US3508912A - Tool steel containing chromium and cobalt - Google Patents

Tool steel containing chromium and cobalt Download PDF

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Publication number
US3508912A
US3508912A US830920A US3508912DA US3508912A US 3508912 A US3508912 A US 3508912A US 830920 A US830920 A US 830920A US 3508912D A US3508912D A US 3508912DA US 3508912 A US3508912 A US 3508912A
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steels
steel
cobalt
hardness
tool
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US830920A
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Vijay K Chandhok
August Kasak
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Crucible Materials Corp
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Crucible Inc
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Assigned to MELLON FINANCIAL SERVICES CORPORATION, MELLON BANK, N.A. AS AGENT FOR MELLON BANK N.A. & MELLON FINANCIAL SERVICES CORPORATION reassignment MELLON FINANCIAL SERVICES CORPORATION SECURITY INTEREST (SEE DOCUMENT FOR DETAILS). 2ND Assignors: CRUCIBLE MATERIALS CORPORATION, A CORP. OF DE.
Assigned to MELLON BANK, N.A. FOR THE CHASE MANHATTAN BANK (NATIONAL ASSOCIATION) AND MELLON BANK N.A., CHASE MANHATTAN BANK, THE (NATIONAL ASSOCIATION) AS AGENT reassignment MELLON BANK, N.A. FOR THE CHASE MANHATTAN BANK (NATIONAL ASSOCIATION) AND MELLON BANK N.A. SECURITY INTEREST (SEE DOCUMENT FOR DETAILS). 1ST Assignors: CRUCIBLE MATERIALS CORPORATION, A CORP. OF DE.
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    • 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
    • C22C38/10—Ferrous alloys, e.g. steel alloys containing cobalt
    • C22C38/105—Ferrous alloys, e.g. steel alloys containing cobalt containing Co and Ni
    • 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
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • 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
    • C22C38/10—Ferrous alloys, e.g. steel alloys containing cobalt
    • 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
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • 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
    • C22C38/30—Ferrous alloys, e.g. steel alloys containing chromium with cobalt

Definitions

  • tool steels of the prior art hot work steels as well as cutting tool steels, depends, by and large, upon the presence in the steel microstructure of simple or complex carbides to provide the necessary strength and wear resistance.
  • a further property requirement in many, if not most, tool steel applications is that the product must be shaped or finished by machining to a final desired configuration, so that machinability of the steel is important.
  • the carboncontaining tool steels must be machined in an annealed condition due to the hardness and relative brittleness of the ferrite-carbide structure that exists at low temperatures. Following machining, a full heat treatment, consisting of austenitizing, quenching or air cooling, and tempering, is necessary to attain the optimum combination of properties for service.
  • the austenitizing heat treatment necessitates the use of high temperatures, e.g., about 1800 F. to 2400 F., and, as a consequence of the dimensional changes attendant upon phase transformations during such heat treatment, warpage of a finished machined tool or tool part is a frequent occurrence. This is particularly troublesome in the case of articles of complex configurations. Additionally, the required high austenitizing temperatures are productive of appreciable surface scaling and/or decarburization unless the environmental conditions are carefully controlled. Such protective procedures are, of course, time consuming and costly. Post-austenitizing corrective finishing operations are often required.
  • articles fabricated from the carbon-containing, hardenable tool steels of the prior art must be tempered immediately following the austenitizing heat treatment because strain cracking of the article is otherwise likely.
  • the mediumor high-carbon martensite resulting from the austenitizing treatment is very brittle so that cracks are prone to occur due to severe internal stresses created by non-uniform cooling rates across the article cross section, or as a result of different cooling rates of cross-sectional variations in complex article shapes.
  • Carbon-containing hot work too] steels of the prior art all suffer from heat checking to a greater or lesser degree. Such steels in service are exposed to relatively high surface temperatures, while a short distance beneath the surface, the temperature is much lower. Such conditions are productive of tremendous fatigue stresses which, upon repeated cycling, cause the formation of small surface cracks which, growing in size and extent, constitute the familiar heat checking condition.
  • the invention constitutes a hot work steel consisting essentially of, by Weight percent, carbon-l-nitrogen up to .08 chromium 2.5 to 6, molybdenum 3 to 10 or 12, cobalt 8 to 15, nickel up to 4, cobalt-I-nickel 10 to 18, manganese up to 1 and balance iron.
  • FIGURE 1 comprises a series of tempering curves, at various austenitizing temperatures from 1700 to 2200 F., showing the change in hardness with change in tempering temperature between 1000" F. and 1350 F., for an inventive steel particularly suited for use as a hot work die steel;
  • FIGURE 2 comprises a series of tempering curves similar to those of FIG. 1, for a steel of the invention particularly suitable for use as a cutting tool steel;
  • FIGURE 3 comprises a series of graphs relating the chromium content of experimental steels with the room temperature and elevated temperature strength properties of the steels;
  • FIGURE 4 is illustrative of, first, the relationship between molybdenum content of certain experimental steels and the maximum attainable tempered hardness thereof, and, second, the effect of that element upon the tempering resistance of those steels, expressed in terms of the percentage difference between the maximum hardness and the hardness observed at progressively higher tempering temperatures;
  • graphs constituting FIGURE constitutes a series of graphs relating the room temperature and elevated temperature strength properties to the proportion of tungsten in the total content of molybdenum plus one-half the tungsten in an approximately 0.05C-5Cr-7.5 (Mo+ /2W)-13 (Co+Ni) base do not exist, and, consequently, no special measures are needed to prevent this undesirable occurrence during mill processing, heat treatment, article manufacture, or inservice application.
  • FIGURE 6 constitutes a pair of graphs comparing the is required after machining of the steels in the austenitized tempering resistance of a high hardness steel of the incondition. Only a relatively low temperature aging or vention (useful as a cutting tool steel) and that of a formationmpering treatment, e.g., at about 1000-l100 F., is rently commonly used high speed steel; needed after finish machining to impart to the optimum FIGURE 7 comprises a series of graphs relating the tool steel properties.
  • balt content of experimental steels with the spread in The martensite formed in those low-carbon or substanhardness in the austenitized condition and in a hardened tially carbon-free steels is considerably softer and tougher condition after tempering; than that formed in hardenable mediumor high-carbon FIGURE 9 constitutes a series of graphs relating the tool steels.
  • the new steels avoid Mo-13.5'to 15.(Co+Ni) base composition, and or minimize the tendency toward strain cracking on cool- FIGURE 10 constitutes a series of graphs illustrative of i h QQ P Q P Ie$i$t?ne of a representative
  • the velftlve Stee ⁇ Wlth that of P art hot Work and heat steels of the invention are producible free and substantially l l l Stamless Steels" l 1 1 f th free of free ferrite, and accordingly exhibit a high degree th f f s 5 o e PH,or of dimensional stability and hot workability.
  • compositions of By a proper proportioning of the Several essential alloy these steels, the heat treatment cond1 t1ons, and the harding elements, and by the use of a proper heat treatment, Hess values P? ( ⁇ btamed are glven m Table In each th ne St l n b h d d to high hardnesses, as case, austenitization was carried out at 2100" F. for one 6065 Rockwell C, i.e., in the high speed steel hardness half hour. Refrigeration of each of the test specimens was range. done at l00 F. for one half hour.
  • the steels of this invention are extremely temper resistant, retaining strengths and hardnesses, at temperatures of 1100 to 1400 F. or higher, clearly supperior to other, known commercial tool steels.
  • a further series of steels was prepared as 10-pound, induction melted heats, these heats processed to bar form, and similarly heat treated and tested for aging hardness response and tempering resistance.
  • the compositions of this second series of steels is given in Table II.
  • peak hardness occurs, in each instance, at a tempering temperature of about 1000- 1100 F., and maximum hardness, about 60 R is obtained at the highest austenitizing temperature, 2200 F.
  • Such steels find particular application as hot work steels.
  • the higher (12-15%) molybdenum steels, I-IW4 and HWS are hardenable from quenched hardnesses of about 43-50 R after a 2200 F. austenitizing treatment, to very high aged hardnesses of about 63-65 R In these steels, hardnesses of about 46-53 R are retained after tempering at temperatures as high as 1350 F.
  • Table II data for Steel HW4 is graphically shown in FIG. 2, wherein the similarity to the FIG. 1 steels is seen together with the higher peak hardnesses which particularly suit these steels for cutting applications.
  • a third series of steels was also prepared, as -pound heats, processed to bar form, and subjected to extensive investigation of hardness, room temperature and elevated temperature strength properties, impact strength, and ductility.
  • the compositions of these latter steels are given in Table IV.
  • the inventive steels are essentially carbon-free, but it is realized that a certain carbon content is necessary to make the steels satisfactorily producible by conventional steelmaking practices.
  • Test results show that an increase in carbon above 0.08% (Steels HW12, l3, and 15, Table V) resulted in a gradual drop in both the room-temperature and elevated-temperature strength properties.
  • carbon or carbon-i-nitrogen may be present in amounts up to 0.08%.
  • Molybdenum is an important strengthening agent in the steel. The tempering resistance is steadily increased with increasing molybdenum content, but the ductility is lowered. At 10% molybdenum (HW21, Table V), some free (delta) ferrite is formed upon austenitizing at 1 800 F.
  • Table V sets forth the nominal compositions of the Table IV steels, rearranged in groups having an approximately constant base composition and wherein one or a pair of elements is varied in amount or proportion (such variable elements being italicized in Table V).
  • the test conditions and observed property characteristics are also shown in Table V, Column 9.
  • Cobalt is an essential alloy ingredient to ensure proper microstructural balance in the steel, because cobalt acts as an austenite former at higher temperatures but has only a small effect on the austenite-to-martensite transformation temperature (the Ms temperature).
  • the proper amount of cobalt allows the steel to be hardened and, at the same time, essentially or completely free from delta ferrite.
  • cobalt increases the effectiveness of the precipitation of intermetallic compounds in strengthening the steels.
  • Graph E represents the tempering resistance part, by tungsten, on a basis of 2 parts by weight of of Steel 64-374, an Graph F that of a commonly used tungsten to one part by weight of substituted molybdenum, g Speed SW61, A151 yp -L containing 035% due to the greater atomic weight of tungsten.
  • Graph A of FIG. 4 is illustrative of the effect of molyb- M0, balance essentially
  • the tempering P denum content upon the maximum attainable hardness eter used in 4 is the common Larsen-Miner P upon tempering (at 1050 F.).
  • Molybdenum also is productive of temper resistance 55 in the new steels, this property increasing with increasingly larger quantities of that element.
  • Graphs B, C and D of FIG. 4 are illustrative of this eiiect of molybdenum, wherein the molybdenum content is related to the percentage difierence in the maximum attainable tempered 6O hardness (1050 F. temper) and the hardness retained after progressively higher tempering temperatures.
  • This spfied Steel eifect is particularly evident at the more rigorous condi- Steel 64-374 was further compared Wlth respect to tions of R and 13000 R illustrated by Graphs B cutting tool life, to commercial high speed tool steel of and C, respectively.
  • the hardness loss 65 the YP P t n(0.85% C, 0.30% on tempering reduces to a relatively low, constant per- 030% 445% F 195% Q cemage level in the molybdenum range of The M0, balance Fe), and with the same composition having U h h h l b t, 0 a higher (0.96%) carbon content.
  • the workpiece was fi t e rr i per i g t e ip eratfir e. ange 1S e88 a mp at the 1 commercial AISI H-13 hot work steel (0.40% C, 0.40%
  • FIG. 8 illustrates the effect of cobalt on this property.
  • the three graphs, G, H and I, there appearing relate the percentage of cobalt in the four steels HW23, 24, and 41, with the difference (Rockwell C points) between the untempered hardness and the tempered hardness at, respectively, 1050 F., 1100 F. and 1200 F. Maximum hardness spread is seen from these graphs to occur, in each instance, at cobalt values of about 14 to 15.5%.
  • the aforementioned test set also shows the appearance, in the tested nominally 0.05% C-5.4% Cr-7.5% Mo base composition, of a substantial proportion (30-40 volume percent) of delta ferrite at the 8% cobalt'level. Traces of this phase still remained at the 11% cobalt level.
  • the steels of the invention in large part due to the aforementioned part played by the cobalt addition, are machinable in the austenitized condition and thereafter hardenable by intermetallic com-
  • the heat check test consisted of a 4-second immersion of the test specimens (mounted on a rod-like spindle) into a molten lead bath at a temperature of 1225 to 1250 F., followed by a 1.5 second quench in a to F. water bath, after which the specimens were dried above the lead bath for 5 seconds. This test cycle was repeated at a rate of about 3 cycles per minute.
  • Each test specimen was in the form of a circular body having a centrally apertured hub and circumferential flange extending from the midline of the hub.
  • the flange hand an outside diameter of 2.000 inches and a thickness of 0.075 inch, while the hub hand had an outside diameter of 1.500 inches, a thickness of 0.350 inch and a hub aperture of inch.
  • the new steels are useful in most hot work applications wherein very high surface temperatures, e.g. 1200-1700 F. are encountered. Water cooling can be used in such applications with relative immunity from the cracking usually exhibited by prior art hot work steels under such What is claimed is: 1.
  • a hot Work steel consisting essentially, by weight percent, of about Carbon nitrogen Up to 0.0.8.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
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  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Articles (AREA)
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US830920A 1965-12-15 1969-05-26 Tool steel containing chromium and cobalt Expired - Lifetime US3508912A (en)

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US83092069A 1969-05-26 1969-05-26

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AT (1) AT278069B (de)
DE (1) DE1533215B1 (de)
FR (1) FR1505060A (de)
GB (1) GB1117999A (de)
SE (1) SE345695B (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4160066A (en) * 1977-10-11 1979-07-03 Teledyne Industries, Inc. Age-hardenable weld deposit
CN112391520A (zh) * 2020-11-27 2021-02-23 上海天竺机械刀片有限公司 一种粉碎机用钨钢刀片热处理工艺

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2099509A (en) * 1935-11-23 1937-11-16 Edgar F Blessing Steel alloy
US2504453A (en) * 1946-11-18 1950-04-18 Thos Firth & John Brown Ltd Alloy steels for use at elevated temperatures
US2598714A (en) * 1950-06-26 1952-06-03 Continental Copper & Steel Ind Machinable high cobalt low carbon alloys for die-casting molds
US3154412A (en) * 1961-10-05 1964-10-27 Crucible Steel Co America Heat-resistant high-strength stainless steel
US3231709A (en) * 1963-06-17 1966-01-25 Mckay Co Welding method and electrode
US3251683A (en) * 1962-01-16 1966-05-17 Allegheny Ludlum Steel Martensitic steel

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT138955B (de) * 1930-05-12 1934-10-10 Ver Stahlwerke Ag Für die Herstellung von Dauermagneten dienende Eisenlegierungen.
DE638652C (de) * 1930-05-13 1936-11-20 Edelstahlwerke Akt Ges Deutsch Verfahren zur Herstellung von Dauermagneten
GB733510A (en) * 1952-01-14 1955-07-13 Reinhard Straumann Improvements in the manufacture of watch and like springs

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2099509A (en) * 1935-11-23 1937-11-16 Edgar F Blessing Steel alloy
US2504453A (en) * 1946-11-18 1950-04-18 Thos Firth & John Brown Ltd Alloy steels for use at elevated temperatures
US2598714A (en) * 1950-06-26 1952-06-03 Continental Copper & Steel Ind Machinable high cobalt low carbon alloys for die-casting molds
US3154412A (en) * 1961-10-05 1964-10-27 Crucible Steel Co America Heat-resistant high-strength stainless steel
US3251683A (en) * 1962-01-16 1966-05-17 Allegheny Ludlum Steel Martensitic steel
US3231709A (en) * 1963-06-17 1966-01-25 Mckay Co Welding method and electrode

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4160066A (en) * 1977-10-11 1979-07-03 Teledyne Industries, Inc. Age-hardenable weld deposit
CN112391520A (zh) * 2020-11-27 2021-02-23 上海天竺机械刀片有限公司 一种粉碎机用钨钢刀片热处理工艺

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FR1505060A (fr) 1967-12-08
DE1533215B1 (de) 1970-11-05
GB1117999A (en) 1968-06-26
SE345695B (de) 1972-06-05
AT278069B (de) 1970-01-26

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