RU2309810C2 - Piercing method for making seamless pipe - Google Patents

Abstract

FIELD: piercing processes for making seamless pipes.

SUBSTANCE: method comprises steps of providing feed angle β and interaxial angle γ of main rolls in range determined according to expressions: 8° ≤ β ≤20°; 15°≤ β + γ ≤ 50°; setting relation of outer diameter do of solid blank with outer diameter d and thickness t of wall of hollow rolled piece after piercing according to expression: 1.5 ≤ - Ψ_r/Ψ_θ≤ 4.5 where Ψ_r =ln(2 t/do) and Ψ_θ = ln{2(d - t)/do}; setting relation of inlet diameter D1 and outlet diameter D2 of main rolls with said do, d and γ according to expression: (d/do)/(0.75 + 0.025γ) ≤ D2/D1.

EFFECT: possibility for suppressing effects of rotary forging and excess shear deformation without excess narrowing of roll diameter.

3 cl, 6 dwg, 2 ex, 2 tbl

Description

Technical field

The present invention relates to a method for flashing a workpiece in a seamless pipe manufacturing process. In particular, the invention relates to a firmware method performed with the possibility of manufacturing a thin-walled hollow roll from a workpiece with a high processing coefficient.

State of the art

The most common methods for manufacturing seamless pipes are the Mannesmann method in a mill for rolling tubes on a mandrel and the Mannesmann method in a mill for rolling seamless tubes on a mandrel. These methods include the steps of flashing a solid billet heated to a predetermined temperature in the furnace on a piercing mill to form a hollow bar, processing a hollow bar mainly by compressing its wall thickness on an extension mill, such as a mandrel tube mill or a mill for rolling seamless tubes on a mandrel, and subsequent processing of the hollow roll to a seamless tube of a given size, mainly by compressing its outer diameter on a reduction mill such as a calibration mill or extension mill. The present invention relates to a first step — a firmware step of the indicated steps.

As a prior art, inventions are proposed by the author of this invention in patent documents 1 and 2, corresponding to the publications of the patent application Hei 5-23842 and Hei 8-4811 considered.

The invention according to patent document 1 relates to a method for manufacturing a seamless pipe, characterized in that they provide a relationship between the feed angle β of the double-cone-shaped main rolls installed in such a way that they are transversely and vertically opposite each other along the rolling line for rolling the workpiece and the hollow roll, and the interaxial angle γ of the main rolls within the expressions (1) and (3) below, determine the relationship between the diameter "d _o " of the continuous billet and the outer diameter "d" and the thickness "t" of the hollow shell After flashing, in accordance with expression (4) below, the flashing coefficient is set to 4.0 or more, and the relative expansion of the pipe to 1.15 or more, or the ratio of wall thickness to outer diameter equal to 6.5 or less.

The feed angle β is the angle of the center line of the rolls with respect to the horizontal plane or vertical plane of the rolling line. The center angle γ is the angle between the center line of the rolls and the vertical plane or horizontal plane of the rolling line.

where Ψ _r = ln (2t / d _o ) and Ψ _θ = ln {2 (dt) / d _o }

The method according to document 1 is aimed at suppressing the effects of rotary forging and shear deformation, which often occur during flashing, especially in thin-walled flashing with a high processing ratio, as much as possible due to the fact that the feed angle β and the center distance γ of the rolls are maintained limits, which prevents the appearance of a defect in the inner surface or delamination in the center of the thickness, which occur in a stainless steel pipe or high alloy steel. This method is also aimed at solving technological problems such as the conicity or flaking of the pipe wall, or stuck ends by streamlining the distribution of circular deformation Ψ _θ and radial deformation Ψ _r , so that the relationship is observed according to the above-mentioned expression (4).

This known solution made it possible to manufacture pipes from difficult to process material according to the extrusion method of Ugine-Sejournet and according to the Mannesmann method for manufacturing pipes. Moreover, this solution provided a method for thin-walled firmware with a high processing ratio and also eliminated or reduced the subsequent elongation process and the compression process. Accordingly, this solution significantly improved the method of manufacturing seamless pipes.

For example, the Mannesmann piercing mill and the rotary rolling mill piercing mill used in the Mannesmann mill system for rolling tubes on a mandrel were replaced by one transverse piercing mill, which reduced the so-called “double-flashing method” to “single flashing method”. The system of the Mannesmann mill for rolling tubes on a mandrel is a system that includes processing using a piercing mill Mannesmann, an extension mill with a turning mandrel, a mill for rolling tubes on a mandrel, a rolling mill and a calibration mill.

In the Mannesmann mill system for rolling seamless tubes on the mandrel, the number of stands of the mill for rolling seamless tubes on the mandrel can be reduced by replacing the Mannesmann piercing mill with a transverse piercing mill. The Mannesmann mill system for rolling seamless mandrel pipes is a system that includes machining with a Mannesmann piercing mill, a mill for rolling seamless mandrel pipes and a crimping device to reduce tension.

Moreover, on the basis of the Mannesmann-Assel rolling system, which includes processing with the Mannesmann piercing mill, Assel mill and crimping device to reduce tension, a transverse piercing mill is also introduced in the indicated sequence. The use of a transverse piercing mill has certain operational advantages such as uniformity of the size of the workpiece and reduction of preparation time, since the so-called “dimensionless rolling” for the manufacture of many sizes of hollow rolls from a one-dimensional workpiece can only be performed when replacing the mandrel.

The invention according to Patent Document 2 has been developed to optimize the relationship between the diameter of the conical main roll and the diameter of the continuous blank. According to this invention, for the maximum possible suppression of the effects of rotary forging and excessive shear deformation, the diameter of the narrowing part of the conical main roll, i.e. the diameter D _{g of the} narrowing part of the roll and the diameter d _{o of the} workpiece are set in accordance with the following expression (a):

According to this solution, in order to stabilize the firmware, it is difficult to process the material, such as stainless steel and high alloy steel, without defects of the inner surface or delamination, it is necessary to minimize the diameter of the narrowing part of the roll relative to the diameter of the workpiece. But to minimize the diameter of the narrowing part of the roll, the diameters of the input side and the output side of the roll shaft must be reduced due to the design of the roll. This will reduce the strength of the bearings on which the roll shaft rests. In the case of a cone roll, the fatigue strength of the input side bearing becomes insufficient, causing problems of durability. Accordingly, an excessive reduction in the diameter of the narrowing part of the roll cannot be recommended for practical implementation.

The purpose of the invention

The purpose of the present invention is to provide a firmware method that is capable of suppressing the effects of rotary forging as much as possible and suppressing excessive shear deformation as much as possible without at the same time reducing the diameter of the narrowing portion of the roll.

Means of achieving the purpose of the invention

As a result of research to achieve the above goals, the author developed the invention related to the firmware method described below. Explanations of the reference signs in the description below are presented in FIG.

According to the firmware method for the manufacture of a seamless pipe, the feed angle β and the axle angle γ of the double-support conical main rolls are mounted opposite each other transversely or vertically along the rolling line in the range of values according to the following expressions (1) - (3), determine the relationship between the outer diameter d _o »solid billet with the outer diameter" d "and thickness" t "wall hollow piece after piercing along the following expression (4), and define the relationship of the inlet diameter d ₁ and outlet diameter d ₂ Basic rolls mentioned "d _o", "d" and γ along the following expression (5).

where Ψ _r = ln (2t / d _o ) and Ψ _θ = ln {2 (dt) / d _o }

The feed angle β is the angle of the center line of the roll with respect to the horizontal plane or vertical plane of the rolling line. The center distance γ is the angle of the center line of the roll with respect to the vertical plane or horizontal plane of the rolling line.

In the method according to the present invention, the relationship between the input diameter D ₁ and the output diameter D _{2 of the} main rolls with said "d _o ", "d" and γ preferably satisfies expression (6).

The effect of the method in accordance with the present invention can, to a sufficient degree, be ensured by flashing with a flashing coefficient of 4.0 or more, with a relative expansion of the pipe of 1.15 or more, and with a ratio of the wall thickness to the outer diameter of the hollow roll, equal to 6.5 or less when the effects of rotary forging and excessive deformation become noticeable.

Brief Description of the Drawings

Figure 1 depicts the implementation of piercing rolling.

Figure 2 shows the effect of the relative expansion of the diameter (D ₂ / D ₁ ) and the relative expansion (d / d ₀ ) of the pipe on the effects of rotary forging (reduction in area during tensile testing of a small test sample).

Figure 3 shows the effect of the relative expansion of the diameter (D ₂ / D ₁ ) and the relative expansion (d / d ₀ ) on the excessive shear deformation (circular shear deformation).

4 is a graph showing the relationship between the relative expansion of the diameter (D ₂ / D ₁ ), the relative expansion (d / d ₀ ) of the pipe and the angle (β) of the feed roll.

5 is a graph showing the relationship between the relative expansion of the diameter (D ₂ / D ₁ ), the relative expansion (d / d ₀ ) of the pipe and the angle (γ) of the feed roll.

6 is a graph of the relationship between the index of the shape of the roll or (d / d ₀ ) / (D ₂ / D ₁ ) and the center axis (γ) of the roll.

Most preferred embodiment of the invention

The ranges of values of the feed angle β and the interaxial angle γ in the method according to the present invention are the same as in the above-mentioned inventions of patent documents 1 and 2. These ranges of values were determined in terms of reducing the effects of rotary forging and suppressing excessive shear deformation - to the maximum possible degrees.

The range of values of the ratio of the radial logarithmic strain Ψ _r with the circular logarithmic strain Ψ _θ , i.e. "-Ψ _r / Ψ _θ ", the same as according to the invention according to patent document 1. This is based on the principle of the distribution of the rolling reduction when flashing in the longitudinal direction, and deviation from this principle causes tapering (leakage phenomenon) or peeling of the pipe wall or stuck in the end, which may stop the firmware itself.

The main characteristic of the present invention is based on the fact that the shape of the roll relative to the diameter of the workpiece significantly affects mainly the effects of rotary forging. This was discovered by the author of the present invention as described below.

In the roll of the cone type, the relationship is between the ratio of the input diameter D ₁ and the output diameter D ₂ between the pipe material and the main roll of the cone type, i.e. relative expansion of the diameter D ₁ / D ₂ ; the ratio of the outer diameter "d" of the hollow roll and the outer diameter "d ₀ " of the workpiece, i.e. the relative expansion of the pipe in relation to the pipe material "d / d _o ", and the interaxial angle γ were investigated from the point of view of suppressing the effects of rotary forging and excessive shear strain.

Before conducting the experiments, a choice was made of the index characterizing the shape of the roll. A study was conducted of the following question: can the various possible indices be indices characterizing the relationship with the effects of rotational forging or excessive shear deformation. Therefore, the ratio between the relative expansion of the pipe in relation to the pipe material "d / d _o " and the relative expansion of the diameter "D ₂ / D ₁ " of the cone roll (d / d _o ) / (D ₂ / D ₁ ) was chosen as an index.

The ratio of the roll width of the roll “L ₁ / L ₂ ” can also be considered an index. L ₁ is the width of the barrel of the roll of the input side in the narrowing position of the roll according to figure 1, i.e. the distance from the initial point of capture by the rolls of the pipe material to the narrowing part of the roll. L ₂ is the width of the barrel roll of the output side roll. But this relationship is not directly related to the effects of rotational forging or excessive shear deformation, and its proper range has been determined from a different perspective. Usually an unnecessary margin is added to the width of the roll barrel, and therefore it is difficult to determine the ratio of the width of the roll roll barrel as such.

As a rule, the relative expansion of the diameter “D ₂ / D ₁ ” of the roll increases with an increase in the center angle γ, as a result of which the taper is sharpened. But if the center axis of the roll is the same and the width L _{2 of the} barrel of the roll of the output side is the same, then the relative expansion D ₂ / D _{1 of the} diameter of the roll inevitably decreases with an increase in the relative expansion "d / d _o " of the pipe in relation to the pipe material . Thus, the design of the roll should provide the necessary D ₂ / D ₁ taking into account "d / d _o ", and the difficulty of the design of the roll depends on this moment.

The design of the roll should be made in terms of reducing the effects of rotary forging in front of the mandrel during flashing and also in terms of reducing excessive shear deformation, i.e. circular shear strain γ _r θ after flashing, since embrittlement of the pipe material due to the effects of rotary forging causes a defect in the inner surface of the pipe, and excessive shear strain is a factor in the propagation of defects in the inner surface.

The author performed experiments on piercing a carbon steel billet as a sample using an experimental transverse piercing mill, while changing the shape of the roll to study in detail the effect of the shape of the roll on the effects of rotary forging and excessive shear deformation. The experimental conditions are presented in Tables 1 and 2. The wall thickness t of the hollow roll after flashing was set so as to obtain the ratio of the wall thickness to the outer diameter, i.e. (t / d) in the values of 2.5-3%.

Table 1 γ Dg (mm) D ₁ (mm) D ₂ (mm) D ₂ / D ₁ d _o (mm) d (mm) d / d _o

Rating 0 ° 400 380 380 1.00 70 70 1.00 1.00

370 0.97 84 1.20 1.24

355 0.93 105 1.50 1.62

325 0.86 140 2.00 2.33

5 ° 400 360 430 1.19 70 70 1.00 0.84

410 1.14 84 1.20 1.05

390 1.08 105 1.50 1.39

370 1.03 140 2.00 1.92

10 ° 400 340 485 1.43 70 70 1.00 0.70

450 1.32 84 1.20 0.91

415 1.22 105 1.50 1.23

395 1.16 140 2.00 1.72

15 ° 4.00 310 525 1.69 70 70 1.00 0.59

500 1.61 84 1.20 0.75

475 1.53 105 1.50 0.98

450 1.45 140 2.00 1.37

20 ° 400 280 560 2.00 70 70 1.00 0.50

540 1.93 84 1.20 0.62

520 1.86 105 1.50 0.81

490 1.75 140 2.00 1.14

25 ° 400 240 600 2.50 70 70 1.00 0.40

575 2.40 84 1.20 0.50

550 2.29 105 1.50 0.65

520 2.17 140 2.00 0.92

30 ° 400 200 650 3.25 70 70 1.00 0.31

630 3.15 84 1.20 0.38

600 3.00 105 1.50 0.50

570 2.85 140 2.00 0.70

table 2 γ Dg (mm) D ₁ (mm) D ₂ (mm) D ₂ / D ₁ d _o (mm) d (mm) d / d _o

Rating 0 ° 500 480 480 1.00 70 70 1.00 1.00

470 0.98 84 1.20 1.22

455 0.95 105 1.50 1.59

425 0.89 140 2.00 2.22

5 ° 500 460 530 1.15 70 70 1.00 0.87

510 1.11 84 1.20 1.08

490 1.07 105 1.50 1.41

470 1.02 140 2.00 1.76

10 ° 500 440 585 1.33 70 70 1.00 0.75

550 1.25 84 1.20 0.96

525 1.19 105 1.50 1.28

495 1.13 140 2.00 1.76

15 ° 500 410 625 1.52 70 70 1.00 0.66

600 1.46 84 1.20 0.82

575 1.40 105 1.50 1.08

550 1.34 140 2.00 1.49

20 ° 500 380 660 1.73 70 70 1.00 0.58

640 1.68 84 1.20 0.71

620 1.63 105 1.50 0.92

590 1.55 140 2.00 1.28

25 ° 500 340 700 2.06 70 70 1.00 0.49

675 1.98 84 1.20 0.61

650 1.91 105 1.50 0.78

620 1.82 140 2.00 1.10

30 ° 500 300 750 2.50 70 70 1.00 0.40

730 2.43 84 1.20 0.49

700 2.33 105 1.50 0.65

670 2.23 140 2.00 0.89

An example of the effect of the relative expansion of the diameter "D ₂ / D ₁ " and the relative expansion of the "d / d _o " pipe on the effects of rotary forging is shown in Fig.2 (a) and (b). An example of the effect of the relative expansion “D ₂ / D ₁ ” of the diameter and the relative expansion “d / d _o ” of the pipe on excessive deformation is shown in FIGS. 3 (a) and 3 (b).

The influence of the roll shape on the effects of rotary forging was evaluated when the main rolls and the disk roll were stopped in the middle of the firmware to form an “intermediate stop material” and then take a sheet-like small sample for tensile testing with a parallel length of 25 mm and a thickness of 3 mm in the diameter direction (wire diameter ) at right angles to the axial direction from the head of the mandrel. A tensile test was then performed at room temperature to determine the effect of the mold on the reduction in area (%). The effects of rotary forging are more pronounced in a decrease in area (%) than in elongation (%) in a tensile test.

The measurement of circular shear strain γ _r θ for excessive shear strain was carried out by the method of "immersion pins". That is, many pins were deepened parallel to the axis along the diameter of the continuous billet and the shear circular strain γ _r θ of the hollow roll after flashing was measured using a hollow roll.

According to figure 2, for example, if we assume that the interaxial angle γ of the roll is fixed, then the reduction in area can be set large, because the relative expansion of the "d / d _o " pipe is smaller or the relative expansion of the "D ₂ / D ₁ " diameter is larger, that is, the effects of rotary forging can be reduced. In other words, the range of the feed angle β, where the reduction in the area of the pipe material in front of the mandrel is larger than that of steel, can be expanded.

Also according to figure 3, the circular shear strain can be reduced, because the relative expansion of the pipe is smaller or the relative expansion of the diameter is larger, that is, excessive shear deformation can be suppressed. Accordingly, even with increased relative expansion of the pipe, the circular shear strain will never become too large if it is ensured that the shape of the roll, with a sufficiently large interaxial angle γ of the roll, increases the relative expansion of the diameter.

If the roll does not have a proper shape or if the roll center angle is small compared to the relative expansion of the pipe, then the output diameter D _{2 of the} roll will approach the narrowing diameter D _g due to too small relative expansion of the diameter to allow for relative expansion of the pipe. Therefore, a decrease in the peripheral speed of the exit side of the rolls at the point of separation of the pipe material will weaken the effect of drawing the pipe material to the exit side. This circumstance makes the slip between the roll and the pipe material noticeable. This slip is also affected by the diameter of the workpiece, slip also increases on the input side, and therefore the effects of rotary forging are manifested due to an increase in the frequency of rotary forging, and the range of feed angle β, due to which the pipe material in front of the mandrel becomes more fragile than steel, increases . The frequency of rotary forging is the number of rotations of the workpiece from the moment when it is captured by the rolls, until the moment when it is carried away to the head of the mandrel.

Of course, excessive shear strain begins to manifest itself. The extreme case of this occurs when the output diameter D _{2 of the} roll approaches the input diameter D ₁ . “Excess shear strain” is a general term for circular shear strain γ _r θ, shear strain due to tilting γ _{θ1 of the} surface and longitudinal shear strain γ _1r .

The relationship between the relative expansion "d / d _o " of the pipe, the relative expansion D ₂ / D _{1 of the} roll diameter and the center axis γ of the roll is shown in Figs. 4 and 5. The result of checking the correct form of the roll is also shown in these drawings. That is, a white circle indicates that the roll has a proper shape, and black - an inappropriate shape.

It is necessary to determine the appropriateness of the shape of the roll based on the effects of rotary forging. As a criterion, the possibility was taken to increase the ductility (decrease in area) of the pipe material in front of the mandrel as compared with the decrease in the area of the material steel, i.e. blanks. The firmware was made with a feed angle β of 12 °, and, as indicated above, the tensile test was performed using a sheet-like small tensile test specimen with a parallel length of 25 mm and a thickness of 3 mm taken from the cross section of the pipe material in front of the mandrel to check whether the decrease in the area of the pipe material in front of the mandrel exceeds the decrease in the area of the steel material. The white circle shows cases with a large decrease in area, and other cases are shown in black circles. From figures 4 and 5 it follows that the condition of the proper form of the roll is as follows:

(5/6) +1/3) (d / d _o ) ≤ (D ₂ / D ₁ )

1 + 0.03γ≤ (D ₂ / D ₁ )

As mentioned above, the relationship between “D ₂ / D ₁ ”, “d / d _o ” and γ can be explained by graphs, taking “D ₂ / D ₁ ” as the index of the roll shape, but then it will be more difficult to express the variables collectively mathematically. To circumvent this difficulty, the author chose the ratio of the relative expansion of the pipe "d / d _o " in relation to the material of the pipe and the relative expansion "D ₂ / D ₁ " of the diameter of the roll, as an index of the shape of the roll, i.e.

"(D / d _o ) / (D ₂ / D ₁ )"

6 shows a graph of the relationship between the index “(d / d _o ) / (D ₂ / D ₁ )” of the roll shape, the relative expansion “d / d _o ” of the pipe and the center angle γ. Although “d / d _o ” remains the parameter with “(d / d _o ) / (D ₂ / D ₁ )” as the ordinate, and γ as the abscissa, respectively, the condition giving the proper shape of the roll can be expressed by the following inequality :

(d / d _o ) / (D ₂ / D ₁ ) ≤0.75 + 0.025γ

From it we can derive the following expression (5)

To solve equipment problems such as strength, durability, etc. bearings, when the diameter D _{g of the} narrowing part of the roll is set to a value 4.5 times or more than the diameter "d _o " of the workpiece, in order to ensure the optimal shape of the roll without unduly reducing the diameter of the roll of the input side, the following expression is obtained:

1.00-0.027γ≤ (d / d _o ) / (D ₂ / D ₁ )

From it derive the expression (6)

The condition for obtaining the desired shape of the roll is that it corresponds to expression (7) deduced from expression (6) and the above-mentioned expression (5).

Tables 1 and 2 show cases where the diameter of the narrowing part of the roll D _g = 400 mm and D _g = 500 mm, respectively, and also the graphs of Figures 2-6 (a) show the case for the diameter D _g = 400 mm of the narrowing part of the roll; and (b) shows the case for a diameter D _g = 500 mm of the tapered portion of the roll. Accordingly, the comparison between (a) and (b) leads to a discussion of the content of the invention disclosed in Patent Document 2. The upper limit of the above expression (expression 7) can be easily obtained by performing the same calculations according to Tables 1 and 2 for D _g = 315 mm.

D ₁ D ₂ are respectively the input diameter and output diameter of the conical main roll, provided that the pipe material is captured on the input surface of the main roll and is separated from the roll on the output surface. More precisely, the diameter of the main roll in the grip position of the workpiece by the rolls is D ₁ , and the diameter of the main roll in the position in which the hollow roll is separated from the rolls is D ₂ .

Finally, the following is a description of the width of the roll barrel. The width L of the roll barrel is the sum of L ₁ and L ₂ in FIG. Exceeding the required margin of the width of the barrel rolls leads to excessive coarsening of the entire structure of the mill. Accordingly, the width L _{1 of the} barrel of the roll of the input side must be determined within the limits that will never violate the stable grip. The width L _{2 of the} barrel of the rolling roll of the output side should be determined taking into account the frequency of rolling the pipe in the rolls during the finish rolling. The ratio of the width of the barrel of the rolling roll L ₂ / L _{1 is} preferably set in the following limit:

1,0≤L ₂ / L ₁ ≤2,0

Example 1

A billet with a diameter of 60 mm made of austenitic stainless steel 18% Cr-8% Ni was used as a sample, and a high processing coefficient and thin-walled firmware with a relative expansion of the pipe equal to 1.5 were made using wiring. The heating temperature of the preform was 1250 ° C. Of course, the hot workability of stainless steel was very low compared to the workability of carbon steel.

1. Roll condition

Center angle: γ = 25 °

The diameter of the tapering part: D _g = 400 mm

Feed angle: β = 12 °

Inlet Diameter: D ₁ = 240 mm

Output Diameter: D ₂ = 550 mm

The relative expansion of the diameter of the roll: D ₂ / D ₁ = 2.29

Inlet roll roll barrel width: L ₁ = 300 mm

Barrel width of the roll roll of the output side: L ₂ = 460 mm

Roll roll barrel width: L ₁ + L ₂ = 760 mm

The ratio of the width of the barrel roll: L ₂ / L ₁ = 1,53

2. Firmware status

The diameter of the mandrel: d _p = 80 mm

Diameter of the workpiece: d _o = 60 mm

Diameter of a hollow roll: d = 90 mm

Wall thickness of a hollow roll: t = 2.7 mm

The relative expansion of the pipe: d / d _o = 1,50

The ratio of piercing rolling: d ₀ ² / 4t (dt) = 3.82

The ratio of wall thickness to outer diameter: (t / d) × 100 = 3%

Roll Form Index: d / d _o / (D ₂ / D ₁ ) = 0.655

Radial logarithmic deformation: Ψ _r = ln (2t / d _o ) = ln0.009 = -2.408

Circular logarithmic deformation: Ψ _θ = ln {2 (dt) / d _o } = ln2.91 = 1.068

Compression distribution ratio: -Ψ _r / Ψ _θ = 2.255.

As indicated above, since the ratio of the distribution of the decrease in the circular direction with respect to the radial direction or the ratio of the radial distribution of the longitudinal direction with the circular direction was provided correctly, the firmware could be performed without tapering or flaking. Since the roll shape was ensured to be correct, defects in the inner surface or delamination were not observed, even if a high machining ratio and ultra-thin walled firmware were difficult to process.

Example 2

The hot processing of high alloy steel is worse than that of stainless steel, which often causes delamination at a piercing temperature in excess of 1275 ° C. In this example, a workpiece with a diameter of 70 mm from high alloy steel 25% Cr-35% Ni-3Mo was used; high processing ratio and thin-walled firmware with a relative expansion of the pipe equal to 2, were performed at a temperature of 1200 ° C using a disk roll.

1. Roll condition

Center angle: γ = 30 °

The diameter of the tapering part: D _g = 500 mm

Feed angle: β = 12 °

Inlet Diameter: D ₁ = 300 mm

Output Diameter: D ₂ = 670 mm

The relative expansion of the diameter of the roll: D ₂ / D ₁ = 2.23

Inlet roll roll barrel width: L ₁ = 300 mm

Barrel width of the roll roll of the output side: L ₂ = 460 mm

Roll roll barrel width: L ₁ + L ₂ = 760 mm

The ratio of the width of the barrel roll: L ₂ / L ₁ = 1,53

3. Firmware status

The diameter of the mandrel: d _p = 130 mm

Workpiece diameter: d _o = 70 mm

Diameter of a hollow roll: d = 140 mm

Wall thickness of a hollow roll: t = 3.5 mm

The relative expansion of the pipe: d / d _o = 2,00

The ratio of piercing rolling: d ₀ ² / 4t (dt) = 2.56

The ratio of wall thickness to outer diameter: (t / d) × 100 = 2.5%

Roll Form Index: d / d _o / (D ₂ / D ₁ ) = 0.897

Radial logarithmic deformation: Ψ _r = ln (2t / d _o ) = ln0.10 = -2.303

Circular logarithmic deformation: Ψ _θ = ln {2 (dt) / d _o } = ln3.90 = 1.361

Compression distribution ratio: -Ψ _r / Ψ _θ = 1,692.

As indicated above, since the ratio of the distribution of the decrease in the circular direction with respect to the radial direction was provided correctly, and the roll shape was also performed correctly, the firmware could be completed without any difficulties, even if a high processing ratio and ultra-thin walled firmware difficult to process were used material.

Industrial applicability

In the firmware method according to the present invention, the correct relationship was established between the relative expansion of the pipe in relation to the pipe material and the relative expansion of the diameter of the conical main roll. Accordingly, the effects of rotary forging during the flashing process can be largely suppressed, in a certain way to prevent the appearance of defects on the inner surface and delamination that can occur with a high degree of processing and with thin-walled piercing rolling of such a difficult to process material as stainless steel or high alloy steel. According to the method of the present invention, firmware with pipe expansion can be performed with a relative pipe expansion of 2.0.

As mentioned above, the present invention proposed a flashing method with a significant center angle to reduce the effects of rotary forging and suppress excessive shear deformation, and also provided some other novelty technical solutions. An increased center angle is a necessary condition for reducing the effects of rotary forging and suppressing excessive shear deformation, but not a sufficient condition. A necessary and sufficient condition is the optimization of the shape of the roll, and an increased center distance is a necessary condition for optimizing the shape of the roll.

Claims (3)

1. The method of firmware for the manufacture of seamless pipes, comprising the following stages: the exposure angle β of the feed and the interaxial angle γ of the two-bearing conical main rolls mounted opposite each other transversely or vertically along the rolling line in the range of values according to the expressions (1) - (3)

setting the relationship of the outer diameter "d _o " of the continuous billet with the outer diameter "d" and the thickness "t" of the wall of the hollow roll after flashing in accordance with the expression (4)

where Ψ _r = ln (2t / d _o ) and Ψ _θ = ln {2 (dt) / d ⁰ }, setting the relationship of the input diameter D ₁ and the output diameter D _{2 of the} main rolls with the above-mentioned "d _o ", "d" and γ in accordance with the expression (5)

. 2. The firmware method according to claim 1, characterized in that the relationship between the input diameter D ₁ and the output diameter D _{2 of the} main rolls with the aforementioned "d _o ", "d" and γ satisfies the expression (6)

. 3. The firmware method according to any one of claims 1 or 2, characterized in that the firmware is performed with a firmware coefficient of 4.0 or more, and the relative expansion of the pipe is 1.15 or more, or the ratio of the wall thickness to the outer diameter of the hollow roll is 6.5 or less.

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