GB2109533A

GB2109533A - Cutting nozzle for flame-cutting with oxygen under an elevated oxygen pressure

Info

Publication number: GB2109533A
Application number: GB08230096A
Authority: GB
Inventors: Manfred Agel; Karl Gallwitz; Traugott Gutermann
Original assignee: Messer Griesheim GmbH
Current assignee: Messer Griesheim GmbH
Priority date: 1981-10-29
Filing date: 1982-10-21
Publication date: 1983-06-02
Also published as: DE3142840A1

Abstract

A cutting nozzle (10) has a cutting-oxygen channel (11) which, in the outflow direction (12) of the cutting-oxygen, widens conically from a throat (13) to an outlet (14). To achieve a further increase in the cutting speed and a higher cutting quality the throat diameter dg should be calculated in accordance with the following equation: <IMAGE> where G (constant)=0.55 at S=5 to 25 mm 0.48 at S=3 to 100 mm, S=thickness of the workpiece in mm and P=oxygen pressure in bars, upstream of the narrowest cross- section, to that the outlet diameter dA is calculated in accordance with the equation: <IMAGE> A being a constant within the range from at least 1.09 and at most 1.23 and FG DIVIDED FK being the widening ratio in Lavel nozzles, with k=1 .4. <IMAGE>

Description

SPECIFICATION Cutting nozzle for flame-cutting with oxygen under an elevated oxygen pressure The present invention relates to a cutting noule for flame-cutting with oxygen, preferably flamecutting under an elevated oxygen pressure, namely an oxygen pressure in the range from 1 5 to 30 kp/cm2.

A nozzle of this type has, for example, been disclosed by German Patent Specification 2,519,919. This nozzle has a special cuttingoxygen channel which, in the outflow direction of the cutting oxygen, widens conically from a throat to an outlet and by means of which an increase in cutting speed can be obtained, as compared with cutting nozzles which are, for example, known from German Offenlegungsschrift 2,046,414 and German Offenlegungsschrift 2,046,415 and which are operated under an oxygen pressure below 1 5 kp/cm2.

Industry is constantly demanding an increase in cutting speed in order to be able to produce workpieces more rapidly and at more favourable costs, an adequate cutting quality having to be preserved of course. Starting from this demand and the known cutting nozzle operating under an elevated oxygen pressure, attempts were made to achieve higher cutting speed values by forming the cutting-oxygen channel as a Laval nozzle (similar to U.S. Patent Specification 2,195,384).

In this case, it was found that the emerging cutting-oxygen jet is not bundled and that an increase in cutting speed and, evidently due to the non-uniform cutting-oxygen jet, adequate cutting qualities cannot be achieved.

Starting from these results and the state of the art, it was the object of the inventors to provide a cutting-oxygen channel design, by means of which a further increase in the cutting speed and cutting quality can be attained.

To achieve this object, it is proposed according to the present invention that the throat diameter dg should be calculated in accordance with the following equation:

where G=0.55 at S=5 to 25 mm and (constant) 0.48 at S=30 to 100 mm, S=thickness of the workpiece in mm and P=oxygen pressure in bars, upstream of the narrowest cross-section, and that the outlet diameter dA is calculated in accordance with the following equation:

A being a constant within the range from at least 1.09 to at most 1.23 and FG FK being the widening ratio in Lavel nozzles, with K=1.4.

With a design of the cutting-oxygen channel according to the present invention, a cutting speed can advantageously be achieved which is 1035% higher than that hitherto achievable with known high-pressure nozzles, and more than 50% higher than that achievable with commercially available standard nozzles.

It has been found to be particularly advantageous that the nozzle design according to the invention leads to a sharply bundled cutting oxygen jet which, in addition to the increased cutting speed, also results in optimum cutting qualities. According to DIN 2,310, the cutting qualities achieved are in quality class 1 ,field 1.

In an advantageous further development of the invention it is proposed, in particular for better guiding of the jet, that the widening angle, that is to say the angle of the cutting channel zone located between the throat and the outlet, should have a value in the range from 20 to 50, and is preferably 30.

Particularly, in order to make the jet more steady, the throat has, according to the invention, a length which is 8 to 17 times, preferably 13 1 5 times, greater than the throat diameter of the cutting-oxygen channel.

Moreover, it is proposed according to the invention that, as viewed in the direction of oxygen flow, the conically widened zone of the cutting-oxygen channel should be adjoined by a cylindrical channel zone which has a length of 3-6 mm, preferably 4 mm. As a result, splashes can readily be cleaned out with a twist drill, and simple production for achieving a constant FG FK ratio becomes possible.

A cutting-oxygen channel made in accordance with the abovementioned features according to the invention provides optimum cutting properties and can therefore be advantageously employed in all cutting nozzles, in particular those which are designed for autogenous flame-cutting, in which the cutting-oxygen channel is surrounded by a heating channel.

The cutting-oxygen channel designed in accordance with the invention has also proved to be particularly advantageous in so-called curtain cutting nozzles. In these curtain-cutting nozzles, the cutting channel is surrounded by a further oxygen channel, through which oxygen flows out of the nozzle rather like a curtain or veil around the cutting-oxygen jet. In conjunction with the high-pressure cutting-oxygen jet flowing out of the cutting channel, cutting speeds are thus achieved which are about 20% higher than those of cutting nozzles which have only the cutting channel design according to the invention, that is to say without a curtain.

In the description which follows, the invention is explained in more detail with the aid of the drawing and by reference to the sub-claims and further advantageous features.

The nozzle for flame-cutting under an elevated oxygen pressure is marked 10 as a whole. The nozzle 10 has a cutting-oxygen channel 11 which, in the outflow direction 12 of cutting oxygen, widens conically from a throat 13 to an outlet 14.

According to Claim 1, the throat diameter dg and the outlet diameter dA have been calculated in accordance with the following equations:

Between the throat 13 and the outlet 14, the cutting-oxygen channel 11 has a conical zone 1 5 with a widening angle 16 in the range from 2 to 5 , and preferably 30. The conical zone 15 is adjoined by a cylindrical zone 1 7 which has a length 18 of 3-6 mm, preferably 4 mm. On the other side of the conical zone 15, there is the throat 13 which is formed as a cylindrical channel and has a length 19, the value of which is 8 to 17 times, preferably 13 to 1 5 times greater than the value of the throat diameter dg.

The throat 1 3 is associated with a conical inflow zone 20, the cone angle 21 of which is 8120, preferably 100.

As also shown in Figure 1, the nozzle 10 has, in addition to the cutting channel 11, an annular heating channel 22 which is connected to a supply device, not shown in more detail, for feeding a fuel gas mixture which serves to form the preheating flame required in autogenous flame-cutting. Moreover, a ring channel 23 for an oxygen curtain is provided in the nozzle 10.

Claims

1. Cutting nozzle for flame-cutting with oxygen, preferably flame-cutting under an elevated oxygen pressure, namely an oxygen pressure in the range from 1 5 to 30 kp/cm2, having a cutting-oxygen channel which, in the outfiow direction of the cutting oxygen, widens conically from a throat to an outlet, characterised in that the throat diameter dg is calculated in accordance with the equation:

where G(constant)=0.55 at S=5 to 25 mm and 0.48 at S=30 to 100 mm, S=thickness of the workpiece in mm and P=oxygen pressure in bars, upstream of the narrowest cross-section, and that the outlet diameter dA is calculated in accordance with the equation::

A being a constant within the range from at least 1.09 to at most 1.23 and FG FK being the widening ratio in Laval nozzles, with K=1.4.

2. Cutting nozzle according to Claim 1, characterised in that the nozzle widening angle (16) is in the range from 2 to 50, and preferably is 30.

3. Cutting nozzle according to Claim 1 or 2, characterised in that the length (19! of the throat (13) is determined in accordance with the equation: L=(8 to 17, preferably 13 to 15)Xdg

4. Cutting nozzle according to one of Claims 1 to 3, characterised in that, in the direction (12) of oxygen flow, a cylindrical channel (17) having a length of 3 to 6 mm, preferably 4 mm, adjoins the conically widened zone (15).

5. Cutting nozzle according to one of Claims 1 to 4, characterised in that the throat (13) is associated with a conical inflow zone !20?, the cone angle (21) of which is b to 120, preferably 100.

6. Cutting nozzle according to one of Claims 1 to 5, characterised in that the cutting-oxygen channel (11) is surrounded by a heating channel (22).

7. Cutting nozzle according to Claim 6, characterised in that the cutting-oxygen channel (11) is surrounded by a channel (23) for an oxygen curtain.

8. Cutting nozzle for flame cutting with oxygen, substantially as hereinbefore described with reference to the accompanying drawing.