US 2131505 A
Description (OCR text may contain errors)
Sept. 27, 1938. H M. GARssoN TREATING STEEL Filed Aug. 16, 1938 |l-f Il| 1|' '11| 'Il f1 Il Ill lll en/jg M. 621/1560,
eunooleuloonuoooonao onuoaoavoonaaanono l 2 of c eaoooocneoo.o nesuonunnonoaccsnorovoao seneca. ncavnuoao'oaoo amaca.. nonacononnvaan NI Patented sept. 27, 193s PATENT ori-"ICE Application August 16,
instruments, and other steel articles in which a bright clean'surface or a colored surface may be desirable or where it may be desirable to remove impurities frorn the metal in order to obtain uniformity of composition. While the invention is adapted for treatment of steel for various uses. for purposes of illustration it will be described mainly in connection with treatment of razor blade strip, in the manufacture and treatment of which the invention is particularly desirable.
Steel employed in the manufacture of razor blades is generally produced in the form of a very thin strip cutinto the shape of a succession of razor blades attached at their ends. The strip, then, is substantially the width of the finished razor blade. For forming the strip it is desirable that the metal be in an unhardened, readily workable condition but before the nal blade is produced the metal must be hardened, tempered and otherwise treated. Inasmuch as the strip is very thin itis highly important that it be free from aws and defects. It is highly desirable that the strip be of a homogeneous character and especially that its surface be of a uniform character throughout the area of the blade. One reason that this is important is that if there is a lack of uniformity portions of the surface may break away or stains, defects or imperfections may appear in the surface. It is highly important not only that the razor blade be of homogeneous character but also that its surface have a pleasing, uniform appearance to aid in its sale by appealing tothe purchasing public. The thinner the blade the more necessary is homogeneousness in the make-up of the steel. Likewise the thinner the blade. the more desirable it is that impurities or imperfections not entirely confined thereto it is a purpose of the present invention to treat strips for the manufacture of blades of unusual thinness, that is, thinner than the majority of blades now on adapted for cutlery including knives and surgical may be removed or eliminated or avoided. While TREATING STEEL Henry M. Gannon, Far Rockaway, N. Y.
1938, Serial No. 225,121
the market. An important attribute of a razor blade is the possibility of flexing or bending to fit neatly and accurately into the-razor blade holder when adjusted to suit the desires of the user. Such an unusually thin blade especially well adapts itself to such appication.
For purposes of ornamentation, beauty, identification and attractiveness it is possible to apply a coating to the blade surface or to so treat the blade surface that the surface layer has different metallurgical characteristics from the body of the blade. Such treatment may be especially undesirable with very thin blades. It is a purpose of the present invention to produce a blade of substantially uniform characteristics throughout its thickness and a satisfactory, pleasing, attractive surface finish or appearance.
After the blade strip has been made in the desired form it is passed through a heating device which raises its temperature to something more than the critical temperature of the metal, say from 1400 C. to 1'100J C. for carbon, chrome or spring steel which is suitable for razor blades. At such temperatures it has been found that there is a rearrangement of the grain formation of the metal at least to some extent but there may also be an undesirable surface effect. One phase of the present invention contemplates this heat treatment of the razor blade strip in a Vfurnace supplied' with an atmosphere of a reducing gas. If oxygen or moisture is present at this temperature oxidation may result producing a colored film of oxide on the surface of the steel. Such a film m-ay be very undesirable and unless it is absolutely regular in appearance it may give an undesirable appearance and. so be a defect from a sales standpoint. In order to avoid this oxidation preferably air is not permitted in the heating chamber through which the strip of steel passes. Oxidationmay be avoided by filling the space in the heating furnace preferably with a reducing gas such as illuminating gas, hydrogen, carbon monoxide, methene, etc. Often in such a furnace the heating action of the razor blade strip may not be satisfactory. Even when a bade looks satisfactory and approximately uniform to the naked eye it may be found on careful examination that the apparently smooth surface is often pitted with minute depressions. The strip of steel which is used for the manufacture of blades often contains imperfections in the form of oxides, etc., which are unaffected by the usual hardening process. There are found in the hight grades oi' carbon or alloy steels used for cutlery and razor blades certain structural features 4crystallization if present be deformed so that the final structure of the steel in the blade is o ahmore rened order. This result of homogeneu ousness in the metal may be accomplished by the introduction bf a catalytic agent in the presence of a reducing gas in the furnace where the heating step of the hardening process takes'lplace. If there are oxide imperfections in the steel oxygen may be liberated athigh temperatures in the presencelof platinum. It is not lmown dei nitely when such tendency to liberation oi oxygen arises but it seems to begin at about 400 tc 600 C. and above. It is especially noticeable at l000 C. and above. The preferred catalyst 'in 'the heating chamber is platinum which may be in the form of pure sponge platinum or in the form of block or strip or a platinum wire. The exact theoretical operation or effect of the platinum is not known. The platinum, however, seems to act as a catalytic agent as the temperm ature in the chamber rises and upon contact with the platinum a very strong adsorption of C. or even as 'high as 1700 C. The eiect or' oxygen is particularly undesirable. The oxygen liberated at high temperatures from the steel or its imperfections may normally be reabsorbed in the steel on cooling but instead of such a. reoxidation taking place the adsorption of the oxygen on the surface of the platinum and the reducing action. due to the presence of the platinumy catalyst results in a chemical reaction of the oxygen. A combustible gas in the presence of oxygen in a very small proportion or viceversa will not operate completely without the presence of a catalytic agent. The catalytic agent preferably used for this purpose is either a glowing platinum wire, pure platinum sponge or solid platinum which acts upon contact. The result upon the steel when no air or oxygen is present but the platinum catalyst is present is` to produce a brighter nish and an improved or greater degree of uniformity inregard to the hardness and granular arrangement of the steel.
i Although ordinarily the presence of an oxide on the surface of the blade strip may be detrimental it may be desired to color the blade by producing an oxide. When a coating is provided for the blade it is a purpose of the present invenais-.ipse
'The usual scheme now used for chilling contemof the furnace not in a continuous movement polishedcrystal magnetite but displaying color due to the oxide. The color may be a. deep blue, purple or the like, depending upon the temperature and the character of the gas present. Even ii oxide should be formed by oxygen being present the presence of the catalytic platinum improves considerably the quality of the steel. It seems to insure an even dispersion of the surface oxide and substantially eliminates the tendency ci the oxide to pull away from the metal on which it is formed. From such a tendency results an uneven hardness which may, in part at least, be due to the variation in thermo-conductivity of the oxide and of the steel.
When it is desired to produce or provide a coating or surface on the blade by oxidizing there may be introduced into the furnace' containing the platinum catalyst atmospheric air or treated or ozonated air which may be produced by any of the Well known ways of treating air' to enrich or change itsoxygen content before it is passed into the furnace. The theoretical effect of the oxygen is not thoroughly understood. The effect of the ozonated air, that is air containing ozone, may be that by its more rapid action in forming the oxide surface or coating it has a beneiicial edect on the metal. It is noted that the operation in the presence of 'the platinum catalyst substantially avoids or eliminates the scaling which usually occurs when rapid oxidation takes place kand leaves a smooth, polished surface on the blade strip the color of which varies generally with the temperature to which the blade strip is subjected in the furnace.
The effect of the presence of the platinum catalyst is also further to improve -the quality of the strip steel during the process of hardening. The integrity or uniformity of the metal is better than that produced by the usual process employed in the manufacture of such strip steel. There is substantially no irregularity of thermo-conductivity throughout an individual blade made by the process here described.
After the razor blade strip has been raised to the critical temperature in the presence of the platinum catalyst and the structure rearranged it is necessary that the uniform arrangement of the steel be made permanent by sudden chilling.
plates conveying the blade strip continuously from the heating furnace past, over or through a cooling element. It is clear that in such an arrangement the leading end of a single blade will be introduced into the cooling device prior to the hind end of the blade in the strip. Thus during the time required for a single blade unit to be chilled there will be a continuous variation or divergence of temperature in the blade unit. This may tend to produce irregularities during the chilling. It is a. purpose of the present invention to avoid this possibility of producing lrregularity by passing the strip through and out with the strip or so that the strip is more or less 'I out of their influence. While.l the blocks remain thus the. strip is led forward and withdrawn from the furnace the length of a blade unit. During this time the strip is not strongly influenced by the cooling blocks. The movement of the strip is then discontinued and while the blade unit remains immovable the chilled cooling blocks are caused to approach the furnace exit andenclose and suddenly chill the blade unit. As soon as the blocks are cooled and are brought together to influence the strip the blade unit as a whole will be cooled and this variation in temperature within the individual unit may tend to be avoided. The stopping of the strip need be only momentary sincethe blade is very thin and will be readily and promptly chilled. Preferably the strip will beJI suddenly chilled from the temperature of approximately 1400 C. in the furnace'to about 40 C. to 60 C. The chilling blocks may conveniently be kept at about this temperature by passing through them water or other chilled materials. While this sudden chilling of the blade -unit may be suilicient to put the strip in proper condition it is preferred to have additional chilling blocks adjacent the moving chilling blocks. Inasmuch as the movable enclosing chilling blocks will'bring the strip to a low temperature the additional chilling blocks need not be movable but the strip may be passed between them for further chilling to substantially atmospheric temperature or below. These additional chilling blocks also act as guides for the strip and they may also prevent curling or physical deformation of the strip which might otherwise occur. By the use of the chilling blocks a substantially constant final temperature of the strip is insured, thus substantially eliminating the possibility of irregularities' or defects occurring in the strip after it has left the chilling blocks. The chilling apparatus may preferably be enclosed in a chamber where no oxygen is present. It may be convenient, therefore, to enclose the chilling blocks in a chamber lled with a reducing gas of the character heretofore referred to.
The chilling blocks may be brought to the desired temperature by any. suitable means. Thus water from a well or the city mains may be employed or previously cooed or refrigerated water or other suitable material may be used in the .cooling blocks or for the purpose of cooling them.
As the strip comes from the cooling blocks after the hardening it will ordinarily be extremely hard and it will also be very brittle. In this condltionit is not suitable for ordinary use as razor blades It is important that the blade acquire a proper combination of hardness and elasticity. This may be accomplished by a tempering process which may conveniently take Y emerging from the tempering chamber the strip is permitted to cool to atmospheric' temperature without `being suddenly chilled. By proper adjustment of temperature, which according to the @te of speed at which the strip passes through the furnace may range from about 300 C. 500 C., the treatment will result in imparting a springiness to the blade which permits it to conform to the shape of the razor or blade holder and to suitably and sa'tisfactorly perform its shaving function. The particular purpose of this part of the process is to relieve any strains in the metal which may be present after the hardening and to produce uniformity of solidness and optimum elasticity and flexibility. During this process as ordinarily carried out many times a yellowish oxide is formed on the blade which must be either polished oif or will spoil the blade to such an extent as to require its rejection upon inspection. During the tempering if there is more than the usual amount of humidity or moisture in the air some oxidation may take place. The oxidation ordinarily mayl not.-cover the blade entirely with the lm of oxide but may result in imperfection and discoloration or spottiness. In order to avoid this and to produce a blade strip of uniform condition and appearance it is preferred `to place in the tempering chamberplatinum which may be pure platinum sponge, or solid platinum, or a platinum wire. Both in the tempering chamber and in the hardening chamber above described the platinum present may be brought to a glow or to incandescence or other suitable temperature by passing an electric current through it. This may be especially important in the tempering chamber in which the temperature is only 300 C. to 500 C. at which temperatures platinum ordinarily will not be incandescent. The tempering chamber in which the platinum is installed may preferably be provided with a nonoxldizing atmosphere. To this end the tempering chamber may be filled with a reducing gas such as referred to above. When such a tempering chamber is used there will' be imparted to the tempered blade strip a bright silvery nish. The surface of the blade thus produced may be somewhat similar to the finish applied to silver articles and generally referred to by jewelers as the platinum finish. This is a soft silvery texture which ordinarily persists until the blade is used and gives to the blade an especially attractive appearance which may be satisfactory and attractive `to the purchaser and user of the finished blade. In the heating chamber the platinum apparently acts as-a catalyst. The theoretical or scientific explanation of the -result may not be known but apparently .while possible imperfections by reason of oxidation are avoided, reducing action von the oxides due to the presence of the platinum catalyst in the reducing gas atmosphere in the heating chamber thoroughly cleans the surface and insures a uniform tempering throughout the blade. The effect of theentire process is to produce a better cutting edge and a more resilient blade.
Even when the blade strip is not hardened in the way above described an improved effect is produced by tempering in the way above described. 'Ihe employment of the entire process above outlined or portions of it will tend to produce a uniform condition in the razor blade whether the blade is colored or not-` and whether or not the reducing gas is employed in one or both chambers. Even ywhen the reducing gas is not present the employment of the platinum catalyst is desirable and advantageous although its best effect maybe produced in the reducing atmosphere.
Similar operations and eflects may be employed and observed in connectionl with the in vention as adapted to steel used .for purposes other than. razor blades. The units to be used may be marked or indicated Kon the strip or it may be cut into proper'un'its and put through the treatment on a conveyor.
The invention is not confined to the use of any specific form of apparatus but as an example one specic form of apparatus especially adapted for the treatment of razor blade strip is illustrated in the accompanying drawing in which' Figure la and Figure lb together illustrate a sectional view in a diagrammatic way of one speciflc-form of apparatus which may be employed for carrying out the invention. Fig. 2 is a transverse vertical section of a pair of cooling blocks illustrated in the closed position. Fig. 3 is a plan view of a fragment of one form of razor` blade strip.
The razor blade strip I8 having been reduced to the outline substantially as indicated in Fig.` 3 is introduced in any suitable way into the furnace ii where it may be treated for hardening. The furnace il is illustrated as an ordinary type of electric furnace provided with external insulation i2 ,surrounding heating coils i3 which surround the heating chamber I4. A pipe I5 provided with an outlet valve i6 is illustrated for introducing into the chamber i4 a suitable gas which preferably will be a reducinggas. The ends of the furnace II are substantially closed leaving only a small slot for the entrance and egress` ofthe razor blade strip l0. At a suitable place in the chamber I4 of the furnace may be arranged platinum in suitable form such as sponge platinum, block platinum or platinum wire. In the drawing is illustrated a platinum bar |1 suitably supported at about the center of the furnace II although this is not essential. In order to allow the gases to come in contact with as much of the platinum surface as possible it is desirable that the platinum bar |1 be mounted freely in the air or be supported by porous or brick work blocks I8. The temperature of the furnace will be kept at slightly above the critical temperature of the steel being employed say from 1400 C. to 1700 C. Preferably a very thin razor blade strip I0 will be employed'in the furnace Il and it has been found that when strip'is raised to the temperature indicated it will sag and may break if a considerable stretch of it is left unsupported. Ordinarily the free portion of the strip should not be over about 8 inches and for this reason there are indicated in the drawing supporting members I9 positioned relative to the,platinum block I1 to leave never morethan seven or eight inches of the blade strip hanging free. The blade strip passes through the heating furnace I| and as it leaves the furnace passes between the upper movable cooling block illustrated at 20 and thev lower movable cooling block illustrated at 2 I. The cooling blocks are diagrammatically illustrated as mounted to slide in a vertical guideway 22. Lever arms 23 connected to the movable blocks 2| and 22 at their other ends are pivoted to a bearing 24 sliding in a horizontal guideway 25. Connected to the bearing 24 is an arm 26 which is .moved by suitable power driving gearing 51 in such a way as to reciprocate the bearingmember 24. As this reciprocates 4it causes the blocks 20 and 2| to separate andto again approach eachc other. Mounted beyond the movable cooling blocks 20 and 2| are illustrated stationary cooling blocks 21 which may be of any suitable size and number. The cooling block groups are shown as longitudinally separated but they may be in close contact with each other and with the movable blocks 28 and 2|. Driven by the gearing 51 is a preferably forked arm 28 which may be caused to rise and engageA the razor blade strip at opposite marginal apertures 29 so as to grasp the blade strip I0 and pull it through and out of the furnace I. The arm'28 will give an intermittent movement to the blade strip ID and this is arranged in cooperation with the arm 2G so that the movable cooling blocks 20 and 2| are separated during the period the arm 28 imparts movement to the razor blade strip. The arm 28 is then freed of the razor blade strip which remains unmoved during the time the arm 25 brings the cooling blocks 2U and 2| together to chill the portion of the blade strip between them. The device preferably s so arranged that the arm 28 moves the razor blade strip at each step the length of a single blade unit as indicated between the marginal apertures 29. This is desirable so as to produce the desired sudden Vchilling; uniformly throughout each blade unit as indicated above. The arm 28 may be so adjusted and operated as to move the strip a distance equal to the length oi' a plurality of razor blade units and likewise the cooling blocks 28 and 2| may be made of any suitable length but preferably will be of a length equal to the length of.a single razor blade unit or of a plurality of razor blade units. The arm 28 pulls `the razor blade strip I0 through the furnace and the cooling blocks 20, 2| and 21 and forces the strip into and through the tempering furnace 59. While not essential the tempering furnace is here illustrated as oi' the electric furnace type having a central chamber 30 through which the razor blade strip passes to be heated and through which it emerges to be cooled slowly and preferably wound Iupon a roller 3| for convenience in further handling. The roller 3| may rotate continuously and between it and the furnace 59 may be n provided a. roller 32 forced by a spring 33 against the razor blade strip IU to take up slack due to the fact that the razor blade strip is moved intermittently or step by step while the roller 3| is rotated continuously.- In the chamber 38 of the furnace 59 will preferably be installed platinpm in the form of pure sponge platinum, solid platinum or platinum wire. For purposes of illustration there is illustrated a platinum wire 34 unsuppported and stretching from end to end of the furnace 59. The platinum wire 34 like the platinum bar I1 may be heated by bringing to incandescence or any suitable temperature by passing an electric current throughit.O This maybe particularly important in connection with the furnace 59 where the temperature is maintained in the chamber at only about 400 C. A pipe 35 A controlled by a valve 38 may be provided to supply the chamber 30 with a reducing gas of the character above indicated.
1- In Fig. 2 the movable blocks 20 and 2| are shown in their closed position in which they enclose and nearly contact the razor blade strip I8. In these' Ablocks as in the blocks 21 pipes may be employed for the ingress and egress of cooling liquid. The pipes 31 may be of flexible material such as rubber so as to allow the cooling blocks 20 and 2| to be moved.
It may be desirable to effect the chilling in the absence of oxygen or air. To this end a casing 38 may be arranged about the chilling blocks 28, 2| and 21 and the interior of the casing 38 may be supplied with an inert gas or a reducing gasof the character indicated. For this purpose there is indicated a pipe '39 provided with a valve. 40 through which the gas may be passed to the interior of the casing 38.
It may be desirable to partially reduce the temperature of the blade strip before it exits from the tempering chamber 30. For this purpose there may be used a plurality of heating coils in the furnace 59. Two heating coil units 4I and 42 are indicated. If desired the heating coil 4| for instance may be maintained at the tempering temperature of approximately 400 C. while the heating coil 42 may be maintained at a somewhat lower temperature, say 250 C. Any suitable muiile 43 may be employed for separating the coils 4| and 42.
The invention has been described as applied to a strip of connected .blade blanks or other articles but it is not limited to such a strip. The blanks for individual blades or other articles may be severed and carried by a conveyor through the treating mechanism. The term razor blade strip or steel strip is here used as broad enough to include one blade or other unit'or more than one blade or other unit whether physically connected together or arranged on a conveyor and irrespective lof the character or form of the unit.
The invention has been described in much detail but all phases described are not essential to the successful production of a satisfactory razor blade and obviously the invention is not confined to all of the specific details herein referred to.
This case is a continuation in part of application Ser. No.\135,599, filed Apr. 7, 193'7.`
I claim as my invention:
1. The method of treating steel strip comprising placing in a chamber platinum to act as a catalyst,'heating the chamber to above the lower critical temperature of the strip, keeping the chamber lled with a reducing gas, feeding the strip through the chamber to cause its molecules to be rearranged and included oxygen to be re-`v moved, moving the strip from the chamber by la step by step movement and between cooling blocks which separate during the movement of the strip and comevtogether to substantially engage the strip while it is stationary, Passing the strip between additional immovable cooling blocks, feeding to the cooling blocks a cooling medium at about 40 C. to 60 C. temperature, from the cooling blocks passing `the strip to a tempering furnaceymaintaining the furnace at about 400 C., maintaining heated platinum in the tempering furnace as a catalyst, keeping the tempering furnace filled with a reducing gas, and removing the strip from the tempering furnace and slowly cooling it to atmospheric temperature.
2. In the method of treating steel strip divided into units to produce a uniform texture the steps of heating the strip to above its lower critical temperature, and cooling a part onlyv of the' strip by4 suddenly applying cooling means to an entire integer at least as large as a single unit.
3.. The method of treating steel strip comprising placing in a chamber platinum to act as a at about 400 C., maintaining heated platinum `in the tempering furnace as a catalyst, and removing the strip from the tempering furnace and slowly cooling it to atmospheric temperature.
4. The method of treating steel strip comprising heating a chamber to above the lower critical temperature of the strip, feeding the strip through the chamber to cause its molecules to be' rearranged and included oxygen to be removed, moving the strip from the chamber to cooling blocks at about 40 C. to 60 C. temperature, from the cooling blocks passing the strip to a tempering furnace, maintaining the furnace at about 400 C., maintaining heated platinum in the tempering furnace as a catalyst, keeping the tempering furnace filled with a reducing gas, and removing the strip from the tempering furnace and slowly cooling it to atmospheric temperature.
5. The method of treating steel strip comprising heating a chamber to above the lower critical temperature of the strip, feeding the strip through the.chamber to cause its molecules to be rearranged and included oxygen to be removed, moving the strip from the chamber by a step by step movement and between cooling blocks which separate during the movement of the strip and come together to substantially engage the strip while it is stationary, passing the strip between additional immovable cooling blocks, feeding to the cooling blocks a cooling medium at about 40 C. to C. temperature, from the cooling blocks passing the strip to a tempering furnace, maintaining the furnace at about400 C., maintaining heated platinum in the tempering furnace as a catalyst, keeping the tempering furnace filled with a reducing gas, and removing the strip from the tempering furnace and slowly cooling it to atmospheric temperature.
6. The method of treating steel strip comprising heating a chamber to above the lower critical temperature of the strip, keeping the chamber filled with a reducing gas, feeding the strip through the chamber to cause its molecules to be rearranged and included oxygen to be removed, moving the strip from the chamber by a step by step movement and between cooling blocks which separate during the movement of the strip and come together to substantially engage the strip while it is stationary, passing the strip beween additional immovable cooling blocks, feeding to the cooling blocks a cooling medium at about 40 C. to 60 C. temperature, from the cooling blocks passing the strip to a tempering furnace, maintaining the furnace at about 400 C., and removing the strip from the tempering furnace and slowly cooling it to atmospheric temperature.
7. The method of treating razor blade strip marked into individual blades comprising producing a smooth shiny surface and a uniform texture by heating the strip to above its lower critical temperature in the presence of a reducing gas and a platinum catalyst, cooling the strip suddenly in integers at least as large as a single blade, heating the strip to a tempering temperature in the presence of a reducing gas and a heated platinum catalyst, and slowly bringing the strip to about atmospheric temperature.
8. The method of treating steel strip comprising producing a smooth shiny surface and a uniform texture by heating the strip to above its lower critical temperature in the presence of a reducing gas and a platinum catalyst, cooling the strip suddenly, heating the strip to a tempering temperature in the presence of a reducing gas and a heated platinum catalyst. and slowly bring- 'ing the strip to about atmospheric temperature.
9. The method of treating steel strip marked into units comprising producing a smooth shiny surface and a uniform texture by heating the strip to above its lower critical temperature in the presence oi a reducing gas and a platinum catalyst, cooling the strip suddenly in integers at least as large as a single unit, heating the strip to a tempering temperature, and slowly bringing lthe strip to about atmospheric temperature.
l0. The method of treating steel strip comprising producing a smooth shiny surface' and a uniform texture by heating the strip to above its lower critical temperature in the presence of a reducing gas and a platinum catalyst, cooling the strip suddenly, heating the strip to a tempering temperature, and slowly bringing the strip to about atmospheric temperature.
11. The method of treating steel strip comprising producing a smooth shiny surface and a uniform texture by heating the stripto above its lower critical temperature, cooling the strip suddenly, heating the strip to a tempering temperature in the presence of a reducing gas and a heated platinum catalyst, and slowly bringing the strip to about atmospheric temperature.
l2. The method of treating razor blade strip marked into individual blades comprisingl producing a smooth shiny surface and a uniform texture by heating the strip to above its lower critical temperature, cooling a part only of the,
strip by suddenly applying cooling means to an l entire integer at least as large as a single blade.
heating the strip to a tempering temperature, and slowly bringing the strip to about atmospheric temperature.
heating it to about 300 C. to 500 C. in the presence of incandescent platinum in a reducing gas. i7. In treating steel strip, the step comprising heating it to about'its critical temperature in the presence of incandescent platinum and an oxyrlizingggagent.
i8. In treatingsteel strip, the step comprising heating it to about its'critical temperature in the presence of incandescent platinum in an atmosphere containing ozone.
i9. ln treating steel strip, the step comprising heating it to about its critical temperature in the presence of incandescent platinum in an atmosobere containing a reducing gas and an oxidizing gas.
20. in they method of treating razor blade strip divided into individual blades to produce a uniiorm texture the steps of heating the strip to above its lower critical temperature, and cooling a part only of the strip by suddenly applying cooling means to an entire integer at least as large as a single blade.
HENRY' M. GARSSON.