JP3815667B2 - Mandrel bar lubricant application method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for applying a lubricant used in a mandrel bar for manufacturing seamless steel pipes.
[0002]
[Prior art]
A seamless steel pipe is a mandrel bar in which a round billet of a material is heated in a rotary hearth type heating furnace or a walking beam type heating furnace and then drilled with a punching machine to form a hollow shell, and a lubricant is applied to the hollow shell. Is inserted into a skewer shape, stretched and rolled to a predetermined size with a mandrel mill, the mandrel bar is pulled out from the pipe, and then finished to a predetermined size with an outer diameter processing stand such as a stretch reducer.
[0003]
In mandrel mill rolling, a hollow shell and a mandrel bar coated with a lubricant are conveyed to the mandrel mill entry side, and inserted into the hollow shell while holding the mandrel bar with a burtainer. Rolling is started by sending the hollow shell to a mandrel mill. The tube stretched and rolled by the mandrel mill is kicked out from the run-out conveyor together with the mandrel bar and sent onto the stripper table, where the mandrel bar is pulled out. The drawn mandrel bar is cooled with water in a cooling tank, and after the lubricant is applied to the surface, the mandrel bar is transported to the mandrel mill entry side and reused.
[0004]
The lubricant applied to the mandrel bar acts as a protective coating for preventing seizure of the mandrel bar inserted into the hollow shell at 1100 ° C. to 1200 ° C., and between the mandrel bar and the hollow shell during stretching and rolling. In order to reduce the friction and stabilize the tube shape and wall thickness distribution and to facilitate the extraction of the mandrel bar, the film thickness control of the lubricant is an important management to ensure these functions. It is an item.
[0005]
Conventionally, various attempts have been made to control the film thickness of the lubricant. At present, as described in Japanese Patent No. 2897700, the amount of protrusion of the mandrel bar from the hollow shell is determined for each pass. It is clarified that it is most effective to adjust the temperature by making the mandrel bar's thermal history uniform by gradually changing the temperature of the mandrel bar and moving the mandrel bar without fixing it. Yes.
[0006]
Further, the above-mentioned Japanese Patent No. 2897700 describes that the basic unit of the lubricant is improved by changing the lubricant application area of the mandrel bar in accordance with the amount of protrusion of the mandrel bar from the hollow shell. ing.
[0007]
[Problems to be solved by the invention]
However, Japanese Patent No. 2897700 does not specifically disclose how the lubricant application region is determined in accordance with the amount of protrusion of the mandrel bar from the hollow shell. Conventionally, the lubricant application area of the mandrel bar is determined from the dimensions of the hollow shell on the rolling schedule and the rolling conditions of the mandrel mill, and the actual dimensions for each piece of the hollow shell perforated by a punching machine are determined. In general, the lubricant application region in consideration is not determined.
[0008]
In other words, conventionally, the actual dimensions of the hollow shells are not taken into consideration, and the variation allowance of the hollow shells in the lot is not increased so that the lubricant is not applied in the region used for rolling the mandrel bar. In view of this, it is necessary to set the lubricant application region longer. This has been a problem through increasing the basic unit of the lubricant.
[0009]
[Means for Solving the Problems]
The present invention has been made to solve such problems of the prior art, and provides a mandrel bar lubricant application method capable of reducing the basic unit of the lubricant by strictly determining the lubricant application region. The task is to do.
[0010]
In order to solve such a problem, the present invention is a method for applying a lubricant on a mandrel bar surface used for mandrel mill rolling of seamless steel pipes, which is obtained by a length meter disposed between a drilling machine and a mandrel mill. The length of the hollow tube before mandrel mill rolling, the protruding length of the mandrel bar at the first stand of the mandrel mill, the moving speed of the mandrel bar during rolling, the hollow tube speed of the inlet and outlet sides of each mandrel mill stand, and the mandrel The present invention provides a mandrel bar lubricant application method, wherein a lubricant application region of a mandrel bar is determined based on a distance between each stand of the mill .
[0011]
Further, in order to solve the above-mentioned problems, the present invention is a method for applying a lubricant on a mandrel bar surface used for mandrel mill rolling of seamless steel pipes, which is obtained by a length meter disposed between a drilling machine and a mandrel mill. The length of the hollow tube before rolling the mandrel mill, the protruding length of the mandrel bar at the first stand of the mandrel mill, the mandrel bar speed ratio at the entrance and exit sides of each mandrel mill, and the distance between the stands of the mandrel mill The present invention is also provided as a mandrel bar lubricant application method characterized in that the lubricant application region of the mandrel bar is determined.
[0012]
Na us, the "mandrel bar velocity ratio of mandrel mill each stand entry side" means a value obtained by dividing the command lever moving speed during rolling at a hollow shell speed of the mandrel mill each stand entry side. Similarly, the “mandrel bar speed ratio at each stand outlet side of the mandrel mill” means a value obtained by dividing the mandrel moving speed during rolling by the hollow shell speed at the outlet side of each mandrel mill.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a plan view showing a schematic equipment configuration around a mandrel mill to which the lubricant application method according to the present embodiment is applied. As shown in FIG. 1, the round billet of the material according to the present embodiment is heated in a heating furnace 6 (indicated by 2e in the figure) and then conveyed in a conveying line (indicated by 2d and 2c in the figure). Then, the holes are sequentially punched by the punching machine 5 to form hollow hollow tubes (indicated by 2b in the figure). After the actual length is measured by the length measuring device 4 arranged on the exit side of the punching machine 5, the hollow shell is conveyed to the rolling line 7 on the entry side of the mandrel mill 3 (indicated by 2a in the figure). On the other hand, the mandrel bar (indicated by 1a to 1e in the figure) is circulated in the direction of the arrow in FIG. 1 in the bar circulation line 8 having the cooling zone 9 and the lubrication zone 10 (in FIG. 1). 5 shows an example in which five mandrel bars are circulated), and is sequentially conveyed to the rolling line 7 and used for mandrel mill rolling of the hollow shell (in the figure, the mandrel bar 1a is used for rolling the hollow blank 2a. ) Here, the rolling order of the hollow shells is determined in advance, and the mandrel bar corresponding to each hollow shell, that is, the mandrel bar to be used for rolling of each hollow shell, is also determined based on the circulation order. become. That is, the hollow shells (including round billets) 2a to 2e are associated with the mandrel bars 1a to 1e, respectively, according to the rolling order, and in applying the method according to the present embodiment, the hollow shells In addition, the tracking of each mandrel bar is not particularly required.
[0014]
The lubricant application region of the mandrel bar 1 b in the lubrication zone 10 is determined by the actual length of the hollow shell 2 b corresponding to the mandrel bar 1 b and the rolling conditions in the mandrel mill 3. That is, (1) the actual length (1) of the hollow shell 2b after drilling, (2) the protruding length (L) of the mandrel bar 1b in the first stand of the mandrel mill 3, and (3) the first length of the mandrel mill 3 The inlet speed (V _{in, 1} ) of the hollow shell 2b in one stand, (4) the moving speed (V _bar ) of the mandrel bar 1b during mandrel mill rolling, (5) the hollow shell in each stand of the mandrel mill 3 Based on the exit speed (V _{out, i} ) of 2b and the distance (L _{i, i-1} ) between the stands of the mandrel mill 3, L + Σ [L _{i, i-1} × {(V _bar / V _{out , i-1} ) -1}] (where i = 2 to n, n is the number of stands) and L + V _bar × (l / V _{in, 1} ), and the mandrel bar 2b The lubricant application area for is determined. Note that the rolling conditions used for calculating the parameters do not necessarily require the above (3) to (5) separately, and the mandrel bar speed ratio (V _bar / V _{in, 1} on the stand entry side). ) And the mandrel bar speed ratio (V _bar / V _{out, i} ) on the stand exit side. Hereinafter, the procedure for determining the lubricant application region will be described in more detail with reference to FIG.
[0015]
FIG. 2 is an explanatory diagram for explaining the movement of the mandrel bar 1a and the hollow shell 2a during rolling in the mandrel mill 3, and represents a state in which time has transitioned in the order from (a) to (d) in FIG. ing.
[0016]
FIG. 2A shows the state of the mandrel bar 1 a and the hollow shell 2 a when the hollow shell 2 a is engaged with the first stand of the mandrel mill 3. Here, as described above, the actual length (l) of the hollow shell 2a is measured and fixed by the length measuring device 4 disposed between the punch 5 and the mandrel mill 3. Further, the protrusion length (L) of the mandrel bar 1a at the time when the mandrel mill 3 is bitten into the first stand is changed for each number of passes in the same manner as in the prior art, and the protrusion length corresponding to each pass. Saga is applied when calculating the lubricant application area. Further, the mandrel bar 1a moves in the rolling direction indicated by an arrow in the figure at the moving speed V _bar . L _2,1 indicates the distance between the first stand and the second stand, and V _{in, 1} indicates the speed of the hollow shell 2a on the first stand entry side.
[0017]
Next, as shown in FIG. 2B, the end of the hollow shell 2a reaches the second stand after the time L _2,1 / V _{out, 1 has} elapsed from the state of FIG. Here, V _{out, 1} indicates the speed of the hollow shell 2a on the first stand exit side. On the other hand, since the mandrel bar 1a moves in the rolling direction by V _bar × (L _2,1 / V _{out, 1} ) from the state of FIG. 2 (a), the protrusion length of the mandrel bar 1a at this time is L + V _bar × (L _2,1 / V _{out, 1} ) −L _2,1 , that is, L + L _2,1 × {(V _bar / V _{out, 1} ) −1}.
[0018]
Thereafter, in the same manner, rolling is sequentially performed at each stand, and as shown in FIG. 2 (c), from the state of FIG. 2 (a), time Σ (L _{i, i-1} / V _{out, i-1} ) ( However, after i = 2 to n), the tip of the hollow shell 2a reaches the nth stand which is the final stand. Here, L _{i, i-1} indicates the distance between the stands of the (i-1) th stand and the ith stand, and V _{out, i-1} is a hollow shell on the exit side of the (i-1) th stand. The speed of 2a is shown. On the other hand, the mandrel bar 1a moves from the state of FIG. _{2 (a) V bar × {} Σ (L i, i-1 / V out, i-1)} only in the rolling direction (where i = 2- through n) Therefore, the protruding length of the mandrel bar 1a at this time is L + Σ [L _{i, i−1} × {(V _bar / V _{out, i−1} ) −1}] (where i = 2 to n). .
[0019]
FIG. 2 (d) shows a state immediately before the hollow shell 1a passes through the first stand. Here, the state shown in FIG. 2D is obtained after the elapse of time 1 / V _{in, 1} from the state shown in FIG. On the other hand, since the mandrel bar 1a moves in the rolling direction by V _bar × (l / V _{in, 1} ), the mandrel bar 1a starts from the position of L from the tip in the first stand as L + V _bar. The region up to x (l / V _{in, 1} ) is used for rolling.
[0020]
Here, since it is usually set to V _{in, 1} ≦ V _{in, 2} ≦ V _{in, 3} ... ≦ V _{in, n−1} , rolling use in the state shown in FIG. While the region extends to the most distal end side of the mandrel bar 1a, the rolling use region in the state shown in FIG. 2D extends to the most proximal side of the mandrel bar 1a. Therefore, the region used for rolling the mandrel bar 1a is L + Σ [L _{i, i-1} × {(V _bar / V _{out, i-1} ) -1}] (provided that i = 2 to 2) from the tip of the mandrel bar 1a. n) is the starting point and the region is up to L + V _bar × (l / V _{in, 1} ).
[0021]
As described above, since the rolling use area of the mandrel bar 1a is calculated, the minimum necessary lubrication area is determined for each piece of the mandrel bar 1a by applying the lubricant to the area. Become. That is, the following two parameters determined by the actual length of the hollow shell 2b corresponding to the mandrel bar 1b located on the entry side of the lubrication zone 10 and the rolling conditions in the mandrel mill of the mandrel bar 1b and the hollow shell 2b. Is calculated from the tip of the mandrel bar 1b, and L + Σ [L _{i, i-1} × {(V _bar / V _{out, i-1} ) -1}] (where i = 2 to n) is used as the starting point. _A lubricant may be applied to a region up to _bar × (l / V _{in, 1} ).
[0022]
The lubricant is applied in the above-described lubrication zone 10 to the lubricant application region determined as described above. FIG. 3 shows a schematic device configuration in the lubrication zone 10. As shown in FIG. 3, when applying the lubricant, the mandrel bar 1 b is conveyed toward the lubrication box 102 by the conveyance conveyor 101 on the lubrication zone 10 entrance side. At this time, after the tip of the mandrel bar 1b is detected by the optical sensor 103 for detecting the tip of the mandrel bar arranged on the entry side of the lubrication zone 10, the conveyance speed of the mandrel bar 1b obtained from the actual speed value of the conveyor 101 is determined. Integration is performed, and the tip tracking of the mandrel bar 1b starting from the position of the sensor 103 is performed.
[0023]
Here, when the tip tracking value (X) of the mandrel bar 1b satisfies the following conditions, the injection valve 106 provided between the lubricating tank 104 filled with the lubricant and the lubricating ring 105 is opened.
X> X ₁ + L + Σ [L _{i, i−1} × {(V _bar / V _{out, i−1} ) −1}] − V × T _don (where i = 2 to n)
Here, X ₁ (for example, 5000 mm) represents the distance between the sensor 103 and the lubrication ring 105, V represents the lubrication speed, and T _don represents the delay time when the injection valve 106 is opened.
[0024]
Further, the injection valve 106 is closed when the tip tracking value (X) of the mandrel bar 1b satisfies the following conditions.
X> X ₁ + L + V _bar × (l / V _{in, 1} ) −V × T _doff
Here, T _doff means a delay time when the injection valve 106 is closed.
As described above, in the lubrication zone 10, the lubricant is appropriately applied to the lubricant application region of the mandrel bar 1b.
[0025]
【Example】
Hereinafter, the features of the present invention will be further clarified by describing examples.
FIG. 4 shows the deviation of the actual length (measured by a length meter) from the length on the rolling schedule in 378 hollow shells (length on rolling schedule: 11.0 m, outer diameter: 265 mmφ) used in this example. Indicates. As shown in FIG. 4, the actual length of the hollow shell varies between −200 mm and +400 mm with respect to the length on the rolling schedule. In this embodiment, the lubricant is applied to the lubricant application area calculated based on the actual length of each hollow shell, and the lubricant is applied to the lubricant application area calculated based on the length on the rolling schedule. As a comparative example, the two were compared. More specifically, in the comparative example, 11.4 mm obtained by adding the upper limit value (+0.4 mm) of variation to the length (11.0 mm) on the rolling schedule is uniformly set as the length of all hollow shells. The lubricant application area was determined based on the value. The target film thickness of the lubricant was 100 μm in both the examples and the comparative examples, and the rolling conditions such as the mandrel bar protrusion length necessary for determining the lubricant application region were the same.
[0026]
FIG. 5 is an explanatory diagram schematically showing the difference in the coating region between the comparative example, that is, the case where the actual length of the hollow shell is not taken into consideration, and the example, that is, the case where the actual length of the hollow shell is taken into account. is there. Here, Fig.5 (a) and FIG.5 (b) show the application range of the comparative example and Example in the case of the protrusion length L, respectively. Moreover, FIG.5 (c) and FIG.5 (d) show the application range of a comparative example and an Example in case protrusion length L '(L'> L), respectively.
[0027]
As described above, in the case shown in FIGS. 5A and 5C, the coating range is calculated based on the length of the rolling schedule × 1.04 in consideration of the variation in the length of the hollow shell by 4%. The application range is fixed within a lot. On the other hand, in the case shown in FIGS. 5 (b) and 5 (d), since the actual length for each piece of the hollow shell is taken into consideration, the minimum application range (FIG. 5 (b) and FIG. d) The application range is determined between the maximum application range (the portion painted in black in FIG. 5 (b) and FIG. 5 (d)). become. In FIG. 5C and FIG. 5D, since the protruding length is increased, the coating range is shifted to the mandrel bar center by that amount. As described above, in the comparative example (FIGS. 5A and 5C), the lubricant is uniformly applied to the range corresponding to the shaded portion in the figure, whereas this In the examples (FIGS. 5B and 5D), the lubricant applied to the shaded portion varies depending on the actual length of the mandrel bar. can do.
[0028]
FIG. 6 shows the amount of lubricant used in the embodiment described above and the amount of lubricant used in the comparative example. As shown in FIG. 6, in contrast to the comparative example, in this example, the amount of lubricant used was reduced by about 16 liters.
[0029]
【The invention's effect】
As explained above, according to the mandrel bar lubricant application method according to the present invention, the actual length of the hollow shell before mandrel mill rolling obtained by a length measuring device disposed between the drilling machine and the mandrel mill, From the rolling conditions in the mandrel mill, the minimum required lubrication application area is determined for each mandrel bar, and by applying the lubricant only to such area, the basic unit of the lubricant can be reduced. It is effective.
[Brief description of the drawings]
FIG. 1 is a plan view showing a schematic equipment configuration around a mandrel mill to which a lubricant application method according to an embodiment of the present invention is applied.
FIG. 2 is an explanatory view for explaining the movement of a mandrel bar and a hollow shell during rolling in the mandrel mill shown in FIG. 1;
FIG. 3 shows a schematic device configuration in the lubrication zone shown in FIG. 1;
FIG. 4 shows an example of deviation of the actual length with respect to the length on the rolling schedule of the hollow shell.
FIG. 5 is an explanatory view schematically showing a difference between an application region of an example and a comparative example.
FIG. 6 shows the amount of lubricant used in Examples and the amount of lubricant used in Comparative Examples.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1a-1e: Mandrel bar 2a-2b: Hollow element tube 2c-2e: Round billet 3: Mandrel mill 4: Length measuring instrument 5: Punching machine 6: Heating furnace 7: Rolling line 8: Bar circulation line 9: Cooling zone 10 : Lubrication zone

Claims (2)

A method of applying a lubricant to the surface of a mandrel bar used for mandrel mill rolling of seamless steel pipes,
The hollow tube length before rolling of the mandrel mill obtained by a length meter placed between the drilling machine and the mandrel mill, the protruding length of the mandrel bar at the first mandrel mill stand, the mandrel bar moving speed during rolling, and the mandrel A mandrel bar lubricant application method, wherein a lubricant application region of a mandrel bar is determined on the basis of the hollow tube speeds at the entrance and exit of each stand of the mill and the distance between the stands of the mandrel mill . A method of applying a lubricant to the surface of a mandrel bar used for mandrel mill rolling of seamless steel pipes,
The hollow tube length before rolling of the mandrel mill obtained by a length meter placed between the drilling machine and the mandrel mill, the protruding length of the mandrel bar at the first stand of the mandrel mill, the entrance side and the exit side of each mandrel mill stand A mandrel bar lubricant application method, wherein a lubricant application region of a mandrel bar is determined based on a mandrel bar speed ratio and a distance between each mandrel mill stand.

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