RU2096113C1 - Method of making sharply bent branch pipes - Google Patents

Abstract

FIELD: plastic metal working, namely, production of sharply bent branch pipes. SUBSTANCE: method comprises steps of power pushing heated tubular blank through horn shaped core with variable cross section in such a way that maximum deformation degree corresponds to leading cross section of shaping portion and subsequent deformation is realized at variable speed selected according to relation concerning to dependance between deformation rate, diameter of branch pipe, diameter of blank, blank wall thickness, size of mean line of core and its current value on deformed portion. EFFECT: enhanced efficiency.

Description

 The invention relates to the field of metal forming, and more particularly to methods for manufacturing steeply bent pipe bends.

A known method of manufacturing steeply curved bends, which consists in the continuous pulling of pipe billets along the press bar, heating and bending on a horn-shaped core with a variable cross section [1]
In the known method, tube blanks welded together on a molding mill when moving along the rod to the horn-shaped core are calibrated by the inner diameter, after which graphite oil lubricant is fed into the blanks. Then, while passing through the horn-shaped core, the workpieces are heated and deformed into a branch. At the exit from the horn-shaped core, the finished tap is cut with a cutter.

 This method is energy-intensive, since it includes welding the workpieces into a bag, heating to the technologically necessary temperature during broaching and subsequent cutting to obtain a finished bend. In addition, all of the above operations require accurate coordination in time and temperature parameters of the entire technological process of manufacturing bends. The absence of such coordination leads to obtaining bends with unequal strength parameters.

 There is also a method of manufacturing steeply curved bends by force pushing a heated tube billet through a horn-shaped core with a variable cross-section [2]. This method has the greatest number of common features with the claimed one and is close to it in technical essence, and therefore we took it as a prototype. It provides for various length-forming parts of the core of the zone of strain intensity. In the first and second zones, the strain intensity increases and then decreases. However, this method does not completely get rid of corrugation and the formation of peaks. This is due to the fact that an increase in the strain intensity in the first and second zones occurs over a lengthy section of the core part of the core. In addition, the presence of even smooth mates between different zones of deformations negatively affects the process of changing the shape of the pipe billet in the bend, which can also lead to thinning of the walls and ovality of the ends.

 The problem to which the proposed method is aimed is to reduce labor costs in the manufacture of bends by reducing the number of bends that require adjusting the geometric shape after passing the pipe billet along the horn-shaped core, that is, to increase the accuracy of manufacture.

 The technical result from the use of the claimed method is expressed in the reduction of corrugation by 90% and the prevention of thinning of the wall and ovality of the ends in the manufacture of bends.

где

v скорость деформации в текущем сечении формообразующего участка (1/мм);
v₀ скорость деформации в начальном сечении формообразующего участка (1/мм);
k коэффициент пропорциональности;
D внутренний диаметр отвода (мм);
d наружный диаметр заготовки (мм);
S толщина стенки заготовки и отвода (мм);
l текущая длина средней рогообразного сердечника (мм);
l₀ длина средней линии рогообразного сердечника (мм).The above technical result is achieved due to the fact that in the manufacture of bent bends by force pushing the heated tube billet through a horn-shaped core with a variable cross section, the maximum strain is carried out in the initial section of the forming section and then it is produced at a variable speed, and the strain rate is chosen from the ratio:

Where

v the strain rate in the current section of the forming section (1 / mm);
v ₀ the strain rate in the initial section of the forming section (1 / mm);
k coefficient of proportionality;
D inner diameter of the outlet (mm);
d outer diameter of the workpiece (mm);
S wall thickness of the workpiece and bend (mm);
l current length of the middle horn-shaped core (mm);
l _{0 the} length of the midline of the horn-shaped core (mm).

The strain rate in the initial section (v ₀ ) is selected depending on the steel grade, heating temperature, friction coefficient, etc. The strain rate varies in a wide range, the specific values of which were obtained experimentally (1 ^o C 100).

 Thus, the essence of the claimed method of manufacturing bends is that the deformation of the tube stock, that is, an increase in its diameter and bending in each section, is determined from the above ratio.

 The proposed method for manufacturing steeply curved bends consists in a certain sequence of actions performed on a pipe billet in the process of its transformation into a bend.

 In FIG. 1 shows a horn-shaped core used for making bends; in FIG. 2 pipe billet.

 The manufacture of curved bends is as follows. The process of directly obtaining bends is preceded by the process of creating a horn-shaped core with a special geometric profile that provides a variable rate of deformation of the tube billet when it is pushed through the core.

,
которое получают преобразуя формулу скорости изменения деформации.The radius of curvature (R) of the horn-shaped core in each section is determined from the ratio:

,
which is obtained by transforming the strain rate change formula.

подставляя в него значения текущего радиуса (R). Зная основные геометрические параметры рагообразного сердечника (R) и (D_c), изготавливают его одним из известных способов. Например отливкой или фасонным фрезерованием. Затем набор трубных заготовок насаживают на рогообразный сердечник, нагревают их до технологически необходимой температуры и с помощью силового пресса проталкивают по сердечнику. Трубная заготовка при этом увеличивается по внутреннему диаметру и одновременно изгибается, приобретая на выходе форму готового отвода.The current diameter (D _c ) of the core for the corresponding section is determined from the ratio known according to the Dolezal formula:

substituting the values of the current radius (R) into it. Knowing the basic geometric parameters of the crustacean core (R) and (D _c ), make it one of the known methods. For example, by casting or shaped milling. Then a set of tube blanks is mounted on the horn-shaped core, heated to the technologically necessary temperature and pushed along the core using a power press. In this case, the pipe billet increases in internal diameter and at the same time bends, acquiring the shape of a finished bend at the outlet.

 Thus, the proposed method of manufacturing bends is feasible using the used horn-shaped core, the geometric parameters of which are determined from the condition of the same volume of the tube billet and the finished bend: the invariance of the length of the outer generatrix of the bend and the tube billet, as well as the invariance of the wall thickness of the billet and the bend when broaching, that the maximum deformation of the tubular billet is produced in the initial section of the forming section of the horn-shaped core, followed by deformation carried out with a variable speed, determined from the formula for changing the strain rate. This method allows to reduce the number of defective bends, reduce the ovality of the ends and get rid of corrugation.

Claims (1)

A method of manufacturing steeply bent bends by force pushing a heated tube billet through a horn-shaped core with a variable cross section, characterized in that the maximum deformation is carried out in the initial section of the forming section, and then the deformation is carried out at a variable speed, which is selected from the ratio

Where

and correspondingly
V is the strain rate in the current section of the forming section (1 / mm);
V ₀ the strain rate in the initial section of the forming section (1 / mm);
K is the coefficient of proportionality;
D inner diameter of the outlet (mm);
d outer diameter of the workpiece (mm);
S wall thickness of the workpieces and bend (mm);
l current length of the midline of the horn-shaped core (mm);
l _{0 the} length of the midline of the horn-shaped core (mm).

Images