US3172457A - Apparatus for thermochemical scarfing - Google Patents

Description

March 9, 1965 c. E. HARTMANN ETAL 3,172,457

APPARATUS FOR THERMOCHEMICAL SCARFING Original Filed May 22, 1959 INVENTORS CARL E. HARTMANN EDWARD H. MOUSTED A T TOR/VE Y United States Patent 3 172,457 APPARATUS FQR THfiRMQCHEMHCAL SCARFING Carl E. Hartmann, Florham Park, and Edward H.

Mousted, Garwood, Ni, assignors to Union Carbide Corporation, a corporation of New York Continuation of application Ser. No. 815,164, May 22, 1959. This application Aug. 14, 1961, Ser. No. 131,412 1 Claim. (Cl. 158-274) This invention relates to method and apparatus for thermochemical scarfing, and more particularly to mech anized oxy-fuel gas flame conditioning of steel blooms, billets or slabs as performed by post-mixed flat-slotted nozzle scarfing machines. From one to eighteen or more nozzle heads, each containing six to nine nozzles, are carried by one such desurfacing machine. More particularly, the invention relates to the discovery of the importance of the character of the preheat flames, particularly the lower, on the surface quality of the steel being flame-conditioned and to an improved desurfacing nozzle of the post-mixed flat-slotted nozzle type which provides the desired preheat flame characteristics.

The standard post-mixed flat-slotted oxy-fuel gas nozzle is of two-piece construction; that is, a nozzle body and a cap at the flame end of the nozzle. A slotted cutting bore in the nozzle produces essentially a flat stream of cutting oxygen. The fuel gas for the preheat flames issues from six orifices in the nozzle body, three above and three below the oxygen slot. The end face of the cap, which has a slot somewhat larger than the'exit slot in the nozzle body, directs the fuel gas into the outer fringes of the oxygen stream to produce the preheat flames. An example of this nozzle is disclosed in Bucknam Patent 2,425,- 710 dated August 19, 1947.

For many desurfacing applications, where shallow cut depths are sufficient, the standard post-mixed flat-slotted oxy-fuel gas nozzles produce satisfactory surface quality on the steel being conditioned. The relatively slight ridges left on the surface after conditioning present no problem in subsequent operations. However, where deeper cuts are desired or high alloy steels are being conditioned, scarfing with the standard post-mixed fiat-slotted oxy-fuel gas nozzles leaves higher, sharper ridges on the scarfed surface. These high, sharp ridges are very undesirable since 'they may contain unscarfed defects or form laps or blemishes on the final rolled surface of the steel.

After considerable laboratory test work, it was discovered that the aforementioned high, sharp ridges on the scarfed surface were caused by uneven distribution of the fuel gas across the bottom edge of the flat cutting oxygen stream of the standard post-mixed fiat-slotted oxy-fuel gas nozzle. It appears that the velocity of the individual fuel gas streams issuing from the three bottom ports in the nozzle body is sufficient to cause them to issuse from the nozzle as three distinct streams and so produce, in effect, three individual preheat flames. The result of this uneven distribution is to cause a concentration of the scarfing reaction in three distinct paths for each nozzle, throughout the length of the scarfing pass. The ridges represent that surface of the steel lying between these paths. While the same fuel gas flow condition exists with respect to the fuel gas issuing from the three upper preheat ports, its effect on the surface quality was less critical.

The main objects of the present invention are, therefore, to avoid these difficulties and to render the velocity of the fuel gas stream more uniform over its width, to provide a solid sheet of preheat flame issuing from the nozzle for the full width of the cutting gas stream, and to produce smooth flat scarfing cuts of good quality.

According to the present invention, a plurality of streams of fuel gas below the flat oxidizing gas stream 3,3?2A57 Patented Mar. 9, 1965 lCC are discharged into a diffusion zone wherein the fuel gas streams are commingled into a single sheet like fuel gas stream, the sheet like fuel gas stream is traveled along inside said diffusion zone to further diffuse the fuel gas therein, and the further diffused sheet like stream of fuel gas is thereafter deflected upwardly into the oxidizing gas stream and aspirated thereinto and discharged therewith onto the reaction zone of the workpiece.

In the apparatus, the bottom of the post-mixed flatslotted oxy-fuel gas nozzle body is transversely slotted, and slabbed off beyond the slot to form a diffusion chamber for the fuel gas in back of the oxygen discharge orifice particularly in the lower preheat portion. With this invention, the velocity of the fuel gas stream is more uniform over its width, a solid sheet of preheat flame issues from the nozzle for the full width of the cutting oxygen stream, and smooth, flat scarfing cuts of good quality are produced. Similar provisions to the upper preheat portion of the nozzle body have substantially no noticeable effect on the cut quality.

In the drawings:

FIG. 1 is a side elevation, partly in section, of an apparatus according to, and for carrying out, the method of the present invention;

FIG. 2 is a view of an end elevation of the structure shown in FIG. 1.

FIG. 3 is a cross section taken along the line 33 of FIG. 1; and

FIG. 4 is a diagram showing the steps of the method.

According to the method of applicants invention, referring to FIG. 4, a sheet like stream A of oxidizing gas is discharged onto a recation zone B on the work surface of a metal body at an acute angle of impingement to said work surface. A plurality of individual streams C of fuel gas are discharged into a wide diffusion zone D spaced ahead of and below said oxidizing gas stream A. In the diffusion zone D, the individual fuel gas streams C are commingled into a single sheet like fuel gas stream, which is traveled along inside of the diffusion zone D to further diffuse the fuel gas therein. At E, the further diffused sheet like fuel gas stream is deflected upward toward the sheet like oxidizing gas stream A to be aspirated thereinto and discharged therewith as a post mixed oxy-fuel gas preheat flame onto the reaction zone B.

The preferred embodiment of apparatus for carrying out the above method is shown in FIGS. 1, 2 and 3.

The two-piece post-mixed oxy-fuel gas scarfing nozzle shown consists of a body it and a cap 12, each being composed of a highly heat conductive metal, such as copper. The body lfi has an oxygen supply passage 14 and a plurality of fuel gas supply passages 15. The oxygen supply passage 14 has an outlet end portion which gradually changes from circular to flat cross section terminating in an oblong discharge orifice 16.

The front end portion of the body if is provided with a transverse slot 20 which is in alignment with and wider than the orifice 16. The cap 12 is also provided with a transverse slot 24 in alignment with the body slot 20. The cap slot 24- is only slightly wider than the body slot 20 to insure an aspirating effect upon the fuel gas. Fuel gas passages or chambers 26 inside the cap 12 in back of the slot 24 are provided by beveled surfaces 28 extending across the end face of the body on each side of the slot 20 at an angle of the order of 30 to the central plane thereof.

In the apparatus according to the present invention, a transverse groove Be is machined into the nozzle body 10 near the flame end, intersecting the three bottom preheat passages, and a flat 34 is milled on the bottom of the nozzle body between the groove 35) and the bevel 28. The portions of the preheat passages 15 which originally ex 3 tended above this flat from the groove 30 to the bevel 28 are plugged up in any suitable manner.

When the cap 12 is positioned over the frame end of the nozzle body, the cylindrical wall of the cap provides the fourth wall of the diffusion chamber. The fuel gas, issuing frcm the preheat passages 15, impinges against the forward wall of the slot 3% and is caused to become substantially equally distributed throughout the diffusion chamber. Thus, the fuel gas passes from the slot 30 through the constricted arcuate passage 35 formed between the milled flat 34 on the bottom of the forward end of the nozzle body and the cylindrical wall of the nozzle cap as a relatively flat stream. This flat stream of fuel gas in then deflected inwardly as aspiration chamber 26 toward the underside of the cutting oxygen stream by the end face of the nozzle cap where it mixes with the outer fringes of the oxygen stream to form a flat sheet of preheat fiame. which impringes upon the workpiece at an angle of about 25.

Though not necessary to the attaining of smooth, flat, good quality scarfed surfaces, this same diffusion chamber construction may be repeated for the upper or top preheat flames to facilitate assembling the nozzles into the nozzle heads of the scarfing machine.

Scarfed surfaces were obtained using the standard postmixed fiat-slotted oxy-fuel gas type nozzle, and the nozzle of the invention, respectively. These scarfing passes were made under identical conditions; that is, on cold steel moving at the rate of 30 f.p.m. using 40 p.s.i. oxygen pressure and 5 p.s.i.'natural gas pressure. The high ridgesleft on the scarfed surface of a steel plate by a scarfing pass made using three old standard nozzles were clearly visible. The smooth fiat surfaces produced by a similar pass, made according to the present invention, were equally clear.

Field trials not only substantiated the greatly improved surface finish obtained, but also permitted this improved surface to be obtained over a period of several weeks, as

application Serial No. 815,164 filed May 22,. 1959, now

abandoned.

What is claimed is:

In apparatus for thermochemically scarfing metal bodies, a nozzle body having a passage for confining the inside and outside of a supply of oxidizing gas to form astream of substantially uniform thickness, said passage having an orifice for discharging said sheet-like stream of oxidizing gas onto a reaction zone extending'transver'sely to a metal body and at an acute angle of impingement thereto, said body having a plurality of fuel gas passages below and extending in the same direction as said oxidizing gas passage, said body having a transverse slot intermediate its ends and intersecting said fuel gas passages, the side of said body between said slot and the discharge end of said bodybeing slabbed olf, and a nozzle cap covering said slot and slabb ed off portion to form a diffusion chamher, said nozzle having a slot registering with said oxidizing gas orifice to aspirate fuel gas from said diffusion chamber.

References Cited in the file of this patent UNITED STATESPATENTS Bucknam et al Aug. 19, 1947

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