JP2682356B2 - Cold rolling method of steel pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE invention, the steel pipe 3 stand more than
The present invention relates to a method of cold-drawing and rolling with the above three-roll drawing mill.

[0002]

2. Description of the Related Art Demand for steel pipes for machine structures is increasing in demand for small-diameter, thick-wall sizes and various types of outer diameter sizes. On the other hand, since the three-roll reducer can be drawn at a high outer diameter reduction ratio even in a cold state, the thickness t ratio to the outer diameter D is t / t.
D can be increased and the outer diameter can be reduced to an arbitrary outer diameter from a mother pipe having the same outer diameter, so that it is possible to meet the demand for the small diameter, thick wall size, and various outer diameter sizes.

For example, in the case of an electric resistance welded steel pipe, in order to manufacture a small-diameter and thick-walled product at the stage of the mother pipe, not only the edge portion but also the base metal portion are heated during the welding and heating of the open pipe, and the welding efficiency is remarkably high. Welding becomes difficult due to deterioration of productivity, blowback of inner surface cooling water, or the like. Further, since the inner diameter of the pipe becomes small, it becomes difficult to cut the inner bead, the productivity is significantly deteriorated, and the inner bead remains. Further, since the difference between the inner and outer diameters is increased, particularly in the step of forming the steel strip into an open pipe, the butted edge shape is deteriorated, so that welding becomes difficult and the wall thickness shape is deteriorated. Therefore, the manufacturable range of a small-diameter thick-walled ERW steel pipe is generally t / D ≦ 2, where the pipe thickness is t and the pipe outer diameter is D.
It is about 0%. As a method of solving the problem at the time of manufacturing small-diameter thick-walled products, if the mother pipe is re-drawn and rolled by a reducer or the like, the outer wall diameter is reduced by the outer diameter drawing, and the outer diameter is reduced. It is known that a small-diameter thick-walled tube having a high thickness ratio t / D with respect to the diameter can be manufactured.

As a method for finishing cold-rolled pipe material such as ERW steel pipe to the outer diameter of the product, as shown in FIG. 7A, a stand 32 incorporating a pair of hole type rolls 31 is used. )
As shown in the figures and (c), the outer diameter of the mother pipe 33 is sequentially reduced at each stand 32 using a reducing mill in which the roll arrangement is continuously shifted by 90 ° between adjacent stands, and the final and final positions are reduced. Finish to the specified outer diameter with the last front stand. In this two-roll type rolling mill, the roll die is deep, and the roll peripheral speed between the bottom of the roll groove and the roll flange is greatly different. It has the drawback that flaws occur on the tube surface. For this reason, the two-roll reduction mill is not suitable for reduction rolling at a high outer diameter reduction ratio.

On the other hand, as shown in FIG. 8, a three-roll type reducer generally used for seamless steel pipes has a stand in which three hole type rolls 41 are assembled at 120 ° intervals in a vertical plane. As shown in FIGS. (A) and (b), the rolls are continuously arranged by changing the roll arrangement between adjacent stands by 60 °. According to this three-roll reducer, since the roll hole type is shallower than the two-roll type, the difference in roll peripheral speed between the roll groove bottom and the roll flange is small, and the flaw generated by the tube surface and the roll seizing is reduced. Since the reduction is remarkable, it is advantageous for reduction rolling at a high outer diameter reduction ratio.

In the conventional cold-rolling with a three-roll reducer, the outer diameter reduction rate per stand is about 10% at maximum, and as shown in FIG. From this, a bite 44 on the surface of the steel pipe 43 occurs. Therefore, as shown in FIG. 10, the roll hole type is made elliptical so that the groove bottom radius r _n−1 of the roll of the front stand 51 is smaller than the flange radius Rn of the roll of the rear stand 52. The roll ellipticity increases as the outer diameter reduction rate per stand increases. Therefore, in order to reduce the outer diameter per stand by a maximum reduction ratio of about 10%, it is necessary to use a roll having a considerably large ellipticity. In the reduction rolling of a mother pipe cold-formed by the three-roll reducer, when the reduction rolling is performed at a high outer diameter reduction rate, the spring roll caused by the cold mother pipe and the insufficient rigidity of the stand cause a reduction in the rigidity of the stand. Although the finish outer diameter after drawing rolling is the same as the roll hole shape, a phenomenon occurs in which a difference occurs depending on the wall thickness, strength, and the like of the mother pipe.

[0007] In order to solve the nonuniform finish outer diameter of the three-roll reducer in the reduction rolling, the reduction amount of the roll may be changed. The relative positional relationship is fixed, and the roll reduction amount of the roll cannot be changed. As a method for solving the nonuniform finish outer diameter in the above-mentioned rolling reduction, 3
The housing of the roll-type roll and the housing of the two-roll type roll are replaceable, and the two-roll type roll is incorporated in at least the final stand or the final stand and the preceding stage. A rolling mill in which a three-roll type grooved roll is incorporated in a stand (Japanese Patent Laid-Open No. 58-116907), and a material to be rolled is given a large amount of reduction by a first row of stands of three rolls. A method of rolling to near the outer diameter size, and then finish rolling with a second row of stands comprising a two-roll stand having roll reduction means and arranged in series on the outlet side of the first row of stands (Japanese Unexamined Patent Publication No. No. 211904),
By eccentrically aligning a bearing axis supporting two roll shafts of a three-roll reducer with a bearing axis supporting two rolls, and rotating the bearings of the two rolls, A reduction mill capable of adjusting the relative distance, further providing a shaft slide mechanism at the ends of the two rolls, and also enabling adjustment of the two rolls in the roll axis direction (Japanese Patent Laid-Open No. 3-2).
No. 94008).

[0008]

SUMMARY OF THE INVENTION The above-mentioned JP-A-58-11
No. 6907, the method disclosed in Japanese Patent Application Laid-Open No. 2-221904 discloses a method in which a first row of stands of three rolls is used to apply a large amount of reduction and roll to a predetermined outer diameter.
Then, since the finish rolling is performed with the second roll row of two rolls with adjustable roll gap, it is possible to improve the accuracy of the outer diameter dimension. There is a problem that the diameter dimension is extremely deteriorated. In addition, the reduction rolling machine of Japanese Patent Laid-Open No. 3-294008 cannot be adjusted online on the production line, and the adjustment is performed offline or replaced with a roll whose roll hole type is changed. Therefore, if this method is selected, the mill must be stopped every time the material and strength of the main pipe changes, despite the fact that the pipes with the same outer diameter are manufactured, resulting in a large operation rate, It is not practical because it leads to a decrease in yield.

SUMMARY OF THE INVENTION It is an object of the present invention to suppress the deterioration of the outer diameter in the reduction rolling at a high outer diameter reduction ratio in a cold drawing process using a three-roll type reducer for a steel pipe, and to reduce the outer diameter with a small number of roll stands. An object of the present invention is to provide a cold rolling method capable of producing a small-diameter thick-walled steel pipe having a high thickness ratio t / D.

[0010]

Means for Solving the Problems The present inventors have conducted various tests and studies to achieve the above object. As a result, the outer diameter throttle step of the steel pipe, 3 a drawing step due to more than a third roll Les <br/> inducer stand, 2 stands or more second roll
Combining the constant- diameter process with a type constant-diameter machine, the ellipticity and the outer diameter reduction ratio of the rolls of the final front stage and the final front stage of the three-roll reducer are set within the predetermined ranges. role of ellipticity of the last stage stand by reduced outer diameter ratio and a roll groove circumferential length and a predetermined range, even if the rolling diaphragm with high have reduced outer diameter ratio, precision finish outside diameter dimension is obtained, It was clarified that a small-diameter thick-walled steel pipe having a high wall-thickness ratio t / D with respect to the outer diameter can be manufactured, and the present invention was reached.

That is, the present invention has three or more stands.
Rolling reducer drawing process and 2 or more stands
In a method for manufacturing a steel pipe having a highly accurate outer diameter by cold-drawing and rolling the steel pipe by combining the constant-diameter process of the two-roll type constant diameter machine, the final two-stage stand before the drawing process by the three- roll reducer is used. The roll ellipticity of each stand up to 2% or more and the maximum outer diameter reduction rate per stand is 1
Squeeze rolling with a high outside diameter reduction rate of 0%, the ellipticity of the roll of the final front stand is 3% or less, and the maximum outside diameter reduction rate is 5%.
And reducing rolling, the products outside the roll groove circumferential length of the final stage stand
Diameter circumference and rather equal, the ellipticity of a roll and 0 to 1.5%,
Performing reduction rolling at an outer diameter reduction rate of 0.5% or more and less than the maximum outer diameter reduction rate determined when the radius of the roll groove bottom of the final stand is equal to or smaller than the roll flange radius of the final stand. Is a method for cold rolling a steel pipe.

[0012]

[Action] In this invention, a process for producing steel pipes having an outer diameter dimension of the cold reducing rolling to high precision steel tube, and drawing step by cold stop 3 roll reducer least 3 stands rolling, 2 more than two-roll type constant stand
Since the constant diameter process using a diameter machine is combined, variations in the finishing outer diameter caused by insufficient wall rigidity and springback and stand rigidity due to strength differences in the three-roll reducer can be adjusted while the subsequent roll gap is in operation. Since it can be adjusted in a constant diameter step using a simple two-roll type constant diameter machine, it is possible to obtain a highly accurate finished outer diameter dimension. In addition, up to the final two-stage stand of the drawing process by the 3-roll type reducer
The ellipticity of the roll of each stand is set to 2% or more, and squeeze rolling is performed at a high outer diameter reduction rate of 10% maximum outer diameter reduction rate per stand, and the ellipticity of the roll of the final front stand is 3% or less.
And, since it is drawn and rolled at the maximum outer diameter reduction rate of 5%, before the final
Deterioration of roundness due to reduction rolling at a high outer diameter reduction ratio in stands up to several steps is adjusted. Further, the roll groove circumferential length of the final stage stand product outside diameter circumference and rather equal, rolls of the ellipse
Rates and 0 to 1.5%, with a reduced outer diameter ratio of 0.5% or more,
Since the roll groove bottom radius of the final front stand is reducing rolling at the maximum outer than size reduction rate to determine when a following roll flange radius of the final stage stand, the case where the rolling diaphragm in circularity caliber 3-roll type reducer 2-stage It is possible to have the same finishing outer diameter dimensional accuracy.

In the present invention, the ellipticity of the rolls of each stand up to the final two-stage stand in the drawing process by the three-roll reducer is set to 2% or more, and the maximum outer diameter reduction rate per stand is set to 10%. , Outer diameter reduction rate up to 10
%, So that when the ellipticity of the roll is 2% or less, biting flaws occur. Also, the ellipticity of the roll of the final front stage is 3% or less , and the maximum outer diameter reduction ratio is 5
% And was of the because extremely roundness when ellipticity of the roll exceeds 3% deteriorates, the maximum outer diameter reduction ratio at that time 5
%Met. Further, the roll groove circumferential length of the final stage stand product outside diameter circumference and rather equal, the ellipticity of a roll 0-1.5
% , The outer diameter reduction rate is 0.5% or more , and the roll groove bottom radius of the final front stand is the roll flange radius of the final stand.
Maximum outer size reduction of the the less small rate, the ellipticity of the roll exceeds 1.5%, the outside diameter finish equivalent to the case of rolling a perfect circle caliber 3-roll type reducer two stages to determine when the following This is because accuracy can not be obtained. Further, if the outer diameter reduction ratio is less than 0.5%, deviation occurs in the finished outer diameter dimension, resulting in 0.
5% or more , the final roll groove bottom radius of the last stand is final
This is because a highly accurate finished outer diameter dimension can be obtained with a maximum outer diameter reduction ratio that is determined when the roll flange radius of the corrugated stand is less than or equal to the radius.

In the present invention, after the drawing process by the three-roll type reducer, the two- roll type of two or more stands is fixed.
The constant diameter process with the diameter machine was installed because the pipe outer diameter after 3 roll rolling becomes larger than the 3 roll hole type due to the spring back of the pipe in the cold 3 roll rolling. Proportional to. On the other hand, 3 roll reducer, since the gap adjustment is difficult, impossible to final finish outer diameter adjustment, the base material strength, the wall thickness is different, final finish outer diameter even in the same roll gap are different Will end up. Therefore, a pair of hole-type rolls are used for adjusting the final outer diameter.
Roll arrangement between stands with built-in stand
More than two stands that are placed 90 degrees apart, for example,
2 rolls composed of a straight roll stand and a horizontal roll stand
Install a ruler type constant diameter machine .

[0015]

Embodiment 1 The details of the present invention will be described below with reference to FIGS. 1 and 2 showing an embodiment. FIG. 1 is a schematic layout view of a reduction rolling mill for carrying out the method of the present invention, and FIG. 2 is a schematic explanatory view of a hole type of a three-roll type reducer. In Figure 1, 1 is a cold steel tube, 2 stand group 3-roll type reducer consisting stand n stages, 3 vertical roll stand 4 and horizontal roll disposed downstream of the stand unit 2 for 3 roll Reducer stand 5 is a two-roll type constant径機Ru Tona. The stand group 2 of the 3-roll type reducer consisting of n-stage stands is
Although not shown in the drawings, the ellipticity of the roll of each stand up to the final two-stage stand is set to 2% or more, and the drawing rolling is performed at a high outer diameter reduction rate of 10%, which is the maximum outer diameter reduction rate per stand. Then
Roll ellipticity of the final front stand is 3% or less, rolling diaphragm with 5% maximum outer size reduction rate, a roll groove circumferential length of the final stage stand product outside diameter circumference and rather equal, the ellipticity of a roll 0
˜1.5% , outer diameter reduction ratio of 0.5% or more , and maximum outer diameter reduction determined when the roll groove bottom radius of the final front stage is equal to or less than the roll flange radius of the final stand. It is configured to be rolled at a rate lower than the rate.

[0017] 2-roll constant径機3 consisting of vertical roll stand 4 and horizontal roll stand 5, performs outer diameter adjustment underwent reducing rolling at high reduced outer diameter ratio tube,
Maintains roundness at the final stage of a 3-roll reducer.
Incidentally, ellipticity Dn of the roll in this invention, as shown in FIG. 2, the radius of the flange portion of the roll 11 Rn, the radius of the groove bottom rn, mean radius _{ln = (Rn + r n)} /
2, n = 1, 2, 3, 4, ... (n = 1 is the first stage stun
As a de) is obtained by the following equation. Roll ellipticity Dn = {( Rn−rn) / ln } × 100 (%) Further, the outer diameter reduction ratio Redn of each stand is Redn =
By {(ln- ₁ -ln) / ln- ₁ } x 100 (%)
It is what I asked for. The performance of the outer diameter reduction ratio Redn
In the calculation, in the case of the frontmost stand (n = 1),
Since there is no stand, the pre-process of the 3-roll reducer
Squeeze roll in (n = 0)
Radius of the flange of the groove is R ₀ , radius of the groove bottom is r ₀ , average
Calculation is performed using a radius l ₀ , where R ₀ = r ₀ = l ₀ .

[0017] With the arrangements as described above, 3 roll ellipticity of each stand by roll reducer at the final stage before the previous stage stand or <br/> the drawing process was 2% or more, the maximum outer diameter per stand The outer diameter of the roll is reduced at a high reduction ratio of 10%, and the ellipticity of the roll of the final stand is 3%.
Follows and, because rolling diaphragm with maximum outer diameter decreasing rate of 5%, most
The deterioration of the roundness due to the reduction rolling at a high outer diameter reduction ratio in the stand up to the last stage before the end is adjusted. Further, the final stage static <br/> product outside diameter circumference a roll groove circumferential length of the command and rather equal, the roll
Ellipticity is 0 to 1.5% and outer diameter reduction rate is 0.5% or more
In, because the roll groove bottom radius of the final front stand is reducing rolling at the maximum outer than size reduction rate to determine when a following roll flange radius of the final stage stand <br/> de circularity caliber 3-roll type reducer 2 It is possible to obtain the finished outer diameter dimensional accuracy equivalent to that in the case of drawing rolling in a step. In addition, the method of the present invention comprises cold drawing rolling using a three-roll reducer with three or more stands and a two-roll type with two or more stands.
Since the constant diameter process by the constant diameter machine is combined, the variation of the finishing outer diameter caused by the lack of rigidity of the spring back and the stand due to the difference in the thickness of the mother tube and strength of the 3-roll reducer is adjusted during the operation of the subsequent roll gap. Possible 2
Since it can be adjusted with a roll type constant diameter machine, it is possible to obtain a highly accurate finished outer diameter dimension.

Example 2 A three-roll reducer consisting of six stands in which mother tubes having different outer diameters of 20.0 to 54.0 mm and arranged with a phase difference of 60 ° for each stand were used to reduce the outer diameter by 20%. After that, it was rolled with a constant diameter using a constant diameter machine consisting of a two-roll vertical roll stand and a two-roll horizontal roll stand. Then, the outer diameter of the three-roll reducer on the exit side of the final stand and the outer diameter after sizing with a two-roll sizing machine were measured. The result is shown in FIG. As shown in FIG. 3, on the outlet side of the final stand of the three-roll reducer, the outer diameter of the pipe becomes larger than the outer diameter of the product as the wall thickness increases. This is considered to be due to the springback of the steel pipe itself caused when the cold material is rolled if the thickness and strength of the mother pipe are different, and the insufficient mechanical strength and rigidity of the three-roll stand. On the other hand, when the diameter is reduced by the two-roll type constant diameter machine after the three-roll type reducer, the diameter is almost set to the outer diameter of the product even if the wall thickness and strength of the mother pipe are different.

Example 3 A three-roll reducer consisting of six stands arranged with a phase difference of 60 ° for each stand was used, and up to the fourth stand, the ellipticity of the roll was 3% or more and a maximum of 10% per stand. Cold-rolled steel pipes drawn and rolled at an outer diameter reduction ratio of 5
The ellipticity of Russia Lumpur stage stand by changing the 3-5% and reducing rolling up to 5% of the reduced outer diameter ratio, the ellipticity of Russia Lumpur final sixth stage stand 0%, 1. Circularity of the obtained product was measured by changing the amount to 25% and 2.75% and reducing the outer diameter at a reduction ratio of 1%. FIG. 4 shows the results. As shown in FIG. 4, when the ellipticity of the roll of the fifth stage, that is, the final front stage stand exceeds 3%, the roundness of the product is extremely deteriorated. Therefore, the roll of the final front stand has an ellipticity
Is 3% or less, and the roll of the final stage stand has an ellipticity
By setting 0 to 1.5% , the ellipticity shown in FIG.
%, A finish outer diameter accuracy equivalent to that obtained by drawing and rolling using a two-stage stand of 3 round caliber caliber is obtained.

Example 4 A three-roll reducer consisting of six stands in which mother tubes having an outer diameter of 54.0 mm and a wall thickness of 1.5 to 7.5 mm are arranged with a phase difference of 60 ° for each stand is used to form four stages. Up to the eye stand, the roll steel ellipticity is 3% or more, and the cold rolling of the cold rolled steel pipe with a maximum outside diameter reduction rate of 10% per stand is performed. Squeeze rolling at 3%, and roll ellipticity of the final 6th stage 0%, 1.0%
In the case of, the outer diameter reduction ratio was 0 to 1.2%, the outer diameter of the obtained product was measured, and the outer diameter deviation (mm) was calculated by subtracting the minimum outer diameter from the maximum outer diameter. . The result is shown in FIG. 5 in relation to the outer diameter reduction ratio in the final stand. As shown in FIG. 5, the outer diameter dimensional accuracy is improved by setting the outer diameter reduction rate in the final stand to 0.5% or more.

Example 5 As described above, the roundness of the pipe after being drawn and rolled by the three-roll type reducer is the best, but the roundness when the outer diameter is adjusted by the two-roll constant diameter machine. Outer diameter 5 for investigation
Using a 3-roll type reducer consisting of 6 stands in which mother tubes of 4.0 mm and a wall thickness of 1.5 to 7.5 mm are arranged with a phase difference of 60 ° for each stand, roll ellipses up to the 4th stand Up to 10 per stand at a rate of 3% or more
% Of the outer diameter reduction rate of the cold rolled steel pipe, the ellipticity of 3 rolls of the 5th stage stand is 3%, and the outer diameter reduction rate of the maximum is 5%. After performing squeeze rolling at 0.0% and an outer diameter reduction ratio of 1.2%, the outer diameter was adjusted using a constant diameter machine composed of a two-roll vertical roll stand and a two-roll horizontal roll stand. The outer diameter of the three-roll reducer on the exit side of the final stand and the outer diameter after adjusting the outer diameter with a two-roll type constant diameter machine were measured. Then, the outer diameter deviation (mm) obtained by subtracting the minimum outer diameter from the maximum outer diameter was obtained, and the outer diameter deviation in relation to the wall thickness is shown in FIG. As shown in FIG. 6, the roundness on the exit side of the final stand of the three-roll reducer is maintained as it is for the product whose outer diameter is adjusted by the two-roll constant diameter machine, regardless of the wall thickness.

[0022]

As described above, according to the method of the present invention, in the cold outer diameter reduction rolling of a steel pipe, it is possible to perform the reduction rolling at a high outer diameter reduction rate, and the thickness ratio t / D to the outer diameter can be reduced. High-precision small-diameter thick steel pipes can be manufactured with high-precision product outer diameter dimensions.

[Brief description of the drawings]

FIG. 1 is a schematic layout diagram of a reduction rolling mill for carrying out the method of the present invention.

FIG. 2 is a schematic explanatory view of a hole type of a 3-roll type reducer.

FIG. 3 is a graph showing the relationship between the wall thickness after drawing rolling and the outer diameter adjustment and the finished outer diameter in Example 2.

FIG. 4 is a graph showing the relationship between the roll ellipticity of the final stage stand and the product roundness when the roll ellipticity of the final front stage stand of the three-roll reducer in Example 3 is changed.

FIG. 5 is a graph showing a relationship between an outer diameter reduction ratio and an outer diameter deviation at a roll ellipticity of 0% and 1% of a final stage stand of a three-roll reducer in Example 4.

FIG. 6 is a graph showing a relationship between a base material wall thickness and an outer diameter deviation after an outer diameter is adjusted by a three roll reducer outlet side and a constant diameter machine in Example 5.

FIG. 7 is an explanatory view of a conventional 2-roll type reducer,
(A) is a schematic side view, (b) is a front view of the first stand, and (c) is a front view of the first stand.

8A and 8B are explanatory views of roll arrangement of a three-roll reducer, in which FIG. 8A is a front stage stand, and FIG. 8B is a front view of a next stage stand.

FIG. 9 is an explanatory diagram of biting out of a three-roll reducer.

FIG. 10 is a roll hole type explanatory view for preventing the 3-roll type reducer from being bitten out.

[Explanation of symbols]

 1 Cold Steel Pipe 2 3 Roll Type Reducer Stand Group 3 Constant Diameter Machine 4 2 Roll Type Vertical Roll Stand 5 2 Roll Type Horizontal Roll Stand 11 Roll 31 Hole Roll 32 Stand 33 Mother Tube 41 Hole Roll 42 Gap 43 Steel Tube 44 Biting out 51 Front stand 52 Rear stand

Claims (1)

(57) [Claims] 1. A three-roll reducer having three or more stands.
Drawing process and 2 roll type constant diameter machine with 2 or more stands
In the method according to the combination of the constant-radius step, to produce a steel pipe having an outer diameter of the cold-reducing rolling with a high precision steel tube, 3
The final stage before the previous stage Stan drawing step by the roll-type reducer
Roll ellipticity of each stand to de set to 2% or more,
1 and reducing rolling stand per maximum reduced outer diameter of 10% of the higher reduced outer diameter ratio, the roll ellipticity of the second last stage stand
3% or less , drawn and rolled at maximum outer diameter reduction ratio of 5%, final
The roll groove circumferential length of the stage stand product outside diameter circumference and rather equal, the ellipticity of a roll and 0 to 1.5%, the reduced outer diameter of 0.5
% Or more , the cold rolling of the steel pipe is characterized by performing reduction rolling at a maximum outer diameter reduction ratio determined when the radius of the roll groove bottom of the final stand is less than the radius of the roll flange of the final stand. Rolling method.