Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B15/00—Layered products comprising a layer of metal
  • B32B15/01—Layered products comprising a layer of metal all layers being exclusively metallic
  • B32B15/013—Layered products comprising a layer of metal all layers being exclusively metallic one layer being formed of an iron alloy or steel, another layer being formed of a metal other than iron or 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
  • C22C38/02—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
  • C22C38/06—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
  • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium 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
  • C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
• • 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
  • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
  • C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
  • C23C2/06—Zinc or cadmium or alloys based thereon

Definitions

• the present invention relates to use of a steel alloy for making tubes to produce compressed gas containers or for making formed structures in light weight steel construction.
• Compressed gas containers are typically made of annealed carbon steel such as, e.g. St 52-3 or STE 460.
• annealed carbon steel such as, e.g. St 52-3 or STE 460.
• SAE 1513 liquid-hardened tempered steels
• compressed gas containers are subsequently tempered with oil or water, sand-blasted and then subjected to a pressure test.
• internal voids of the compressed gas containers are scaled during oil tempering or water tempering.
• scale must be removed by a complicated sand blasting process.
• Another drawback is the application of oil cooling which entails health hazards.
• the use of liquid hardening results in a relative wide range of hardness values in view of the geometric shape of the compressed gas containers (hollow bodies).
• German Pat. No. 195 33 229 C1 discloses the use of a steel alloy as material for making pressure containers in the presence of inert gas.
• the steel alloy contains in particular expensive nickel as alloy element and can be air-tempered only after the pressure container has been made. After air hardening, it is hereby necessary to temper the pressure container in an additional process to realize the desired toughness.
• the tempering process is accompanied by a sooting of the surface which contradicts the need for a clean surface.
• Another drawback involves the high content of carbon which renders the steel alloy unsuitable when, for economical reasons, quick welding processes such as active-gas metal-arc welding with mixed gas (MAG) or laser beam welding, are demanded for making pressure containers, because of the risk of cracks.
• MAG active-gas metal-arc welding with mixed gas
• laser beam welding are demanded for making pressure containers, because of the risk of cracks.
• water-tempered fine-grained steel with a tensile strength Rm of 1,400 N/mm 2 , yield point Rp0.2 of 1,000 N/mm 2 , and stretch A5 of 8% is used in light weight steel construction, in particular automobile industry, for producing formed structures.
• This type of steel can be tempered only with water and only in the tool so that the overall production is cumbersome. Without tempering, this steel would lack a required strength, while tempering results in scaling that can be eliminated only by a comparably long pickling process which in turn leads to hydrogen embrittlement.
• Another drawback of this type of steel is a substantial loss in strength in heat impact zones that have been formed by welding seams, when tempered formed structures are joined together by welding.
• Dual phase steel with a tensile strength Rm of 600 N/mm 2 , yield point Rp0.2 of 400 N/mm 2 , and stretch A5 of 20% has insufficient base strength. Increase in strength can be realized by higher transformation strain which, however, is undesired for many formed structures used in the automobile industry. This type of steel also experiences significant structural changes during high temperature galvanizing.
• TRIP (short for “transformation induced plasticity”) steel (multiphase steel) having a tensile strength Rm of 700 N/mm 2 , yield point Rp0.2 of 480 N/mm 2 , and stretch A5 of 24% has also insufficient base strength. Although the strength could conceivably be increased by higher transformation strain, this course of action is, as stated above, undesired for many formed structures used in the automobile industry. Significant structural changes can also be encountered during high temperature galvanizing, and the strength profile of such steels is critical in the area of the welding seams and in the heat impact zones.
• Special steel having a tensile strength Rm of 800 N/mm 2 , yield point Rp0.2 of 370 N/mm 2 , and stretch A5 of 53% results in high material costs while exhibiting an insufficient base strength.
• the strength of special steel can also only be increased by higher transformation strain which cannot always be attained in components of the automobile industry.
• European Patent publications EP 1 143 022 A1, EP 1 041 167 A1 and EP 1 052 301 A1 disclose steel compositions which contain, in mass %, 0.09-0.12% C, 0.15-0.30% S, 1.10-1.60% Mn, max. 015% P, max. 0.011% S, 1.00-1.60% Cr, 0.30-0.60% Mo, 0.02-0.05% Al, 0.12-0.25% V, the balance iron and incidental impurities.
• a method of using a steel alloy includes the steps of forming a tube from the steel alloy, air hardening the tube in the presence of inert gas, and incorporating the tube in the production of a compressed gas container.
• the present invention resolves prior art problems by using a steel composition for making compressed gas containers by applying the heat treatment step on the semi-finished tube during passage, thereby eliminating the need for tempering.
• the produced tube is clean and free of soot so that the manufacturing costs are reduced.
• the absence of the expensive alloy element nickel and the reduction in the content of chromium results in a cost-efficient steel composition.
• the steel alloy according to the present invention is suitable for application of quick welding processes such as MAG or laser beam welding to thereby further significantly reduce costs, when manufacturing compressed gas containers.
• the steel composition according to the present invention can have a tensile strength Rm of ⁇ 950 N/mm 2 , a yield point Rp0.2 of ⁇ 700 N/mm 2 , and a stretch A5 of ⁇ 14%. In-house tests have shown that this steel composition has the required notch impact toughness of ⁇ 35 Joule/cm 2 according to ISA V at ⁇ 40° C.
• the cost saving is especially crucial when producing compressed gas containers on a large scale, e.g. as reaction containers for airbag systems, fire extinguisher containers or compressed gas bottles in beverage vending machines.
• the tube for making the compressed gas container is a seamless precision steel tube made from annealing a hot-rolled, seamless tubular blank until becoming soft, pickling the blank, phosphatizing the blank, soaping the blank, and drawing the blank to form the tube.
• Air hardening step is carried out in a continuous furnace at a temperature of 950° C. ⁇ 15° C. in the presence of inert gas.
• the precision steel tube is straightened and subjected to an inspection, in particular ultrasonic inspection and/or eddy current testing. After cutting the tube to length, each sized tubular section is shaped to produce first the bottom and the neck of a compressed gas container and then shaped into the finished compressed gas container.
• a method of using a steel alloy includes the steps of forming a formed structure; and incorporating the formed structure in light weight steel construction.
• light weight constructions include crash-relevant vehicle parts such as crash boxes, rollover bars, side impact elements or column reinforcements.
• Light weight construction should have a certain strength while still showing certain elasticity (plastic deformation reserve), in order to be able to convert crash energy. The use of super high strength steel is unsuitable because of the limited capability of transformations and the absence of a needed plastic deformation in the event of a crash.
• a steel composition according to the present invention meets these criteria.
• the formed structure may be subjected to high temperature galvanizing.
• High temperature galvanizing even at a temperature of about 600° C. does hereby not adversely affect the strength of the air-tempered and air-hardened steel composition for making the formed structure for light weight steel construction.
• the impact of high temperature galvanizing is positive in conjunction with air-hardened components because the temperature control transforms the components into the air-tempered state which is characterized by increased fatigue strength.
• application of high temperature galvanizing enables each formed structure to be provided with a slight layer thickness of zinc of about 20 ⁇ m to attain a sufficient long term protection against corrosion at slight zinc weights.
• the use of a steel composition according to the invention is especially applicable for light weight purposes as increasingly desired for formed structures, especially in the automobile industry.
• a steel composition according to the invention for making, in particular thin-walled formed structures in light weight steel construction, results in a higher base strength at acceptable stretch. Hardening in the heat impact zones ensures a reliable strength of the welded joints. A slight zinc weight is assured by small layer thickness while affording sufficient protection against corrosion through application of high temperature galvanizing.
• the application of a steel composition according to the invention is especially advantageous in the automobile industry for producing underbody parts such as struts or axle supports, because light weight and protection against corrosion at extreme conditions, as well as fatigue strength in the presence of dynamic loads are relevant criteria for these components. Using aluminum as alternative is not an option because of the significant added costs.
• a method of using a steel alloy includes the steps of forming a tube from the steel alloy; air hardening the tube in the presence of inert gas; and incorporating the tube in the production of a compressed gas container.
• This steel composition is especially suitable, when the wall thickness of the compressed gas container is at least 2 mm. In the event of a wall thickness of less than 2 mm, the steel alloy contains max. 0.2% of Ni.
• a method of using a steel alloy includes the steps of forming a formed structure; air-hardening and tempering the formed structure to have a tensile strength of Rm of >850 N/mm 2 , a yield point Rp0.2 of >700 N/mm 2 , and a stretch A5 of >15%; and incorporating the formed structure in light weight steel construction.
• the formed structure may have a tensile strength of Rm of >950 N/mm 2 , a yield point Rp0.2 of >700 N/mm 2 , and a stretch A5 of >14%.
• the steel alloy can be provided through targeted adjustment of the alloy elements with intended properties such as:
• a steel composition according to the present invention may, in general, contain traces of nickel up to a maximum of 0.20%. This content is the result of steel scrap when melting the steel alloy. The same is true for copper which is encountered as a result of scrap but limited to a maximum of 0.20% by weight.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Heat Treatment Of Articles (AREA)
• Rigid Pipes And Flexible Pipes (AREA)
• Coating With Molten Metal (AREA)
• Heat Treatment Of Steel (AREA)
• Filling Or Discharging Of Gas Storage Vessels (AREA)

Applications Claiming Priority (7)

Related Parent Applications (1)

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Cited By (4)

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Citations (4)

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• 2003
  • 2003-02-11 WO PCT/DE2003/000394 patent/WO2003069005A2/de active IP Right Grant
  • 2003-02-11 JP JP2003568115A patent/JP2006503175A/ja active Pending
  • 2003-02-11 AU AU2003214000A patent/AU2003214000A1/en not_active Abandoned
  • 2003-02-11 EP EP03709605A patent/EP1474538B1/de not_active Expired - Lifetime
  • 2003-02-11 ES ES03709605T patent/ES2276047T3/es not_active Expired - Lifetime
  • 2003-02-11 DE DE50305680T patent/DE50305680D1/de not_active Expired - Lifetime
  • 2003-02-11 AT AT03709605T patent/ATE345403T1/de not_active IP Right Cessation
• 2004
  • 2004-08-05 US US10/911,937 patent/US20050006011A1/en not_active Abandoned

Patent Citations (4)

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