US3378367A - Weldable, corrosion-resisting steel - Google Patents

Weldable, corrosion-resisting steel Download PDF

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Publication number
US3378367A
US3378367A US625452A US62545267A US3378367A US 3378367 A US3378367 A US 3378367A US 625452 A US625452 A US 625452A US 62545267 A US62545267 A US 62545267A US 3378367 A US3378367 A US 3378367A
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steel
austenite
nickel
temperature
chromium
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US625452A
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English (en)
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Friis Wilhelm Lars-Eije
Noren Tore Mans Ivan
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Saab Bofors AB
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Bofors AB
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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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • 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

Definitions

  • a steel alloy comprising:
  • the steel is martensitic 2 in structure and has therein about 15-40% dispersed induced austenite. The steel is obtained by heating to effect complete austenization, cooling and reheating to about 550-650 C.
  • This invention relates to a hardenable, corrosion-resistant steel, preferably cast steel, which possesses a combination of good weldability and good mechanical properties hitherto never attained and to a process for the preparation of said steel.
  • a hardenable, corrosion-resistant steel preferably cast steel
  • Such a steel is very useful, for instance, for the manufacture of items such as cast blanks for blades for impellers in water turbines in which a combination of good physical properties and corrosion resistance 'as well as the possibility of welding is desirable.
  • the so-called 13 chromium steel has hitherto been most widely used.
  • these steels after hardening with subsequent tempering at a com- 55 paratively high temperature (hardening and tempering). In the normal condition, these steels have an ultimate tensile strength in the range of 60-70 kg./mm.; a yield point in the range of 45-55 kg./mm. and an impact strength at room temperature according to 60 Charpy V in the range of 2-5 kg./cm.
  • the steels with carbon contents and nickel contents m'thin the upper portion of the previously mentioned analysis range are designated as martensitic, i.e., entirely hardenable.
  • Steels with carbon contents or nickel contents within the lower portions of the analysis range are terrific-martensitic. This means that they cannot, at any temperature, be entirely austenitized and consequently cannot be given an entirely martensitic structure on hardening.
  • the quantity of ferrite in the structure in a typical ferritic-martensitic steel of the said type can amount, e.g., to 30- 50%.
  • l8 chromium/ 8 nickel steel is often used. This is the traditional austenitic stainless steel which can be welded without prehatin'g and without subsequent annealing, but it is not suitable when there are requirements for other desirable physical properties, because it has an ultimate tensile strength of 50-60 kg./ mm. and a yield point of 18-25 kg./mm. Consequently, structures made of this material will be very heavy; and,
  • the hardenable, corrosion resistant steel with good weldability and good mechanical properties according to the present invention contains,1l14% chromium, 4-8% nickel, 0.03-0.025% carbon, 0.252.00% manganese, and 0.10-0.70% silicon, the remainder being iron with the usual amounts of impurities and accessory elements, the carbon content of said steel being low when the chromium content thereof is low, the ratio of the nickel equivalent, calculated as (percent nickel+0.5 percent manganese), and the chromium equivalent, calculated as percent chromium 15 X percent carbon) +1.5 percent silicon), in the steel ranging from 0.4 to 1.0, the steel having been heat treated to effect a complete austenitizing followed by a cooling to room temperature and then having been reheated to a temperature within the range of 550 C.650 C.
  • the steel in accordance with the invention preferably contains 0.05-0.10% carbon, 0.20-0.40% silicon, 0.802.00% manganese and 5-7% nickel.
  • a steel produced in accordance with the present invention possesses good mechanical properties. Its tensile strength lies within the range of 85-95 kg./mm. and the yield point within the range of 55-75 kg./mm. In addition, the impact strength within the high-value lies within the range of 11-13 kg./cm. and with the lower transition temperature of less than 80 C., and in many cases within the range of 100 to -120 C. Moreover, the steel according to the present invention not only has a very good weldability, but it can be welded without any special precautions in form of preheating or subsequent heat treatments, and nevertheless Without risk for the formation of cracks.
  • the previously known type of austenite is that which will be retained after the direct hardening of a steel.
  • such type of austenite has a very bad influence on the mechanical properties of the steel in the way, e.g., that it decreases the tensile strength.
  • the austenite induced by the reheating according to the present invention does not have any bad influence on the mechanical properties of the steel. On the contrary, it increases to some extent said properties.
  • the hitherto usual type of austenite obtained after hardening a steel is not stable during rapid temperature changes, whereas the austenite induced by the reheating ccording to the present invention is stable. This property is very essential for Welds.
  • austenite retained after hardening does not remain stable under the same temperature changes. Consequently, although it is possible to obtain retained austenite after hardening (e.g., by using a high carbon content and a high hardening temperature), such retained austenite does not improve the weldability of the steel, as this type of retained austenite is not stable during the rapid temperature changes which always occur during welding.
  • the retained austenite is a more or less continuous phase with martensite being present therein as inclusions.
  • the induced austenite constitutes inclusions present in martensite as the continuous phase.
  • the induced austenite has greater concentration gradients than the retained austenite. In one very important respect, however, the difference between the two types of austenite is very marked.
  • the retained austenite has a very bad influence on the mechanical properties of the steel, whereas the induced austenite, on the contrary, improves said mechanical properties.
  • the amount of retained austenite depends, among other things, on the amount of nickel content. An increase of the nickel content results in an increase of th amount of retained austenite.
  • a hardened steel is reheated, the hardness at room temperature is normally decreased; and this is due to the formation of tempered martensite.
  • the reheating temperature after hardening, is increased at a certain point, the hardness of the steel after cooling to room temperature no longer decreases but instead increases.
  • the explanation of this minimum function is that, at a certain temperature, the tempered martensite to some extent is transformed into austenite which, after cooling to room temperature, gives rise to untempered martensite with an increased hardness as a consequence.
  • the temperature (A at which the formation of austenite during reheating starts is also a function of the nickel content in such a way that an increase of the nickel content will give a lower temperature for the transformation of tempered martensite into austenite.
  • An increase of the temperature for reheating above the upper limit of this critical range results in the formation of austenite which is not stable on cooling to room temperature.
  • the maximum amount of stable induced austenite which it is possible to obtain in the critical temperature range increase from zero upwards, provided that the nickel content is increased above a certain level.
  • the steels used in these investigations had the following compositions:
  • the nickel content of the steel is low (e.g., those corresponding to steels 1 and 2), all the austenite formed on reheating is converted directly into untempered martensite, when the steel is cooled to room temperature.
  • the steel contains 2.8%nickel (N0. 3) a certain formation of stable austenite (which is not converted into untempered martensite on cooling) occurs upon reheating to a very narrow temperature range of about 600 C.
  • the amount of stable austenite formed in this case is less than 5% and thus is not sufficient to give the steel the desired good weldability.
  • the temperature range which produces the desired amount of 15-40 of induced austenite (formed on reheating) is very critical.
  • FIG. 1 shows that in foregoing steel No. 5 the percentage of austenite at room temperature is a function of the annealing temperature.
  • curve A the annealing is carried out during 3 hours and followed by cooling in air; in curve B two heating periods, each of 3 hours duration with cooling to room temperature between the heatings is used; and in curve C there is one heating for 24 hours.
  • curve B two heating periods, each of 3 hours duration with cooling to room temperature between the heatings is used; and in curve C there is one heating for 24 hours.
  • the transformation from tempered martensite to austenite is insufficient; and at temperatures above 650 C. the transformation of the formed austenite into untempered martensite upon subsequent cooling it too great to give the desired amount of stable austenite left.
  • FIG. 2 is a reproduction (enlarged 200x) of a photomicrograph of a steel not within the scope of this invention. This photograph shows the retained austenite (light areas) in the steel, the darker needle-formed areas being the typical martensitic needles. The form designated as retained austenite exists in a continuous phase with martensite islands being the discontinuous phase. As the austenite is present in a coherent, continuous phase, this steel has poor physical properties.
  • FIG. 3 is a reproduction (enlarged 200x) of a photomicrograph of a steel of this invention.
  • the induced austenite obtained by applying the process of this invention exists in a finely distributed form in the martensite matrix.
  • FIG. 4 is the same photomicrograph reproduction as in FIG. 3, except that it has been enlarged 600x. At this enlargement the austenite is seen in the form of light, isolated parts in the darker, needle-shaped martensite matrix. This form of induced austenite, present in a finely dispersed condition in the martensite matrix, gives the unexpected result of this invention, i.e. with a stainless steel it has now been possible to obtain essentially improved weldability in relation to the previously used 13 Cr steel without any loss in other desirable physical properties which, on the contrary, have been improved in certain respects.
  • the blank was given the following heat treatment:
  • the blank had the following physical properties in the uninfluenced base material:
  • Example 2 A steel containing as alloying elements Percent C 0.05 Si 0.39 Mn 0.82 Cr 13.3 Ni 6.6
  • the blank had the following physical properties:
  • the blank had the same good weldability and the transformation zones contained approximately 30% austenite.
  • the blank had the following physical properties:
  • a 20 mm. deep V groove was milled in the blank, which was filled with welding material having the followand the remainder Fe with the normal impurities.
  • the welding was carried out without preheating. Two test bars for tensile tests were taken over the weld. During the testing the rupture took place in the center of the weld. This was also considerably deformed in the immediate vicinity of the fusion line. No signs of cracking or ruptures could be noted in the fusion lines or in 8 the heat-influenced base material. The austenite content in the base material varied between 25 and 35%, which values were also found in the transformation zones adjacent to the weld.
  • Example 4 A steel containing as alloying elements Percent C 0.07 Si 0.47 Mn 0.58 Cr 13.2 Ni 1 5.9
  • the blank was subjected to the following heat treatment:
  • the blank had the following physical properties:
  • Example 5 A steel containing as alloying elements Percent C 0.07 Si 0.47 Mn 0.62 Cr 13.6 Ni 7.0
  • the blank had the following physical properties.
  • 0' indicates the stress of proof limit, viz the stress at which a non-proportional elongation equal to 0.2 percent of the original gauge length occurs (see ISO Rec. R82, Item 3.13).
  • :1 indicates the tensile strength (Rm), viz the maximum load divided by the original cross section area of the test piece, i.e., the stress corresponding to the maximum load (see ISO Rec. R82, Item 3.10).
  • ⁇ // indicates percentage reduction of area (Z), viz the ratio of the maximum change in the cross-section area, which has occurred during the test S -S to the original cross section area S expressed as a percentage (see ISO Rec. R82, Item 3.4).
  • a weldable, hardenable and corrosion-resisting steel consisting essentially of:
  • essential alloying elements are present in an amount of:

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
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US625452A 1959-06-24 1967-03-23 Weldable, corrosion-resisting steel Expired - Lifetime US3378367A (en)

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BE (1) BE592192A (fr)
CH (1) CH415067A (fr)
DE (1) DE1230232B (fr)
GB (1) GB948964A (fr)

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3501334A (en) * 1966-03-16 1970-03-17 Gillette Co Razor blades
US3661658A (en) * 1969-10-08 1972-05-09 Mitsubishi Heavy Ind Ltd High-strength and high-toughness cast steel for propellers and method for making propellers of said cast steel
JPS5010216A (fr) * 1973-06-01 1975-02-01
US3920490A (en) * 1971-08-18 1975-11-18 Ford Motor Co Thermally processed steel
US3956989A (en) * 1966-12-08 1976-05-18 The United States Of America As Represented By The Secretary Of The Army Fragmentation device
US3967036A (en) * 1974-07-11 1976-06-29 The International Nickel Company, Inc. Flux-coated arc welding electrode
US4041274A (en) * 1974-07-11 1977-08-09 The International Nickel Company, Inc. Maraging stainless steel welding electrode
US4058417A (en) * 1975-02-24 1977-11-15 General Electric Company Turbine bucket alloy
JPS62124218A (ja) * 1985-08-27 1987-06-05 Nisshin Steel Co Ltd 加工性に優れ溶接軟化のない高強度ステンレス鋼材の製造方法
JPS63210234A (ja) * 1987-02-27 1988-08-31 Nisshin Steel Co Ltd 加工性に優れ溶接軟化のない高強度ステンレス鋼材の製造方法
JPS63213619A (ja) * 1987-02-27 1988-09-06 Nisshin Steel Co Ltd 加工性に優れ溶接軟化のない高強度ステンレス鋼材の製造方法
EP0293165A3 (fr) * 1987-05-25 1990-06-13 Nippon Metal Industry Co.,Ltd. Acier inoxydable martensitique du type susceptible au durcissement a une température inférieure a zéro

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ZA847054B (en) * 1983-09-14 1986-04-30 Chamber Of Mines Services Ltd A new steel

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1404907A (en) * 1913-06-25 1922-01-31 Strauss Benno Heat treatment of nickel-chrome steel
US2747989A (en) * 1952-05-28 1956-05-29 Firth Vickers Stainless Steels Ltd Ferritic alloys
US2802755A (en) * 1953-01-21 1957-08-13 Armco Steel Corp Weld-electrode and product
US2903386A (en) * 1955-10-27 1959-09-08 Armco Steel Corp Heat-hardened stainless steel and method for cold treating same

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT146720B (de) * 1931-06-23 1936-08-10 Krupp Ag Herstellung von Gegenständen, die besondere Festigkeitseigenschaften, insbesondere eine hohe Schwingungsfestigkeit besitzen müssen und/oder hohe Beständigkeit gegen Brüchigwerden durch interkristalline Korrosion aufweisen sollen.
CH123017A (it) * 1926-11-22 1927-10-17 Terni Ind Elettr Lega metallica per parti di macchinario idraulico.

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1404907A (en) * 1913-06-25 1922-01-31 Strauss Benno Heat treatment of nickel-chrome steel
US2747989A (en) * 1952-05-28 1956-05-29 Firth Vickers Stainless Steels Ltd Ferritic alloys
US2802755A (en) * 1953-01-21 1957-08-13 Armco Steel Corp Weld-electrode and product
US2903386A (en) * 1955-10-27 1959-09-08 Armco Steel Corp Heat-hardened stainless steel and method for cold treating same

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3501334A (en) * 1966-03-16 1970-03-17 Gillette Co Razor blades
US3956989A (en) * 1966-12-08 1976-05-18 The United States Of America As Represented By The Secretary Of The Army Fragmentation device
US3661658A (en) * 1969-10-08 1972-05-09 Mitsubishi Heavy Ind Ltd High-strength and high-toughness cast steel for propellers and method for making propellers of said cast steel
US3920490A (en) * 1971-08-18 1975-11-18 Ford Motor Co Thermally processed steel
JPS5010216A (fr) * 1973-06-01 1975-02-01
US4041274A (en) * 1974-07-11 1977-08-09 The International Nickel Company, Inc. Maraging stainless steel welding electrode
US3967036A (en) * 1974-07-11 1976-06-29 The International Nickel Company, Inc. Flux-coated arc welding electrode
US4058417A (en) * 1975-02-24 1977-11-15 General Electric Company Turbine bucket alloy
JPS62124218A (ja) * 1985-08-27 1987-06-05 Nisshin Steel Co Ltd 加工性に優れ溶接軟化のない高強度ステンレス鋼材の製造方法
US4878955A (en) * 1985-08-27 1989-11-07 Nisshin Steel Company, Ltd. Process for preparing a high strength stainless steel having excellent workability and free form weld softening
JPS63210234A (ja) * 1987-02-27 1988-08-31 Nisshin Steel Co Ltd 加工性に優れ溶接軟化のない高強度ステンレス鋼材の製造方法
JPS63213619A (ja) * 1987-02-27 1988-09-06 Nisshin Steel Co Ltd 加工性に優れ溶接軟化のない高強度ステンレス鋼材の製造方法
JP2826819B2 (ja) 1987-02-27 1998-11-18 日新製鋼株式会社 加工性に優れ溶接軟化のない高強度ステンレス鋼材の製造方法
EP0293165A3 (fr) * 1987-05-25 1990-06-13 Nippon Metal Industry Co.,Ltd. Acier inoxydable martensitique du type susceptible au durcissement a une température inférieure a zéro
EP0748878A1 (fr) * 1987-05-25 1996-12-18 Nippon Metal Industry Co.,Ltd. Acier inoxydable martensitique du type susceptible au durcissement à une température inférieure à zéro degré

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CH415067A (de) 1966-06-15
GB948964A (en) 1964-02-05
DE1230232B (de) 1966-12-08
BE592192A (fr) 1960-10-17

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