RU2380179C1 - Method of helical rolling - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention is related to pipe rolling and technology for manufacturing of hot-rolled seamless pipes (cartridges) of short length by helical rolling, in particular to method for production of hot-rolled pipes on mills of helical rolling of heated billet on mandrel in caliber produced by rollers and bars. In method for production of hot-rolled pipes on mills of helical rolling of heated billet on mandrel in caliber produced by rollers and bars, prior to rolling, lubricant is applied onto rod, and feed of another billet into rollers is realised directly after back end of pierced cartridge exits from deformation zone, besides number of rolled pipes is identified based on ratio 2≤n≤L_rod/L_{single pipe}, where L_rod is rod length, L_{single pipe} is length of single pipe.

EFFECT: invention provides for improved efficiency of helical rolling mill using short-length billets, and improved quality of internal surface of cartridges (pipes).

1 dwg

Description

The invention relates to pipe rolling production and relates to a technology for producing hot-rolled seamless pipes (sleeves) of short length by screw rolling.

A known method of screw rolling of short hollow products with a bottom, implemented on the piercing mill, including: feeding the workpiece to the mill, rolling in caliber on the mandrel, removing the mandrel and unloading the finished product on an inclined tray under the weight of its own weight, the operation of rolling and removing the mandrel from the product combined in time [SU 556855, B21B 19/04, publ. 05/05/77]. This method allows to obtain short products with a short time auxiliary operations, providing high performance. This method is inconvenient in that short sleeves are characterized by the formation of oxides on the inner surface of the sleeves (pipes). These oxides during subsequent rolling operation cause intense wear of the mandrels and worsen the condition of the inner surface of the pipes. The disadvantages of the method include possible malfunctions of the mill associated with the unloading of products. If you change the length of the finished product, the sleeves may become stuck in the tray, resulting in loss of productivity.

The closest technical solution adopted for the prototype is a method for the production of hot-rolled pipes (sleeves) on helical rolling mills of a heated billet on a mandrel in caliber formed by rolls and rulers, including feeding the billet to the mill, rolling on the mandrel, removing the mandrel and issuing the sleeve (pipe ) from the camp [F.A. Danilov, A.Z. Gleyberg, V. G. Balakin "Hot Rolling and Tube Pressing", 1972]. However, this method is characterized by low productivity in the case of switching to short workpieces. The rolling rate is characterized by a rolling cycle, which consists of machine time and auxiliary operation time. Typically, the time of auxiliary operations is constant for a particular mill design, so the transition to rolling short billets, as a rule, is accompanied by a loss in productivity. In addition, this method is characterized by the formation of oxides on the inner surface of the pipes during the transition to short workpieces.

The objective of the invention is to increase the productivity of the helical rolling mill when using blanks of short length and improve the quality of the inner surface of the liners (pipes).

The task is achieved by the fact that before rolling the rod is lubricated, and the next workpiece is fed into the rolls immediately after the rear end of the stitched sleeve comes out of the deformation zone, and the number of rolled pipes is determined from the ratio

where L _article - the length of the rod;

L one _tr - the length of one pipe.

It is suggested that after rolling, the workpiece should not be pulled out of the outlet side of the mill, but left on a water-cooled long mandrel bar and the next workpiece should be rolled, after which several short sleeves (pipes) should be removed from the bar. The location of several liners on the rod can significantly reduce the time of auxiliary operations and increase the productivity of the mill.

It is also suggested that the mandrel bar be lubricated with phosphate grease during rolling. When the sleeve is on the rod, the volumes of air interacting with the inner surface of the sleeve decrease (accordingly, the formation of oxides decreases), and the applied lubricant melts and reacts with the oxides, thereby reducing their formation.

Together, these signs provide a solution to the problem: increasing the productivity of the rolling mill using short lengths and improving the quality of the inner surface of the liners (pipes).

The invention is illustrated in the drawing, which shows the firmware diagram of several blanks. In the drawing, the following notation:

1 - first blank

2 - second workpiece

3 - third workpiece

4 - work rolls

5 - working mandrel

6 - centering rollers

7 - mandrel rod

8 - persistently adjusting mechanism

The sequential rolling process is as follows. The workpiece enters the mill, is set in the rotating rolls 4, then the rolling process takes place on the mandrel 5 mounted on a long mandrel bar 6. After rolling, the workpiece 1 is not removed from the mill, but left to hang on the mandrel bar 6, and continue rolling the subsequent workpieces 2, 3 ... n. The number of rolled products n is determined from the relation (1). Then, all blanks are removed from the rod and the rolling cycle is repeated.

This method is implemented when screw rolling (flashing) pipes on the mill 130D MISiS. A batch of 8 initial billets of steel 45 with a diameter of 60 mm and a length of 200 mm was heated to a temperature of 1160 ... 1180 ° C. The blanks were stitched in a mill with barrel-shaped rolls on a mandrel with a diameter of 35 mm into sleeves with a diameter of 60 mm and a wall thickness of 12 mm. The diameter of the rolls is 430 mm, the barrel length is 320 mm. The angle of inclination of the generatrix of the input cone 3 ° and the output cone 3 °. We set the feed angle of the rolls to 14 °, the working length of the rod was 1800 mm. An aqueous solution of sodium tripolyphosphate with an initial density was applied to the mandrel rod

Four blanks were stitched at once and the firmware cycle was fixed. With a draw ratio of 1.56, the length of each sleeve was 312 mm, the total length of the workpieces on the rod was 1248 mm. Cycle time τ _c = τ _m + τ _vp , where τ _m is the machine time; τ _vp is the time of auxiliary operations. The total cycle time was τ _C = 4 · 5 + 20 = 40 s.

Then the remaining 4 blanks were flashed in the usual way, after each flashing the blank was removed from the rod and the next one was flashed. The cycle time for obtaining one sleeve was 15 s, and the total firmware flashing time for four blanks was 60 s.

As a result, when rolling (flashing) several billets at once for the same number of billets, the time spent was 20 s less, the increase in mill productivity when implementing the described method is 33%.

In addition, on the inner surface of the sleeves obtained by the proposed method, there are practically no iron oxides.

Claims (1)

A method for producing hot-rolled short-length tubes on helical rolling mills by rolling a heated billet on a mandrel in a gauge formed by rolls and rulers, characterized in that lubricant is applied to the mandrel rod before rolling, and the next billet is fed into the rolls immediately after the rear end of the stitched sleeve from the deformation zone, and the number n of rolled tubes on the rod is determined from the ratio

where L _c - the length of the rod, mm;
L one _tr - the length of one pipe, mm.

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