US3706542A

US3706542A - Fuel gas for cutting operations

Info

Publication number: US3706542A
Application number: US80470A
Authority: US
Inventors: James Harris Gilks
Original assignee: Imperial Chemical Industries Ltd
Current assignee: Imperial Chemical Industries Ltd
Priority date: 1970-10-13
Filing date: 1970-10-13
Publication date: 1972-12-19
Anticipated expiration: 1989-12-19

Abstract

A FUEL GAS CONTAINING LOW MOLECULAR WEIGHT HYDROCARBONS AND BEING SUBSTANTIALLY FREE OF HYDROCARBONS CONTAINING MORE THAN 4 CARBON ATOMS AND INCLUDING PROPORTIONS, ON VOLUME BASES, OF METHYL ACETYLENE AND/OR ALLENE WITHIN THE RANGE OF FROM 5 TO 39%, PROPYLENE WITHIN THE RANGE OF FROM 30 TO 90%, AND PROPANE WITHIN THE RANGE OF FROM 0 TO 30%.

Description

United States Patent 3,706,542 FUEL GAS FOR CUTTING OPERATIONS James Harris Gilks, Stockton-on-Tees, England, assignor to Imperial Chemical Industries Limited, London, England No Drawing. Filed Oct. 13, 1970, Ser. No. 80,470 Int. Cl. B23k 7/00; C] 3/00 US. Cl. 48-197 FM 5 Claims ABSTRACT THE DISCLOSURE A fuel gas containing low molecular weight hydrocarbons and being substantially free of hydrocarbons containing more than 4 carbon atoms and including proportions, on volume bases, of methyl acetylene and/or allene within the range of from 5 to 39% propylene within the range of from 30 to 90%, and propane within the range of from 0 to 30%.

This invention concerns fuel gases suitable for use in welding or torch cutting operations.

Currently, acetylene, and commercial propane which contains a variable proportion of propylene, are principal fuel gases for industrial cutting operations. For many purposes, either acetylene or commercial propane can satisfactorily be used and the selection of one or other in given instances then turns more on considerations of cost, availability, equipment suitability, and, very often, the personal preference and experience of the operators concerned. There are, however, other important areas of operation where fundamental differences in the burning characteristics, including flame temperature and profile, require the use of one and not the other of these fuel gases; this is especially the case with acetylene which realises a very high flame temperature and needs substantially less oxygen than propane for its combustion.

Militating against even wider use of acetylene are its high production and distribution costs which in part stem from the need for special equipment and care in the storage and handling of what is intrinsically a very hazardous material.

The present invention provides a cutting gas possessing substantial advantages over propane in terms of flame temperature and profile and oxygen requirements but which can be safely stored, distributed and handled broadly after the manner of commercial propane, that is to say, without the need for special packed cylinders and many other elaborate safety measures which are a common feature of acetylene usage. It is, however, important that copper and phosphor bronze and related alloys should be excluded from equipment in which the gas is used or stored. The fuel gas according to the present invention is a mixture containing low molecular weight hydrocarbons and being substantially free of hydrocarbons containing more than 4 carbon atoms and including proportions, on volume bases, of methyl acetylene and/or allene within the range of from 5 to 39%, propylene within the range of from 30 to 90%, and propane (if any) not exceeding 30%. It is preferred that there be no substantial quantity of C hydrocarbons present. Thus, the proportion of C hydrocarbons should very desirably not exceed around 7%. Particularly important are compositions as so defined in which the proportion of methyl acetylene and/ or allene is at least and the proportion of propylene is at least 50%, the remainder being preferably essentially propane or being propane and not more than 5% of C hydrocarbons. Thus, a typical preferred composition would essentially consist of 20 to methyl acetylene/allene, 50 to 60% propylene and 15 to 20% propane.

The invention further provides an improvement in processes for cutting, scarfing and brazing metal sheet, plate, pieces, or section, the improvement consisting in using as the fuel gas instead, say, of commercial propane, a composition comprising methyl acetylene and/ or allene, propylene, and, optionally, propane as aforedescribed. The composition is not suitable for welding materials requiring a reducing atmosphere. Principally envisaged are processes in which commercial propane has heretofore been used although the use of the said composition as a replacement for acetylene in many operations other than welding in which acetylene is now used is contemplated. Thus, other applications for the composition include soldering, flame hardening, flame spraying and descaling.

EXAMPLE 1 A cutting gas composition (mixture 1) was produced containing 22% methyl acetylene/allene, 58% propylene, 18% propane and 2% C hydrocarbons.

EXAMPLE 2 A cutting gas composition (mixture 2) was produced containing 15% methyl acetylene/allene, 70% propylene, and 15 propane.

EXAMPLE 3 A cutting gas composition (mixture 3) was produced containing 10% methyl acetylene/allene, propylene and 5% propane.

The gases were tested for flame temperature properties and in metal cutting by standard industrial techniques and their performance was compared with commercial propane containing propane and with acetylene. In the case of acetylene and propane, the equipment used was of standard optimised design for these gases. In the case of the present compositions, suitable equipment was of course, designed for the compositions having regard to their particular oxygen requirements and burning characteristics.

The following results were obtained in initial trials.

Length of cut per minute for mild steel plate of The quality of cut in each case for mixtures 1, 2 and 3 was excellent.

In subsequent plant trials by operators who had acquired familiarity with the present compositions outstanding performance was achieved. Thus, with a composition of the preferred make-up (as typified by the composition used in Example 1) 1 inch thick mild steel plate was cut at a rate of 70 feet per hour, and the finished was assessed as extremely good.

Thus, a file rubbed along the face and bottom edge left a completely clean material.

Other examples of important time savings and economies made possible by the use of this composition were in the weld preparation time of steel tube (eg 12 inch diameter, 0.33 inch thick) and in the greatly increased life of tungsten carbide tipped cutting tools, the depth of hardness penetration being typically 0.038 inch at Brinell (cf. oxy-acetylene giving hardness penetration of 0.104 inch at Brinell).

Additionally, high withdrawal rates from cylinders without the addition of vaporisers were found possible and the withdrawn gas was not found to vary to any detectable extent in composition throughout cylinder usage. There was no polymer formation and thus regulators and tool tips remain unclogged. The outstanding capability of preferred compositions according to the invention was demonstrated by cutting through a feet thick 100 ton billet of steel. In general, also, brazing was found to be as fast or faster than with acetylene or mild steel, galvanised steel, copper, brass and aluminium. A typical set of physical and chemical properties for a preferred composition according to the invention is:

Liquid density33 to 35 lbs/ft. at 60 F.

Specific volume of gas9 to ft. /lb. at 60 F.

Net heat of combustion-2000 to 2500 B.t.u./lb. at 60 F. Vol. of 0 vol. of fuel for complete combustion-4 to 4.5. Flammability limits in air-2.2% to 11%.

Flame temperature-about 5500 F.

The working pressure of the fuel gas and oxygen will of course vary with the job to be done but for many operations a fuel gas pressure in the range 3 to 10 p.s.i.g. and a corresponding oxygen pressure in the range 35 to 90 p.s.i.g. will be suitable.

I claim:

1. A fuel gas composition for use in welding and torch cutting consisting essentially of from to of an unsaturated hydrocarbon selected from the group consisting of methyl acetylene, allene and mixtures thereof, from to propylene and the balance being propane.

2. A fuel gas composition for use in welding and torch cutting consisting essentially of from 20% to 25% of unsaturated hydrocarbon selected from the group consisting of methyl acetylene, allene and mixtures thereof, from 50% to 60% propylene, up to 5% C hydrocarbons and the balance being propane.

4 3. A fuel gas composition for use in welding and torch cutting consisting essentially of the following components:

Percent Methyl acetylene/allene 22 Propylene 58 Propane 18 C hydrocarbons 2 4. A fuel gas composition for use in welding and torch cutting consisting essentially of the following components:

Percent Methyl acetylene/allene 15 Propylene Propane 15 5. A fuel gas composition for use in welding and torch cutting consisting essentially of the following components:

Percent Methyl acetylene/allene 10 Propylene Propane 5 References Cited UNITED STATES PATENTS 3,226,213 12/ 1965 Nelson et al 48-197 PM 3,352,652 11/1967 Belfit, Jr. 48197 PM 3,337,314 8/ 1967 Belfit, Jr. 48-197 FM 1'. SCOVRONEK, Primary Examiner US. Cl. X.-R.