Coating processes – Immersion or partial immersion – Molten metal or fused salt bath
Patent
1998-01-09
2000-03-28
Beck, Shrive
Coating processes
Immersion or partial immersion
Molten metal or fused salt bath
427329, 427328, 4273981, 427367, 427436, 295274, 72 47, 723652, B05D 118, B05D 312, B21B 146
Patent
active
060428910
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to roll forming structural steel profiles with galvanised coating and has been devised particularly though not solely for roll forming profiles from hot rolled steel strip.
BACKGROUND ART
It is well known to provide in-line galvanising of steel sections such as round tube where the section is formed to substantially the desired shape and then passed through an in-line galvanising bath or trough to provide the coating of galvanising material which is typically zinc. This works well for most closed sections but problems are encountered with some open profile shapes, such as channels, in obtaining an even coating of galvanising material after the bath due to the difficulty in quickly blowing excess material from various areas of the section.
It has also been known to form open structural profiles of galvanised steel by taking pre-galvanised flat steel strip and roll forming that strip to the desired profile, e.g. angle or channel sections by a conventional roll forming process. The bending of the flat strip in the roll forming process does however impose significant elongations of the outer surface of each corner formed when the strip is thick enough to form a structural profile. (Throughout this specification the term "structural profile" is taken to refer to profiles formed from strip having a thickness generally greater than 2 mm.) To deal with this situation, the industry standard has been to use a zinc coating where the galvanising material incorporates alloys such as aluminium and where the base metal strip to which the galvanised coating has been applied is formed either by the cold rolling process or by hot rolled, pickled and oiled. The combination of the cold rolled steel base layer and significant percentages of alloy in the zinc coating when correctly applied according to known processes results in a thin and ductile galvanising layer on the base metal which can withstand the significant elongation required in the bending of corners during the roll forming of the structural profile.
However there are instances in the manufacturing process where the zinc coating may not always be correctly applied according to the most desirable parameters and in such cases less ductile coatings than desired result which in some instances can crack through significant elongation of the outer surface during the roll forming process. This problem may also exist where the strip has been galvanised in simpler galvanising operations which do not use aluminium alloys or where the parent material has a surface which can be regarded as highly reactive to the galvanising process (such as shot blasted strip).
When using both cold rolled and hot rolled base material it is desirable to provide a method of forming a structural section where some allowance can be made for less than ideal zinc coating parameters so that forming of the material to the desired shape after galvanising has taken place does not result in unacceptable levels of cracking in the zinc layer.
SUMMARY OF THE INVENTION
The present invention therefore provides a method of manufacturing a continuous length of steel having a structural profile incorporating at least one corner of predetermined included angle and a coating of galvanising material. The method includes the steps of: partially bent to an included angle significantly greater than the predetermined included angle, applying the coating of galvanising material by passing the preformed profile through an inline galvanising stage, rapidly quenching the profile exiting from the in-line galvanising stage, and further roll forming the profile to the desired structural profile.
In one form of the invention the steel strip comprises hot rolled steel strip.
Preferably the hot rolled steel strip is shot blasted to clean its surfaces prior to galvanising.
Preferably the steps of forming the corner in the preformed profile and further roll forming to conform the corner to the predetermined included angle together comprise constant length bending of the corner.
Prefera
REFERENCES:
patent: 3607366 (1971-09-01), Kurokawa
patent: 3696503 (1972-10-01), Krengel et al.
patent: 4123261 (1978-10-01), Moren et al.
patent: 4237154 (1980-12-01), Garrison
patent: 4358887 (1982-11-01), Creps
patent: 4533606 (1985-08-01), Teng et al.
patent: 5666714 (1997-09-01), Height et al.
Crossingham Brian Roy
Dickson Andrew Robert
Langford Rodney Matthew
Moore Douglas Ian
Townsend Darrell St Clair
Barr Michael
Beck Shrive
Tubemakers of Australia Limited
LandOfFree
Roll forming structural steel profiles with galvanised coating does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Roll forming structural steel profiles with galvanised coating, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Roll forming structural steel profiles with galvanised coating will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1324097