Metal working – Method of mechanical manufacture – Combined manufacture including applying or shaping of fluent...
Patent
1995-05-30
1997-09-16
Arbes, Carl J.
Metal working
Method of mechanical manufacture
Combined manufacture including applying or shaping of fluent...
295272, 427239, 427433, 4274342, B21B 142
Patent
active
056667140
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The following invention relates to a method of manufacturing galvanised open or closed steel sections. More particularly, though not exclusively, the invention relates to the manufacture of galvanised pipes.
PRIOR ART
Conventional hot dip galvanising processes rely on acid pickling to ensure a clean steel surface which facilitates the subsequent metalurgical bonding of zinc to the steel in the galvanising bath. The steps of pickling and rinsing involve high space requirements, high operating costs, the requirement of effluent streams and their associated, and increasing, burden in treatment activities.
OBJECT OF THE INVENTION
It is the object of the present invention to remove the need for pickling and subsequent rinsing in a hot dip galvanising process.
DISCLOSURE OF THE INVENTION
This invention in one broad form provides a method of manufacturing galvanised open or closed steel sections, the method comprising a roll forming process followed by a hot dip galvanising process, in-line shot blasting prior to forming the strip into an open section or hollow welded section, solution, and rinsing step.
By way of the above described process, the requirement of pickling the surfaces and the necessary subsequent step of rinsing the acid residues prior to fluxing is eliminated.
Preferably, the in-line shot blasting step occurs after accumulation.
Preferably, the abrasive action of the blasting is designed to achieve a Class 21/2 finish.
Preferably, a synthetic water based lubricant is used as a mill coolant in the process.
Preferably, the mill coolant is passed through a cleaning or filtration station to remove suspended solids from the mill coolant prior to use in the forming process.
Preferably, in a welding step of the process, use is made of air cooled or reverse flow impeders.
DEFINITIONS
As used herein the phrase "open section" means a formed steel structure having U-shaped channels, V-shaped channels, open boxed channels, typically roll formed from a flat sheet. For example, a corrugated sheet having smooth corrugations, square corrugations or V-shaped corrugations is intended to fall within the scope of the term "open section".
The term "hollow welded section" is intended to encompass any closed section such as for example a circular pipe, or pipe of other cross section or shape, square or rectangular duct or any other form of closed cavity wherein transversely opposed longitudinal edges are mutually welded together to inscribe a closed space.
BRIEF DESCRIPTION OF THE DRAWINGS
A preferred form of the present invention will now be described by way of example with reference to the accompanying drawings, wherein:
FIG. 1 is a schematic flow chart of the process steps in pipe making, and
FIG. 2 is a schematic flow chart of the subsequent steps in a hot dip galvanising process.
DESCRIPTION OF A PREFERRED FORM OF THE INVENTION
FIGS. 1 and 2 set out the two parts in the formation of hot dip galvanised pipe. In each of the two processes shown, those being pipe making and hot dip galvanising, the top line of boxes represent individual stages in conventional manufacture. However, one additional step to the conventional process is the addition of filtration to the mill coolant to and from the forming location.
In the pipe making process, the additional process steps are shown below the horizontal dotted line A.
In the hot dip galvanising process, the optional degrease and rinse steps in the conventional process are illustrated in a dotted box B.
Conventional fully hot dip galvanising of electric resistance welded (ERW) steel pipe involves a processing train with the steps of degreasing, rinsing, pickling, rinsing, fluxing, galvanising, quenching, coating and collection as depicted in FIG. 2.
The first two stages are required if the steel surfaces are contaminated with grease or oily films. Both can usually be waived if synthetic mill lubricants are employed in place of oil based emulsions as coolants in the pipe making processes.
The pickling section is necessary in order to pr
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Height Trevor Maxwell
Shester Gary Anthony
Sutton Ross Herbert
Arbes Carl J.
Tubemakers of Australia Limited
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