US2322288A - Method of treating castings - Google Patents

Description

June 22, 1943.

w. e. EDWARDS METHOD OF TREATING CASTINGS Filed Aug. 20, 1941 INVENTOR WILLIAM G. EDWARDS ATTORNEY Patented June 22, 1943 I UNITED STATE s PATENT OFFICE Marnon or TREATINGCASTINGS William G. Edwards, Kenmore, N. Y., assignorto cts Company, a corporation The Linda Air Produ of Ohio -Application August 20, 1941, Serial No. 401,54i

7 Claims.

This invention relates to amethod of thermally treating freshly poured cast bodies of metal to reduce the size of the shrinkage cavities and pipes which normally form during the solidification of the metal. More particularly, the invention concerns the treatmentof steel ingots and castings risers.

Castings have been treated in the past by pro-,

viding a blanket of a finely-divided carbonaceous solid fuel on the top surface of the hot casting and applying jets of air or gaseous oxygen against the blanket to burn the fuel and add heat to the top portion of the casting. In this way a pool of molten metal may be maintained in the top of the mold'to feed down into the casting while solidification proceeds from the bottomtoward the top, thereby inhibiting the formation of, and reducing the size and depth of, pipes and other shrinkage cavities. Finely-divided coke, coal, graphite, and charcoal have been sug ested for use asthe fuel. Y

Experience has shown that the carbonaceous fuels of the prior art; when finely divided, do' not cohere under the action of flowing jets of gas but tend to blow away from the regions of gas impingement, leaving bare the top surface of the casting at those regions. Gaseous oxygen then Y may attack themetal directly, with the production of undesirable effects. For example, with steel castings, the oxygen may cause a boil in the molten metal, which may result in deepseated porosity in .thecasting. metallurgical changes in the metal likewise may be produced.

The principal object of the present invention.

is to provide a method of treating metal cast- Undesirable ingswhich will not be subject to the undesirable features of prior methods discussed above. Another object is to provide such a method characterized by, the use 'of a carbonaceous fuel divided lampblack-on the top surface of the "molten casting, impinging one or more jets of gaseous oxygen from a stationary source or sources against the blanket to cause intense combustion of the lampblack and maintain the top portion of the casting molten, and after a predetermined interval of time discontinuing the application of gaseous oxygen and permitting the metal to-solidify completely in the mold.

Surprisingly, it has been found that lainpblack, although lightand fiuify in nature, has theproperty'of remarkable coherence under the erodin action of a stream of gaseous oxygen. The blanket thus remains substantially intact on the top of a casting during the treatment with oxygen, except for what is actually consumed, and

the residual layer of lampblack effectively insulates the metal against rapid heat loss after the oxygen flow is discontinued. Castings thus are protected against excessive upwardheat loss and the consequent crusting which may result if bare 'steel is exposed, as well as against boils and known to theart.

blanket which will not blow away and expose bare metal underthe normal action of oxygen jets.

The above and other objects, and the novel features of the invention'will become apparent from the following description, having reference to the-accompanying drawing, wherein: I,

Fig. 1 is a vertical sectional view, taken along the line l 'l in Fig. 2, of a large casting mold and casting with apparatus inposition for performing the method of the invention; and

Fig. 2 is aplan view of the mold and apparatus of Fig.1.

Briefly, the method of the invention comprises pouring molten metal into a mold, applying and maintaining a blanket of finely By lampblackis meant generically the carbon collected from smoke produced by burning ahydrocarbon in insufficient air or with insuificient oxygen for complete combustion. Among the sources of lampblack are hydrocarbon oils and hydrocarbon gases, suchas natural gas. The

lampblack collected by the deposition on relativelycold metal surfaces of the smoke from burning hydrocarbon gases in insufficient air sometimes is known as carbon black. The invention,-of course, is not to be limited by the which exhibits the coherent property method of manufacture of the carbonaceous black but embraces carbonaceous black from any ource of lampblack under an oxygenjet. 4

In Figs. 1 and 2 of the drawing is shown a typical arrangement of equipment for treating a large freshly poured cast body of metal by the method of the invention. A molten steel casting 1| having a riser I2 iscontainedin a mold comprising a flask ll lined with baked sand 14. A cover I! of any suitable heat-resistant material, which covers the top of the mold and forms a substantially enclosed chamber over the top of the casting, has a plurality of ports l6 spaced from one another adjacent to the periphery of the riser l2, and a central vent and observation port H. A rectangular header ll resting on the top of the cover I! is supplied with gaseous oxygen through inlets I! and 2|. A plurality of small substantially non-combustible .stationary discharge tubes 2|, of copper for example, take oil from the header I! and extend within the several ports I. for discharging jets of oxygen against a blanket 22 of lampblack covering the top of the riser l2. As soon as the molten steel has filled the mold to the desired level a-layer of lampblack, which is ordinarily so finely-divided that all will pass through a screen of 325 meshes per inch, is applied to the top of the casting, the cover is placed over the mold, and the oxygen is discharged against the carbon from the stationary sources provided by the tubes 2|. With this arrangement, the zone of greatest heat intensity lies close to the edges of the casting, where metal ordinarily tends to' solidify first. When a large casting is treated, additional lampblack may be added to the top of the casting from time to time through the vent [1.

The number of oxygen jets required for the treatment may be varied in accordance with the size of the casting under treatment. For small risers and ingots, a single oxygen stream discharged from a single centrally arranged stationary source sometimes may be suflicient. The a, main requisite is that enough oxygen streams be used that the whole top surface of the casting will be kept molten and free from crusting.

Substantially pure undiluted gaseous oxygen is most eflicient and produces the best results in the method of the invention, so that it is preferred despite its relatively high cost. It is evident, however, that the relatively less expensive compressed air, or oxygen-enriched air, may

sometimes be used to good advantage eventhough it is recognized that the intensity of heating will be less.

As an example of the practical application of the method of the invention a 10,000 pound 'steel millroll casting surmounted by a riser 24 inches in diameter was poured to a height 3- inches lower than previous practice and treated with 7 pounds of lampblack and 300 cu. ft. of oxygen. 'On sectioning the riser, inches of sound steel was found above the cut-oil. line, being equal to or greater than the margin of safety obtained with previous practice. The saving in steel was approximately 500 pounds.

In one month 17 such steel roll castings were treated bythe method 26f the invention with entirely successful results. The average riser diameter was 21 inches, the average oxygen consumption was'250 cu. ft., and the average amount of lampblack used was 8 pounds for each casting. The average saving in steel was 10 percent of the total weight poured, as contrasted with previous practice.

T of metal comprising covering the top of such What is claimed is! 1. A method of treating a molten cast body cast body with a blanket of carbonaceous black,

and impinging a stream of gaseous oxygen flow-' pinging a stream of gaseous oxygen flowing from I a stationary source against said lampblack, thereby burning said lampblack, and supplying heat to said cast body to maintain the metal fluid in the upper portion thereof.

3. A method of treating a molten cast body of metal comprising covering the top surface of such cast body with a blanket of lampblack, and impinging a plurality of streams of gaseous oxygen against said lampblack on zones spaced from one another over the top surface of such cast body, thereby burning said lampblack and supplying heat to said cast body to maintain the metal fluid in the upper portion thereof.

4. A method of treating a molten cast body of metal comprising covering the top surface of such cast body with a blanket of lampblack, and impinging a plurality of streams of gaseous oxygen against 'said lampblack on zones spaced from one another and adjacent to the edges of such cast body, thereby burning said lampblack and supplying heat to said cast bodyto maintain the metal fluid in the upper portion thereof.

5. A method of treating a molten cast body of metal by maintaining a pool of molten metal in the upper portion thereof as solidification of the metal proceeds from the bottom toward the top, thereby feeding metal downwards and inhibiting the formation of shrinkage cavities, which method comprises: substantially enclosing the top of said casting within a chamber, applying a layer of lampblack to the top of said body, and impinging a stream of gaseous oxygen flowing from a stationary source against said lamp-- cast body.

black, thereby burning the ing heat to said cast body.

6. A method of treating a molten cast body of metal which comprises covering the top of such molten body with a blanket of carbonaceous black having the coherence under the eroding action of a stream of gaseous oxygen, and the WILLIAM G. EDWARDS.

latter and supply-

Images