EP1831417A1 - Precipitation hardenable martensitic stainless steel - Google Patents

Precipitation hardenable martensitic stainless steel

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Publication number
EP1831417A1
EP1831417A1 EP05819793A EP05819793A EP1831417A1 EP 1831417 A1 EP1831417 A1 EP 1831417A1 EP 05819793 A EP05819793 A EP 05819793A EP 05819793 A EP05819793 A EP 05819793A EP 1831417 A1 EP1831417 A1 EP 1831417A1
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EP
European Patent Office
Prior art keywords
max
content
stainless steel
martensitic stainless
steel alloy
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.)
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Application number
EP05819793A
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German (de)
French (fr)
Inventor
Håkan HOLMBERG
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Sandvik Intellectual Property AB
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Sandvik Intellectual Property AB
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Publication date
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Publication of EP1831417A1 publication Critical patent/EP1831417A1/en
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—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
    • 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
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing 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
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • 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
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium

Definitions

  • the present disclosure is concerned with the precipitation hardenable stainless chromium nickel steels, more especially those that are hardenable with a fairly simple alloy treatment. More particularly, the concern is with the precipitation hardenable stainless chromium nickel steels which are hardened at a low temperature and also have good machinability when subjected to drilling, turning, milling and other cutting operations.
  • Precipitation hardenable martensitic stainless steels are for example used in various high strength applications, such as springs, surgical needles, clips, fine tubes, parts for instruments and parts exposed to wear.
  • the material needs to posses certain properties.
  • the steel should be able to be produced by an easy manufacturing process, including alloying, casting, hot working as well as cold working, rendering a high strength material that is easy to fabricate by mechanical cutting methods into finished parts starting from wire, sheet, strip, bar or tube material.
  • the material should preferably be ductile and thus allowing severe forming such as bending, coiling, pressing, twisting etc. in the as received condition, hi addition to the mechanical properties above a very good corrosion resistance is often required, allowing the material to be used in different environments without having to consider additional corrosion protection such as painting or any other type of surface coating.
  • the steel should be able to be hardened to a high final hardness by a simple, low temperature, alloy treatment that causes minimal shape disturbance.
  • Austenitic stainless steels are, dependent on their composition, either soft and ductile in the annealed condition or hard and less ductile in the cold deformed condition. In the harder conditions austenitic steels are also very difficult to machine.
  • a further group is the precipitation hardenable stainless steels that can be formed in fairly soft condition and subsequently alloy treated to achieve a high hardness. Also this group of steels are more difficult to machine compared e.g. to the group of hardenable martensitic steels.
  • a precipitation hardenable stainless chromium nickel steel having the following composition in weight %:
  • the stainless steel according to the invention comprises titanium sulphides.
  • the stainless steel is hardened at a low temperature and has good machinability when subjected to drilling, turning, milling and other cutting operations.
  • Figure 1 SEM photograph of a reference alloy.
  • Figure 2a SEM photograph of Figure 1 marked with test point Spectrum 1.
  • Figure 3 a SEM photograph of Figure 1 marked with test point Spectrum 2.
  • Figure 4 a SEM photograph of Figure 1 marked with test point Spectrum 3.
  • Figure 4b EDX result of Spectrum 3 of Figure 4a.
  • Figure 5 SEM photograph of an alloy according to the invention.
  • Figure 6 a SEM photograph of Figure 5 marked with test point Spectrum 1.
  • Figure 7 a SEM photograph of Figure 5 marked with test point Spectrum 2.
  • Figure 7b EDX result of Spectrum 2 of Figure 7a.
  • Figure 8a SEM photograph of Figure 5 marked with test point Spectrum 3.
  • Carbon is a powerful element that affects the steel in many ways.
  • a high carbon content will affect the deformation hardening in a way that the strength upon cold deformation will be high and thus reducing the ductility of the steel.
  • a high carbon content is also disadvantageous from corrosion point of view as the risk of precipitation of chromium carbides increase with increasing carbon content.
  • the carbon content should therefore be kept low, max 0,07 %, preferably max 0,05 % and more preferable max 0,025 %.
  • Silicon is a ferrite-forming element and may also in higher contents reduce the hot working properties of the steel.
  • the content should therefore be max 1,5% more preferably max 1,0 %.
  • Manganese is an austenite-forming element that in a similar way as nickel makes the steel less prone to a martensitic transformation at cold deformation.
  • the minimum content of manganese of the steel according to the invention is 0,2 % by weight.
  • the manganese content has to be max 5%, preferably max 3% and most preferably 2,5%.
  • Manganese will together with sulfur form ductile non-metallic inclusions that for example are beneficial for the machining properties.
  • Sulfur is an element that will form sulfides in the steel. Sulfides are beneficial during machining as they will act as chip-breakers. The content of sulfur is therefore min 0,01% and more preferably min 0,015 %, even more preferably 0,05 % and most preferably min 0,1%. Sulfides may however act as weak areas in the steel from a corrosion resistance point of view. Further, high contents of sulfur may also be detrimental for the hot working properties. The content should therefore be max 0,4% and preferably max 0,3%.
  • the composition of the alloy according to the invention is so selected that the alloy comprises titanium sulphides. The titanium sulphides are principally present in the form of TiS or Ti 2 S .
  • Chromium is essential for the corrosion resistance and must in the steel according to the invention be added in a content of at least 10%, or more preferably at least 11,5 %. Chromium is however also a strong ferrite former that in higher contents will suppress the martensite formation upon deformation. The content of chromium therefore has to be restricted to max 15%, preferably max 14%.
  • Nickel is added to the steel according to invention to balance the ferrite forming elements in order to obtain an austenitic structure upon annealing.
  • Nickel is also an important element to moderate the hardening from cold deformation.
  • Nickel will also contribute to the precipitation hardening together with elements such as titanium and aluminum.
  • the minimum content of nickel is therefore 7% or more preferable at least 8%.
  • a too high content of nickel will restrict the possibility to form martensite upon deformation.
  • Nickel is also an expensive alloying element. The content of nickel is therefore maximized to 14 or preferably 13%.
  • Molybdenum is essential for the steel according to the invention, as it will contribute to the corrosion resistance of the steel. Molybdenum is also an active element during the precipitation hardening. The minimum content is therefore 1 % or preferably, minimum 2% and most preferably minimum 3%. A too high content of molybdenum will however promote the formation of ferrite to a content that may result in problems during hot working. Further, a high content of molybdenum will also suppress the martensite formation during cold deformation. The content of molybdenum is therefore maximized to 6% and more preferable maximum 5%. Furthermore, it is expected that Mo could be partly or totally replaced by tungsten according to the common practice known to a person skilled in the art while still achieving the desired properties of the alloy.
  • Copper is an austenite former that together with nickel stabilizes the austenitic structure that is desired. Copper is also an element that increases the ductility in moderate contents. The minimum content is therefore 1% and more preferably at least 1,5%. On the other hand copper in high contents reduces the hot workability why the copper content is maximized to 3%, preferably maximum 2,5%.
  • Titanium is an essential alloying element in the invention due to at least two reasons. Firstly, titanium is used as a strong element for precipitation hardening and must therefore be present to be able to harden the steel for the final strength. Secondly, titanium will together with sulfur form titanium sulfides (TiS or possibly Ti 2 S). In general, titanium is a stronger sulfide former than manganese. As TiS are electrochemically nobler that MnS it is possible to achieve improved machining properties without deterioration of the corrosion resistance that is the normal case for free machining steels that utilize MnS for the increased machinability. Therefore, the minimum content of titanium is 0,3% and more preferably 0,5 %. Too high titanium contents will promote ferrite formation in the steel and also increase the brittleness. The maximum content of titanium should therefore be restricted to 2,5 % preferably 2 % and most preferably not more than 1,5%.
  • Aluminum is added to the steel in order to improve the hardening effect upon heat treatment.
  • Aluminum is known to form intermetallic compounds together with nickel such as Ni3 Al and NiAl.
  • the minimum content should be 0,2 % and most preferably min 0,3 %.
  • Aluminum is however a ' strong ferrite former why the maximum content should be 1,5 % or more preferably max 1,0 %.
  • Nitrogen is a powerful element as it will increase the strain hardening. However, it will also stabilize the austenite towards martensite transformation at cold forming. Nitrogen also has a high affinity to nitride formers such as titanium, aluminum and chromium. The nitrogen content should be restricted to maximum 0,1 %, preferably 0,07 % and most preferably max 0,05 %.
  • the alloy is substantially free of manganese sulfides.
  • the alloy has the following approximate composition in percent by weight:
  • compositions given in Table 1 of the alloy according to the invention can be classified as having a Mn content of approx. 0,5 % or approx. 2,5 % and a S content of approx. 0,015 % or 0,1 %.
  • the drawn wires according to Table 2 were heat treated at 475 °C for 4 h and tensile tested in order to evaluate the increase in mechanical strength upon precipitation hardening (PH).
  • the tensile strength after heat treatment resulting in the precipitation hardening can be seen in Table 3.
  • Table 3 Tensile strength in MPa after wire drawing at various reduction and subsequent precipitation hardening.
  • the drilling test was made with the drilling parameters shown in Table 6.
  • the drills used were 02mm uncoated cemented carbide drills, HAM 380, with a tip angle of 130°. Drilling depth was two times the bar diameter.
  • the machinability was evaluated regarding chip formation, drill wear and drillability.
  • the chip shape at drilling was judged by use of "Svenska Mekanf ⁇ rbundets Spanskala” (Karlebo Haiidbok, 15 -t m h Edition, 2000, page 449-450) as a reference chart.
  • the optimal chip formation for best productivity is No 5-7.
  • the wear was measured as the wear at clearance face on the cutting edge (flank wear), corner wear by built up edge and possible edge damages.
  • the tests were in some cases performed for two samples of each alloy composition.
  • the damages/wear was then graded after a scale with respect of the different types of wear/damages wherein as low of a grade as possible is desirable. A low value indicates a longer tool life compared to a high value.
  • Table 8 The results are disclosed in Table 8.
  • the ranking of the average of the tool wear of the two tests per alloy is seen in Table 9. A lower ranking indicates a longer tool life than a higher ranking.
  • the reference alloy 830207 and the 830211 alloy according to the invention were analyzed by means of Scanning Electron Microscope (SEM) using Back Scattered Electrons (BSE). The surfaces of the materials were in un-etched condition. A photograph of the reference alloy taken in the SEM is shown in Figure 1. Three different test points; Spectrum 1 illustrated in Figure 2a, Spectrum 2 illustrated in Figure 3 a and Spectrum 3 illustrated in Figure 4a; were investigated by Energy Dispersive X-ray analysis (EDX). The results are shown in Figures 2b, 3b, and 4b, respectively. As can be clearly seen from the results, there are no titanium sulfides. This is considered to be a result of the low sulphur content of the alloy.
  • SEM Scanning Electron Microscope
  • BSE Back Scattered Electrons
  • FIG. 5 A photograph of the 830211 alloy of the invention taken in the SEM is shown in Figure 5. The difference can be clearly seen when comparing to Figure 1.
  • Four different test points; Spectrum 1, Spectrum 2, Spectrum 3 and Spectrum 4; are given in the Figures 6a, 7a, 8a, and 9a.
  • the composition of these test points were analyzed with EDX and the results are given in Figures 6b, 7b, 8b and 9b, respectively.

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

Abstract

A precipitation hardenable stainless chromium nickel steel is disclosed having the following composition in weight %: C max 0,07 Si max 1,5 Mn 0,2-5 S 0,01-0,4 Cr 10-15 Ni 7-14 Mo 1-6 Cu 1-3 Ti 0,3-2,5 Al 0,2-1,5 N max 0,1 balance Fe and normally occurring impurities.

Description

PRECIPITATION HARDENABLE MARTENSITIC STAINLESS STEEL
The present disclosure is concerned with the precipitation hardenable stainless chromium nickel steels, more especially those that are hardenable with a fairly simple alloy treatment. More particularly, the concern is with the precipitation hardenable stainless chromium nickel steels which are hardened at a low temperature and also have good machinability when subjected to drilling, turning, milling and other cutting operations.
BACKGROUND AND PRIOR ART
Precipitation hardenable martensitic stainless steels are for example used in various high strength applications, such as springs, surgical needles, clips, fine tubes, parts for instruments and parts exposed to wear. In order to be a satisfactory material selection for such high strength applications the material needs to posses certain properties. For example, the steel should be able to be produced by an easy manufacturing process, including alloying, casting, hot working as well as cold working, rendering a high strength material that is easy to fabricate by mechanical cutting methods into finished parts starting from wire, sheet, strip, bar or tube material.
Also, despite the high final strength the material should preferably be ductile and thus allowing severe forming such as bending, coiling, pressing, twisting etc. in the as received condition, hi addition to the mechanical properties above a very good corrosion resistance is often required, allowing the material to be used in different environments without having to consider additional corrosion protection such as painting or any other type of surface coating. Furthermore, the steel should be able to be hardened to a high final hardness by a simple, low temperature, alloy treatment that causes minimal shape disturbance.
Presently several alloys of different alloying concepts exits that covers many of the above mentioned requirements both by means of a trouble free production of parts as well as the properties required for the product itself during service. In several cases however, the properties required are difficult to combine in one single material. Carbon steels are, dependent on their composition, more or less formable and can with higher carbon contents be hardened to a high hardness. The low corrosion resistance makes however these steel impossible to use in environments that are even only slightly corrosive. Ferritic chromium steels may exhibit good corrosion resistance but cannot be hardened to a high strength. Martensitic chromium steels can be hardened but suffers from low ductility that limits their usage. Austenitic stainless steels are, dependent on their composition, either soft and ductile in the annealed condition or hard and less ductile in the cold deformed condition. In the harder conditions austenitic steels are also very difficult to machine. A further group is the precipitation hardenable stainless steels that can be formed in fairly soft condition and subsequently alloy treated to achieve a high hardness. Also this group of steels are more difficult to machine compared e.g. to the group of hardenable martensitic steels.
Consequently, it is need to provide the market with a material that satisfies the above criteria.
SUMMARY
A precipitation hardenable stainless chromium nickel steel is disclosed having the following composition in weight %:
C max 0,07
Si max 1,5
Mn 0,2-5
S 0,01-0,4
Cr 10-15
Ni 7-14
Mo 1-6
Cu 1-3
Ti 0,3-2,5
Al 0,2-1,5
N max 0,1
Balance Fe and normally occurring impurities. The stainless steel according to the invention comprises titanium sulphides.
The stainless steel is hardened at a low temperature and has good machinability when subjected to drilling, turning, milling and other cutting operations.
BREIF DESCRIPTION OF THE DRAWINGS
Figure 1 SEM photograph of a reference alloy.
Figure 2a SEM photograph of Figure 1 marked with test point Spectrum 1. Figure 2b EDX result of Spectrum 1 of Figure 2a.
Figure 3a SEM photograph of Figure 1 marked with test point Spectrum 2.
Figure 3b EDX result of Spectrum 2 of Figure 3a.
Figure 4a SEM photograph of Figure 1 marked with test point Spectrum 3.
Figure 4b EDX result of Spectrum 3 of Figure 4a. Figure 5 SEM photograph of an alloy according to the invention.
Figure 6a SEM photograph of Figure 5 marked with test point Spectrum 1.
Figure 6b EDX result of Spectrum 1 of Figure 6a.
Figure 7a SEM photograph of Figure 5 marked with test point Spectrum 2.
Figure 7b EDX result of Spectrum 2 of Figure 7a. Figure 8a SEM photograph of Figure 5 marked with test point Spectrum 3.
Figure 8b EDX result of Spectrum 3 of Figure 8a.
Figure 9a SEM photograph of Figure 5 marked with test point Spectrum 4.
Figure 9b EDX result of Spectrum 4 of Figure 4a.
DETAILED DESCRIPTION
In order to fully understand the influence of composition on the properties of the invented precipitation hardenable stainless steel it is necessary to discuss all elements individually. All element contents are in weight percent.
Carbon is a powerful element that affects the steel in many ways. A high carbon content will affect the deformation hardening in a way that the strength upon cold deformation will be high and thus reducing the ductility of the steel. A high carbon content is also disadvantageous from corrosion point of view as the risk of precipitation of chromium carbides increase with increasing carbon content. The carbon content should therefore be kept low, max 0,07 %, preferably max 0,05 % and more preferable max 0,025 %.
Silicon is a ferrite-forming element and may also in higher contents reduce the hot working properties of the steel. The content should therefore be max 1,5% more preferably max 1,0 %.
Manganese is an austenite-forming element that in a similar way as nickel makes the steel less prone to a martensitic transformation at cold deformation. The minimum content of manganese of the steel according to the invention is 0,2 % by weight. As the steel has to have a significant content of martensite for the precipitation hardening the manganese content has to be max 5%, preferably max 3% and most preferably 2,5%. Manganese will together with sulfur form ductile non-metallic inclusions that for example are beneficial for the machining properties.
Sulfur is an element that will form sulfides in the steel. Sulfides are beneficial during machining as they will act as chip-breakers. The content of sulfur is therefore min 0,01% and more preferably min 0,015 %, even more preferably 0,05 % and most preferably min 0,1%. Sulfides may however act as weak areas in the steel from a corrosion resistance point of view. Further, high contents of sulfur may also be detrimental for the hot working properties. The content should therefore be max 0,4% and preferably max 0,3%. The composition of the alloy according to the invention is so selected that the alloy comprises titanium sulphides. The titanium sulphides are principally present in the form of TiS or Ti2S .
Chromium is essential for the corrosion resistance and must in the steel according to the invention be added in a content of at least 10%, or more preferably at least 11,5 %. Chromium is however also a strong ferrite former that in higher contents will suppress the martensite formation upon deformation. The content of chromium therefore has to be restricted to max 15%, preferably max 14%.
Nickel is added to the steel according to invention to balance the ferrite forming elements in order to obtain an austenitic structure upon annealing. Nickel is also an important element to moderate the hardening from cold deformation. Nickel will also contribute to the precipitation hardening together with elements such as titanium and aluminum. The minimum content of nickel is therefore 7% or more preferable at least 8%. A too high content of nickel will restrict the possibility to form martensite upon deformation. Nickel is also an expensive alloying element. The content of nickel is therefore maximized to 14 or preferably 13%.
Molybdenum is essential for the steel according to the invention, as it will contribute to the corrosion resistance of the steel. Molybdenum is also an active element during the precipitation hardening. The minimum content is therefore 1 % or preferably, minimum 2% and most preferably minimum 3%. A too high content of molybdenum will however promote the formation of ferrite to a content that may result in problems during hot working. Further, a high content of molybdenum will also suppress the martensite formation during cold deformation. The content of molybdenum is therefore maximized to 6% and more preferable maximum 5%. Furthermore, it is expected that Mo could be partly or totally replaced by tungsten according to the common practice known to a person skilled in the art while still achieving the desired properties of the alloy.
Copper is an austenite former that together with nickel stabilizes the austenitic structure that is desired. Copper is also an element that increases the ductility in moderate contents. The minimum content is therefore 1% and more preferably at least 1,5%. On the other hand copper in high contents reduces the hot workability why the copper content is maximized to 3%, preferably maximum 2,5%.
Titanium is an essential alloying element in the invention due to at least two reasons. Firstly, titanium is used as a strong element for precipitation hardening and must therefore be present to be able to harden the steel for the final strength. Secondly, titanium will together with sulfur form titanium sulfides (TiS or possibly Ti2S). In general, titanium is a stronger sulfide former than manganese. As TiS are electrochemically nobler that MnS it is possible to achieve improved machining properties without deterioration of the corrosion resistance that is the normal case for free machining steels that utilize MnS for the increased machinability. Therefore, the minimum content of titanium is 0,3% and more preferably 0,5 %. Too high titanium contents will promote ferrite formation in the steel and also increase the brittleness. The maximum content of titanium should therefore be restricted to 2,5 % preferably 2 % and most preferably not more than 1,5%.
Aluminum is added to the steel in order to improve the hardening effect upon heat treatment. Aluminum is known to form intermetallic compounds together with nickel such as Ni3 Al and NiAl. In order to achieve a good hardening response the minimum content should be 0,2 % and most preferably min 0,3 %. Aluminum is however a ' strong ferrite former why the maximum content should be 1,5 % or more preferably max 1,0 %.
Nitrogen is a powerful element as it will increase the strain hardening. However, it will also stabilize the austenite towards martensite transformation at cold forming. Nitrogen also has a high affinity to nitride formers such as titanium, aluminum and chromium. The nitrogen content should be restricted to maximum 0,1 %, preferably 0,07 % and most preferably max 0,05 %.
According to one embodiment of the invention the alloy is substantially free of manganese sulfides.
The alloy of the invention has according to a preferred embodiment the following approximate composition in percent by weight:
C max 0,2
Si max 0,3
Mn 0,5
S 0,1
Cr 12
Ni 9
Mo 4
Cu 2
Ti 1
Al 0,4
N max 0,1 balance Fe and normally occurring impurities According to another preferred embodiment of the invention, the alloy has the following approximate composition in percent by weight:
C max 0,2
Si max 0,3
Mn 2,5
S 0,1
Cr 12
Ni 9
Mo 4
Cu 2
Ti 1
Al 0,4
N max 0,1 balance Fe and normally occurring impurities
The present disclosure will now be described in more detail with the aid of some illustrative examples.
Example 1
Five 270-kg melts, with chemical composition according to Table 1, were melted in a vacuum induction melting (VIM) furnace and cast into 9", i.e. 229 mm, ingots. Alloy 830207 is included as a reference alloy and does not make a part of the present invention. The ingots were forged into 103 x 103 mm slabs. The slabs were then heated to 1150°C and hot rolled to 5,5 mm wire rod. The wire rod was pickled and drawn to 2,1 mm in a multi block drawing machine without any intermediate annealing. The tensile strength in MPa as a function of the degree of area reduction at drawing of the hot rolled wire in diameter 5,5 mm to diameter 2,1 mm is found in Table 2. The tensile testing was made without any heat treatment and in accordance with SS-EN10002-l.
The compositions given in Table 1 of the alloy according to the invention can be classified as having a Mn content of approx. 0,5 % or approx. 2,5 % and a S content of approx. 0,015 % or 0,1 %.
Example 2
The drawn wires according to Table 2 were heat treated at 475 °C for 4 h and tensile tested in order to evaluate the increase in mechanical strength upon precipitation hardening (PH). The tensile strength after heat treatment resulting in the precipitation hardening can be seen in Table 3. Table 3. Tensile strength in MPa after wire drawing at various reduction and subsequent precipitation hardening.
Example 3
The corrosion resistance, of the alloys according to Table 1, was tested in the precipitation hardened condition. The Critical Pitting Temperature (CPT) was measured in a 0,1 % NaCl solution. The potential was kept on 300 mV Vs. Standard Calomel Electrode (SCE). After grinding to 600 grit finish 6 specimens per alloy in diameter 3,5 mm were tested to establish the critical pitting temperature of each material. Table 4 shows the CPT values per alloy.
Table 4. CPT values in 0,1 % NaCl solution at 30OmV Vs SCE. 6 specimen tested alloy
Example 4
The machinability of the compositions according to Table 1 was also tested. Straightened bars in diameter 3,5 mm were manufactured by drawing wire from a diameter of 5,5 mm to 3,5 mm followed by a straightening operation. Drilling tests were performed in the as straightened, not heat treated, condition with mechanical properties according to Table 5. Hardness testing was made according to SS-EN ISO 6507.
Table 5. Dimension and mechanical properties of straightened bars used for machinability test.
The drilling test was made with the drilling parameters shown in Table 6. The drills used were 02mm uncoated cemented carbide drills, HAM 380, with a tip angle of 130°. Drilling depth was two times the bar diameter.
Table 6. Machining data at drilling
The machinability was evaluated regarding chip formation, drill wear and drillability. The chip shape at drilling was judged by use of "Svenska Mekanfδrbundets Spanskala" (Karlebo Haiidbok, 15 -tmh Edition, 2000, page 449-450) as a reference chart. The optimal chip formation for best productivity is No 5-7.
Table 7. Chip form at drilling.
The wear was measured as the wear at clearance face on the cutting edge (flank wear), corner wear by built up edge and possible edge damages. The tests were in some cases performed for two samples of each alloy composition. The damages/wear was then graded after a scale with respect of the different types of wear/damages wherein as low of a grade as possible is desirable. A low value indicates a longer tool life compared to a high value. The results are disclosed in Table 8.
Table 8. Graded results of wear tests.
The ranking of the average of the tool wear of the two tests per alloy is seen in Table 9. A lower ranking indicates a longer tool life than a higher ranking.
Table 9. Tool wear at drilling, average of the two tests in Table 8.
Large scale drilling tests were made on material from heat 830207 and 830209. The drillability was measured by means of the number of drilled parts until worn out drill. Also, the number of drilled holes per hour was measured. The results are shown in Table 10.
Table 10. Results of large scale drilling test
The drilling tests show that all alloys according to the invention show an improved macbinability compared to the reference alloy 830207 in form of chip formation that is important for minimizing the risk of chips tangling during drilling. All alloys according to the invention also show less tool wear compared to the reference alloy 830207, which means that more parts can be produced before the drill must be replaced. Example 5
The reference alloy 830207 and the 830211 alloy according to the invention were analyzed by means of Scanning Electron Microscope (SEM) using Back Scattered Electrons (BSE). The surfaces of the materials were in un-etched condition. A photograph of the reference alloy taken in the SEM is shown in Figure 1. Three different test points; Spectrum 1 illustrated in Figure 2a, Spectrum 2 illustrated in Figure 3 a and Spectrum 3 illustrated in Figure 4a; were investigated by Energy Dispersive X-ray analysis (EDX). The results are shown in Figures 2b, 3b, and 4b, respectively. As can be clearly seen from the results, there are no titanium sulfides. This is considered to be a result of the low sulphur content of the alloy.
A photograph of the 830211 alloy of the invention taken in the SEM is shown in Figure 5. The difference can be clearly seen when comparing to Figure 1. Four different test points; Spectrum 1, Spectrum 2, Spectrum 3 and Spectrum 4; are given in the Figures 6a, 7a, 8a, and 9a. The composition of these test points were analyzed with EDX and the results are given in Figures 6b, 7b, 8b and 9b, respectively.
Surprisingly, no manganese sulphides were found in the alloy 830211 even though the Mn content was quite high (approximately 2,5 %).
It is clear form the Examples that a new alloy has been developed which has substantially improved machining properties without a reduced corrosion resistance in comparison with the previously known alloy. It is likely that increasing the sulfur content further would increase the machinability further without reducing the corrosion resistance as long as the content of manganese sulfides are not substantially increased.

Claims

1. Martensitic stainless steel alloy characterized in having the following composition in weight-%:
C max 0,07
Si max 1,5
Mn 0,2-5
S 0,01-0,4
Cr 10-15
Ni 7-14
Mo 1-6
Cu 1-3
Ti 0,3-2,5
Al 0,2-1,5
N max 0,1 balance Fe and normally occurring impurities wherein it comprises titanium sulphides.
2. Martensitic stainless steel alloy according to claim 2 characterized in that it is substantially free from manganese sulfides.
3. Martensitic stainless steel alloy according to claims 1 or 2 characterized in that the content of S is 0,015-0,3 %.
4. Martensitic stainless steel alloy according to any of claims 1-3 characterized in that the content of Ti is at least 0,5 %.
5. Martensitic stainless steel alloy according to claim 4 characterized in that the content of Ti is max 2 %.
6. Martensitic stainless steel alloy according to claim 1 characterized in that the content of Mo is 2-5%.
7. Martensitic stainless steel alloy according to claim 1 characterized in that the content of Cr is 11,5-13 % and that the content of Ni is 8-13 %.
8. Martensitic stainless steel alloy according to claim 1 characterized in being precipitation hardened.
9. Martensitic stainless steel alloy according to claim 1 characterized in that it is produced by conventional metallurgy techniques.
10. Martensitic stainless steel alloy according to any of claims 1-3 and 4-9 wherein it has an approximate composition of
C max 0,2
Si max 0,3
Mn 0,5
S 0,1
Cr 12
Ni 9
Mo 4
Cu 2
Ti 1
Al 0,4
N max 0,1 balance Fe and normally occurring impurities.
11. Martensitic stainless steel alloy according to any of claims 1-3 and 4-9 wherein it has an approximate composition of
C max 0,2
Si 0,2
Mn 2,5
S o,i -
Cr 12
Ni 9
Mo 4
Cu 2 Ti 1
Al 0,4
N max 0,1 balance Fe and normally occurring impurities
EP05819793A 2004-12-23 2005-12-22 Precipitation hardenable martensitic stainless steel Withdrawn EP1831417A1 (en)

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SE0403176A SE528454C3 (en) 2004-12-23 2004-12-23 Extractable curable martensitic stainless steel including titanium sulfide
PCT/SE2005/001997 WO2006068610A1 (en) 2004-12-23 2005-12-22 Precipitation hardenable martensitic stainless steel

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EP1831417A1 true EP1831417A1 (en) 2007-09-12

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WO (1) WO2006068610A1 (en)

Families Citing this family (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2887558B1 (en) * 2005-06-28 2007-08-17 Aubert & Duval Soc Par Actions MARTENSITIC STAINLESS STEEL COMPOSITION, PROCESS FOR MANUFACTURING A MECHANICAL PART THEREFROM, AND PIECE THUS OBTAINED
WO2009126954A2 (en) * 2008-04-11 2009-10-15 Questek Innovations Llc Martensitic stainless steel strengthened by copper-nucleated nitride precipitates
US7931758B2 (en) * 2008-07-28 2011-04-26 Ati Properties, Inc. Thermal mechanical treatment of ferrous alloys, and related alloys and articles
WO2011040876A1 (en) * 2009-10-02 2011-04-07 Nanoxis Ab Screening of binders on immobilized native membrane proteins
JP5502575B2 (en) * 2010-04-16 2014-05-28 株式会社日立製作所 Precipitation hardening martensitic stainless steel and steam turbine blades
DE102010025287A1 (en) 2010-06-28 2012-01-26 Stahlwerk Ergste Westig Gmbh Chromium-nickel steel
CN102168228A (en) * 2011-03-28 2011-08-31 徐英忱 Medical precipitation-hardening stainless steel material and preparation method thereof
JP5764503B2 (en) * 2012-01-19 2015-08-19 三菱日立パワーシステムズ株式会社 Precipitation hardening type martensitic stainless steel, steam turbine long blade, turbine rotor and steam turbine using the same
JP6111763B2 (en) 2012-04-27 2017-04-12 大同特殊鋼株式会社 Steam turbine blade steel with excellent strength and toughness
CN105908099A (en) * 2016-04-18 2016-08-31 和县隆盛精密机械有限公司 Terrace grinding mechanical arm and preparation method of same
SE1650850A1 (en) * 2016-06-16 2017-11-21 Uddeholms Ab Steel suitable for plastic moulding tools
CN107326300A (en) * 2017-06-20 2017-11-07 上海大学兴化特种不锈钢研究院 A kind of anti-corrosion antibacterial medical surgical device martensitic stain less steel and preparation method thereof
CN107587080B (en) * 2017-10-17 2019-06-18 中国华能集团公司 A kind of precipitation strengthening heat-resistant steel and preparation process thereof
US11692232B2 (en) 2018-09-05 2023-07-04 Gregory Vartanov High strength precipitation hardening stainless steel alloy and article made therefrom
WO2020115531A1 (en) * 2018-12-06 2020-06-11 Aperam Stainless steel, products made of this steel and methods of manufacturing same
KR102270898B1 (en) * 2019-11-06 2021-06-30 주식회사 한중엔시에스 Heat treating method for hardening type stainless steel and coupler manufacturing method using the same

Family Cites Families (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3658513A (en) * 1969-03-06 1972-04-25 Armco Steel Corp Precipitation-hardenable stainless steel
SE346813B (en) * 1970-11-12 1972-07-17 Sandvikens Jernverks Ab
JPH0647708B2 (en) * 1985-07-31 1994-06-22 大同特殊鋼株式会社 Austenitic free-cutting stainless steel
SE469986B (en) * 1991-10-07 1993-10-18 Sandvik Ab Detachable curable martensitic stainless steel
US6238455B1 (en) * 1999-10-22 2001-05-29 Crs Holdings, Inc. High-strength, titanium-bearing, powder metallurgy stainless steel article with enhanced machinability
JP2001131713A (en) * 1999-11-05 2001-05-15 Nisshin Steel Co Ltd Ultra-high-strength metastable austenitic stainless steel containing Ti and manufacturing method
JP3491030B2 (en) * 2000-10-18 2004-01-26 住友金属工業株式会社 Stainless steel for disk shakers
DE10251413B3 (en) * 2002-11-01 2004-03-25 Sandvik Ab Use of a dispersion hardened martensitic non-rusting chromium-nickel steel in the manufacture of machine-driven rotating tools, preferably drilling, milling, grinding and cutting tools
US7901519B2 (en) * 2003-12-10 2011-03-08 Ati Properties, Inc. High strength martensitic stainless steel alloys, methods of forming the same, and articles formed therefrom
US6899773B2 (en) * 2003-02-07 2005-05-31 Advanced Steel Technology, Llc Fine-grained martensitic stainless steel and method thereof
SE522813C2 (en) * 2003-03-07 2004-03-09 Sandvik Ab Use of a precipitable, martensitic stainless steel for the manufacture of implants and osteosynthetic products
JP4030925B2 (en) * 2003-06-06 2008-01-09 山陽特殊製鋼株式会社 Free-cutting precipitation hardening stainless steel
JP4152872B2 (en) * 2003-12-12 2008-09-17 山陽特殊製鋼株式会社 Precipitation hardening stainless steel for cold work with excellent machinability

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO2006068610A1 *

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CN101087897A (en) 2007-12-12
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SE528454C2 (en) 2006-11-14
SE0403176L (en) 2006-06-24
KR20070086564A (en) 2007-08-27
JP2008525637A (en) 2008-07-17
SE528454C3 (en) 2007-01-09
WO2006068610A1 (en) 2006-06-29
US20080210344A1 (en) 2008-09-04

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