Classifications

• • 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
  • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
  • C23C4/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21B—ROLLING OF METAL
  • B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
  • B21B45/04—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for de-scaling, e.g. by brushing
  • B21B45/08—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for de-scaling, e.g. by brushing hydraulically
• • 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
  • C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
  • C21D8/08—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires for concrete reinforcement
• • 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
  • C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
• • 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
  • C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
  • C23C2/024—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by cleaning or etching
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21B—ROLLING OF METAL
  • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
  • B21B1/38—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling sheets of limited length, e.g. folded sheets, superimposed sheets, pack rolling
  • B21B2001/383—Cladded or coated products

Definitions

• the invention relates to a method for treating rolled steel, in particular reinforcing steel, prestressing steel or the like, to increase the corrosion resistance by applying a coating of a non-ferrous metal, preferably zinc, the rolled steel being descaled from the rolling heat and then preventing scale from forming again on the hot rolled steel the coating is applied.
• a non-ferrous metal preferably zinc
• Rolled steel products are used, among other things, in construction as structural steel, here primarily in the form of reinforcing steel, as prestressing steel for prestressed concrete and for anchoring for ground and rock anchors, etc.
• an alkaline solution with a pH value of more than 12 is formed by dissolving the lime particles contained in the cement.
• an iron oxide cover layer forms on the surface of the reinforcement elements, which passivates the steel surface and protects it from surface corrosion .
• the reinforcement elements are usually located in the edge areas of the components, where they join certain minimum distance to the outer surface, the so-called concrete cover, must be observed. Due to air pollution, especially in bridge structures, due to the increasing use of de-icing salts for the removal of snow and ice, chlorides dissolved in these media, with insufficient, often sufficient, concrete cover, have the opportunity to penetrate to the steel, where they destroy the passivation layer and so on can attack the steel directly. The same applies to the tension members of earth and rock anchors, where the corrosive influence of the steel is caused by soil moisture, water and acidic soil components. For this reason, there is a need for additional corrosion protection measures for such rolled steel products used in construction.
• metals in particular ferrous metals
• a thin zinc layer as rust protection.
• Various methods are known for this.
• hot or hot galvanizing the parts to be protected are immersed in a bath of molten zinc, which can also be alloyed with aluminum if necessary.
• Acidic sulphate, sulphate chloride or cyanide-caustic baths are used for electrolytic or galvanic galvanizing.
• metal coatings by spraying the metal in liquid form, the metal being fed to a spray gun in wire or powder form, melted by oxygen / fuel gas mixtures and atomized by compressed air.
• the rolled stock is passed through a closed chamber filled with a deoxidizing gas, preferably carbon monoxide, in which the carbon monoxide burns to carbon dioxide, at a temperature of approximately 980 to 760 degrees C.
• a deoxidizing gas preferably carbon monoxide, in which the carbon monoxide burns to carbon dioxide
• the rolling stock passes through another chamber, in which it e.g. is coated with zinc in the form of zinc powder, which melts as a result of the heat still inherent in the rolling stock. Since the coated rolling stock still has a temperature of approx. 700 to 600 degrees C when it leaves this chamber, it must be cooled down immediately after coating in order to prevent the applied zinc powder from burning to zinc oxide.
• This process is also relatively complex. Keeping the descaled surface of the rolling stock clean by means of an atmosphere of deoxidizing gas requires not only its provision, supply and maintenance of a deoxidizing atmosphere in a correspondingly sealed chamber, but also the maintenance of a corresponding temperature before the rolling stock after the Coating is quickly cooled using other media.
• the invention is based on the object of being able to coat rolled steel products in a continuous operation immediately following the rolling process, utilizing the rolling heat and thereby keeping the procedural and apparatus expenditure as low as possible.
• this object is achieved in that the rolling steel is subjected to press water in a continuous continuation of the rolling process for descaling, that the steel surface immediately after the descaling to prevent the formation of new scale by application of water quickly to a temperature of below 600 degrees C. is cooled and that the coating is then applied.
• the advantage of the invention is to be seen primarily in the fact that only one medium, namely water, is used both for descaling and for preventing the new formation of scale, and at the same time for cooling, so that the cooling can be carried out in such a way that the rolling heat can be optimally used for the coating. It is thereby achieved that all process steps or treatment processes can proceed in a continuous continuation of the rolling process, that is to say at the rolling speed, so that the finished coated product leaves the production line in an analogous manner to a normal, non-post-treated rolled product.
• the phenomenon is exploited that the scale adhering to the rolled steel from the rolling process, that in the last roll stand deformation of the rolling stock, for example during a transition from an oval to a circular cross-section, has already been loosened relatively easily immediately after the rolling stock has left the rolling stand.
• the pressure of the press water should be over 200 bar, preferably 300 to 400 bar; if necessary, it can be increased to around 1,000 bar. This requires only a very short treatment, namely the passage of the rolled steel through a spray nozzle, which results in an insignificant reduction in the temperature of the rolled steel.
• the descaling is carried out by press water from the rolling heat at a temperature of about 900 to 1,000 degrees C
• the cooling is carried out in a continuous pass by using the same medium in such a way that the scaling temperature of 600 degrees C is as rapid as possible is below that no new scale can form and temperatures are reached at which the coatings can be applied.
• This can be done according to the invention in that the rolled steel is passed through a water bath or sprayed with water.
• Suitable temperatures for applying corrosion-resistant coatings are, for example, a temperature of approximately 560 to 570 degrees C for pure aluminum and a temperature of approximately 415 degrees C for pure zinc; intermediate stages can be activated for alloys.
• it is readily possible to use any desired alloy for the coating since, starting from the rolling heat until it is completely cooled, all temperature ranges are run through.
• the coating can be applied in any way.
• the non-ferrous metal forming the coating can be sprayed on in powder form, whereby it melts; the Rolled steel can also be passed through a bath with the liquid non-ferrous metal.
• this treatment can also be carried out in the form of heat treatment methods known per se using water.
• One such process is the process known, for example, for low-carbon and therefore weldable concrete steels under the name "Tempcore” process, in which the water treatment is carried out in such a way that an edge zone consisting of martensite and bainite is present in the rolled steel immediately after quenching, while that remaining in the steel core Heat content during the subsequent cooling does not cause the edge zone to temper beyond the bainite stage.
• the water treatment is carried out in such a way that the steels are quenched from a final rolling temperature between 860 and 1,060 degrees C in such a way that the surface layer forms a completely martensitic structure and the temperature of the surface layer is compensated for by temperature compensation in the period between 2 to 6 seconds after the start of the quenching process is 400 to 500 degrees C.
• the cooling to be carried out according to the invention can be used in a particularly advantageous manner to improve the strength of the steels.
• a further advantage of the invention lies in the fact that all work steps are carried out in a continuous process immediately following the rolling process in individual treatment stations downstream of the last rolling stand. While the rolling process, which is inevitably discontinuous due to the rolling of billets, has largely evened out until the last rolling stand is left, the method according to the invention naturally also has particular advantages if the rolling process has previously been made endless by welding the billets. This is achieved in a particularly advantageous manner by the known flash butt welding of the billets in the area between leaving the furnace or leaving a trio mill stand and the first tapping of the fine rolling mill.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Physics & Mathematics (AREA)
• Plasma & Fusion (AREA)
• Manufacturing & Machinery (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Metal Rolling (AREA)
• Heat Treatment Of Steel (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Preventing Corrosion Or Incrustation Of Metals (AREA)
• Coating With Molten Metal (AREA)
• Prevention Of Electric Corrosion (AREA)
• Pit Excavations, Shoring, Fill Or Stabilisation Of Slopes (AREA)
• Excavating Of Shafts Or Tunnels (AREA)
• Electric Cable Arrangement Between Relatively Moving Parts (AREA)
• Laminated Bodies (AREA)
• Heat Treatment Of Articles (AREA)
• Heat Treatments In General, Especially Conveying And Cooling (AREA)
• Heat Treatment Of Strip Materials And Filament Materials (AREA)
• Electroplating Methods And Accessories (AREA)
• Reduction Rolling/Reduction Stand/Operation Of Reduction Machine (AREA)
• Rolls And Other Rotary Bodies (AREA)
• Chemical Treatment Of Metals (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (3)

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Family Applications (1)

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• 1987
  • 1987-09-01 DE DE3729177A patent/DE3729177C1/de not_active Expired
• 1988
  • 1988-08-17 DK DK460688A patent/DK460688A/da not_active Application Discontinuation
  • 1988-08-18 HU HU884397A patent/HU203586B/hu unknown
  • 1988-08-24 NO NO883781A patent/NO176578C/no unknown
  • 1988-08-25 PL PL1988274389A patent/PL158408B1/pl unknown
  • 1988-08-26 EP EP88113916A patent/EP0305914B1/de not_active Expired - Lifetime
  • 1988-08-26 ES ES198888113916T patent/ES2028964T3/es not_active Expired - Lifetime
  • 1988-08-26 SU SU884356320A patent/SU1674689A3/ru active
  • 1988-08-26 DE DE8888113916T patent/DE3866998D1/de not_active Expired - Fee Related
  • 1988-08-26 AT AT88113916T patent/ATE70568T1/de not_active IP Right Cessation
  • 1988-08-29 DD DD88319281A patent/DD282246A5/de not_active IP Right Cessation
  • 1988-08-30 PT PT88371A patent/PT88371B/pt not_active IP Right Cessation
  • 1988-08-31 CN CN88106460A patent/CN1031724A/zh active Pending
  • 1988-08-31 JP JP63215357A patent/JPS6475692A/ja active Granted
  • 1988-08-31 CA CA000576161A patent/CA1306391C/en not_active Expired - Fee Related
• 1992
  • 1992-03-18 GR GR920400458T patent/GR3004067T3/el unknown

Non-Patent Citations (1)

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