Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
  • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
  • C21C5/52—Manufacture of steel in electric furnaces
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P10/00—Technologies related to metal processing
  • Y02P10/20—Recycling

Definitions

• This invention relates to the manufacture of steel and more particularly to improved steel alloys and products thereof, and procedure for making the same, which have unusual strength and toughness and are susceptible of ready fabrication, by forming or welding, without loss of the desired mechanical properties. More specifically the invention is concerned with compositions that may be classified as low-alloy steel, containing substantially less than 1% carbon, but designed and prepared, as will be explained below, in a manner to attain new and exceptional results, and to attain such results without requiring relatively large amounts of expensive alloying ingredients. Moreover the products of the invention are characterized by unusual cleanliness of the alloy, specifically in an es sentially complete absence of non-metallic inclusions.
• the mechanical properties of the metal are very notably superior to those of prior steels of similar type and purpose.
• the invention moreover, provides a product having exceptional uniformity of composition and structure, with a remarkable absence of internal notches, cracks and the like.
• this aspect of the alloy is particularly significant w here weight is critical and it is undesirable to allow extra weight as a factor of safety.
• the present improvements have the object of providing a steel with a yield strength in the range of 100,000 to 175,000 p.s. i. or more, a tensile strength in the range of 115,000 to 190,000 p.s.i. or more, and a ductility, expressed as percent reduction in area, of between 40% and 80%, the steel being such that it can achieve these properties by and after heat treatment.
• the steel is characterized by unusual qualities of toughness including high impact resistance, a further feature of preferred embodiments being that the superior mechanical properties, especially toughness, are exhibited over a relatively wide temperature range, notably extending to quite low temperatures.
• the invention extends to plate or the like,
• Heat treatment of the alloys is in general effected in conventional ways, especially including a quench from a high temperature, e.g. 1500 F. and above, and then temper-ing at any desired temperature but with special advantage (as explained below) in a range upwards of 1 000" F., references herein to heat treatment being thus generally employed with the usual meaning of conventional operations for developing desired properties of strength and toughness, and also, ordinarily, hardness.
• heat treatment of the steel is performed after 3,254,991 Patented June 7, 1966 any desired forming, and may comprise appropriate operations embracing one or more, and in many cases all, of the known steps of normalizing, austenitizing and tempering.
• the metal, from the ingot, can be worked or deformed in any usual manner, for instance by rolling (e.-g. hot rolling), forgin-g'or the like, and maybe produced as plate, sheet,.strip, rod, bar or other suitable stock, or for-gings of desired shape.
• Forming e.g. as may be needed for fabrication, is ordinarily effected in the annealed condition and can involve bending, stamping, pressing, drawing, punching, or the like.
• forming, es pecially all drastic forming is done before full heat treatment; a suitable operation being to carry out the forming of plate, sheet or the like after an anneal at-about 1400 F. with cont-rolled cooling to about 1000" F. followed by air cooling to ambient temperature.
• the steel When well annealed, the steel forms readily in the cold. Some operations, such as cutting, punching and in some cases (at the lowest carbon values) mild forming, may be pe-rformed after heat treatment. As explained above, in the case of alloys in the lower carbon range, welding may be done after as well as before the article is heat treated,
• the improved alloys of about 0.35% to about 0.60% carbon require welding in the annealed state, as in the case of forming, and before heat treatment.
• alloys include an unusually low content of oxygen, and also of hydrogen and nitrogen, while at the same time there is a similarly unusual freedom from non-metallic inclusions as well as unusual-1y low inclusions of non-metallic elements such as phosphorus and sulfur. It is believed that alloys of the present general type have not heretofore been produced with this low order of concentration of the impurities or inclusions stated. For example, attempts to reduce correspondingly the amount of oxygen and some other elements have ordinarily involved the inclusion of such elements as silicon, aluminum or others, which in turn have invariably resulted in a residue of non-.rnet-allic inclusions, e.g. as compounds of one or another of the added elements.
• alloy is complete or virtual' absence, in steel of the defined character and purity, of such elements as named above (and of com- 0 pounds of them); thus in the compositions described below, aluminum is wholly absent, and silicon is present,
• the alloy is also prepared and designed to have up to 1% but but preferably not more than a relatively small amount of manga: nese, say 0.08% to 0.18% or even essentially zero manganese, limitation to this small amount of manganese being an unusual and advantageous feature, with corresponding avoidance of undesired contamination (e.g. detectable inclusions of non-metallic compounds) that often accompanics or results from a larger quantity of this element.
• the major or significant nonferrous elements in the composition e.g.
• Table I represents the overall ranges of A B c D ingredients, including alloying ingredients (i.e. the effective or required elements in addition to iron), and also 1 H T H T H T H the absence or near-absence of residue or other unwanted 0 0 0 5 0 0 5 0 1 O O 5 ingredients, that characterize the compositions of the in- 15 vention. It may be noted that in a limited, low range manganese can be deemed an alloying ingredient, al- It will be understood that A, B and C refer respectively though it is conceived that very useful products may be to sulfide, alumina and silica type inclusions, D to globmade without manganese.
• the t h i f i d promotes th d nt invention resides i alloys as Prescribed in Table but characteristics, including facility in heat treatment, while limited to a Carbon range of 015% to 035%, PP molybdenum likewise contributes to the strength of the y- In the upper range of Carbon, from above about Composition, especially at high temperatures, and inhibits to about 050%, y advantages of the Steel embrittlement which might occur as the result of temper- Can Still be realized, including a high Order Of toughness, ing or similar treatment.
• the pettieulafiyimpoftaht feature of the aiioysih being some aspects of the significance of these ranges are as characterized by essentially complete absence of nonfollows; chromium i amount above about 130% metallic elements, especially y and being free pears tocause embrittlement of the alloy, while decrease essentially tree of Silicon, Will e evident at Once 'b of the chromium below about 1.40% results in reduction Table A f'ufthel' and y Significant aspect of in the hardenability of the composition.
• a significant elfect of manganese is that it serves to tie up sulfur in steel; the resulting manganese sulfides have a high melting point, and the action of manganese thus prevents the formation of undesirable ferrous sulfides. If not thus avoided, the latter compounds, having low melting points, and collecting in the grain boundaries, tend to melt during hot working, so as to produce so-called hot shortness.
• the sulfur content is very low, so that a limited amount of manganese, usually up to about 0.18%, suffices to account for the sulfur although it is permissible to use amounts up to about 1% to promote other desirable properties.
• the resulting small quantity of manganese sulfide appears to be soluble, i.e. to be dissolved in the alloy. Hence it does not form contaminating inclusions; indeed essentially none such are found on examination, as shown by Table II above.
• manganese keeps the steel from becoming hot short, but manganese in substantially greater amount (combining with more sulfur), would tend to form precipitated inclusions, and also to promote the erosion of pouring refractories, entraining additional nonmetallic particles in the metal. Furthermore, because of its relatively low vapor pressure, manganese in larger quantities may be vaporized and lost, in part, during presently preferred processes of preparing the alloys, with consequent difficulty in controlling the analysis.
• Columbium is a very expensive ingredient and the advantages of using it in relatively small amounts, as achieved with the present invention, are correspondingly important. It is included primarily to promote grain refinement as in accordance with A.S.T.M. Specification El9-46. Grain refinement data for the present alloys have been obtained at 925 C. after 8 hours of carburizing, and show that the degree of grain refinement obtainable with this element can be reached in the present alloys with substantially lower amounts of the element than as prescribed in prior practice. Below about 0.03%, columbium shows no substantial grain refinement, while over 0.10% further addition is at least wasteful in accomplishing no further function; indeed the present understanding is that increase of the content of columbium beyond this limit may start to reverse the operation and coarsen the grain size.
• Silicon in the alloy is simply a residual, there being no deliberate addition.
• the alloys are prepared in such way that silicon is kept as close to zero as possible.
• it has not been feasible to reach this low a content of silicon at least unless undesirably high quantities of oxygen have been allowed to remain or unless other undesirable conditions or additions have been permitted.
• silicon tends to form various reaction products which are retained as silicate or silica inclusions.
• Oxygen is particularly undesirable, especially in that it tends to react with various other elements to form oxides which also remain as non-metallic inclusions.
• the defined, extremely low content of oxygen represents a particularly significant feature of the alloy, under the circumstance of the relative absence of certain other elements, as explained.
• Hydrogen is also kept extremely low; with the hydrogen content above 5 p.p.m., there is risk of the formation of difiicultly detectable flaws known as flakes, such being internal hairline stress cracks in bloom and billet stock and heavy section forgings. Nitrogen is also undesirable in general respects, the maintenance of a very low nitrogen content being specifically advantageous in affording good ductility.
• compositions and characteristics are effected in a manner to achieve the desired composition and characteristics, especially with respect to cleanliness of the product and avoidance of unwanted elements or contaminations as explained herein.
• particularly effective procedures include at least one stage of high vacuum melting employing a consumable electrode which has the desired composition of iron and alloying ingredients.
• the material of the electrode is melted to form an ingot or the like by the passage of electric current which produces an electrical discharge between the electrode and the resulting pool of metal.
• a further and preferred feature of very special significance is the utilization of carbon, e.g. incorporated in the electrode composition in appropriate excess of aim, for deoxidizing the material during at least one high vacuum step.
• one 'efiective operation involves the utilization of iron powder of very high purity, such as electrolytic iron, which is then blended with carbon and desired alloying metals or with powder or powders consisting of one or more alloys of iron with such metals, the resulting mixture being formed or briquetted, as with the aid of pressures of the order of 50,000 pounds per square inch, so as to form consumable electrodes.
• the consumable electrode is then melted under vacuum by the use of electric current, discharging between the electrode and the rising body or pool of metal melted therefrom in the vacuum vessel (or at the outset a suitable base in such vessel) whereby a cast ingot results.
• This ingot is then further refined by repeating the vacuum melting operation, utilizing the ingot as electrode, or an electrode formed from the ingot by forging or by assembly of appropriate pieces derived from the first in got.
• the mode of electrical heating is similar to the first, so as to yield a final ingot constituting the desired alloy, which can then be converted by rolling or other operations into ultimate stock for use, such as plate, sheet or the like.
• the vessels preferably comprise suitably cooled crucibles of copper or the like so as to avoid danger of refractory contamination.
• the high purity iron used as starting material may be such, in accordance with known practices, as to have very low contents of sulfur and phosphorus, and preferably as little oxygen as possible, although it is not ordinarily contemplated that oxygen as low as is required in the present alloys will be characteristic of the purified iron powder. Indeed such iron powder may be expected to have from 0.06% to as much as 0.2% oxygen, far above the low requirements of the present compositions. It will be understood that removal of sulfur, for example, from electrolytic iron, can be satisfactorily efiected byhigh temcarbon already present in the alloy material.
• the briquetting of the electrode material for the first vacuum. melting step can involve, as well as pressing, vacuum sintering of the electrode or its sections at about 1750 F., or indeed sintering in an inert gas, such as argon, at temperatures up to 2200 F. Indeed any suitable technique may be employed for making these electrodes, so long as they contain the required materials of appropriate purity and have sufiicient strength for the operation whereby the electrode is melted off by the discharge or are to form the ingot.
• first vacuum melting step pressure is maintained at not more than 1 millimeter (1000 microns).
• second vacuum melting step utilizing an electrode forged or otherwise derived from the product of the first step, a still higher vacuum is used, not more than 100 microns (0.1 mm.) and preferably no more than microns (0.01 mm), all such definitions of vacuum being expressed as pressure in microns or millimeters of mercury.
• a particularly important feature of the vacuum melting operations is the utilization of carbon for removal of oxygen.
• excess carbon is included in the electrode of the first step, in amount suflicient to deoxidize by combination of carbon and oxygen to yield carbon monoxide, which passes off and out, under the action of the vacuum pumping instrumentalities.
• the amount of carbon to be employed is roughly equal to the amount of carbon desired in the ultimate alloy (i.e.
• the carbon may be added in any suitable, finely divided form of high purity, such as graphite.
• any suitable, finely divided form of high purity such as graphite.
• proportions of carbon of the above order are desirable, the excess carbon, beyond that consumed by reaction with ox gen and beyond that desired to remain in the alloy, being lost in the course of the operations, by mechanisms which are not entirely understood but the extent of which can be accurately predicted, i.e. as is implicit in the above recital of a mode of determining the excess carbon requirement.
• carbon included in the amounts described it is found that the steel is deoxidized in an unusually effective way, such reaction occurring chiefly or indeed essentially wholly in the first vacuum melting step, the second step functioning for further refinement and also to eliminate product gases and provide a melt free of holes or pores.
• a single vacuum melting operation is sufficient, both to remove the oxygen by carbon deoxidation and to yield a highly pure, nongassy ingot.
• the single melting step should be performed with relatively high vacuum, i.e. pressure below 100 microns, such operation being attainable. in this single step, providing the nature of the electrode material or other conditions are such that the gas emanation is limited or the vacuum maintenance is otherwise correspondingly effective to maintain the requisite low pressure. This process is described in the second of the above-mentioned applications (Process B).
• a first melting stage which may be characterized as an air-melting step, in a suitable furnace of conventional sort (very preferably an electric, i.e. electric-arc furnace), operated under ordinary rather than vacuum conditions and utilizing conventional charge material, including steel scrap (if desired), the composition of the charge being of course determined and adjusted so as to achieve the desired ultimate alloy analysis, taking into account the purifying operations that occur in thisfirst furnace stage.
• This step yielding an open or non-killed steel, for example, whether as performed in electric arc, open-hearth, pneumatic, e.g.
• Linz-Donawitz process, or induction melting is conducted in accordance with normal practice for the operation of such furnaces or melting procedures, except that when the melt is tapped, the melt is essentially free of strong metallic deoxidizers.
• an electric furnace is at present preferred because of available large capacities and because of the capability of maintaining a deoxidizing type of slag and thus a flexibility of composition; such furnace also affords a particularly good control of sulfur in the melt.
• a presently preferred mode .of carrying out the operation in the electric furnace is to start with an oxidizing slag, utilized in a known manner; the initial melting, by use Of electric are from appropriate electrodes extending to the charge, is thus effected under an oxidizing slag of such type.
• the melt is blown with highly concentrated dry oxygen gas using a suitable lance to introduce oxygen below the surface of the metal, or alternatively an iron oxide or other suitable composition preferably low in manganese may be added.
• the oxygen addition is of the nature of decarburization, reducing the carbon, and promotes the development of high temperature, and uniformity of temperature, and likewise the elimination of metallic deoxidizers such as aluminum and silicon.
• the oxygen addition also serves to reduce the hydrogen content in the metal.
• the first slag is run off and replaced with a finishing slag of a reducing type, viz. a calcium carbide type of known character.
• a finishing slag of a reducing type viz. a calcium carbide type of known character.
• sulfur can be reduced to low levels and, in the absence of silicon and only a low manganese residual, the carbon and oxygen contents can approach equilibrium at the desired carbon aim for the electric furnace heat.
• the carbon aim for the electric furnace heat produced by the carbon deoxidation practice is several percentage points (i.e. hundredths of one percent) higher than the final carbon aim desired in the product resulting from the subsequent vacuum consumable electrode melt (which is a following stage in the process). This is done to allow for the carbon drop experienced during vacuum remelting of carbon deoxidized electrode ingots.
• certain adjustments can be made in the ladle to achieve precisely the carbon aim desired.
• carbon losses and carbon utilization can be quite accurately predicted and controlled by anyone skilled in the art so that the carbon content of the melt will meet the carbon aim within close limits.
• the oxygen content of the ingot metal as used in the subsequent vacuum consumable electrode melt can usually be kept to not more than 0.005% and it is found that for carbon deoxidation in such melt, the carbon adjustment (as in the ladle from the electric furnace) need only suffice to exceed the carbon aim by an amount of 0.02% to 0.03% or thereabout (of carbon in the steel), i.e. the few percentage points mentioned above.
• the carbon aim is 0.23%
• the electric furnace ingot should ordinarily contain 0.250.26% carbon.
• the amount of carbon to be reached, by addition or other adjustment, in the steel from the electric furnace is generally the carbon aim plus 1 to 1.5 times the stoichiocarbon monoxide.
• the molten metal is tapped from the electricarc furnace and poured into suitable ingot molds, the ingots being utilized as such, or by suitable shaping or assembly, to constitute the consumable electrode of the vacuum melt. Since there is no residual silicon in the molten metal and very little manganese, the steel may be poured as an open steel, into ingot molds without hot tops, and gas evolution may be continued during solidification in the ingot. It is at present deemed preferable, and indeed particularly desirable in order to avoid more than one stage of vacuum melting, that the gas content of the metal be reduced as much as possible.
• One effective way of accomplishing this operation is by so-called vacuum degassing or vacuum lift degassing, or especially by socalled vacuum ladle degassing, e.g.
• the metal produced from the electric furnace operation preferably with such degassing, is then utilized for the second melting stage, being a vacuum melting step with the metal supplied as a consumable electrode.
• Operations are as described above for such vacuum melting, the pressure being kept below 100 microns and preferably not higher than microns.
• this stage further or effective carbon deoxidation occurs, whereby a highly purified ingot is achieved, having unusually low oxygen content and yet remarkably free, as is likewise the case of the other processes defined above, of non-metallic inclusions.
• the product of the electric arc furnace may be subjected to a two-stage vacuum melting sequence, similar to the first above-mentioned process, except that the consumable electrode in the first stage is prepared from the electric furnace product rather than by the use of high purity iron.
• the low alloy, low silicon, high strength steels constituted by the alloys of the present invention afford the advantages of a high strength structural steel, e.g. in the range of 100,000 to 175,000 p.s.i. yield strength, with ductilities greater than and notch sensitivities less than current structural steels.
• the properties of high'ductility and low notch sensitivity, both at normal and room temperatures and at elevated temperatures are equal to or superior to the corresponding properties of structural steels such as currently available, which have strength levels generally less than those of the present alloys.
• the steels herein disclosed are superior to current structural steels; for instance, tested specimens have generally (and advantageously) been found to possess a ductile-brittle transition point, as measured by Charpy Impact Testing and as rated in accordance with US. Naval Research Laboratory Drop Weight and Explosive Bulge Tests, of lower than -40 F.
• the alloys of this invention exhibit very little or no directionality, i.e. have essentially nil anisotrophy, that is'to say, little or no variation of mechanical properties with respect to direction of test for such properties when taken in reference to the direction in which 10 the steel has been worked. It is believed that this highly desirable characteristic is a direct result of the very low content of non-metallic inclusions, and possibly because of a lower trace element content as attained preferably by melting practice of the sort described above.
• temper embrittlement in the present alloys appear to be distinctive.
• Ordinary structural steels usually have a so-called temper brittle range at about 500 to 700 F., in that steel tempered at one or another. point in this nange exhibits a minimum impact resistance (the embrittlement also being noted in tensile tests), as compared with the effect of such treatment at other temperatures (above and below), is being understood that in general such resistance rises as the tempering is effected at temperatures successively higher.
• the curve which rel-ates temperature to impact resistance appears to be smoothed out in the lower temperature range mentioned above, but to exhibit a dip in the vicinity of 950 F.
• the present alloys can be tempered at a variety of temperatures (even in the last-mentioned range); in general, however, and as presently preferred for optimum results, tempering is recommended at higher temperatures, such as 1000 F. and above (e.g. l050 to 1075), where the toughness of the product is 'very high.
• the ductile-brittle transition value is that temperature at which the mode of fracture of a specimen changes from a ductile or fibrous mode to a brittle or cleavage (conchoid-al or fiat surface) mode of failure, the latter being considered a failure of nil ductility.
• the ductile-brittle transition point is that temperature at which the failure is judged to be 50% fibrous.
• par- No aluminum is included at all.
• aluminum is employed as a deoxidizer, there is likewise the invariable result of non-metallic inclusions in the steel, being hard, abrasive particles of aluminum ticularly high strength and high toughness, the latter oxide.
• Aluminum moreover, acts preferentially, relabeing indicated by exceptionally high impact properties, tive to carbon, in combining with oxygen in steel.
• the invention further extends, as will be appreciated, to and a Sound, Solid, fully deoxidized ingot is always the method of producing alloys and to the method of proachieve ducing steel stock such as plate, sheet and the like, espe- While endeavor has been made above to explain h Chilly in that thew P Q new high Strength alloys i unusual properties and uniformity of the improved steel, P and indeed ena b 1ed to be prodflced Wlth including its superior notch toughness, as due to various the Speclfied chemlcal composmonsr by followmg one or stated factors, it will be appreciated that these explanaanother of the stated melting and deoxidizing practices.
• nese is likewise usually maintained sufliciently low in amount so that no trouble is caused by formation of its compounds; indeed optionally (if this element is not otherwise needed) it may be omitted entirely should correspondingly extreme cleanliness be required in this respect, such omission being most readily accomplished by melting procedure of the first type (above) utilizing high purity electrolytic iron.
• mangacarbon content of about 0.20% to about 0.30% is at present prefer-red, both as above and within the otherwise broader ranges of Table I.
• manganese is included only in such amount (often only 0.08 to 0.12%) as will take up the sulfur present, without forming an appreciable quantity of detectable inclusions, i.e. sulfide particles. Analysis may sometimes show aluminum in extremely low values, eg below 0.01%, but such can be deemed an essentially nil content in view of the nature of this element.
• the complete procedure of making steel for use advantageously involves heat treatment (usually after any considerable forming operations for fabrication) for purposes of attaining hardness and the desired mechanical properties.
• appropriate heat treatmentfor these steps of the process includes normalizing (usually after forging and preferably also after hot rolling) and particularly (in ness.
• normalizing usually after forging and preferably also after hot rolling
• particularly in ness.
• the very highest strength is retained with tempering at a lower range, but greatest toughness at the higher temperature of tempering.
• the choice of operations in heat treatment depends on conventional principles: for example, normalizing may be omitted if its efifects are not needed; or if extreme toughness at the expense of strength should be required for some limited, special use, it is conceived that the treatments might be only normalizing and tempering.
• Heats Nos. 309, 493, 528 and 515 Four specific examples of particular alloys produced in accordance with the'invention are represented by Table IV, below. These are specifically designated as Heats Nos. 309, 493, 528 and 515. More particularly each' of Heats Nos. 309 and 493 was prepared by procedure start ing with high purity electrolytic iron powder and utilizing two successive consumable electrode'vacuum meltingstages as specifically described above for Process A. Heats Nos. 528 and 515 were prepared by the process designated above as C, starting with electric furnace melting under conditions as defined and then followed by consumable electrode vacuum remelting. In these instances, a degassing operation intermediate the furnace melt and the vacuum operations was not employed, and in consequence, two stages of consumable electrode vacuum melting were utilized, in accordance with such stages as described for Process A. In all of the operations carbon deoxidation was effected during vacuum melting, utilizing excess carbon in proportion and manner as explained hereinabove.
• a steel alloy consisting essentially of about: 0.15% to 0.35% carbon, 1.40% to 1.80% chromium, 2.0% to 4.0% nickel, 0.60% to 1.20% molybdenum, metal selected from the group consisting of columbium and vanadium, in an amount of from 0.03% to 0.10% columbium when the selected metal is columbium alone and with vanadium in approximately twice the amount manganese, and quantities ranging from nil to not more Table VI A B C D P.p.111.
• a heat treated steel article made of steel alloy consignificant advantage for the preferred practice of the insisting essentially of about: 0.15 to 0.60% carbon, vention, in steel of this character.
• a steel alloy consisting essentially of about: 0.15 drogen and 40 ppm. nitrogen, and the balance iron; to 0.60% carbon, 1.40% to 1.80% chromium, 2.0% to said alloy being essentially free of non-metallic inclusions; 4.0% nickel, 0.60% to 1.20% molybdenum, metal seand said heat treated article having a yield strength of lected from the group consisting of columbium and at least 100,000 p.s.i.
• a steel alloy consisting essentially of about: 0.20% to 0.30% carbon, 1.50% to 1.70% chromium, 2.65% to 3.25% nickel, 0.80% to 1.0% molybdenum, metal selected from the group consisting of columbium and vanadium, in .an amount of from 0.04% to 0.09% columbium when the selected metal is columbium alone and with vanadium in approximately twice the amount of replaced columbium to the extent that vanadium replaces columbium in the selected metal, nil to 0.18% manganese, and quantities ranging from nil to not more than the following amounts of the following impurities, 0.02% silicon, 0.01% phosphorus, 0.008% sulfur, 15 p.p.m. oxygen, 2 p.p.m. hydrogen and 30 p.p.m. nitrogen, and the balance iron.
• a process of making a steel article having high strength and high toughness comprising: preparing, by melting into ingot form, an alloy consisting essentially of about: 0.15% to 0.60% carbon, 1.40% to 1.80% chromium, 2.0% to 4.0% nickel, 0.60% to 1.20% molybdenum, metal selected from the group consisting of columbium and vanadium, in an amount of from 0.03% to 0.10% columbium when the selected metal is columbium alone, and with vanadium in approximately twice the amount of replaced columbium to the extent that vanadium replaces columbium in the selected metal, nil to 1.0% manganese, and quantities ranging from nil to not more than the following amounts of the following impurities, 0.05% silicon, 0.01% phosphorus, 0.01% sulfur, 20 p.p.m.
• said preparation including the step of melting an electrode which comprises the aforesaid ingredients, into an ingot form, by passage of electric current, under a vacuum constituting a pressure of not more than 100 microns, so as to yield an ingot having the aforesaid composition; converting metal of said ingot into the form of said article; and subjecting said metal in the form of said article to heat treatment to produce said article having high strength and high toughness.
• the electrode in which in the recited melting step the electrode includes additional carbon to remove excess oxygen, said carbon reacting to remove said oxygen during said melting by passage of electric discharge, and in which the heat treatment comprises heating in the range of 1500" F. and above, quenching and tempering in the range of 1000 F. and above.
• a process of making a steel article having high strength comprising: preparing, by melting into ingot form, an alloy having the composition defined in claim 1; converting metal of said ingot into the steel article by deforming operation, and subjecting the article to heat treatment comprising heating at a temperature in the range of 1500 F. and above, quenching, and tempering.
• a process of making steel capable of providing high strength and high toughness comprising: preparing, by melting into ingot form, an alloy having the composition defined in claim 1; said preparation including the step of melting an electrode which comprises the ingredients defined as aforesaid and additional carbon to remove excess oxygen, into said ingot form, said melting of the electrode being effected by passage of electric current, under a vacuum constituting a pressure of not more than microns, so as to yield an ingot which has the aforesaid composition.
• a process of making steel capable of providing high strength and high toughness comprising: preparing, by melting into ingot form, an alloy having the composition defined in claim 5; said preparation including the step of melting an'electrode which comprisesthe ingredients defined as aforesaid and additional carbon to remove excess oxygen, into said ingot form, said melting of the electrode being effected by passage of electric current, under a vacuum constituting a pressure of not more than 100 microns, so as to yield an ingot which has the aforesaid composition.
• preparation by melting includes a preceding step, for preparation of first-stage metal from which the electrode is derived, of open melting of ingredients defined as aforesaid to yield said first-stage metal by open pouring.

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Citations (3)

• 1962
  • 1962-06-29 US US206182A patent/US3254991A/en not_active Expired - Lifetime
• 1963
  • 1963-06-28 CA CA879037A patent/CA921291A/en not_active Expired
  • 1963-06-28 DE DE19631303616D patent/DE1303616B/de active Pending
  • 1963-06-28 GB GB25791/63A patent/GB1009924A/en not_active Expired
  • 1963-06-29 LU LU43979D patent/LU43979A1/xx unknown

Patent Citations (3)

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