US1492804A - Heat treatment of metals and apparatus therefor - Google Patents

Description

May e, 1924. 1,492,804

H. P. MACONALD ET AL HEAT TREATMENT OFMETALS AND APPIRATUS THEREFOR Filed Dec. 23 1916 3 Sheetsheet 1 7 /l l.) l2 /6 (,:u A I /0 l I i ll Il I3 I :I :I ti ii I Il abn i: 1 ,l

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H. P.fW/\C[NDPALD ET l\L HEAT TREATMENT OF METALS AND APPARATUS THEREFOR Filed Dec. 23, 1916 3 Sheets-Sheet 2 M L 'rl alf/S .Madvzald May s, 1924. www@ H. P. MACDONALD ET lAL HEAT TREATMENT OF METALS AND APPARATUS THEREFOR Filed Dec. 23f 191e 5 sheets-sheet 2@ l y Patented May 6, 1924.

PATENT oFFlcE.

UNITED STATES HARRY P. MACDONALD. 0F MONTCLAIB. NEW JERSEY, .AND ANGUS S. MACDONALD, OF GREAT NECK STATION, NEW YORK, ASSIGNORSTO THE SNEAD CO. IRON WORKS,

OF JERSEY CITY, NEW JERSEY, A CORPORATION OF NEW JERSEY.

HEAT TREATMENT 0F METALS AND APPARATUS THEREFOR.

Application led December 23, 1916. Serial No. 138,596.

To all whom t may concern:

Be it known that we, HARRY P.MAC DONALD, of Montclair, county of Essex, and State of New Jersey, and ANGUs S. MAG- DoNALD, of Great Neck Station, county of Nassau, and State of New York, have invented certain new and useful Improvements in the Heat Treatment of Metals and Apparatus Therefor, of which the following is a specification. f

This invention relates to an improvement" in heat treatment of metals for tempering,

bending and other operations and to apparatus for carrying out the same.

One of the primaryobjects of our invention is the provision of an improved practical method of.determining the point of decalescence of metals undergoing heat treatment which is simple vin character and which can be carried out during the heat treatment of the metalsby those ordinarily in charge of such operations. Stated in other words, one of the primary objects of our invention is the ovision of a simple practical method of etermining the point of decalescence right in the machine shop or mill as a substitute -for the expensive, complicated laboratory experiments which are usually undertaken by experienced investigators previous to instituting any heat treating operations in order to determine just what the heat treatment should be in the particular case.

Another object of our.l invention is the provision of such an' im roved practical method by means of which the time when any meta lic article reaches the point of decalescence regardless of variations in size, shape or cross-section or in chemical composition, can be automatically indicated to those in charge of the heat treating opera-l tions.

Our invention also-contemplates in this connection, an improved ap aratus of simple character which can be use in carrying out our improved method, the advant es of which will be set forth more speclically hereinafter. n

In addition to the foregoing, our invention is also directed to an improved 'method of heat treating and bending rods or tubes, such for example as tubular iront axles for automobiles and the like.

The foregoing, together with such other objects as may hereinafter appear, or are incident to our invention, we obtain by means of a method and construction, the preferred embodiments of which are shown in the accompanying drawings, wherein:

Figures 1 and 2 arefrespectively' front and side elevations of rod or tube tempering apparatus illustrated in Figures 1, 2, and 3,

which is particularly adapted for the tempering of rods and tubes. In brief this apparatus consists of a vertical frame-work 7 which is provided with two contact terminals' A and B, suitably insulated. The upper contact A is relatively fixed while the lower contact B is movably mounted on the frame 7 by means of bolts 8 freely slidable in the slots 9, as shown in Figure 3. Each contact terminal comprises a pair of jaws 10 adapted to receive and clamp the tube or rod 11 to be heat treated, the jaws being held4 in closed clamping position by yielding means such as springs 12. A common o erating means comprising the'vertical sha 13 and hand lever 14, is provided for opening \00 and closing the jaws, all as more fully shown and described in said copendin application.

The ositive and negative lea s to the termina s are indicated at 15 and 16, current being supplied from any suitable source -95 under the control of switch mechanism 17.

Intermediatel of the contact terminals, the

rod 11 is enc osed in a box 18, in order to .prevent radiation and to maintain external conditions uniform The lower terminal B 100 is yieldingl held in raised position by such means as t e counterweight 18 shown in Figure 2.

Located at the bottom of the apparatus and in position to receive` the heated tubes discharged therefrom is a quenching bath, such as the receptacle 19 which is filled with oil or other suitable quenching material or liquid, the receptacle beingvtilted so that the tubesdischarged therein will yfall to one side by the action of gravity out of the direct ath of discharge.,

As t us far described, this apparatus is substantially the same as that shown and described in the aforementioned application of Macdonald and Huggins, and its operation is substantially the same, to wit: the tube 11 is inserted into the jaws 10, the box 18 is closed, and then the circuit is closed at switch 17, whereby .the tube is heated by its internal resistance to the current of electricity flowing therethrough. Then the tube has been brought to the correct temperature, the jaws are released and the tube discharges into the quenching bath and is hardened.

As a general rule, metals suchl as steel rods, tubes and the like should be heated to what is commonly called the decalescent point, which corresponds to the correct point to which it should be heated for hardenin purposes. The point of decalescence o' course varies with the different metals, and also with variations in chemical compositions, as for example with the carbon and manganese content of steel. As previously pointed out, it is customary to conduct careul experiments to determine the decalescent points of the metal to b e treated before' and heat treatment is attempted, and we propose to automatically determine the point of decalescence of each piece to be heat treated without the necessity of previously instituting v any such experiments as are customary.

In carrying out our rocess we take advantage of the fact t at the decalescentI point is somewhat analogous to the boiling oint of water in that the material being llieated will absorb some heat thereat without its temperature being raised. In other words, the heat at the point of decalescence is that. which effects the chemical and physical changes of the structure of the material and consequently it is at this point of decalescence that the expansion of the material, due to the heat being supplied to it, pauses tem orarily. We propose therefore to automatically indicate the instant that the metal being treated reaches the point of decalescence, by indicating the point at which ex ansion of the metal substantially pauses. y this mea-ns we can determine both the lower and upper points of decalesence.

We accomplish this in the apparatus just described by providing an indicating mechanism C associated wlth the lower or movable block B. This indicating mechanism may be of any type and may' set in operation any desired indicating medium, but we prefer to use a simple graduated dial 20 having an indicating hand 21 rotatably mounted thereon. This hand is provided with a pinion 22 which is engaged by gear segment 23 rotatably mounted on the framework 7 by means of a pin 24, the end of such gear segment being in the form of a rounded shaft 25 sildably but snugly fitting into 4the clevis member 26 threaded into the block B. It will be seen that as the tube 11 expands under the action of the heat, the block B will be carried downward, .its movement being transmitted to the hand 21. It will also be observed that the operating mechanismisso arranged as to greatly multiply the movement of the block so that the hand 21 will be caused to move quite noticeably. After turning on the electric current the operator observes the movement of the hand 21 and at thesinstant the hand temporarily stops moving, the operator knows that the particular piece of metal being treated has reached the point of decalescence and he then cuts od the current or relases the rod, either singly or together.

By such a method of automatically indicating the point of decalescence, it will at once be seen that we have obvated the necessity for conducting the slow and expensive experiments heretofore noted, and have placed it within the capacity of any vordinary workman to successfully and uniformly heat treat any different kinds of metal or metals having varying chemical properties. In addition to the advantages already noted, it. will be apparent that the invention is particularly valuable where a large number of similar articles are to be heat treatedbecause of the great facility with which uniform heat conditions and therefore uniform product can be maintained. `Thus ideal uniform heat conditions can be arrived at I'egardless of variations in the length, shape or section of the articles being treated, as well as regardless of the particular chemical composition of the metal.

It will of course be understood by those familiar with the art that a far greater degree of accuracy can be obtained by carrying out our invention than is the case where the operator must depend upon the color of the metal in order to determine whether or not the metal has been heated to the proper degree. The value of our invention 1s particularly increased when applied to heating processesin which the heating medium is electricity, and therefore capable of nicet in control.

It wil of course be understood that our invention is applicable to the heat treatment of metals for a variety of purposes. Theis for example, it is well adapted for use in bending processes such as the bending of steel tubes. in order to conveniently determine the point at which the application of further heat should be cut off and the bending instituted. Such ,an application of our invention can be made in connection with tube bending apparatus such as shown in Figures 4 to 7. inclusiveaalthough it is only specifically shown in Figure 4, in which a ortion of the indicating apparatus has been illustrated.

In this case the dial 2O is adjustably mounted on the rod 27 mounted adjacent to the tube to be heat treated and bent. The gear segment 23 is yielding-ly held in upper position against the stop 28 by means of a spring 29 in such manner that the nose 23 of the gear segment will extend in down osition so as to engage the movable contact mounted on the tube. As the tube 11 is heated by the current passing therethrough it expands and the up-ward movement of the contact B is transmitted to the indicator hand 21 through the medium of the nose 23 in substantially the manner indicated. By adjust-ably mounting the dial 20 on the rod 27 it will be seen that the indicating mechanism can be readily accommodated to different spacings of contact blocks.

The remaining features of our invention have to do with the heat treatment of tubes for bending operations, and consist in heat treating the tube by it's internal resistance to a current of electricity passed therethrough. while it is in position on the bending apparatus. As one means for carrying out the foregoing we have illustrated the mechanism sh wn in Figure 4 in which the tube 11 is supported in a fixed contact terminal or block A so aslto extend between.

the die or form 30 andthe bending wheel 31 carried in the arm 32 plvotally mounted on the shaft 33, which in turn is supported in a suitable jaw casting or base 34. The other terminal or block B is adjustablymounted upon the tube 11 so that it may be readily shifted so as to heat that portionof-jthe tube only which it is necessary to heat."V

After the parts have been properly positioned, the current is turned on and when the tube has been raised to the proper degree of heat, as established by the indicating mechanism, the current is turned ofi and the tube l1 is bent around its'form or die 30,I

during which operation it is firmly held by the lower contact block A', while the relation between the contact B and the indicating mechanism is such that no impediment is offered to the bending operation.

In addition to the prevention of scale and the consequent loss of material, our improved method is advantageous in that it operations. and avoids the loss of time entailed 4by the use of such apparatus. Furthermore, we are enabled to carry out the bending operation at the very point when the metal has been raised to the proper degree of temperature, and We are also enabled to secure superiority and uniformity in product as will further appear.

In Figures 5 and 6. we have also shown one form of bending apparatus used for example in bending tubular front axles for automobiles. such apparatus comprising the die or form 30 and the bending rolls 3l which are adapted to be moved outwardly and downwardly. The terminal blocks A and B are adj ustably mounted on the tube l1 so as to heat only the required portion of the tube and it is to be understood that indicating mechanism is arranged in cooperation with one or the other of said blocks substantially in the manner indicated in Figure 4.

In Figure 7 is illustrated still another ty'pe of apparatus which might be used to bend a tubular front axle.. In this construction two fixed bottom rolls 35 are mounted in a suitable base 36 and a third roll 37 is located at a point above such rolls and mounted for vertical movement so as to bend the tube 11 in the desired manner, the stationary wing rolls 38 cooperating therewith.

It will of course be understood that in carrying out our tube bending process we fill the tube to be bent with suitable material such as sand or the like` but we prefer to use an inertmaterial which Will assist in preventing oxidation.

By our improved process of tube bending, the molecules of metal of the tube are heated uniformly throughout, thus maintaining uniform heat conditions and always insuring that every portion1 of the tube is in proper condition for the bending, which ofcourse will produce not only a uniform product'but also a superior product.

The term decalescent point, as found in this specification, is employed in a broad sense and is to be understood asincluding. what is technically more properly termed the critical point, i. e., that temperature at which certain changes take place in the steel which place it in the proper condition for quenching in some cooling medium for hardening purposes, and at which point the steel will absorb a consider'ableamount of heat without corresponding rise in the temperature, and therefore, Without a change in tliedimensions of the steel, such for instance, as a chan e in the length of the' piece being treated. t will be apparent that our invention will be found most useful in determining this technical critical point,

but since, as previously pointed out, our invention can be employed in simply determining the points of decalescence of metal, of which there are several, we have used the term decalescent in' a broad sense.

- lWe claim:

l. In the commercial heat treatment of metallic articles, the method of ensuring certainty of results in the condition of the metal which consists in heating the article, and in utilizing variations in the rate of physical changes of the-article during heating as a medium through which the allot-ropic changes in the article will be indicated by the article itself.

2. In the commercial heat treatment of metallic articles, the method of ensuring certainty of results in the condition of the metal which consists in heating the article, and in utilizing variations in the rate of physical changes of the article during heating as a medium through which the allotropic changes in the article will be indicated by the article itself, and in cutting 0E the heat and quenching the article when the desired properties are indicated.

3. In the commercial heat treatment of metaliic articles, the method of ensuring certainty of results in the condition of the metal which consists in heating the article, and in utilizing variations in the rate of physical changes of the article during heating as a medium through which the internal conditions of the article will be indicated by the article itseif through indicator means associated with the article and responsive to said ysical change.

4. n the commercial heat treatment of metallic articles, the method of ensuring Y certainty of results in the conditions of the metal which consists in suspending the article for discharge from the heating apparatus in heating the article, in indicating the internal condition of the metal by variations in the rate of physical change of the article itself through means associated with the lower end of the article and responsive to such change, and in discharging the article when the desired internal conditions are indicated.

5. In the commercial heat treatment of metallic articles, the method of ensuring certainty 'of results in the condition of the metal which consists in sus ending the article for discharging from t e4 heating apparatus in heating the article, in indicating the internal condition of the metal by variations in the rate of physical change of the articie itself thro h means associated -with the lower end of the article and responsive to such change, and in discharging the article when the desired internal conditions are indicatedand in quenching the article.

6. In a machine for commercially heat treatingmetallic articles, the combination of a releasable su port for suplportin the article in the macIhine for disc ar e t erefrom on release, means for heating t e article by its internal resistance to a passage 0f electric current therethrough, an mechanism associated with one end of the article and adapted to translate change in dimension of the article as it is heated into an indication of temperature.

7. In a machine or commercially heat treating metallic articles, the combination of a frame, a pair of article engaging supports carried thereby, one of said supports being iixed and the other being slidable in the frame, and indicator mechanism operatively associated with an end of the article to indicate physical change in the article during heating whereby1 the operator may be -apprised of the condition of the article by the article itself.

8. In a machine for commercially heat` treating metallic articles, the combination of aA frame, means for releasably supporting the article in a substantially vertical position, means for heating the article, and indicator mechanism associated with the lower end of the article and adapted to indicate physical change in the article during heating whereby the o erator may be apprised of the condition ol the article by the article itself.

9. In a machine for commercially heat treating metallic articles, the combination of a frame, an upper and a lower support adapted to releasably receive the article and support the same in substantially vertical position, the upper support being relatively xed while the lower support is slidable in the frame, and indicator mechanism operated by the movement 'of the movable support as. the latter shifts during change 1n physical dimension of the article whereby the operator is apprised of the temperature of the article by the article itself.

10. In the commercial heat treatment of metallic articles, the method of ensuring certainty of results in the condition of the metal which consists in heating the article and in utilizing variations in the rate of physical change of the article during heatlng as a medium through which the temperature of the article 1s indicated by the article itself, and in stopping the further heating ofthe article when it has reached thev desired temperature. Y

11. The method of determinin when metal, as steel or an alloy thereo passes through a critical point, which consists in changing the heat content of the metal, determining the rate of change of dimension of the metal and noting the time of occurrence of a substantial change in the rate of change of dimension. l

12. The method of determinintg metal, as steel or an alloy thereo when passes indicator throu h a critical point, which consists in changing the heat content of the metal and in determining the time of occurrence ofl ing the rate of change of dimension of the 10 metal, and noting the time of occurrence of abrupt change in said rate of change of dimension. I

vIn testimony whereof, we have hereunto signed our names.

HARRY P. MACDONALD. ANGUS S. MACDONALD

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