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
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
• • 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 by deformation combined with, or followed by, heat treatment
  • C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
• • 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

Definitions

• the invention relates to a corrosion-resistant chromium steel which consists of 3 to 45% chromium, 0.001 to 0.5% carbon, O to 10% nickel, O to 10% manganese, O to 10% molybdenum, O to 5% vanadium, O. up to 2% silicon, O up to 2% titanium, niobium and / or tantalum, O up to 1% cerium, O up to 0.3% aluminum and the rest iron and the structure of which contains at least 50% ferromagnetic structure components.
• the invention further relates to a method for producing this steel.
• a nitrogen-containing steel with a high yield strength and good toughness properties which contains up to 0.6% carbon, 5 to 40% chromium, up to 30% manganese, up to 5% molybdenum, up to 20% Contains nickel, 1.5 to 5% nitrogen and the rest iron and has an austenitic structure.
• the nitrogen content is introduced into the steel by first sticking the melt. Iron-chromium or iron-manganese alloys containing substance are added and then gaseous nitrogen is introduced into the melt or into the slag.
• the chromium steels with a ferromagnetic structure are characterized by higher strength properties and very good resistance to stress corrosion cracking. Even in the temperature range up to 400 ° C, the strength properties of ferritic chromium steels, which have a ferromagnetic structure, are far above the values of austenitic chromium-nickel steels, while the deformation parameters are clearly below the values of austenitic steels. However, the heat resistance of the ferritic chrome steels drops considerably by 450 ° C as a result of the embrittlement phenomena that begin in this temperature range. The use of these steels for continuous operation is therefore restricted to temperatures below 300 ° C (see Materials Science of Common Steels, Part 2, Verlag Stahleisen mbH, Düsseldorf, 1977, page 165).
• the corrosion-resistant chromium steels with ferromagnetic structure which consist of 12 to 18% chromium, 0.5 to 1% manganese, 0.05 to 1.2% carbon, O to 1% silicon, O to 2.5% nickel, O. up to 1.3% molybdenum, O to 2% vanadium, O to 0.3% aluminum and the rest iron, in the annealed or tempered condition the following material properties:
• the ferromagnetic structure of these corrosion-resistant steels consists of ferrite or of ferrite and pearlite in the annealed state and of ferrite and transformation structure or transformation structure or martensite in the tempered state.
• a corrosion and heat-resistant chrome-nickel steel which contains 0.005 to 0.065% carbon, 0.1 to 1.0% silicon, 0.5 to 4.0% manganese, 22.5 contains up to 28.0% chromium, 3.5 to 8.0% nickel, 0.08 to 0.40% nitrogen and the rest iron, which with a ferrite content of 30 to 70% by primary deformation at temperatures above 1155 ° C and a further deformation at temperatures below 1000 to 800 ° C to a 0.2% proof stress of at least 75 kp / mm 2 with simultaneous good notch toughness and for the manufacture of objects in the chemical industry, in particular in the fermentation technology and food and Paper industry is used.
• the invention is therefore based on the object of providing a corrosion-resistant chromium steel which, even at temperatures above 400 ° C., has the favorable strength properties of chromium steels with a ferromagnetic structure, without any signs of embrittlement occurring. Furthermore, the invention is intended to provide a method for producing this steel.
• the chromium steel of the type mentioned has a nitrogen content which is between 0.2 and 5% and is at least 10% greater than the nitrogen solubility limit at 1 bar and 20 ° C., which is at 400 ° C has a yield strength R p0.2 > 400 N / mm 2 and at 600 C a yield strength R p0.2 > 250 N / mm 2 and which can be magnetized.
• a corrosion-resistant chrome steel with predominantly ferromagnetic microstructure components would have a high heat resistance at temperatures of more than 400 ° C.
• the corrosion-resistant chrome steel according to the invention also has a high heat resistance at temperatures above 400 ° C. without that brittle phases occur.
• the steel from the invention manufactured components can be dimensioned smaller because of the favorable relationship between tribo-chemical resistance and high heat resistance.
• the good heat resistance of the chrome steel according to the invention is attributed to the high nitrogen content, which must be considerably greater than the nitrogen solubility limit at 1 bar and 20 ° C. Since the nitrogen content of the steels known from the two DD patents 115 508 and 142 894 is far below the nitrogen solubility limit at 1 bar and 20 ° C., the person skilled in the art was not encouraged by this prior art to exceed the nitrogen solubility limit and he was able to also do not expect this measure to result in a significant improvement in properties.
• the object is further achieved by the creation of a corrosion-resistant chromium steel, in which a master alloy consisting of 3 to 45% chromium, 0.0 0 1 to 0.5% carbon, O to 10% nickel, 0 up to 10% manganese, 0 to 10% molybdenum, O to 5% vanadium, 0 to 2% silicon, O to 2% titanium, niobium and / or tantalum, O to 1% cerium, O to 0.3% aluminum and the rest Iron is present and there is a structure with at least 50% ferromagnetic structure components.Nitrification under pressure introduces a nitrogen content that is between 0.2 and 5% and must be at least 10% greater than the nitrogen solubility limit of the master alloy at 1 bar and 20 ° C , in which the embroidered alloy is thermoformed, in which the embroidered thermoformed alloy is annealed at 800 to 1250 ° C and then cooled to room temperature.
• a corrosion-resistant chromium steel in which a master alloy consisting of 3 to 45%
• the master alloy is embroidered on under pressure and can in particular by. Electroslag remelting can be carried out.
• the glow time can be, for example, 0.5 to 10 hours.
• the process produces a corrosion-resistant chrome steel with predominantly ferromagnetic structure components, which can also be used at temperatures above 400 ° C because it contains no brittle phases.
• the steel after it has been cooled at 450 to 750 ° C., is subjected to a tempering treatment and then cooled to room temperature.
• the duration of the tempering treatment is, for example, 1 to 10 hours.
• the tempering treatment advantageously achieves an additional improvement in the strength properties, in particular the deformation parameters.
• the corrosion-resistant chrome steel is used for the production of parts for steam and gas turbines, since particularly high demands must be made on these parts with regard to their heat resistance.
• the ferritic chromium steel 1.4002 which consists of 0.06% carbon, 0.5% silicon, 1% manganese, 13% chromium, 0.01% nitrogen, 0.1% aluminum, the rest iron and has a ferromagnetic structure, is proven its annealing at 800 ° C the following mechanical properties:
• the structure of the chrome steel consists of ferrite. At a test temperature of 400 ° C, the yield strength of the steel is approx. 200 N / mm 2 .
• the steel After annealing at 950 to 1000 ° C and cooling in oil or air and after tempering at 700 to 750 ° C and cooling in air, the steel has the following mechanical characteristics:
• a nitrogen content of 0.51% was introduced into a master alloy with a composition that corresponds to the composition of the material 1.4002 by means of electroslag remelting under pressure.
• the embroidered master alloy was hot worked by forging at 1180 ° C and then subjected to various heat treatments. It was found that three significantly different strength levels can be set by slightly changing the heat treatment, especially at room temperature. It was also found that at a test temperature of over 400 ° C there is no sudden drop in the heat resistance properties. The results of these tests are summarized in Table 1.
• the materials characterized in Table 1 have an extremely fine-grained structure.
• Annealing at temperatures above 800 ° C with subsequent cooling in air without tempering treatment cause the formation of a nitrogen-induced martensitic structure, which, in contrast to carbon martensite, has a higher ductility with significantly higher strength properties.
• Tempering treatments following the annealing in turn cause a regression to a ferritic structure with simultaneous formation of the finest precipitates, primarily chromium nitride.
• the composition of the material 1.4002 was changed by adding 2.9% nickel and 3.5% molybdenum and by reducing the carbon content to 0.03%.
• the structure of this starting alloy was largely ferritic.
• a nitrogen content of 0.51% was introduced into this predominantly ferritic master alloy by electroslag remelting under pressure.
• the embroidered alloy was hot worked by forging at 1180 ° C and then subjected to different heat treatments.
• Table 2 shows that the materials characterized there have strength properties that are far above those of conventional corrosion-resistant ferritic chromium steels.
• the different heat treatments result in a change in the R p0.2 / R ratio, among other things.
• the strength level of the steels according to the invention characterized in Table 2 is far above the strength level that the austenitic chromium-nickel steels have.
• Metallographic investigations have shown that the materials characterized in Table 2 are mainly composed of ferrite, transformation structure and chromium nitride precipitates.
• composition of the materials and alloys are% by weight.
• percentages that relate to the individual structural components are vol%.
• the structural components can be determined by electron microscopy or by X-ray diffraction.
• room temperature means a temperature of 20 ° C.

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• Chemical & Material Sciences (AREA)
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• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Heat Treatment Of Steel (AREA)
• Heat Treatment Of Articles (AREA)
• Manufacturing Of Steel Electrode Plates (AREA)
• Preventing Corrosion Or Incrustation Of Metals (AREA)

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• 1983
  • 1983-03-24 DE DE19833310693 patent/DE3310693A1/de active Granted
• 1984
  • 1984-02-25 AT AT84101992T patent/ATE27005T1/de not_active IP Right Cessation
  • 1984-02-25 EP EP84101992A patent/EP0123054B1/fr not_active Expired
  • 1984-03-22 JP JP59053666A patent/JPS59179757A/ja active Pending
• 1985
  • 1985-03-01 US US06/706,945 patent/US4610734A/en not_active Expired - Lifetime

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