EP3017072A1 - Stainless steel resistant to delayed cracking and a method for its production - Google Patents

Stainless steel resistant to delayed cracking and a method for its production

Info

Publication number
EP3017072A1
EP3017072A1 EP14820539.6A EP14820539A EP3017072A1 EP 3017072 A1 EP3017072 A1 EP 3017072A1 EP 14820539 A EP14820539 A EP 14820539A EP 3017072 A1 EP3017072 A1 EP 3017072A1
Authority
EP
European Patent Office
Prior art keywords
stainless steel
steel
delayed cracking
heat treatment
hours
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.)
Withdrawn
Application number
EP14820539.6A
Other languages
German (de)
French (fr)
Other versions
EP3017072A4 (en
Inventor
Juho Talonen
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.)
Outokumpu Oyj
Original Assignee
Outokumpu Oyj
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.)
Filing date
Publication date
Application filed by Outokumpu Oyj filed Critical Outokumpu Oyj
Publication of EP3017072A1 publication Critical patent/EP3017072A1/en
Publication of EP3017072A4 publication Critical patent/EP3017072A4/en
Withdrawn legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D3/00—Diffusion processes for extraction of non-metals; Furnaces therefor
    • C21D3/02—Extraction of non-metals
    • C21D3/06—Extraction of hydrogen
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/001—Heat treatment of ferrous alloys containing Ni
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/002—Heat treatment of ferrous alloys containing Cr
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/04—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for drawing, e.g. for deep-drawing
    • C21D8/0421—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for drawing, e.g. for deep-drawing characterised by the working steps
    • C21D8/0436—Cold rolling
    • 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
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • 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
    • 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
    • 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
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • 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
    • 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
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/001—Austenite

Definitions

  • This invention relates to an unstable stainless steel exhibiting transformation- induced plasticity (TRIP) effect, which is highly resistant to so-called delayed cracking phenomenon.
  • the stainless steel is an unstable austenitic stainless steel or an unstable austenitic-ferritic duplex stainless steel.
  • the invention also relates to a method for producing the stainless steel in order to improve the resistance to delayed cracking, which method leads to a lower hydrogen content compared to conventional stainless steel production method.
  • Delayed cracking is a serious problem, as it limits the use of unstable stainless steel in a wide range of application areas, where severe forming operations are needed. Particularly problematic are forming methods which result in high residual tensile stresses in the formed component. Deep drawing is an example of such forming process. Therefore, it is of high importance to be able to control and avoid the delayed cracking phenomenon. In particular, steels having a low nickel content to improve the cost efficiency of the steel are highly susceptible to delayed cracking.
  • Stainless steels susceptible to the delayed cracking phenomenon cover a wide range of chemical compositions, contents of main alloying elements ranging typically as follows: chromium 15-20 weight %, nickel content 0-8 weight %, manganese content 0-10 weight %, nitrogen content 0-0.3 weight %, carbon content 0-0.1 weight %, copper content 0-3 weight %.
  • Examples of such commercially available steels are, for instance, steel grades AISI 301 , AISI 301 LN, AISI 201 , AISI 201 LN and AISI 204Cu.
  • New low-nickel austenitic stainless steels have also been disclosed in several patent documents. Examples of these patent documents include, for instance, EP 0694626, US 3893850 and EP 0593158. However, none of these documents reveal means to avoid the delayed cracking.
  • Delayed cracking is related to the formation and presence of strain-induced martensite phases during the plastic deformation.
  • delayed cracking can be prevented by careful fine tuning of the chemical composition of the stainless steel so that the formation of martensite during plastic deformation is prevented, i.e., the stainless steel is made stable against the martensite formation.
  • Such an austenitic stainless steel is described in WO publication 201 1 /138503.
  • the problem of such an approach is that the mechanical properties of the steel must be compromised. Formation of strain- induced martensite phases during deformation enhances the tensile strength and elongation due to the TRIP (TRansformation Induced Plasticity) effect, which results in a superior combination of strength and elongation compared to a stable stainless steel.
  • Stainless steels according to WO publication 201 1 /138503 are stable and do not exhibit the TRIP effect. Thus, their combination of tensile strength and elongation is inferior to stainless steels exhibiting strain-induced martensite formation and the TRIP effect.
  • low-nickel austenitic stainless steels exhibiting the TRIP effect and thus desirable mechanical properties without the susceptibility to delayed cracking cannot be produced.
  • Conventional austenitic-ferritic duplex stainless steels consist of ferrite phase and stable austenite phase, which does not transform to martensite during plastic deformation. Thus, conventional austenitic-ferritic stainless steels are not susceptible to delayed cracking phenomenon.
  • a recently developed novel austenitic-ferritic duplex steel contains unstable austenite phase transforming to strain-induced martensite phase during plastic deformation, i.e. the steel exhibits the TRIP effect.
  • This feature makes the combination of strength and elongation of the novel austenitic-ferritic stainless steel superior compared to conventional austenitic-ferritic stainless steels.
  • the steel is also susceptible to delayed cracking phenomenon, which limits its applicability.
  • the steel is described in the publications WO 2012/143610 and WO 201 1 /135170, but in these publications there is no means to avoid delayed cracking in such austenitic-ferritic stainless steel exhibiting the TRIP effect.
  • the EP patent application 2 108 710 discloses a method to remove hydrogen from an austenitic stainless steel.
  • this EP patent application does cover only austenitic stainless steels containing more than 8% nickel, i.e., does not consider low-nickel austenitic stainless steels or austenitic-ferritic stainless steels.
  • the steels of this EP patent application do not exhibit TRIP effect enhancing mechanical properties.
  • the steels of this EP patent application are known to be practically stable against the strain-induced martensite transformation and thus resistant to delayed cracking.
  • This EP patent application does not provide means for avoiding delayed cracking phenomenon in unstable austenitic stainless steels, but focuses on reduction of fatigue crack growth rate by control of hydrogen content.
  • the method of this EP patent application aims to reduce the hydrogen content to unnecessarily low level, and suggests that the heat treatment should be carried out in a very low pressure (vacuum), which is not practical in industrial scale production.
  • the JP patent applications 1998-121208 and 2005-298932 relate to an unstable austenitic stainless steel wire.
  • a heat treatment method to reduce hydrogen content of the steel is proposed.
  • these JP patent publications do not consider delayed cracking phenomenon in flat stainless steel products, and do not provide means to avoid the delayed cracking phenomenon in austenitic or austenitic-ferritic stainless steels.
  • the object of the present invention is to prevent drawbacks of the prior art and to produce a stainless steel exhibiting transformation-induced plasticity (TRIP) effect with improved resistance to delayed cracking by limiting the hydrogen content, which stainless steel is an unstable austenitic stainless steel or an unstable austenitic-ferritic duplex stainless steel.
  • TRIP transformation-induced plasticity
  • the present invention relates also to a production method of such a stainless steel.
  • the essential features of the present invention are enlisted in the appended claims.
  • the present invention relates to a stainless steel, an unstable low-nickel austenitic stainless steel or an unstable austenitic-ferritic duplex stainless steel particularly in the form of a flat product, which stainless steel exhibits formation on strain-induced martensite during deformation (TRIP effect) enhancing their mechanical properties, but which is resistant to delayed cracking.
  • the resistance to delayed cracking is achieved limiting the hydrogen content of the steel below 4 weight ppm (parts per million), preferably below 3 weight ppm measured by inert gas fusion method.
  • the steel according to the invention combines desired features, such as low nickel content, excellent combination of strength and elongation due to formation of strain-induced martensite phase during plastic deformation (TRIP effect), and low susceptibility to the delayed cracking phenomenon.
  • the material is heat treated at the temperature range of 100 - 700 °C to control the hydrogen content of the stainless steel and to improve the resistance of the stainless steel to delayed cracking.
  • the improved resistance for delayed cracking in the stainless steel of the invention is shown by deep drawing, and in this deep drawing a drawing ratio up to 2.0 or even higher is achieved without occurrence of delayed cracking.
  • the stainless steel of the invention is an austenitic stainless steel containing in weight % 0-0.15% C, 0-3% Si, 0-15% Mn, 10-30% Cr, 0-8% Ni, 0-3% Mo, 0-3% Cu, 0-0.5% N, 0-0.5% Nb, 0-0.5% Ti, 0-0.5% V, the balance of Fe and inevitable impurities including hydrogen.
  • the stainless steel of the invention is a duplex austenitic ferritic stainless steel which microstructure contains 10-95%, preferably 30-90% ferrite phase and which contains in weight % 0-0.10% C, 0- 2% Si, 0-10% Mn, 10-30% Cr, 0-8% Ni, 0-3% Mo, 0-3% Cu, 0-0.4% N, 0-0.5% Nb, 0-0.5% Ti, 0-0.5% V, the balance of Fe and inevitable impurities including hydrogen.
  • the stainless steel exhibiting transformation-induced plasticity (TRIP) effect according to the invention is advantageously in the form of a flat product such as a plate, a sheet, a strip, a coil.
  • the stainless steel and its production method according to the invention is based on the reduction and the control of the hydrogen content of the stainless steel by a heat treatment.
  • the heat treatment shall be carried out at a temperature so that the microstructure and other properties of the stainless steel are not significantly affected, but to enable sufficient rapid effusion of hydrogen from the material.
  • the duration of the heat treatment is determined by reaching sufficient reduction in the hydrogen content, so that a desired improvement in cracking resistance is achieved.
  • the resistance to delayed cracking is improved by a heat treatment performed at temperature ranging between 100°C and 700 °C for 0.1 - 300 hours, preferably at 200 - 600 °C for 1 -100 hours, and more preferably at 250-500 °C for 1 -100 hours.
  • the stainless steel according to the invention is produced via the conventional stainless steel process route including among others melting in electric arc furnace, AOD (Argon Oxygen Decarburization) converter and ladle treatments, continuous casting, hot rolling, cold rolling, annealing and pickling.
  • the material is heat treated according to the invention to control the hydrogen content of the stainless steel and improve the resistance of the steel to delayed cracking.
  • this heat treatment can be carried out in air atmosphere, in atmosphere containing at least partly protective gas or in vacuum. Either continuous or batch process may be used.
  • the stainless steel according to the invention may also be strengthened by temper rolling, i.e. by subjecting the steel to desired cold rolling reduction of 0.1 - 60 % either before or after the heat treatment according to the invention.
  • Fig. 1 shows cup samples deep drawn to drawing ratio of 2.12 from austenitic stainless steel of the invention in cold-rolled, annealed and pickled condition (as supplied) and after heat treatment of cold-rolled, annealed and pickled material at 400 °C for 3 (400 °C / 3h), 24 (400 °C / 24h) and 72 hours (400 °C / 72h) in air atmosphere,
  • Fig. 2 shows cup samples deep drawn to drawing ratio of 2.0 from austenitic stainless steel of the invention in cold-rolled, annealed and pickled condition (as supplied) and after heat treatment of cold-rolled, annealed and pickled material at 400 °C for 3 (400 °C / 3h), 24 (400 °C / 24h), and 72 hours (400 °C / 72h) in air atmosphere, Fig.
  • FIG. 3 shows cup samples deep drawn from austenitic-ferritic duplex stainless steel of the invention in cold-rolled, annealed and pickled condition (as supplied) and after heat treatment of cold-rolled, annealed and pickled material at 300 °C for 24 (300 °C / 24h) and 72 (300 °C / 72h), hours and at 400 °C for 24 (400 °C / 24h) and 72 hours (400 °C / 72h) in air atmosphere,
  • Fig. 4 shows the influence of heat treatment at 400 °C on total hydrogen content of austenitic stainless steel of the invention measured by inert gas fusion method with Leco TCH 600 analyser
  • Fig. 5 shows the influence of heat treatment at 300 °C and 400 °C on total hydrogen content of the austenitic-ferritic duplex stainless steel of the invention measured by inert gas fusion method with Leco TCH 600 analyser.
  • the stainless steel of the invention was tested by deep drawing, and a drawing ratio up to 2.0 or even higher is achieved without occurrence of delayed cracking.
  • the drawing ratio is defined as the ratio of the diameters of a circular blank having a varying diameter and a punch with a constant diameter used in the deep drawing operation.
  • Fig. 1 shows the effect of heat treatment at 400 °C on delayed cracking of austenitic stainless steel of the invention containing 17% chromium, 4 % nickel and 7 % manganese as the main alloying elements and deep drawn to drawing ratio of 2.12.
  • the as-supplied steel was in cold-rolled, annealed and pickled condition and 0.8 mm thick. The results show that the as-supplied material was susceptible to the cracking, whereas the heat treated steel was completely immune to the cracking.
  • Fig. 2 shows the effect of the heat treatment at 400 °C on delayed cracking of austenitic stainless steel of the invention containing 15% chromium, 1 % nickel, 9 % manganese and 2 % copper as the main alloying elements and deep drawn to drawing ratio of 2.0.
  • the as-supplied steel was in cold-rolled, annealed and pickled condition and 1 .0 mm thick.
  • the results show that the extent of cracking was substantially reduced by the heat treatment in this 1 % nickel containing austenitic steel, which is inherently very prone to delayed cracking. Although the cracking could not be fully avoided, the substantially reduced number of cracks in the very severe cup forming operation indicates much improved material performance in practical applications.
  • Fig. 3 shows the effect of the heat treatment at 300 and 400 °C on delayed cracking of an unstable austenitic-ferritic duplex stainless steel of the invention containing 20 % chromium, 1 % nickel, 3 % manganese and 0.2 % nitrogen as the main alloying elements and exhibiting TRIP effect deep drawn to drawing ratio of 2.12.
  • the as-supplied stainless steel was in cold-rolled, annealed and pickled condition and 1 .0 mm thick. According to the results, the as-supplied material was susceptible to delayed cracking, whereas the cracking was fully avoided in the material heat treated according to the invention.
  • Fig. 4 shows the influence of heat treatment at 400 °C on total hydrogen content of austenitic stainless steel of the invention.
  • Fig. 5 shows the influence of heat treatment at 300 °C and 400 °C on total hydrogen content of the austenitic- ferritic duplex stainless steel of the invention.
  • the delayed cracking resistance of austenitic stainless steels or austenitic-ferritic stainless steel exhibiting the TRIP effect is improved by reducing the hydrogen content to level of about 2 ppm by performing a proper heat treatment for the material.
  • the temperature and the time for the heat treatment are selected so that enough hydrogen is effused from the material. At temperatures lower than 300 °C too slow hydrogen diffusion would lead to impractically long holding times. At temperatures higher than 400 °C there is a risk of precipitation of carbides and nitrides and other undesired changes in the microstructure of the steel.
  • the heat treatment according to the invention was carried out in air atmosphere, which at the studied temperatures leads to oxidation of the surfaces.
  • a protective atmosphere like in nitrogen or argon, or most preferably, in vacuum.
  • Minimization of hydrogen partial pressure of the atmosphere will also facilitate effusion of the hydrogen from the material and enable reaching lower hydrogen contents.
  • the heat treatment according to the invention can be realized by utilizing a batch furnace, such as a bell furnace and the gas atmosphere which contains at least partly inert protecting gas such as nitrogen or argon. Also the utilization of a continuous annealing line is possible if the atmosphere, temperature and holding time are properly chosen to enable sufficient removal of hydrogen from the material.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Sheet Steel (AREA)
  • Heat Treatment Of Steel (AREA)

Abstract

The invention relates to a stainless steel exhibiting transformation-induced plasticity (TRIP) effect resistant to delayed cracking and to the method for producing the stainless steel. The resistance to delayed cracking in the stainless steel is achieved limiting the total hydrogen content of the stainless steel measured by inert gas fusion method below 4 weight ppm, preferably below 3 weight ppm by a heat treatment performed at the temperature range between 100° C and 700° C for 0.1 - 300 hours, preferably at 200 - 600° C for 1-100 hours, and more preferably at 250-500°C for 1-100 hours.

Description

STAINLESS STEEL RESISTANT TO DELAYED CRACKING AND A METHOD FOR ITS PRODUCTION
This invention relates to an unstable stainless steel exhibiting transformation- induced plasticity (TRIP) effect, which is highly resistant to so-called delayed cracking phenomenon. The stainless steel is an unstable austenitic stainless steel or an unstable austenitic-ferritic duplex stainless steel. The invention also relates to a method for producing the stainless steel in order to improve the resistance to delayed cracking, which method leads to a lower hydrogen content compared to conventional stainless steel production method.
Low-alloyed and unstable austenitic and duplex stainless steels exhibiting so- called transformation induced plasticity (TRIP) effect due to transformation of unstable austenite phase to strain-induced ε and/or cc'-martensite phases during plastic deformation are susceptible to delayed cracking phenomenon, sometimes also called as season cracking. Delayed cracking manifests itself by cracking of formed metal parts immediately after the forming process or after a certain period of time after the forming. According to the prior art, sensitivity of the ε and/or cc'-martensite, most probably that of cc'-martensite phase, to the hydrogen inherently contained by the steel is the main cause of the cracking phenomenon.
Delayed cracking is a serious problem, as it limits the use of unstable stainless steel in a wide range of application areas, where severe forming operations are needed. Particularly problematic are forming methods which result in high residual tensile stresses in the formed component. Deep drawing is an example of such forming process. Therefore, it is of high importance to be able to control and avoid the delayed cracking phenomenon. In particular, steels having a low nickel content to improve the cost efficiency of the steel are highly susceptible to delayed cracking. Stainless steels susceptible to the delayed cracking phenomenon cover a wide range of chemical compositions, contents of main alloying elements ranging typically as follows: chromium 15-20 weight %, nickel content 0-8 weight %, manganese content 0-10 weight %, nitrogen content 0-0.3 weight %, carbon content 0-0.1 weight %, copper content 0-3 weight %. Examples of such commercially available steels are, for instance, steel grades AISI 301 , AISI 301 LN, AISI 201 , AISI 201 LN and AISI 204Cu.
New low-nickel austenitic stainless steels have also been disclosed in several patent documents. Examples of these patent documents include, for instance, EP 0694626, US 3893850 and EP 0593158. However, none of these documents reveal means to avoid the delayed cracking.
Delayed cracking is related to the formation and presence of strain-induced martensite phases during the plastic deformation. Thus, delayed cracking can be prevented by careful fine tuning of the chemical composition of the stainless steel so that the formation of martensite during plastic deformation is prevented, i.e., the stainless steel is made stable against the martensite formation. Such an austenitic stainless steel is described in WO publication 201 1 /138503. However, the problem of such an approach is that the mechanical properties of the steel must be compromised. Formation of strain- induced martensite phases during deformation enhances the tensile strength and elongation due to the TRIP (TRansformation Induced Plasticity) effect, which results in a superior combination of strength and elongation compared to a stable stainless steel. Such property combination is particularly useful in lightweight structures where high crash resistance and energy absorption capacity is required. Stainless steels according to WO publication 201 1 /138503 are stable and do not exhibit the TRIP effect. Thus, their combination of tensile strength and elongation is inferior to stainless steels exhibiting strain-induced martensite formation and the TRIP effect. According to the prior art, low-nickel austenitic stainless steels exhibiting the TRIP effect and thus desirable mechanical properties without the susceptibility to delayed cracking cannot be produced. Conventional austenitic-ferritic duplex stainless steels consist of ferrite phase and stable austenite phase, which does not transform to martensite during plastic deformation. Thus, conventional austenitic-ferritic stainless steels are not susceptible to delayed cracking phenomenon. However, a recently developed novel austenitic-ferritic duplex steel contains unstable austenite phase transforming to strain-induced martensite phase during plastic deformation, i.e. the steel exhibits the TRIP effect. This feature makes the combination of strength and elongation of the novel austenitic-ferritic stainless steel superior compared to conventional austenitic-ferritic stainless steels. However, due to the TRIP effect, the steel is also susceptible to delayed cracking phenomenon, which limits its applicability. The steel is described in the publications WO 2012/143610 and WO 201 1 /135170, but in these publications there is no means to avoid delayed cracking in such austenitic-ferritic stainless steel exhibiting the TRIP effect. It is known that the susceptibility of austenitic stainless steel to hydrogen embrittlement can be reduced by controlling the hydrogen content of the steels. However, no means for avoiding delayed cracking of unstable austenitic or austenitic-ferritic duplex stainless steel exhibiting the TRIP effect have been disclosed.
The EP patent application 2 108 710 discloses a method to remove hydrogen from an austenitic stainless steel. However, this EP patent application does cover only austenitic stainless steels containing more than 8% nickel, i.e., does not consider low-nickel austenitic stainless steels or austenitic-ferritic stainless steels. The steels of this EP patent application do not exhibit TRIP effect enhancing mechanical properties. Furthermore, the steels of this EP patent application are known to be practically stable against the strain-induced martensite transformation and thus resistant to delayed cracking. This EP patent application does not provide means for avoiding delayed cracking phenomenon in unstable austenitic stainless steels, but focuses on reduction of fatigue crack growth rate by control of hydrogen content. Furthermore, the method of this EP patent application aims to reduce the hydrogen content to unnecessarily low level, and suggests that the heat treatment should be carried out in a very low pressure (vacuum), which is not practical in industrial scale production. The JP patent applications 1998-121208 and 2005-298932 relate to an unstable austenitic stainless steel wire. In these JP patent applications in order to avoid so-called longitudinal cracking phenomenon in drawn wire, a heat treatment method to reduce hydrogen content of the steel is proposed. However, these JP patent publications do not consider delayed cracking phenomenon in flat stainless steel products, and do not provide means to avoid the delayed cracking phenomenon in austenitic or austenitic-ferritic stainless steels.
The object of the present invention is to prevent drawbacks of the prior art and to produce a stainless steel exhibiting transformation-induced plasticity (TRIP) effect with improved resistance to delayed cracking by limiting the hydrogen content, which stainless steel is an unstable austenitic stainless steel or an unstable austenitic-ferritic duplex stainless steel. The present invention relates also to a production method of such a stainless steel. The essential features of the present invention are enlisted in the appended claims.
The present invention relates to a stainless steel, an unstable low-nickel austenitic stainless steel or an unstable austenitic-ferritic duplex stainless steel particularly in the form of a flat product, which stainless steel exhibits formation on strain-induced martensite during deformation (TRIP effect) enhancing their mechanical properties, but which is resistant to delayed cracking. The resistance to delayed cracking is achieved limiting the hydrogen content of the steel below 4 weight ppm (parts per million), preferably below 3 weight ppm measured by inert gas fusion method. The steel according to the invention combines desired features, such as low nickel content, excellent combination of strength and elongation due to formation of strain-induced martensite phase during plastic deformation (TRIP effect), and low susceptibility to the delayed cracking phenomenon. In the method of the invention the material is heat treated at the temperature range of 100 - 700 °C to control the hydrogen content of the stainless steel and to improve the resistance of the stainless steel to delayed cracking. The improved resistance for delayed cracking in the stainless steel of the invention is shown by deep drawing, and in this deep drawing a drawing ratio up to 2.0 or even higher is achieved without occurrence of delayed cracking.
In accordance with one embodiment the stainless steel of the invention is an austenitic stainless steel containing in weight % 0-0.15% C, 0-3% Si, 0-15% Mn, 10-30% Cr, 0-8% Ni, 0-3% Mo, 0-3% Cu, 0-0.5% N, 0-0.5% Nb, 0-0.5% Ti, 0-0.5% V, the balance of Fe and inevitable impurities including hydrogen.
In accordance with another embodiment the stainless steel of the invention is a duplex austenitic ferritic stainless steel which microstructure contains 10-95%, preferably 30-90% ferrite phase and which contains in weight % 0-0.10% C, 0- 2% Si, 0-10% Mn, 10-30% Cr, 0-8% Ni, 0-3% Mo, 0-3% Cu, 0-0.4% N, 0-0.5% Nb, 0-0.5% Ti, 0-0.5% V, the balance of Fe and inevitable impurities including hydrogen.
The stainless steel exhibiting transformation-induced plasticity (TRIP) effect according to the invention is advantageously in the form of a flat product such as a plate, a sheet, a strip, a coil. The stainless steel and its production method according to the invention is based on the reduction and the control of the hydrogen content of the stainless steel by a heat treatment. The heat treatment shall be carried out at a temperature so that the microstructure and other properties of the stainless steel are not significantly affected, but to enable sufficient rapid effusion of hydrogen from the material. The duration of the heat treatment is determined by reaching sufficient reduction in the hydrogen content, so that a desired improvement in cracking resistance is achieved.
According to invention the resistance to delayed cracking is improved by a heat treatment performed at temperature ranging between 100°C and 700 °C for 0.1 - 300 hours, preferably at 200 - 600 °C for 1 -100 hours, and more preferably at 250-500 °C for 1 -100 hours.
The stainless steel according to the invention is produced via the conventional stainless steel process route including among others melting in electric arc furnace, AOD (Argon Oxygen Decarburization) converter and ladle treatments, continuous casting, hot rolling, cold rolling, annealing and pickling. After the conventional processing of the stainless steel to a cold rolled flat product, the material is heat treated according to the invention to control the hydrogen content of the stainless steel and improve the resistance of the steel to delayed cracking. According to the invention, this heat treatment can be carried out in air atmosphere, in atmosphere containing at least partly protective gas or in vacuum. Either continuous or batch process may be used. The stainless steel according to the invention may also be strengthened by temper rolling, i.e. by subjecting the steel to desired cold rolling reduction of 0.1 - 60 % either before or after the heat treatment according to the invention.
The present invention is described in more details referring to the following drawings, in which
Fig. 1 shows cup samples deep drawn to drawing ratio of 2.12 from austenitic stainless steel of the invention in cold-rolled, annealed and pickled condition (as supplied) and after heat treatment of cold-rolled, annealed and pickled material at 400 °C for 3 (400 °C / 3h), 24 (400 °C / 24h) and 72 hours (400 °C / 72h) in air atmosphere,
Fig. 2 shows cup samples deep drawn to drawing ratio of 2.0 from austenitic stainless steel of the invention in cold-rolled, annealed and pickled condition (as supplied) and after heat treatment of cold-rolled, annealed and pickled material at 400 °C for 3 (400 °C / 3h), 24 (400 °C / 24h), and 72 hours (400 °C / 72h) in air atmosphere, Fig. 3 shows cup samples deep drawn from austenitic-ferritic duplex stainless steel of the invention in cold-rolled, annealed and pickled condition (as supplied) and after heat treatment of cold-rolled, annealed and pickled material at 300 °C for 24 (300 °C / 24h) and 72 (300 °C / 72h), hours and at 400 °C for 24 (400 °C / 24h) and 72 hours (400 °C / 72h) in air atmosphere,
Fig. 4 shows the influence of heat treatment at 400 °C on total hydrogen content of austenitic stainless steel of the invention measured by inert gas fusion method with Leco TCH 600 analyser, and Fig. 5 shows the influence of heat treatment at 300 °C and 400 °C on total hydrogen content of the austenitic-ferritic duplex stainless steel of the invention measured by inert gas fusion method with Leco TCH 600 analyser.
The stainless steel of the invention was tested by deep drawing, and a drawing ratio up to 2.0 or even higher is achieved without occurrence of delayed cracking. The drawing ratio is defined as the ratio of the diameters of a circular blank having a varying diameter and a punch with a constant diameter used in the deep drawing operation. Fig. 1 shows the effect of heat treatment at 400 °C on delayed cracking of austenitic stainless steel of the invention containing 17% chromium, 4 % nickel and 7 % manganese as the main alloying elements and deep drawn to drawing ratio of 2.12. The as-supplied steel was in cold-rolled, annealed and pickled condition and 0.8 mm thick. The results show that the as-supplied material was susceptible to the cracking, whereas the heat treated steel was completely immune to the cracking.
Fig. 2 shows the effect of the heat treatment at 400 °C on delayed cracking of austenitic stainless steel of the invention containing 15% chromium, 1 % nickel, 9 % manganese and 2 % copper as the main alloying elements and deep drawn to drawing ratio of 2.0. The as-supplied steel was in cold-rolled, annealed and pickled condition and 1 .0 mm thick. The results show that the extent of cracking was substantially reduced by the heat treatment in this 1 % nickel containing austenitic steel, which is inherently very prone to delayed cracking. Although the cracking could not be fully avoided, the substantially reduced number of cracks in the very severe cup forming operation indicates much improved material performance in practical applications.
Fig. 3 shows the effect of the heat treatment at 300 and 400 °C on delayed cracking of an unstable austenitic-ferritic duplex stainless steel of the invention containing 20 % chromium, 1 % nickel, 3 % manganese and 0.2 % nitrogen as the main alloying elements and exhibiting TRIP effect deep drawn to drawing ratio of 2.12. The as-supplied stainless steel was in cold-rolled, annealed and pickled condition and 1 .0 mm thick. According to the results, the as-supplied material was susceptible to delayed cracking, whereas the cracking was fully avoided in the material heat treated according to the invention.
Fig. 4 shows the influence of heat treatment at 400 °C on total hydrogen content of austenitic stainless steel of the invention. Fig. 5 shows the influence of heat treatment at 300 °C and 400 °C on total hydrogen content of the austenitic- ferritic duplex stainless steel of the invention. According to the results, the hydrogen content of the material was clearly reduced by the heat treatment. However, it is apparent that still moderate hydrogen content, around 2 ppm, can be accepted. This is an important because reaching very low hydrogen content may require impractically long heat treatment time and use of vacuum, which both are not desired from the industrial applicability viewpoint. When assessing the influence of hydrogen content on delayed cracking phenomenon it is important to bear in mind that the accurate measurement of low hydrogen contents is rather difficult. There is scatter between individual measurements and measurements performed with different instruments can show inconsistency.
According to the invention the delayed cracking resistance of austenitic stainless steels or austenitic-ferritic stainless steel exhibiting the TRIP effect is improved by reducing the hydrogen content to level of about 2 ppm by performing a proper heat treatment for the material. The temperature and the time for the heat treatment are selected so that enough hydrogen is effused from the material. At temperatures lower than 300 °C too slow hydrogen diffusion would lead to impractically long holding times. At temperatures higher than 400 °C there is a risk of precipitation of carbides and nitrides and other undesired changes in the microstructure of the steel. The heat treatment according to the invention was carried out in air atmosphere, which at the studied temperatures leads to oxidation of the surfaces. This can be avoided by carrying out annealing in a protective atmosphere, like in nitrogen or argon, or most preferably, in vacuum. Minimization of hydrogen partial pressure of the atmosphere will also facilitate effusion of the hydrogen from the material and enable reaching lower hydrogen contents. In industrial scale the heat treatment according to the invention can be realized by utilizing a batch furnace, such as a bell furnace and the gas atmosphere which contains at least partly inert protecting gas such as nitrogen or argon. Also the utilization of a continuous annealing line is possible if the atmosphere, temperature and holding time are properly chosen to enable sufficient removal of hydrogen from the material.

Claims

1 . Stainless steel exhibiting transformation-induced plasticity (TRIP) effect resistant to delayed cracking, characterized in that the resistance to delayed cracking for a flat stainless steel product is achieved limiting the total hydrogen content of the steel measured by inert gas fusion method below 4 weight ppm, preferably below 3 weight ppm by a heat treatment performed at the temperature range between 100°C and 700 °C for 0.1 - 300 hours, preferably at 200 - 600 °C for 1 -100 hours, and more preferably at 250-500 °C for 1 -100 hours.
2. Stainless steel exhibiting transformation-induced plasticity (TRIP) effect according to the claim 1 , characterized in that the stainless steel is an austenitic stainless steel containing in weight % 0-0.15% C, 0-3% Si, 0-15% Mn, 10-30% Cr, 0-8% Ni, 0-3% Mo, 0-3% Cu, 0-0.5% N, 0-0.5% Nb, 0-0.5% Ti, 0-0.5% V, the balance of Fe and inevitable impurities including hydrogen.
3. Stainless steel exhibiting transformation-induced plasticity (TRIP) effect according to the claim 1 , characterized in that the stainless stainless steel is a duplex austenitic-ferritic stainless steel whose microstructure contains 10-95% and preferably 30-90% ferrite phase and which contains in weight % 0-0.10% C, 0-2% Si, 0-10% Mn, 10-30% Cr, 0-8% Ni, 0-3% Mo, 0-3% Cu, 0-0.4% N, 0- 0.5% Nb, 0-0.5% Ti, 0-0.5% V, the balance of Fe and inevitable impurities including hydrogen.
4. Stainless steel exhibiting transformation-induced plasticity (TRIP) effect according to any of the preceding claims 1 -3, characterized in that the stainless steel is in the form of a flat product such as a plate, a sheet, a strip, a coil.
5. Stainless steel exhibiting transformation-induced plasticity (TRIP) effect according to any of the preceding claims 1 -4, characterized in that for the stainless steel after deep drawing a drawing ratio up to 2.0 or even higher is achieved without occurrence of delayed cracking.
6. Method for producing a stainless steel exhibiting transformation-induced plasticity (TRIP) effect and resistant to delayed cracking, characterized in that for the resistance to delayed cracking the steel is heat treated at the temperature range between 100°C and 700 °C for 0.1 - 300 hours, preferably at 200 - 600 °C for 1 -100 hours, and more preferably at 250-500 °C for 1 -100 hours.
7. Method according to the claim 6, characterized in that the steel is heat treated in a batch furnace, to reduce hydrogen content of the steel and improve the resistance to delayed cracking
8. Method according to the claim 6, characterized in that the steel is heat treated in a continuous annealing line to reduce hydrogen content and improve the resistance to delayed cracking.
9. Method according to the claim 6, 7, or 8, characterized in that the heat treatment is performed in atmosphere containing at least partly protective gas to enhance effusion of hydrogen from the steel.
10. Method according to the claim 6, 7 or 8, characterized in that the heat treatment is performed in vacuum to enhance effusion of hydrogen from the steel.
1 1 . Method according to the claim 6, 7 or 8, characterized in that the heat treatment is performed in air atmosphere to enhance effusion of hydrogen from the steel.
12. Method according to any of the preceding claims 6-1 1 , characterized in that the steel is strengthened by cold-rolling before the heat treatment.
13. Method according to any of the preceding claims 6-1 1 , characterized in that the steel is strengthened by cold-rolling after the heat treatment.
EP14820539.6A 2013-07-05 2014-06-19 Stainless steel resistant to delayed cracking and a method for its production Withdrawn EP3017072A4 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI20135739A FI126798B (en) 2013-07-05 2013-07-05 Stainless steel with strength against delayed cracking and process for its manufacture
PCT/FI2014/050496 WO2015001177A1 (en) 2013-07-05 2014-06-19 Stainless steel resistant to delayed cracking and a method for its production

Publications (2)

Publication Number Publication Date
EP3017072A1 true EP3017072A1 (en) 2016-05-11
EP3017072A4 EP3017072A4 (en) 2017-08-02

Family

ID=52143159

Family Applications (1)

Application Number Title Priority Date Filing Date
EP14820539.6A Withdrawn EP3017072A4 (en) 2013-07-05 2014-06-19 Stainless steel resistant to delayed cracking and a method for its production

Country Status (13)

Country Link
US (1) US20160145701A1 (en)
EP (1) EP3017072A4 (en)
JP (1) JP2016527394A (en)
KR (2) KR20160025031A (en)
CN (1) CN105518161A (en)
AU (1) AU2014286035B2 (en)
CA (1) CA2915556A1 (en)
EA (1) EA201592217A1 (en)
FI (1) FI126798B (en)
MX (1) MX2015017548A (en)
TW (1) TW201510239A (en)
WO (1) WO2015001177A1 (en)
ZA (1) ZA201600314B (en)

Families Citing this family (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017117128A1 (en) 2015-12-28 2017-07-06 The Nanosteel Company, Inc. Delayed cracking prevention during drawing of high strength steel
DE102016110661A1 (en) * 2016-06-09 2017-12-14 Salzgitter Flachstahl Gmbh Process for producing a cold-rolled steel strip from a high-strength, manganese-containing steel
CN105886956B (en) * 2016-07-01 2017-10-31 东北大学 A kind of economizing type two-phase stainless steel sheet and preparation method thereof
DE102016117508B4 (en) * 2016-09-16 2019-10-10 Salzgitter Flachstahl Gmbh Process for producing a flat steel product from a medium manganese steel and such a flat steel product
CN106544600A (en) * 2016-12-15 2017-03-29 陆照福 A kind of Austenitic precipitation-hardening stainless steel forging and its processing method
CN109778077B (en) * 2017-11-10 2021-01-08 大连华锐重工集团股份有限公司 A kind of smelting method of nuclear main pump casing material
EP3778960B1 (en) * 2018-03-30 2023-12-27 NIPPON STEEL Stainless Steel Corporation Duplex stainless-clad steel plate and production method thereof
CN109536686A (en) * 2018-12-12 2019-03-29 贵阳市白云区科创生产力促进中心 The preparation method of manganese TRIP steel in a kind of Nb-microalloying
CN111020406A (en) * 2019-12-13 2020-04-17 浦项(张家港)不锈钢股份有限公司 Low-nickel all-austenite nonmagnetic stainless steel and manufacturing method and application thereof
KR102403849B1 (en) 2020-06-23 2022-05-30 주식회사 포스코 High strength austenitic stainless steel with excellent productivity and cost saving effect, and method for manufacturing the same
CN111996345A (en) * 2020-07-30 2020-11-27 中国科学院金属研究所 Oxidation-free dehydrogenation treatment process for austenitic stainless steel welding material
CN114457215A (en) * 2021-04-02 2022-05-10 中国科学院金属研究所 A kind of hydrogen reduction treatment method of austenitic steel seamless pipe
CN113695847A (en) * 2021-08-12 2021-11-26 江苏钜顺链业科技有限公司 Production method of stainless steel hoisting gourd chain
CN115198182B (en) * 2022-06-30 2023-08-18 江西宝顺昌特种合金制造有限公司 A kind of Ti-containing duplex stainless steel and its manufacturing method
CN117210767B (en) * 2023-07-11 2025-10-17 天津重型装备工程研究有限公司 Diphase stainless steel, large-diameter diphase stainless steel liquid steel slip ring forging and preparation method thereof
CN119615020B (en) * 2025-02-14 2025-04-25 辽宁冠达新材料科技有限公司 Diphase stainless steel powder for laser additive manufacturing and preparation method and application thereof

Family Cites Families (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS4937877B1 (en) * 1970-02-24 1974-10-12
EP1342799B1 (en) * 2000-12-07 2007-01-17 Aoyama Seisakusho Co., Ltd. Method for baking steel parts
JP2003113449A (en) * 2001-10-10 2003-04-18 Nisshin Steel Co Ltd High strength and high toughness stainless steel sheet excellent in delayed fracture resistance and method for producing the same
JP4212553B2 (en) * 2002-05-08 2009-01-21 新日鐵住金ステンレス株式会社 High-strength stainless steel wire with excellent twist value and rigidity and manufacturing method thereof
SE531305C2 (en) * 2005-11-16 2009-02-17 Sandvik Intellectual Property Strings for musical instruments
CA2649355A1 (en) * 2007-01-31 2008-08-07 National Institute Of Advanced Industrial Science And Technology Austenitic stainless steel and process for removing hydrogen therefrom
JP5014915B2 (en) * 2007-08-09 2012-08-29 日新製鋼株式会社 Ni-saving austenitic stainless steel
EP2248918A4 (en) * 2008-02-29 2013-07-03 Nat Inst Of Advanced Ind Scien AUSTENITIC STAINLESS STEEL AND METHOD FOR REMOVING HYDROGEN THEREFROM
US8092620B2 (en) * 2008-07-18 2012-01-10 Northwestern University High strength austenitic TRIP steel
JP5206239B2 (en) * 2008-08-29 2013-06-12 新日鐵住金株式会社 Continuous casting method of high N content duplex stainless steel
JP5398574B2 (en) * 2010-02-18 2014-01-29 新日鐵住金ステンレス株式会社 Duplex stainless steel material for vacuum vessel and manufacturing method thereof
FI122657B (en) * 2010-04-29 2012-05-15 Outokumpu Oy Process for producing and utilizing high formability ferrite-austenitic stainless steel
KR20120132691A (en) * 2010-04-29 2012-12-07 오또꿈뿌 오와이제이 Method for manufacturing and utilizing ferritic-austenitic stainless steel with high formability
FI125442B (en) * 2010-05-06 2015-10-15 Outokumpu Oy Low nickel austenitic stainless steel and use of steel
FI126574B (en) * 2011-09-07 2017-02-28 Outokumpu Oy Duplex stainless steel

Also Published As

Publication number Publication date
CA2915556A1 (en) 2015-01-08
US20160145701A1 (en) 2016-05-26
WO2015001177A1 (en) 2015-01-08
AU2014286035A1 (en) 2016-01-21
EA201592217A1 (en) 2016-06-30
EP3017072A4 (en) 2017-08-02
CN105518161A (en) 2016-04-20
AU2014286035B2 (en) 2018-05-10
TW201510239A (en) 2015-03-16
FI126798B (en) 2017-05-31
MX2015017548A (en) 2016-04-26
KR20160025031A (en) 2016-03-07
KR20170103029A (en) 2017-09-12
FI20135739L (en) 2015-01-06
ZA201600314B (en) 2019-09-25
JP2016527394A (en) 2016-09-08

Similar Documents

Publication Publication Date Title
FI126798B (en) Stainless steel with strength against delayed cracking and process for its manufacture
KR102890661B1 (en) Steel plate and method for manufacturing the same
KR102119333B1 (en) High-strength steel sheet and its manufacturing method
CA2734978C (en) High strength steel sheet and method for manufacturing the same
KR102544884B1 (en) High-strength hot-dip galvanized steel sheet and manufacturing method thereof
CN105671447B (en) The excellent high yield of hole expandability is than type high strength cold rolled steel plate and its manufacture method
KR101690441B1 (en) Ferritic stainless steel sheet having excellent heat resistance
US10995386B2 (en) Double annealed steel sheet having high mechanical strength and ductility characteristics, method of manufacture and use of such sheets
RU2721767C2 (en) Superhigh-strength, air-hardening, multiphase steel, having excellent process characteristics, and method of producing said steel
JP5759535B2 (en) Production and utilization of ferritic / austenitic stainless steel with high formability
RU2707769C2 (en) High-strength air-quenched multiphase steel, having excellent process characteristics, and method of making strips of said steel
RU2682913C2 (en) Ultrahigh-strength air-hardening multi-phase steel comprising excellent processing properties and method for production of steel strip from said steel
US20160115562A1 (en) Ferritic stainless steel sheet, method for the production thereof, and use of the same, especially in exhaust lines
UA128251C2 (en) Cold rolled and heat treated steel sheet and a method of manufacturing thereof
JPWO2013047739A1 (en) High-strength hot-dip galvanized steel sheet excellent in mechanical cutting characteristics, high-strength galvannealed steel sheet, and methods for producing them
JP6719903B2 (en) Heat treatment method for manganese steel and manganese steel
KR20120132691A (en) Method for manufacturing and utilizing ferritic-austenitic stainless steel with high formability
CN111433382B (en) Ferritic stainless steel having excellent high-temperature oxidation resistance and method for producing same
KR102948946B1 (en) Method for manufacturing cold-formable high-strength steel strips and steel strips
JP2016053213A (en) Duplex stainless steel sheet and its manufacturing method
CN113227414A (en) Cr-based stainless steel sheet having excellent hydrogen embrittlement resistance
US20190203311A1 (en) Method for producing a flat steel product made of a manganese-containing steel, and such a flat steel product
KR20250138756A (en) Martensitic stainless steel and its manufacturing method, and its blade manufacturing method
CA3177102C (en) Cold rolled flat steel product for packaging and method for producing a steel flat product
CA2857281C (en) High silicon bearing dual phase steels with improved ductility

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 20160112

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

AX Request for extension of the european patent

Extension state: BA ME

RAP1 Party data changed (applicant data changed or rights of an application transferred)

Owner name: OUTOKUMPU OYJ

DAX Request for extension of the european patent (deleted)
RIC1 Information provided on ipc code assigned before grant

Ipc: C21D 3/06 20060101AFI20170203BHEP

Ipc: C21D 8/00 20060101ALI20170203BHEP

Ipc: C21D 3/00 20060101ALI20170203BHEP

Ipc: C21D 8/02 20060101ALI20170203BHEP

Ipc: C21D 7/02 20060101ALI20170203BHEP

Ipc: C22C 38/40 20060101ALI20170203BHEP

A4 Supplementary search report drawn up and despatched

Effective date: 20170629

RIC1 Information provided on ipc code assigned before grant

Ipc: C21D 8/02 20060101ALI20170626BHEP

Ipc: C21D 8/00 20060101ALI20170626BHEP

Ipc: C21D 3/00 20060101ALI20170626BHEP

Ipc: C21D 3/06 20060101AFI20170626BHEP

Ipc: C22C 38/40 20060101ALI20170626BHEP

Ipc: C21D 7/02 20060101ALI20170626BHEP

17Q First examination report despatched

Effective date: 20190730

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN

18D Application deemed to be withdrawn

Effective date: 20191210