RU2702666C1 - Method of large-diameter pipes step molding - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to metal forming and can be used in production of large diameter welded pipes. Performing step-by-step forming of sheet with bending of its edges on press forming press from the first side to impart J-shape to the section. Then the sheet is moved, installed for the second side to be bent and the second side of the sheet is bent to produce C- and O-shaped profile. Folding of sheet second side is performed at deformation mode different from first side bending deformation mode, with stroke value providing equality of radii in deformation center of first and second sides of sheet after unloading R_p2=R_p1. By changing stroke value equality of radii of front and rear ends of pipe is provided after unloading R_p3=R_pn.

EFFECT: increased quality of pipes and reduced time for equipment adjustment.

1 cl, 4 dwg, 4 tbl

Description

The invention relates to the field of metal forming and can be used in the manufacture of welded pipes of large diameter line TESA 1420.

A known method of forming welded pipes of large diameter UOE, including bending the edges of the workpiece, preliminary molding in the press in a U-shaped profile and final molding in an O-shaped profile [Analysis of methods of forming a workpiece for the production of large diameter pipes. / Steel. 2009.12, p. 46-49. - S.V. Samusev, A.V. Lyuskin, V.V. Boldt].

The disadvantages of this method is to obtain a limited range of sizes of pipes with a wall thickness of up to 40 mm, high energy consumption of the equipment.

A known method of forming welded pipes of large diameter, including step-by-step molding of one side, resulting in a cross section of a J-shaped, then the second side to obtain a C-shaped profile and, ultimately, O-shaped profile of the molded pipe with an open seam.

[Presentation of SMS MEER "New Technologies for the Economical & Flexible Production of Large-diameter Pipes", 1 ^st Iranian Pipe & Pipeline Conference, 07.17.2007., P. 12-17].

The disadvantages of the method due to multi-junction free bending are the complexity of control and rigid fixation of the geometric parameters of the workpiece during its formation in steps, which can lead to defects in the pipe workpiece, and is also associated with insufficient study of the curvature of the workpiece, leading to uneven curvature of the workpiece profile.

Closest to the invention is a method of forming welded pipes of large diameter (see RF patent No. 2486981, published July 10, 2013), including stepwise bending of the longitudinal edges is carried out to obtain sections with a constant radius of curvature and edge sections with a variable radius of curvature when molding the main section on the press step-by-step molding (FFS) carry out the formation of edge sections.

The disadvantage of this method is that the step-by-step press does not take into account the differences in the deformation modes of the second side from the first and the uneven distribution of the mechanical properties of the workpiece, which can lead to excess ovality and shape deviation along the length associated with its springing, as well as asymmetry blanks relative to the weld.

The technical result of the claimed invention provides for improving the quality of products by reducing deviations in the geometry of the pipes and increasing productivity by reducing the time to configure the equipment.

The specified technical result is achieved by the fact that step forming is carried out taking into account the difference in deformation modes of the second side of the workpiece from the first and uneven distribution of the mechanical properties of the sheet in the transverse and longitudinal directions.

Studies have shown that step-by-step molding of the first and second sides of a workpiece with an identical stroke of the punch for two halves, with an even distribution of mechanical properties in the transverse direction, leads to asymmetry of the pipe, because the second half is underformed. The asymmetry of the workpiece, after step forming, is visually determined as the displacement of the edges in height, in the absence of the specified deviation, this defect can be detected after assembly and welding.

When bending the initial sheet blank to obtain an O-shaped blank with a gap and a symmetrical profile, the stroke of the upper tool for each step is determined individually, both for the first side and for the second. In order to reduce the setup time of the equipment, the value of the stroke of the second half h2 is determined from the following relation k = h ₂ / h ₁ , where h ₁ is the stroke of the first half, mm

The asymmetry coefficient is determined depending on the location of the i-th step along the perimeter of the workpiece, dividing the area of the pipe workpiece into the following four segments (Fig. 1):

from the 12 o’clock position to 2 o’clock, the stroke of the second half is greater than or equal to the stroke of the first half, i.e. k ₁ = 1 - 1.05;

from the 2 o’clock position to 3 o’clock, the stroke of the second half is greater than the stroke of the first, i.e. k ₁ = 1.05 - 1.1;

from the 3 o'clock position to 4 o’clock, the stroke of the second half is greater than or equal to the stroke of the first half, i.e. k ₁ = 1.1 to 1;

from the 4 o’clock position to 6 o’clock, the stroke of the second half is equal to the stroke of the first, i.e. k ₁ = 1.

The mode of forming the workpiece should be developed taking into account the distribution of mechanical properties. Depending on the assortment and method of production of sheet metal, the initial sheet blank has a different distribution of mechanical properties in width and length.

The reasons for the asymmetry of the tubular billet under correctly selected modes is the uneven distribution of mechanical properties, because strength properties affect the amount of unloading of the workpiece at each step. To take into account the influence of the uneven distribution of mechanical properties across the width, we use the asymmetry coefficient k2.

R_р2=R_р1=… R_рi;On FFS (figure 2) presents the focus of deformation of the workpiece at the i-th step, including the workpiece (1), the punch (2) and the matrix (strikers) (3). To solve the problem at the i-th step (figure 2 a) the molding of the second side is provided that

R _p2 = R _p1 = ... R _pi ;

where R _p1 and R _p2 are the averaged radii in the deformation zone after unloading from the first and second, respectively; those. R _p = R _n1 β ₁ = R _n2 β ₂ ;

where R _n1 and R _n2 are the average radii in the deformation _zone under load from the first and second sides, respectively, mm;

β ₁ and β ₂ are the unloading coefficients at the i-th step from the first and second sides.

The molding from the second side is performed by the amount of compression h at the i-th step, based on the specified condition according to the parameters determined by the following formulas:

)

)

where _T1 and _T2 are the yield stress of the initial billet at the i-th step from the first and second sides, respectively, MPa;

L is the length of the deformation zone, mm

Therefore, the magnitude of the stroke of the tool when stepping the second side h ₂ = h ₁ × k ₁ + k ₂ .

The step-by-step forming of the blank on PShF is performed simultaneously along the entire length. Due to the difference in the mechanical properties of the initial billet along the length, after step forming, the deviation of certain geometric parameters along the length, namely the distance between the edges of the front and rear ends, of the tube billet exceeds 40%.

To eliminate the deviation in the geometry of the tubular billet in the longitudinal direction, the tubular billet should be molded taking into account the condition that the radii after unloading at the ith step from the front R _rp and the rear R _rz wound ends R _rn = R _rz . Therefore, the radius after unloading at the i-th step is equal to R _p = R _np β _p = R _nz β _s , where R _np and R _nz are the average radii in the deformation zone under load from the front P.T. and rear ends Z.T. respectively mm; β _p and β _s - unloading coefficients at the i-th step from the front and rear ends. The coefficient k is determined by the formulas:

)

)

where at _TP . and _Tz . - the yield stress of the initial billet at the i-th step from the front and rear ends, respectively, MPa.

Consequently, the value of the tool stroke during step forming of the rear end is h _З = h _П + k, where h _П is the stroke value of the front end of the upper tool.

In FIG. 3 shows the position of the upper tool of the punch (2) and the forming knife (3) at the i-th step along the length and the change in the rise of the rear end relative to the front (3B):

 in position 1, k = ∆1 is the difference in the stroke value of the front and rear ends of the upper tool, provided that the strength of the rear end is lower than the front, i.e. k is less than 0;

in position 2, k = Δ2 is the difference in the magnitude of the stroke of the front and rear ends of the upper tool, provided that the strength of the rear end of the pipe billet is higher than the front, i.e. k is greater than 0;

at position 0, the tool position is not changed, t the strength of the rear end is equal to the strength of the front, i.e. k = 0.

As an example of application of the proposed molding method, we use a large diameter pipe 1422x25mm, strength class K60. The starting workpiece is a sheet with bent edges. The height of the bent edge Y ^/ = 100 mm; the distance between the edges X = 4322mm

1. Determine the number of steps N = 21

2. Determine the magnitude of the ten steps of the first side (table. 1)

Table 1
The amount of stroke of the upper tool of the first side Step number one 2 3 four 5 6 7 8 9 10 h ₁ 40 thirty 40 35 25 thirty 35 35 35 35

3. We determine the asymmetry coefficient k1 depending on the location of 10 steps of the second side around the perimeter of the pipe billet after step forming (Fig. 4)

table 2
Asymmetry coefficient k1 Step number one 2 3 four 5 6 7 8 9 10 Pos.hour 12–2 12–2 2-3 2-3 3-4 3-4 3-4 4-6 4-6 4-6 k ₁ one 1,03 1.05 1,07 1,1 1.05 one one one one

4. We determine the coefficient k2, taking into account the uneven distribution of mechanical properties along the width of the original sheet

)

)

Table 3
Asymmetry coefficient k2 σ _T1 543 545 540 537 532 531 529 522 520 523 β ₁ 1,233 1,283 1,231 1,251 1,308 1,274 1,247 1,243 1,241 1,243 R _P 731.4 885.7 730.5 797.7 986.3 879.4 794.7 792.2 791.5 792.5 σ _T2 540 541 538 533 531 529 530 528 524 522 β ₂ 1,209 1,251 1,215 1,219 1,300 1,258 1,255 1,291 1,274 1,235 k ₂ -0.04 -0.06 -0.03 -0.06 -0.01 -0.03 0.01 0.08 0.05 -0.01

5. We calculate the magnitude of the ten steps of the second side according to the formula h ₂ = h ₁ xk ₁₊ k ₂

Table 4
The amount of stroke of the upper tool of the second side k ₁ one 1,03 1.05 1,07 1,1 1.05 one one one one k ₂ -0.04 -0.06 -0.03 -0.06 -0.01 -0.03 0.01 0.08 0.05 -0.01 h ₁ 40 thirty 40 35 25 thirty 35 35 35 35 h ₂ 39.96 30.84 41.97 37.39 27.49 31.47 35.01 35.08 35.05 34,99

In tab. 4 presents data on the magnitude of the front end stroke from the first and second sides. To determine the magnitude of the back end stroke in 21 steps, it is necessary to calculate the coefficient k by analogy with the coefficient k2.

Claims (21)

A method of step forming large diameter pipes, including step forming a sheet with bending its edges on a step forming press from the first side to give a J-shaped cross section, moving the sheet, setting the manipulator to bend the second side and bending the second side of the sheet to produce C- and O -shaped profile of the molded pipe with an open seam, characterized in that the bending of the second side of the sheet is carried out under a deformation mode other than the deformation mode of bending of the first side, with a value of x yes, ensuring equal radii in the deformation zone of the first and second sides of the sheet after unloading R _p2 = R _p1 , component h _2i = h _1i × k _1i + k _2i , where h ₁ - the magnitude of the stroke of the tool when bending the first side; k _1i = 1-1,1 - asymmetry coefficient, taking into account the difference between the deformation modes of the second side of the sheet from the first; k _2i is a coefficient that takes into account the uneven distribution of mechanical properties along the width of the sheet, while

, where R _p is the average radius in the deformation zone after unloading; L is the length of the deformation zone, mm; β ₁ and β ₂ - unloading coefficients at the i-th step from the first and second sides of the sheet, wherein

), where σ _T1 , σ _T2 - yield strength of the initial workpiece at the i-th step from the first and second sides, respectively, MPa, the value of the stroke value, ensuring the equality of the radii of the front and rear ends of the pipe after unloading R _pz = R _pn , is h _C.t. = h _p.t. + k where h _z.t. - the magnitude of the stroke of the tool when bending the rear end of the sheet; h _p.t. - the magnitude of the stroke of the tool when bending the front end of the sheet; k is a coefficient that takes into account the uneven distribution of the mechanical properties of the sheet in the longitudinal direction, while

, where β _p and β _s are the unloading coefficients at the i-th step from the front and rear ends of the sheet, while

), where σ _Тп , σ _Тз - yield strength of the initial workpiece at the i-th step from the front and rear ends, respectively, MPa.

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