VII) into a round long section profile of maximum diameter D _max = 90 mm.

Thanks to the preliminary draft of the rail in height, heated with a given temperature distribution, an increase in the cross-sectional area of the obtained long products is achieved. The use of heating in a furnace with an oxidizing atmosphere prevents the formation of scale, and, as a result, reduces the cross-sectional area of the rail.

Implementation options of the proposed method and indicators of their effectiveness are presented in the table.

Table.

Modes of rolling rails type P65 and the maximum diameter of round profiles

No. p / p T _a , ° C T _p , ° C T _W , ° C D1 mm ε,% D _max mm one. 940 1240 1190 650 9 76 2. 950 1250 1200 700 10 90 3. 1000 1270 1225 800 twenty 90 four. 1150 1290 1250 900 thirty 90 5. 1160 1300 1300 950 35 78 6 [3]. 1149 - - 600 not regl. 68

From the data given in the table, it follows that when implementing the proposed method (options No. 2-4), a round profile rolled product with the largest cross-sectional area with a maximum diameter of D _max = 90 mm is obtained. The high-quality rolled steel obtained by rolling the rails does not have defects in the form of folds, sunsets, stripes.

With prohibitive values of the declared parameters (options No. 1 and No. 5), as well as the implementation of the closest analogue (option No. 6), the cross-sectional area and the maximum diameter of high-quality round profiles are reduced.

The technical and economic advantages of the proposed invention are that the initial general heating of the rail initially to a temperature of 950-1150 ° C and subsequent heating to 1250-1290 ° C of the interface between the head and the bottom of the rail and the neck along its entire length allows the rail to settle up in height 10-30% by rolling in rolls with a diameter of 700-900 mm. In this case, a thickening of the transverse profile is achieved in the places of heating. Additional heating of the middle part of the neck to a temperature of 1200-1250 ° C allows you to completely eliminate the loss of stability (bends) of the rail neck during draft and give it a thickened shape that is most favorable for the subsequent rolling of profiles of a given shape while ensuring the maximum possible cross-sectional area. Heating the rails in an oxidizing atmosphere eliminates scale formation and the associated reduction in the cross section of the original rail and the loss of mass of steel.

As the base object adopted the known method [3]. Using the proposed method will increase the profitability of rolling the rails into long products by 10-15%.

Literary sources

1. US Patent No. 1086789, IPC B21B 1/08, 1914

2. US Patent No. 4123927, IPC B21B 1/08, 1978

3. US patent No. 4982591, IPC B21B 1/08, 1991

Claims (3)

1. Method for the production of long and shaped profiles by rolling the rails, including heating the rails and subsequent multi-pass compression in rolls with calibers, characterized in that the rail is heated to a temperature of 950-1150 ° C, then subjected to local heating in a tunnel tunnel furnace with gas burners to temperature 1250-1290 ° C at the interface between the head and the sole of the rail with the neck, after which the rail is sedimented in height by 10-30% by rolling in rolls with a diameter of 700-900 mm. 2. The method according to claim 1, characterized in that the middle part of the neck is subjected to local heating to a temperature of 1200-1250 ° C. 3. The method according to claim 1, characterized in that the rail is heated in a non-oxidizing atmosphere.

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