US3690868A - Method of making steel having an improved hardenability - Google Patents

Method of making steel having an improved hardenability Download PDF

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Publication number
US3690868A
US3690868A US28997A US3690868DA US3690868A US 3690868 A US3690868 A US 3690868A US 28997 A US28997 A US 28997A US 3690868D A US3690868D A US 3690868DA US 3690868 A US3690868 A US 3690868A
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US
United States
Prior art keywords
steel
melt
hardenability
aluminium
temperature
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US28997A
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English (en)
Inventor
Barry A J James
Gordon T Brown
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
G K K GROUP SERVICES Ltd
Gkk Group Services Ltd
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G K K GROUP SERVICES Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
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    • 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
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/10—Handling in a vacuum
    • 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
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • 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
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0087—Treatment of slags covering the steel bath, e.g. for separating slag from the molten metal
    • 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
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0006—Adding metallic additives

Definitions

  • Field of the invention relates to a method of making steel.
  • the hardenability of a steel essentially depends upon the transformations which ta'ke place during cooling. The less transformation there is to non-martensitic transformation products such as pearlite or bainite then the greater is the hardness of the steel.
  • Steels are hardened by quenching at a sufficiently fast rate to prevent transformation to phases other than martensite.
  • the hardenability of a steel is limited by the maximum rate at which the steel can be quenched and this is dependent upon the rate at which heat can be lost from the interior of the steel through the surface of the steel.
  • a plain carbon steel such as, for example, EN15 having few alloying elements has less inherent hardenability than a more alloyed steel such as, for example, EN24 which has more alloying elements present to retard the transformation.
  • a plain carbon steel is more economical to make than an alloying steel.
  • An object of the present invention is to provide a steel having good hardenability and which is economical to produce.
  • a method of making a steel having an improved hardenability including the steps of heating a hardenable steel melt, prior to teeming, so that the Whole of the melt is at a temperature of not less than 1675 C. ascertaining that the whole of melt is at a temperature of not less than 1675 C. and maintaining the whole of the melt at a temperature of not less than 1675 C. for a predetermined time lying approximately in the range of 2 minutes to 30 minutes, adding to the melt a hardening element selected from the group comprising aluminium, titanium and, aluminium and titanium to achieve a final melt content of between 0.03% and 0.10% aluminium, and about Patented Sept. 12, 1972 0.03% titanium, and between 0.03% to 0.10% aluminium and about 0.03% titanium.
  • a steel of improved hardenability we mean a steel having an improved hardenability compared with a steel identical in composition, but which has not been subjected to heating to a temperature of at least 1675 C.
  • the aluminium and/ or titanium may be added whilst the metal is at a temperature of not less than 1675 C. or may be added after the metal has been allowed to cool from a temperature of not less than 1675 C.
  • the temperature of the melt may normally lie in the range 1575 to 1600 C.
  • the method may include the further step of adding to the steel melt, prior to teeming, or to the metal stream during teeming, a substance or substances in such proportions as to render nitrogen or nitrides in the melt ineifective as nuclei for precipitation of non-martensitic transformation products during transformation of the steel.
  • the desired composition of the steel melt is by arranging the composition to give a predetermined hardenability factor in accordance with the formula set out below.
  • the composition of the melt is adjusted by adding elements, within the ranges mentioned in the preceding paragraph, in order to bring the hardenability factor, as determined by the formula set out below, to the desired value.
  • a steel of t he same hardenability may be obtained even though the coinposition of the steel is different to that of another steel whose composition is arranged in accordance with the formula to give the same hardenability factor.
  • the aim is to produce a steel with a factor of not less than 0.80.
  • the melt is made by roughly making up the charge using elements selected within the ranges specified in the paragraph above and then performing a rapid analysis on the melt, and then making adjustments to the composition so that the factor determined by the formula set out above is brought to the desired value.
  • composition having a hardenability factor of 0.825 is as follows:
  • Approximately 0.25% copper and/or 0.030% tin may also be present.
  • compositions of the melt was as follows:
  • the temperature of the melt was raised to a temperature of approximately 1700 C. and the temperature of the melt was ascertained, and the melt was maintained at approximately the above mentioned temperature for a sufficient time for the desired enhanced hardenability properties of the steel to be achieved. It has been found that in practice a time lying within the range 2 minutes to 30 minutes in suitable. If desired, however, the time may exceed 30 minutes without any deterioration in the hardenability. It has been found that approximately 2 minutes is the minimum time required.
  • titanium may be added to give a final melt content of up to 0.03%.
  • the additions of aluminium and/or titanium may be made to the ladle or to the metal stream during teeming and the temperature of the metal may be allowed to fall below 1675" C. during the making of aluminimum and/or titanium additions to the metal during teeming.
  • the steels were all of the same composition but it will be appreciated that if desired the steels could have been of different composition but having their compositions determined by the formula set out above so that all the steels had the same hardenability factor. In this case the same results would have been obtained as were obtained in the examples shown in the figure.
  • nitrogen is present and is usually present in the form of nitrides.
  • the nitrogen either when present as a nitride or in some other form, can normally act as nuclei during cooling transformations of the steel and thus increase the rate of the transformation and so reduce the hardenability of the steel.
  • vacuum treatment of the melt may be performed to remove hydrogen because the presence of the relatively large amount of aluminium which can be present in the steel as a result of performance of the method according to the invention can give rise to ingot cracking due to hydrogen retention.
  • the vacuum degassing may be performed in the ladle in conventional manner.
  • a steel having the specific melt composition described hereinbefore and subjected to the method of the present invention has an optimised performance in terms of hardenability, temper resistance and impact strength.
  • a method of making a steel having an improved hardenability relative to a steel of substantially the same formulation not subjected to the method hereinbelow comprising the steps of providing a hardenble steel melt, heating the steel melt prior to teeming so that the whole of the melt is at a temperature of not less than 1675 C., ascertaining that the whole of the melt is at a temperature of not less than 1675 C. and maintaining the whole of the melt at a temperature of not less than 1675 C.
  • a hardening agent selected from the group consisting of aluminium to achieve a final melt content of between 0.03% and 0.10% aluminium, titanium to achieve a final melt content of about 0.03% titanium and aluminium and titanium to achieve a final melt content of between 0.03% and 0.10% aluminium and about 0.03% titanium and teeming the melt.
  • melt has the following composition:
  • composition of the melt is in accordance with the following formula:
  • melt is vacuum treated to remove hydrogen.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Analytical Chemistry (AREA)
  • Treatment Of Steel In Its Molten State (AREA)
  • Heat Treatment Of Articles (AREA)
US28997A 1969-04-17 1970-04-16 Method of making steel having an improved hardenability Expired - Lifetime US3690868A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB1965669 1969-04-17

Publications (1)

Publication Number Publication Date
US3690868A true US3690868A (en) 1972-09-12

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ID=10132986

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Application Number Title Priority Date Filing Date
US28997A Expired - Lifetime US3690868A (en) 1969-04-17 1970-04-16 Method of making steel having an improved hardenability

Country Status (4)

Country Link
US (1) US3690868A (de)
JP (1) JPS5428369B1 (de)
DE (1) DE2018561B2 (de)
GB (1) GB1308607A (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5094923A (en) * 1990-04-24 1992-03-10 Kennametal Inc. Air hardening steel

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ES2820335T3 (es) 2007-04-16 2021-04-20 Corium Inc Matrices de microagujas coladas con disolvente que contienen agente activo

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5094923A (en) * 1990-04-24 1992-03-10 Kennametal Inc. Air hardening steel
US5279902A (en) * 1990-04-24 1994-01-18 Kennametal Inc. Air hardening steel

Also Published As

Publication number Publication date
JPS5428369B1 (de) 1979-09-17
DE2018561A1 (de) 1971-10-14
GB1308607A (en) 1973-02-21
DE2018561B2 (de) 1975-11-13

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