SU449788A1 - Method of multi-pass surface plasma-arc cutting - Google Patents

Description

The invention relates to methods for plasma-arc surface cutting, mainly in the smelting of deep grooves of great length, for example, in the smelting of defective sections of welds on plate structures, cutting of cracks in castings, and preparation of edges for welding.

The known method of multi-surface plasma-arc cutting, performed by successively grooved with the change of the angle of inclination of the cutter during each pass.

The most significant disadvantages of this method when sampling large grooves are the following:

by increasing the number of passes, the conditions for removing the metal from the cut cavity deteriorate, resulting in a significantly increased thickness of the metal layer that is not removed from the cut cavity;

Inability to get grooves with legs

scheniem. These circumstances make it necessary to increase the width of the sample during each pass, which leads to a decrease in productivity when performing cutting work and to additional costs of welding materials and electricity during the subsequent welding of the cut sections.

2

With the elimination of these drawbacks, the proposed method, after sampling the first groove next to it to a predetermined smelting depth, is performed by a plasma arc

samples of limited length, and these samples are positioned relative to the cutting direction at an angle of at least, and the length of the samples is set such that the edge of the groove during each pass overlaps the end of the sample. The number of additional samples is related to the total length.

L

cut by the following ratio rm-g; Where

0, 5

n is the number of samples, L is common

cut length

in meters.

The proposed method can significantly improve the quality of the cut edges.

FIG. 1 illustrates the process of smelting a groove during the first pass; FIG. 2 - performing additional samples after melting the first groove; in fig. 3 shows the section after multipass melting of the groove to a predetermined depth.

The proposed method is carried out as follows.

The plasmatron is set to position I

and do not move in the direction shown

arrow, relative to the workpiece 1, while the plasma arc is oriented at an angle of 20-30 ° to the surface of the workpiece 1. As a result of the first pass, a groove 2, which has a width B and a depth, is obtained on the workpiece / ii. Then the plasmatron is installed at an angle of attack ai 135-150 ° with respect to the direction of cutting. With a smaller angle, the metal melted from the cut cavity during the subsequent, their passes, does not flow into additional samples. The angle of inclination of the plasma arc is equal to 30-45 °. With such a value of this angle, a sufficiently flat sample is obtained, which is necessary to remove the molten metal from the cutting cavity during the melting of the main groove.

Additional samples were taken at a fixed position of the plasmatron, and the depth of the samples was taken equal to the depth of the main sample H. The width of the additional BI samples is greater than the width of the main sample B 1.5–2 times. Then the plasmatron is again set to position I and the second pass is made to a depth h, the angle of inclination of the plasmatron to the surface of the workpiece is increased when the second pass is performed compared to the first. By such an increase in the angle, the plasma arc is deepened into the workpiece, while the width of the groove B is practically unchanged. Metal 3, melted from the groove when making the second pass under the action of arc pressure and a gas jet, is removed through additional samples, which helps to reduce the volume of molten metal in the cut cavity, and this in turn ensures effective heat input to the workpiece. This process scheme provides multi-pass cutting of almost unlimited length, with

this increases the ratio - to the value

AT

equal to 1.5-2.

After the second sample, which provides grooves 4 with depth h, again

the plasmatron is set to position I. Again, increase its angle of inclination to the surface of the workpiece and make the third passage to a depth of, which provides the groove 5. The subsequent passages to obtain the depth I of the melted groove 6 are performed in the described sequence. The most appropriate range of variation of the angle of inclination of the plasmatron with each pass is 5-10 °.

An important process parameter is the number of additional samples. With a large distance between them, the metal melted from the cut cavity cannot be removed through these samples, which leads to the formation of traffic jams in the main groove. With a small distance between the additional samples, the processing capacity is reduced due to the increased labor costs per sample and their subsequent brewing.

Subject invention

1. A multi-pass surface plasma-arc cutting method, performed by successive melting of grooves with a change in the angle of inclination of the cutter during each pass, characterized in that, in order to improve the quality of the cut edges and process performance, mainly in the smelting of deep grooves of large extent, intersecting grooves of the sample of limited length, which are positioned at an angle of 135-150 ° to the cutting direction, are made between the aisles. 2. The method according to claim 1, wherein

That the number of additional samples is related to the total length of the cut as follows Z.

bearing: where n is the number of choices V (j -r and, 5

rock, and L is the total length of the cut in meters.