RU2580262C2 - Mandrel for calibrating the internal channel pipes - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metal forming and is used in the production tubing in the manufacture of pipes for very precise internal diameter. Mandrel has an operating part and positioned behind it in the form of a gauge portion of the cylindrical portion.

EFFECT: decrease in intensity of non-contact deformation of the pipe during the dispensing provided by the fact that the mandrel has a guide portion of the elastic member, and the working portion of the mandrel has a parabolic shape which blends in with the half-angle conical surface α vertex = 1÷3°.

2 cl, 3 dwg, 1 tbl

Description

The invention relates to the processing of metals by pressure and is used in the manufacture of pipes in the manufacture of particularly precise pipes in internal diameter, and can be used, for example, in the manufacture of bimetallic tubing, automobile shock absorbers, plungers and bodies of deep pumps and hydraulic cylinders, as well as in the manufacture of pipes for a high pressure fuel line for diesel engines and capillary pipes.

A mandrel is widespread (Shevakin Yu.F. et al. Pipe production. M.: Metallurgizdat, 1968), when distributed, the pipe is deformed on the working part of the mandrel, which has the form of a truncated cone with a half-angle α at apex = 8 ÷ 12 ° ( Fig. 1). In FIG. 1 depicts: 1 - the original pipe with the minimum allowable inner diameter; 2 - source pipe with the maximum allowable inner diameter; 3 - mandrel with a conical working part; 4 - calibrated pipe with a maximum inner diameter; 5 - calibrated pipe with a minimum inner diameter.

The process features are a small value of the degree of distribution (up to 10-15%) along the inner diameter, which is limited by the maximum allowable tensile tangential stresses. The disadvantage of this method is the low stability of the mandrel in the deformation zone due to the small contact length l _{k of the} inner surface of the pipe with the mandrel during the steady-state calibration process and the increased length of the zone of extrafocal deformation. Depending on the spread in the values of the radii of the inner surface of the original pipes r _0min ÷ r _0max during the distribution process, a different degree of non-contact distribution at the exit from the deformation zone h _min ÷ h _max and a distortion of the dimensions of the inner diameter at the outlet, expressed by the range of radii of the inner surface of the calibrated pipe δ = r _max -r _min , as a result of which the necessary accuracy of the internal channel of calibrated pipes is not provided. In this case, with an increase in the degree of distribution, there is an increase in the degree of non-contact deformation and a decrease in the accuracy of the size of the pipes. In addition, the small contact area reduces the stability of the distribution process and can lead to the appearance of curvature and irreparable marriage of the calibrated pipe.

Known prefabricated mandrel for the distribution of pipes (patent SU 1574326 A1 from 06/30/90), adopted as a prototype, which allows to increase the stability of the distribution process and the accuracy of calibrated pipes shown in FIG. 2. When pulling, through the element for connecting the mandrel with the traction body 8 through the rod 1 and nut 2, through the tube of the prefabricated mandrel with cylindrical guides 6, 7 and working elements 3-5 having a conical surface, the pipe is gradually deformed in sections 3-5 . In this case, the cylindrical guides 6, 7 are located after the working elements 3, 4 and 5. The working elements are separated from each other by the distance sleeve 9. The spread of the values of the internal diameters is reduced due to the fact that the required degree of distribution is crushed into several stages and a reduction is provided at each stage intensity of non-contact deformation.

In the prototype, for stable holding of the prefabricated mandrel on the axis of the pipe being processed, cylindrical guides are used with the ratio of the outer diameter D _n (d _n ) to the inner diameter of the pipe D _t (d _t ) in the area of the guide, determined by the following mathematical dependence:

where σ _t - yield strength of the pipe material;

E is the modulus of elasticity of the pipe material.

When the ratio of diameters is greater than 1 + 0.8 σ _t / E, it is difficult to conduct the distribution process due to the appearance of scoring on the inner surface of the pipe. When the ratio of diameters is less than 1 - 0.8 σ _t / E, a stable position of the mandrel is not ensured and the accuracy of the inner channel of the pipe is reduced by ovality and small-period curvature. This dependence shows that under certain conditions the inner diameter of the calibrated pipe can be both smaller and larger than the diameter of the calibrating girdle (cylindrical guide). When distributing pipes for structural purposes on a conical mandrel, it was noted that in order to fulfill condition (1), the degree of distribution should be limited to ~ 1%.

The listed methods have one and the same main drawback - the small extent of contact of the working part of the mandrel with the inner surface of the pipe and the large extent of the zone of extrafocal deformation due to the use of working parts with a conical surface.

The objective of the invention is to improve the accuracy and quality of the internal channel of the pipe. This is achieved due to the fact that the mandrel for calibrating the inner diameter of the pipes, having a working part and a calibrating part located behind it in the form of a cylindrical section, is characterized in that the working part of the mandrel is made in the form of two sections successively arranged along the axis of the mandrel, the first of which has the parabolic shape of the surface, and the portion located behind it - the conical shape of the surface with a half-angle at the apex equal to 1 ÷ 3 °, and also the fact that the mandrel has an input guide sleeve of elastic material.

The invention is illustrated by the diagram in FIG. 3, which shows a diagram of the distribution of the pipe mandrel, with the proposed profile of the working and guide parts. The mandrel 3 has an input guide sleeve of elastic material 2, a working element consisting of sections 4 and 5, and a calibrating section 6. Section 4 has a parabolic surface shape and is designed to deform pipes with relatively large degrees of deformation, and section 5 has a conical surface shape with a half-angle α at an apex equal to 1-3 ° and is intended for pipe deformation at small degrees of deformation.

After installing the pipe 1 in the drawing mill and applying lubricant to the inner surface, a mandrel 3 is introduced into the cavity of the pipe, connected through the rod to the traction body. The guide sleeve of elastic material 2 provides uniform distribution of lubricant on the inner surface of the pipe, as well as alignment of the distribution process. In the process of distribution, the pipe is sequentially deformed in sections 4-6 having lengths A, B and C. In this case, the initial pipe 1, which has an internal diameter value before distribution d _{dn0, is} first deformed in section 4 having a parabolic surface, then in conical section 5 and then on the calibrating girdle 6 with the diameter of the outer surface d _ODA and at the exit from the deformation _zone , after elastic unloading, the calibrated pipe 7 has an internal diameter value d _ext1 . The minimum value of the scatter of the values of the inner diameter of the pipes, and, therefore, the technical result is achieved by the deformation of the pipe first on the parabolic section 4, then on the conical section 5 and then on the calibrating girdle 6, which ensures the minimum degree of non-focal deformation.

The geometric parameters of the parabolic surface of section 4 are selected depending on the range of values of the internal diameters of the original pipes so as to ensure the maximum contact length of the inner surface of the pipe with the mandrel. The half-angle at the apex of the conical section 5, equal to 1-3 °, is due to the fact that with a lower half-angle, there may be cases of no contact of the inner surface of the pipe with the conical section 5, and with a larger angle, the inner surface of the pipe does not contact the calibrating girdle 6.

, где

- среднее значение внутреннего диаметра, S - среднеквадратическое отклонение d_вн, которое рассчитывается по формуле

. Этот показатель учитывает статистическое распределение размеров, поэтому является наиболее объективной формой оценки точности труб. Из рассчитанных показателей точности следует, что при калибровании труб по прототипу повышение точности достигается в 6,54 раза, а по предлагаемому способу - в 18,9 раза.A specific example of using the method of distributing pipes when calibrating carbon steel pipes (GOST R 52203-2004) is 73 × 5.5 for an inner diameter of 62.5. The calibrated pipes recorded the values of internal diameters in two mutually perpendicular directions, as well as the values of micro roughness. The results of the control of the geometric dimensions and values of micro roughness are given in the table. The coefficient of variation of the inner diameter was adopted as a criterion of accuracy.

where

is the average value of the inner diameter, S is the standard deviation of d _ext , which is calculated by the formula

. This indicator takes into account the statistical size distribution; therefore, it is the most objective form of pipe accuracy assessment. From the calculated accuracy indicators it follows that when calibrating the pipes according to the prototype, an increase in accuracy is achieved by 6.54 times, and by the proposed method - by 18.9 times.

Claims (2)

1. A mandrel for calibrating the inner diameter of the pipes, having a working part and a calibrating part located behind it in the form of a cylindrical section, characterized in that the working part of the mandrel is made in the form of two sections arranged in series along the axis of the mandrel, the first of which has a parabolic surface shape, and the section located behind it is a conical surface with a half-angle at the apex equal to 1 ÷ 3 °. 2. The mandrel according to claim 1, characterized in that it has an input guide sleeve of elastic material.

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