SU507415A1 - Pipe breaking method - Google Patents

Description

(54) METHOD FOR CUTTING PIPES

The invention relates to machine-building and can be used in the preparation shops of bearing plants for the cold breaking of pipes made of steel SH-15,

There are known methods for cold breaking of pipes, which consist in the fact that the separation f of the pipe is carried out according to the three-point bend scheme, which does not ensure the sufficient quality of the resulting pipe billet and requires significant technological equipment.

GG of power and dimensions

The known method of cold pipe breaking is that the breaking force in the pipe, in the zone with the concentrator, is created by applying a uniformly PS to the perimeter of the wall from the outside and inside of the distributed hydrostatic load.

However, the load must be applied from the inside and outside of the pipe, besides, high hydrostatic pressure must be strictly measured from the outside and inside to eliminate the crushing or buckling of the pipe wall during loading.

The purpose of the invention is to reduce hydrostat

(chesky pressure and increase performance

This is achieved by the fact that a pipe with stress concentrators applied along the entire length and loaded from the inside with a high hydrostatic pressure is pulsed from the outside with liquid nitrogen, and then the shock wave is compressed from one end of the pipe and broken into dimensional workpieces.

Fig.1 shows the schematic diagram of pipe breaking; Fig. 2 shows a plot of stresses when a pipe is subjected to all breaking loads; in fig. 3 - plot Nv-przheniyev2,7, along the conditional axis of symmetry of the pipe from all loads; Fig. 4 is a diagram of pipe separation.

The pipe 1 with the concentrators of the stresses 2 preliminarily applied along the entire length is loaded from the inside with a high hydrostatic pressure P, and then cooled for 15–2 o sec with liquid azo Nt washing the pipe from the outside, as a result of loading the pipe from the inside side high hydrostatic pressure in it there are voltages g (V) Hf) (Fig. 2), which can be described by the following equations

b. R

ez

b, R

- (1 - ft-p #.

(E, R

(l, T о С Е гЮ - 2ТГГ7 У

NO - 77G7G

te

G

ZLCn-where E is Young's modulus, kg / cm; L - coefficient of linear metal expansion, 1 / degree; Poisson ratio

sQ.er- (P-i

b., g, .. 1

u (p, t) 2 (MM) j (f7J

K / V Jj5 "JL ™ /

e (p.f) Y оС), J г-current radius. It is assumed that ttf, we get anach ash b & eSRD)) StflP-i) -, z (P-t) inside the outer wall and the outer surface of the wall (om. FIG. 2). The total stresses 6g, S (rl) need to be in the order of 0.5-0.7 :. in 9, i.e. it is THIN, when the destruction is impossible, but in its beginning the elastic energy stored Off P, t, will be enough to move the breaking fracture. 15-20 seconds after the start of cooling with liquid nitrogen, the outer surface of the Tpyfei wall on one of the end faces excites a shock wave of compression

where P is the hydrostatic pressure; pipe radii.

Wherein . the top of the hub have a positive sign, and S is negative,

B - as a result of cooling of the pipe from the aneshne side, voltage (b) arises in it; i (i) i ((.o) reaching a significant value due to the fast cooling mode (see Fig. 2), and which can be described by the following equations

(,

 ...

(2 | -sf) "

1-2C "if

ZYG

2 (-. C

IFT temperature difference with respect to external and internal pipe dimensions. The simultaneous action of pressure and temperature can be determined by expressions of intensity O, which propagates along the pipe until it is dead; the opposite of the free end face is reflected from it by an extension pulse having the same the shape and magnitude as the impulse is compressed. If the tensile stress (ts y created by impulse impulse, exceeds in sum with the previously created total, voltage ej / p, {) the strength of steel SHKh - 15Sb (, p) then the destruction from the stress concentrator of the inner pipe will develop (see Fig. 4). The velocity of the expansion shock wave along the pipe should not be greater than the pressure decompression rate of the blueness inside the pipe to prevent removal

The stresses in the walls are coarse before the shock wave reaches.

The proposed method of cold pipe breaking with its relative simplicity and cost price allows to increase the productivity of breaking pipes from ShKh-15 steel in comparison with the existing separation means. In addition, the fracture has a clean surface with microroughness in the grain limits, without chips, tears, macro-, microcracks and smth.

/ 2

Claims (1)

Claims method of pipe lambing, including applying stress capacitors to the outer surface of the pipe and applying a high hydraulic pressure to the internal surface of the pipe, characterized in that, in order to reduce the hydrostatic pressure and increase the breaking performance, the pipe is cooled from the outside g to the temperature of liquid nitrogen, and then from one of the ends excite a longitudinal shock wave of compression. Fig 1 g (i (tJ .g I; Valia grow 2