SU1585046A1 - Method of producing tubes - Google Patents

Abstract

The invention relates to the processing of metals by pressure and can be used in the manufacture of pipes from stainless steels by drawing on a deformable core. The purpose of the invention is to improve the quality of pipes by increasing their resistance to intergranular corrosion. The core before entering the pipe is subjected to heating in a decarburizing environment. Subsequent drawing of stainless steel pipes prevents carburization of the inner surface of the pipes. 1 tab.

Description

The invention relates to the processing of metals by pressure and can be used in the manufacture of pipes from stainless steels by drawing on a deformable core.

The purpose of the invention is to improve the quality of pipes by increasing their corrosion resistance to intergranular corrosion.

The core is heated in a decarburizing atmosphere before entering the pipe. When drawing stainless steel pipes on a core with a pre-decarburized outer layer, carburization of the inner surface of the pipes is avoided due to a decrease in the carbon concentration gradient.

As an example, consider the manufacture of 2x2.0 mm pipes from ОХ18Н10Т steel on a manganese steel deformable core.

EI-94 (C 0.7-0.9%; Mp 13-15%; Ni 2.75-3.75).

At a size of 0 6.5 mm, the core is heated in a decarburizing hydrogen-water atmosphere (99% H2 and 1% H40) to 950-1000 ° C for 60-70 minutes.

At 900-1000 ° C, an increased intensity of steel decarburization takes place.

By drawing along a route of 6,5-5,5 mm, the core is hardened to 6V 130-140 kg / mm2, then it is inserted into a pipe 10 x 1.2 mm in size and the first pass is performed on the hardened core as on a long rigid movable mandrel along route:

10 x 1.2 - 7.4 x 0.95 mm.

After heat treatment (heating temperature 950-1000 0, cooling in water), further drawing is carried out along the route:

SS

(P CZ

el oo

SL

four.

oh

P. 7.4 x 0.95 mm;

1.5.5 x 0.67 mm;

2.4.5 x 0.54 mm;

3.3.5 x 0.41 mm;

4.2.8 x 0.32 MMJ

5.2.3 x 0.26 mm; 6 ,. 2.0 x 0.2 mm.

After each passage, the pipe together with the core is subjected to a softening rmo-processing. On finished size

ten

2x0,

2 mm core removed from the pipe

stretching to break.

The effectiveness of the proposed method was evaluated by the quality of the inner surface of the pipes for carburization (through the thickness of the layer with a high carbon content).

In parallel, the shapes of tubes made by the prototype were investigated. The research results are summarized in the table. It follows from the table that the pipes manufactured according to the proposed method are about eight times smaller than the pipes made according to the prototype. Thus, the proposed method of manufacturing pipes on a deformable core in comparison with the prototype allows an increase in the quality of the pipe, since the tendency is reduced

pipes to intercrystalline corrosion due to a decrease in diffusion carburizing of the inner surface.

Claims (1)

Formula from. bratis A method of manufacturing pipes, which involves drawing a stainless steel billet on a deforming core, characterized in that, in order to improve the quality of the pipes by increasing their resistance to intercrystalline corrosion, the core is heated in a decarburizing environment before entering the pipe. Size of pipes, mm The thickness of the inner layer with a high carbon content, mm The proposed method one Prototype 2x0.2 2x0.2 2x0.2 2x0.2 2x0.2 0.01 0,008 0,008 0.01 0,009 0.07 O, 10 O, 10 0.09 0.09