SE448310B - Hot dip coating of ferrous metal with aluminium-zinc alloy - using protective atmos. of hydrogen and nitrogen with very low dew point - Google Patents

Hot dip coating of ferrous metal with aluminium-zinc alloy - using protective atmos. of hydrogen and nitrogen with very low dew point

Info

Publication number
SE448310B
SE448310B SE7800147A SE7800147A SE448310B SE 448310 B SE448310 B SE 448310B SE 7800147 A SE7800147 A SE 7800147A SE 7800147 A SE7800147 A SE 7800147A SE 448310 B SE448310 B SE 448310B
Authority
SE
Sweden
Prior art keywords
dew point
hydrogen
protective
gas
aluminum
Prior art date
Application number
SE7800147A
Other languages
Swedish (sv)
Other versions
SE7800147L (en
Inventor
L B Caldwell
J J Connolly
Original Assignee
Bethlehem Steel Corp
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 Bethlehem Steel Corp filed Critical Bethlehem Steel Corp
Priority to SE7800147A priority Critical patent/SE448310B/en
Publication of SE7800147L publication Critical patent/SE7800147L/en
Publication of SE448310B publication Critical patent/SE448310B/en

Links

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
    • 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
    • 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
    • C23C2/04—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
    • C23C2/12—Aluminium or alloys based thereon
    • 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
    • C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
    • C23C2/36—Elongated material
    • C23C2/40—Plates; Strips

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Coating With Molten Metal (AREA)

Abstract

Parent Patent described the coating of a ferrous metal profile with a molten alloy of Al and Zn, effected in a hood contg. hot gas of compsn. by vol. 20% min. H2, balance N2 and dew point (d.pt) max. -18 degrees C. In this addn. the profile is fed continuously through a protective hood and into a bath contg. 25-70 wt % Al, rest Zn, the surface of the bath being covered by gas fed into the hood at min. 400 degrees C, and contg. by vol. min. 6% B2, pref. 615% H2, balance N2 and max. d.pt. -73 degrees C. Part of the gas circulates near the inlet for the profile, and part flows in counter-current to the profile. Only 6-15% H2 is needed to protect the ferrous profiles from oxidn. when the d.pt. is below -73 degrees C.

Claims (1)

1. v44sa1u i oz -ning avser sålunda ett sätt, enligt vilket ett band av järnmetall bclägges med*en legering av aluminium och zink genom en varmdopp- överdragningsmetod, där den reducerande skyddsatmosfären, som användes i metoden, är korrelerad på sådant sätt att man undviker mf oxidation av badets yta inom skyddskâpan, genom vilken bandet av järnmetall_passerar in i beläggningsbadet. Närmare bestämt inne- fzzefl für fattar den reducerande skyddsatmosfären en gas, som är uppvärmd till en temperatur på minst 399°C, vilken gas innehåller från 6 till :fl l5vol% väte och resten väsentligen kväve, och som har en daggpunkt" ej överstigande ca ~73°C, då den införes i skyddskåpan. Minst en väsentlig del "färsk skyddsgas får komma i kontakt-med eller 'svepa_över den del av det smälta beläggningsbadet, som befinner sig inom kåpan, innan den passerar i motström i förhållande till -bandets rörelse längs bandet. Man har nu upptäckt att sambandet mellan väteinnehållet och_ den varma reducerande atmosfärens daggpunkt kan utvidgas utöver de tidigare kända gränserna till värden så låga som 6-15 % väte med daggpunkter lägre än ca ~73°C. Denna upptäckt var mycket överraskande eftersom man hittills ansett att höga väteinnehâll i den reducerande atmosfären erfordrades i närvaro av det smälta beläggningsbadet, som innehöll höga halter aluminium, såsom det beläggningsbad av aluminium och zink, som avses enligt uppfinningen. På en värmedoppöverdragningsanordning, som arbetar vid hastigheter upp_till l64O m/min (5OQ'fipm) och med gasflödeshastigheter på 300 m3/h 'erhölls exempelvis ett aluminiumzinkbelagt.band, som var utan I kraterbildning och järnfläckar med'en reducerande atmosfär (1) som uppvärmts till minst-39990 (2y, vilken atmosfär hade ett genom- snittligtfväteinnehållrpå lO % och resten kväve, och (3) hade en daggpunkt på ca ~80?C;f:_» __ 'i ÉÅTENTKRÅV* _ _ _ 1Sätt"att_bildafen beläggning på ett järnunderlag med I en aluminiumfsinklegering bestående huvudsakligen y av 25-70 vikt% aluminium ooh resten väsentligen zink, varvid _ j järnunderilàgeti"bringasffipassera 'genom en. skyddskåpa in i ett i smält had av ïegefinggfi,sjärnunderlaget_och.delen av-ytan av deff smälta oibadéf' 150m s-kyaaskâpan kontinuerlig: utsattes _ för varm gas, som då den iniöres i skyddskåpan har en tempe- ratur pä-minstr399?C, odh varvid åtminstone en del av den .vi Ü] ' få; *W Všb h: .\¿_'”l th! u; :RM u*|\ tt44ßts1o xzzarmaïgasen först pringas att evepa över badets' yta vid det omrâde) .där jarnunderlaget inträder Ai badet, och eedan strömma ilrnotström mot järnnnderlagßatš röreleseritktning, ktä n n e - t e C k arta-t 'av att den vafma gas-en innefattar från 6 till l5 vol% gíväte och :festen väsentligen kväve och har en dagg- punktteljí överstigande -73°C._ I1. v44sa1u in oz -ning thus relates to a method in which a strip of ferrous metal is coated with * an alloy of aluminum and zinc by a hot dip coating method, wherein the reducing protective atmosphere used in the method is correlated in such a way that avoids mf oxidation of the bath surface within the protective cover, through which the strip of ferrous metal_passes into the coating bath. More specifically, the reducing protective atmosphere comprises a gas which is heated to a temperature of at least 399 ° C, which gas contains from 6 to: 25% vol% hydrogen and the remainder substantially nitrogen, and which has a dew point "not exceeding approx. ~ 73 ° C, when inserted into the protective cover. At least a substantial portion of "fresh shielding gas" may come into contact with or sweep over the portion of the molten coating bath located within the cover before passing in countercurrent to the band. movement along the band. It has now been discovered that the relationship between the hydrogen content and the dew point of the hot reducing atmosphere can be extended beyond the previously known limits to values as low as 6-15% hydrogen with dew points lower than about ~ 73 ° C. This discovery was very surprising since it was hitherto considered that high hydrogen contents in the reducing atmosphere were required in the presence of the molten coating bath containing high levels of aluminum, such as the aluminum and zinc coating bath contemplated by the invention. On a heat dip coating device operating at speeds up to 640 m / min (50 ° F heated to at least-39990 (2y, which atmosphere had an average hydrogen content of 10% and the remainder nitrogen, and (3) had a dew point of about ~ 80? C; f: _ »__ 'in ÉÅTENTKRÅV * _ _ _ 1Sätt" att_bildafen coating on an iron substrate with an aluminum phinc alloy consisting mainly of 25-70% by weight of aluminum and the remainder essentially zinc, the iron substrate being "passed through" through a protective shell into a molten had of the finger, the substrate deff melt oibadéf '150m s-kyaaskäpan continuously: exposed to hot gas, which when it is inhaled in the protective cabinet has a temperature of at least 399? C, odh whereby at least part of it .vi Ü]' få; * W Všb h:. \ ¿_ '”l th! u;: RM u * | \ tt44ßts1o xzzarmaï the gas is first forced to sweep over the surface of the bath at the area). vol% gíväte och: festen essentially nitrogen and has a dew point exceeding -73 ° C._ I
SE7800147A 1978-01-05 1978-01-05 Hot dip coating of ferrous metal with aluminium-zinc alloy - using protective atmos. of hydrogen and nitrogen with very low dew point SE448310B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
SE7800147A SE448310B (en) 1978-01-05 1978-01-05 Hot dip coating of ferrous metal with aluminium-zinc alloy - using protective atmos. of hydrogen and nitrogen with very low dew point

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
SE7800147A SE448310B (en) 1978-01-05 1978-01-05 Hot dip coating of ferrous metal with aluminium-zinc alloy - using protective atmos. of hydrogen and nitrogen with very low dew point

Publications (2)

Publication Number Publication Date
SE7800147L SE7800147L (en) 1979-07-06
SE448310B true SE448310B (en) 1987-02-09

Family

ID=20333611

Family Applications (1)

Application Number Title Priority Date Filing Date
SE7800147A SE448310B (en) 1978-01-05 1978-01-05 Hot dip coating of ferrous metal with aluminium-zinc alloy - using protective atmos. of hydrogen and nitrogen with very low dew point

Country Status (1)

Country Link
SE (1) SE448310B (en)

Also Published As

Publication number Publication date
SE7800147L (en) 1979-07-06

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