US1996181A - Process of forming castings - Google Patents

Description

April 2, 1935.

F. WAIT I 2 Sheets-Sheet l April 1935- J. F. WAIT PROCESS OF FORMING CASTINGS 1930 2 Sheets-Sheet 2 Filed Nov.

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UNITED sTATEs PATENT OFFICE v 1,996,181 PROCESS OF FORMING CASTINGS Justin F. Wait, New York, my.

Application November 1, 1930, Serial No. 492,712

20 Claims. (01. 29-1482) This invention relates to improvements in alloys to which my invention pertains in particumethods of constructing such objects as cylinders, lar, are possessed of properties which permit of vessels and other forms which adapt themselves their being worked slightly or somewhat to im to fabrication from a metallic alloy. It involves prove the quality thereof especially as regards 5 a process of pouring or casting the metal into a rendering them while avoiding appreciable 5 shape or form which approximates'the ultimate change in shape of the main portion or substanas to general form and in some instances as to tially all thereof. By casting the unworkable size or dimension of substantially all portions of metal or metal not adaptable to extensive workthe form. ing or metals workable with great "difficulty or Common procedurefor making similar objects greater expense, to a form which approximates 10 involves one oftwo methods. These are briefly disthe ultimate or desired form and working but cussed to aid in distinguishing them from the slightly or materially less than has heretofore process or method which I have invented. been done, the final object may be had in accept- C'astings are generally made from a special able or improved quality as regards permeability composition which is controlled to give high fluof gases for example and with a great saving in 15 idity suflicient to cause the molten metal to flow cost of working, wastage and other items inherto all parts of the imprint of a shaped mould. ent to the ingot or bloom manner of forming such This generally is based on the general principle objects or ordinary castings which are of poor or that the melting point of a pure substance is less quality than that obtainable by my method.

lowered by the addition of another metal which I have found that it is P l to Create metals 20 is an impurity with reference to the pure metal. which may be cast into a form approximating for It involves the use of special ingredients to lower the most part the ultimate or desired form. By the melting point and/or to increase fluidity. form I mean the figure of the object as defined For example, cast iron is different from steel in by lines and surfaces. In some instances the size composition and bronzes and brasses likewise difand dimensions of the cast object may be sub- 25 fer in fluidity from the pure or near pure metals stantially the same as that of the finally desired composing the same. Acasting is generally made article. Since the object is cast for the most for the purpose of being machined to final dipart to the ultimate figure as defined .by lines and mension and to give smooth surfaces as required. surfaces, it is obviously required that most of Such castings are considered as being unworkcasting is required to be maintained at approxi- 30 able as by forging. mately the same shape, size and dimension as the A second method of construction involves casting first formed. If acylinder is desired, the plates, tubing, structural forms and the like which metal may be poured into a mould and a casting are made by casting an ingot and piercing, drawobtained, which approximates the final desired ing, forging or otherwise working the same. The shape. This cylinder may then be worked as by ingot bloom is cast in an unshaped mould which rolling to give the desired grain. The general techproduces a solid mass of metal of appropriate nique and procedure required to thus perform is size and shape of outer surface. The composiknown and details are established in accordance tion of the ingot is such as to give the required with experiment with each alloy and form. This ductility. On the other hand it is commonly generally improves strength and reduces porosity considered that the fluidity of the melt is such of such metals which, when cast, have undesired that the metal could not be economically poured pervious properties especially when operated at or cast into forms even approximating that dea temperature yielding a visible color. sired as to shape and quality of metal. Metals The process of casting generally involves the so worked have special desired properties such formation of portions of metal which are of low as high n th and Smal r in Structure. quality as for example, at the lower and upper My invention relates particularly to castings regions of a casting. My invention therefore of such alloys as are not adaptable to extensive preferably involves the design of a casting in such working as is commonly applied to metals such shape that upper and/or lower portions may be as iron and soft and mild steel which have, by discarded. Porous parts or their equivalent such prior methods, been cast into the well known inas portions containing slag are preferably regot or bloom which has later been commonly moved'so that the remaining portion is substansubjected to extensive working and drawing as tially homogeneous.

for example to predetermined length, diameter The casting is preferably made of a metal which and wall thickness. On the other hand, such does not harden or temper at elevated temperatures or which would otherwise act in a manner to reduce the ductility and/or strength at the temperature of working. The metallurgy of alloys suitable for applying my' process is known and casting procedure in general is known. A temperature at a near yellow heat or lower is generally satisfactory for working wherefore, the composition is preferably controlled so as to make the metal resistant to oxidation at the working temperature. If the conditions are such that this cannot be conveniently done it is desirable that the working be carried out in a non-oxidizing or in a reducing atmosphere. This may be done as by enclosing the rolls or other working means within a casing'or as by excluding substantial amounts of oxygen from a room or chamber in which the piece is worked. If the presence of workmen is required as to control the operation they may be protected as by windows, booths or hoods. An inert gas may be recirculated between the vicinity of the rolls and an outside heat exchange medium to facilitate temperature control.

The working process may involve such steps as rolling, forging and spinning and appropriate combination of such steps. The cylindrical or other form may thus be drawn, upset or otherwise treated at selected points while, as is elsewhere indicated, the main portion of the casting which originally approximated the desired ultimate figure is so held or maintained as to prevent appreciable deviation from the desired form. In producing some objects, the operations may thus include a design alteration, as compared with the desired form such as by enlarging the sectional thickness to furnish the metal required at the selected points. While my invention thus involves casting to the general shape and size, selected portions may be varied as to shape and/or thickness to allow for subsequent change thereof as in the working or for alloting portions which will be caused to contain metal of poor quality and which may then be discarded.

The cast form may be varied somewhat as to shape so as to differ from the final form. For example, if the final section is to be elliptical in shape, a simple and lesscostly circular form may be cast and the shape varied during the working. It is obvious that where the variation in form is as simple as changing from circle to an ellipse the process is substantially the same and involves no appreciable amount of drawing, forging or similar extensive working. My invention may thus involve steps for altering form such as by cupping, rolling or pressing and with the general limitation that such steps shall not materially lower the quality of the metal as regards the proposed use. Since the main portion of the casting is of the ultimate form or approximately so, such operations are of very limited order except at selected points whereat somewhat more extensive alteration in form may be performed upon portions of the casting preferably particularly made for such working as by enlargement of metal and the like.

The process may be applied to heat resisting metals such as iron containing say about 10% nickel and about 20% chromium and with carbon of say about Such metals are expensive and diilicult to machine. The porisity obtained by casting is undesired for some uses of vessels or other objects made therefrom. Such metal is expensive to weld and the weld is generally of dissimilar composition and otherwise unsatisfactory and is obstinate as regarding working in general.

The above described methods are now usable. A casting may be made. It is porous and requires machining which is quite costly. Many shapes of commercial objects require welding. The method involving ingot production and piercing and/or rolling, etc. is extremely costly because of the vast amount of working that would. be required. To do this, at less or reasonable cost, it would probably be necessary to operate at very high temperatures. Many metals oxidize rapidly at temperatures conducive to easy working.

The process may be illustrated as indicated in Figs. 1, 2. 3, 4, 5, 6 and 7. Fig. 1 shows the general procedure used in rolling the casting illustrated as a cylinder. Fig. 2 is representative of a reaction through the rolls and the cylindrical casting being rolled. Fig. 3 shows the shape of the end of the illustrated cylinder after it has been upset or enlarged to yield greater thick ness of this selected portion of the casting. Fig. 4 shows the upset" end after it has been worked inwardly by a small amount. Fig. 5 is illustrative of the result of continued inward working of the end.' Fig. 6 shows the end after it has been worked to reach the general form of an open dome. Fig. '7 shows the form of the end after the opening of the dome has been closed. It will be noted that the general form of the main body of the casting has been preserved and substantial distortion thereof has been avoided while a selected part, the end, has been appreciably worked.

The roll of Fig. l is shown schematically with its fixed frame I and removable end 2 carrying driven roll 3, rotating as indicated by the arrow. This roll operates with roll 4 which may be an idler or which may also be driven. The bearings 5 and 6 of roll 4 are capable of causing roll 4 to press against an object I being treated. Set screws 8 and 9 or power, hydraulic or other screws may be used to cause the desired pressure.

A section of the arrangement of rolls is shown in Fig. 2. The exaggerated decrease in thickness of the piece 1 between point I 0 and the point of contact with roll 4 is illustrative of the working to produce a better quality and to yield the desired final dimensions. The final shape as indicated by the section between point In and roll 4 is thus indicative-that the final shape approximates that of the original. Such rolls may coact with other operative parts as required to thus maintain the original shape and form as with particularly obstinate alloys which cannot be subjected to much stress when hot and while being worked to improve grain structure, smooth out irregularities and slightly modify the form to meet the requirements. Such other operative parts may be of known kind or those utilizing known principles of light working.

When treating oxidizable metals or when a gaseous nonoxidizing atmosphere is desired for other purposes as to produce a reducing atmosphere the piece and rolls may be housed to exclude free air. In this manner metal may be treated with a gas. The working effect may facilitate the treatment. Electricity may be passed through the metal as by causing a potential difference between roll 3 and roll 4. Likewise a magnetic or other effect may be used. This or the equivalent is sometimes desirable as while a metal is a conductor in an electric and/or magnetic circuit unusual molecular and/or value in the treatment especially in combination with working as under the exerted pressure of the rolls.

The working of an object less simple in form is illustrated in the third and succeeding figures. A casting may be made of the general shape such as shown in Fig. 3 with appreciable diameter and walls which are relatively thin as regards the diameter. The long body ll may be worked as by placing the piece on a mandrel carrying a cylinder, either moving or stationary. Outside rolls may be caused to roll relative with the body ll so as to react with the internal roll in conditions analogous to that of Figs. 1 and 2.

The enlarged lip I 2 is what remains after a portion previously existing above has been cut off or otherwise removed. The lips are of greater thickness than that finally desired as they must be enlarged or extended as to surface dimension.

By operating rolls, preferably against a bucker up or mould, the lip l2 may be worked as shown in Figs. 4, 5, 6 and 7. The selected portion I2 is shown as relatively small part of the total casting the walls ll of, which comprise the greater portion of the casting. These walls and hence the greater portion of the casting are cast to the exact or approximate final form that is desired. Aside from light working to improve the grain or crystal structure, the major portion of the casting is not appreciably, if at all, altered in form the initial form being retained thus yielding a figure at the end of treatment which is defined by practically or exactly the same lines and surfaces as was the initial casting, except at the selected point I 2 which is worked fairly extensively through the stages illustrated by Figs. 4 and 5 and to some stage such as is illustrated by Fig. 6. While in the shape of Fig. 6 a tapered or threaded plug may be inserted into opening 13 and welded tight to yield the form as shown by H of Fig. 7. The method renders the amount of machining that is necessary very small or practically negligible. After welding the dome may be rolled or otherwise worked if desired. With some metals other than the chrome nickel metal described, the plug is not always necessary as the hole l3 may be worked completely closed. Chrome alloys seem to be difficult to forge or work together in a solid manner for such a shape as that described. While the illustration shows inwardly working to form a dome or part thereof, it is to be understood that the working at a selected point need be to effect other change such as that of expanding outwardly or bending over or facing flanges or other parts that may be initially cast. The selected part may also be other than at the end of a cast piece or there may not be a. point of appreciable working or there may ,be a multiplicity thereof and the process may be modified to meet industrial requirements in view of the properties of the alloy.

The aforedescribed process thus involves casting of a large portion of the body II to approximate shape. The remaining selected portion at I2 is worked to a greater extent than that of the body I I. Other methods such as pressing and spinning may be used to work the cast object.

I do-not limit my claims to the exact method or procedure as illustrated. Other methods may be used for equivalent purposes, the selection generally depending upon conditions of the metal and the equipment available.

I claim:

1. In the process of forming a cylindrical shell of heat resisting alloy of iron containing nickel, chromium and a smaller amount of carbon and closing one end thereof, the steps which comprise casting into a cylinder approximating the size and shape finally-desired, forming an enlarged end,

heating to a yellow heat and rolling and spinning the enlarged end to nearly close the end of the cylinder, closing the end, and thereby forming a vessel which is substantially impervious to gaseous fluids.

2.. The process which comprises casting a heat resisting, stainless steel alloy of iron containing nickel, chromium and carbon into a cylinder approximating that finally desired, heating to a yellow heat, rolling said casting to render it substantially impervious to gaseous fluids and spinning an enlarged end to nearly close the end of cylinder and closing the end.

3. In a process of forming a shell with a closed end of heat resisting alloy of iron containing nickel, chromium and carbon the method comprising casting the main body to approximately the desired shape and size, rolling the casting at above a red heat to render the casting substantially impervious to gaseous fluids and simultaneously enlarging the end of the cylinder, working the enlarged end inwardly to approach a closed dome and closing the end forming a closed dome and thereby forming a cylindrical shell and connecting dome which are substantially impervious to gaseous fluid.

4. The process of forming a metallic object of selected shape and size of a metal which cannot be worked extensively wh ch comprises casting the object to a size, shape and thickness of metal which is substantiallythat of the final desired object, removing the portion of the casting con taining substantial amounts of slag, working the casting to reduce the porosity thereof while retaining the approximate size and shape of the casting and preventing appreciable change of the main part thereof.

5. The process which comprises forming a casting of metal not adaptable to extensive working said casting being made of the approximate shape and size of a desired object, with a cylindrical body possessed of wall thickness approximating that finally desired, heating to a near yellow heat, working the casting to render the casting substantially-imperv ous to gaseous fluids, and working a selected portion of cylindrical shape inwardly to decrease its diameter appreciably while maintaining the main port on of the cylindrical body at approximately the same shape and size as of the casting first formed.

6. The process which comprises forming a casting of metal not adaptable to extensive working said casting being made of the approximate shape and size of a desired object, with a cylindrical body of appreciable diameter and relatively thin walls. heating to a near yellow heat, working the casting to render the casting substantially (ill impervious to gaseous fluids, and working a setility by casting the main portion of the body thereo to the desired shape and size of the final product, the method comprising working walls thereof at above about a red heat to reduce the permeability of the walls to gaseous fluid while retaining substantially the same size and shape proximately the same wall thickness as of the first cast object.

8. In the process of forming a cylindrical shell 01' heat resisting alloy of iron containing nickel, chromium and a smaller amount of carbon and closing one end thereof, the steps which comprise forming a cast cylinder approximating the size and shape finally desired, forming an enlarged end, heating to a yellow heat and working the enlarged end'so that it will receive a covering piece'and applying a covering piece of approxi-' mately the same composition and forming a completed dome therewith and so forming a vessel the walls .of whichare substantially impervious to gaseous fluids.

9. in a process of forming cylinder-like walls of a vessel of heat resisting alloy of iron containing nickel, chromium and carbon which is capable of operating at a red heat and containing gaseous fluid and preventing escapage thereof, the method of casting the object to about the form desired and working the casting at above a red heat to render the casting substantially impervious to gaseous fluid and while preventing appreciable change in the form of the main portion of the casting.

10. The process of forming an impervious cylinder of an alloy which may be worked sl ghtly but not extensively at above a red heat and which alloy is appreciably pervious to gaseous fluid on formation but may be rendered substantially impervious by slight working, which comprises casting the pervious cylinder to a form approximating that desired. working the casting at a near white heat while maintaining its form and so rendering the cylinder substantially impervious.

11. The process which comprises making a casting of a normally gas pervious but resisting alloy in a cylindrical shape in main approximating the desired form of a cylindrical vessel and wherein end is cast in enlarged thickness, working the main cylindrical portion at about a near white heat to render the same substantially impervious while retaining the cast form thereof with practically its initial wall thickness, and working the enlarged end appreciably more than the main body of the casting so as to render it impervious and to shape it that the end of the cylinder may be closed by addition of a separate number.

12,.The process which comprises casting an alloy, which may be worked somewhat at a near white heat but which is normally pervious and which is readily oxidized in air at such heat, to a form closely approximating the form of a desired structure, working the casting slightly at a near white heat while excluding air therefrom and imposing a non-oxidizing atmosphere thereon to render the structure impervious and maintaining the casting in approximately the same form during the working and avoiding appreciable distortion of the main body of the casting.

13. The process of forming a structural part of an iron alloy containing about 10% of nickel, 20% of chromium and about of carbon which comprises casting the part to approximately the form desired, working the metal a little at aboutor near white heat to render it substantially impervious as regards gaseous fluid at high temperatures of application of the metal and maintaining approximately the same cast form and thickness throughout the working.

tensively working the same to attain a cylindrical form, the method of casting the cylindrical form to the approximate diameter and wall thickness as finally desired, and working the casting at above a red heat and below a white heat while preventing appreciable alteration in diameter and wall thickness.

16. The process of improving a cylindrical casting of heat resisting alloy while avoiding substantial change in size and shape of the main portion thereof which comprises casting the alloy to about the desired form and size and subsequently working the casting at about a near yellow heat in a manner largely to improve the grain structure and render the metal practically impervious to gaseous fluid and while avoiding substantial change in the size and thickness of the main portion of the casting.

17. The process of forming a metallic object of substantial diameter and relatively thin walls while avoiding extensive working of the main portion thereof which comprises casting the object in approximately cylindrical form to a size and of a shape about as desired and working the casting at high temperature to decrease the pore size while preventing appreciable change in the form and the size and thickness of the main portion of the casting and so producing an improved object with but little change in size and of about the same thickness of metal as regards the main portion of the original casting.

18. The process of improving a casting of heat resisting alloy by small working at elevated temperature which comprises casting the object so that the main portion of the casting conforms fairly closely with the size, shape and thickness of that of the desired structure, working the casting at substantially elevated temperature to remove most of the permeability to gaseous fluid inherent to the casting and while maintaining its approximate form and avoiding substantial distortion of the main portion of the casting.

19. The process of forming an object of selected shape and size of a metallic alloy which is obstinateas regards working and cannot be extensively worked and is normally porous which comprises casting the object to substantially the desired metal thickness, size and shape and working the casting to improve the grain structure and reduce the porosity while avoiding material change in form, size and thickness of the main part of the casting.

20. In forming a metallic object of a metal which cannot be extensively worked but which may be worked by a small amount, the *steps comprising casting the obJect to a form approximating that desired and removing portions of undesired metal and working the casting to improve the grain structure and reduce inherent porosity of the casting while retaining the approximate size and shape of the casting and avoiding material distortion of the main part thereof.

JUSTIN F. WAIT.

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