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Colour Coated Sheets

 

Galume Sheets & Coils

 
  The depth of profile and the pitch of colour coated sheets play an important role in their capability to drain water. Profiles with large depths coupled with wider pitch areas are recommended to provide optimum water drainage gutters, especially to suit Indian conditions. All the profiles available at Mamata Agency are chosen keeping in mind the available width of coils in India and optimally use them without sacrificing any of the design factors. This means that the profiles are not burdened with wastages of coil width and slitting costs, making them the MOST COST EFFECTIVE choice from every angle.

Mamata Agency is the authorized distributor of two renowned brands available in India.
 
PRODUCT INTRODUCTION

Definition


GALUME is the trade name for a sheet steel product with a highly corrosion resistant coating containing nominally 55% aluminium and 43% zinc, by weight; the balance, primarily silicon, is used to effect excellent adhesion to the steel substrate. This metallic coating, which is applied using a continuous hot-dip coating process, combines the galvanic corrosion protection of zinc with the barrier protection of aluminium.

Product Introduction GALUME is the world's fastest-growing metallic coating. This position has been earned by marrying the strength, formability and recyclibility of steel with the proven long-term anti-corrosion performance of the Al-Si-Zn coating. This marriage results in an economical product with the superior eco-friendliness attributes of durability, recyclibility, energy-efficiency and scarce-resource utilization.

GALUME also displays excellent heat reflection properties, similar to aluminized steels, and is more resistant to higher temperatures than hot-dip galvanized steel. Its will maintain its bright appearance and reflectivity in prolonged exposures at temperatures of 320° C and is not heavily oxidized by continuous exposure to temperatures of up to 650° C. these high temperature oxidation and heat resistance attributes of GALUME enable the potential applications to be expanded beyond the traditional metal building market. In particular, automotive exhaust systems, furnace and oven hardware, and white goods that require heat resistance [ovens, cookers, etc.] also used for Roofing and cliding, pre-painted sheets, air conditioners, refrigerators and ductings etc. are potential applications of GALUME.

Basic difference in production of Galume 55% AlSi-Zn as against Galvanized

The most signiifacnt processing difference is the composition of the coating bath; the bath for 55% AlSi-Zn coated sheet production is comprised of a 55% AlSi-Zn coated alloy rather than near pure zinc for galvanized sheet. The 55% AlSi-Zn coated bath is operated at a higher temperature (660° C or 1120° F) than the zinc bath used for galvanizing which is operated at about 450° C (840° F). the higher temperature for 55% AlSi-Zn coated is required because of the higher melting point of the 55% AlSi-Zn coating alloy. The melting point of the 55% AlSi-Zn alloy is about 580°C (1180°F) while that of the zinc coating is about 417°C (780°F). because of the higher bath temperature and the increased corrosiveness of the aluminium rich alloy, the 55% AlSi-Zn coated pot is lined with a special refractory and is induction fired. The general galvanizing principle of the strip heating the bath metal does not apply to 55% AlSi-Zn coated, where the strip entering the bath considerably cooler than the bath (depending on base quality). Much of the bath's heat is derived from the operation of the inductors.

Prior to the strip entering the coated bath, the hydrogen content of the protective atmosphere is increased for 55% AlSi-Zn coated compared to galvanized to provide maximum protection for the strip and to minimize oxidation of the bath surface.

After coating, in the ‘upleg' as the strip raises in the cooling tower, air is blown onto the surface to cool the coating at a specified rate for generating the required coating microstructure for optimum corrosion resistance, also fast cooling arrangement, resin coater, Induction Furnace for resin coater.
 
S. No. Parameters Technical details / specifications / Stds
1 Product Name GALUME
2 Reference standard ASTM A 792/ A 792M
3 Other ref: standards En 10326/ En 10327 , AS 1397, JIS G 3321
4 Chemical composition (base metal) Low carbon steel
%C: 0.12 max, % Mn: 1.2 max
%S: 0.0 max, %P: 0.003 max
5 Strip thickness mm 0.20 to 1.5 (< 0.20 & above 1.5 in special cases)
6 Strip widths mm 900 to 1250 mm
7 Chemical Composition (Coating) 55% Al. 43% Zinc with 1.6% Silicon
8 Yield Strength MPA
Tensile Strength MPA
340 Min for GR 50 & 550 Min for GR 80
410 Min for GR 50 & 570 Min for GR 80
9 % Elongation as per ASTM Std.
10 Coating Mass Gms / m2 70 to 165
11 Coating Class AZM 150 / 165 as per ASTM Std.
12 Surface Condition / Treatment Spangle skin passed- Surface Chrome Passivated & oild/ Resin Coated
Surface Treatement Chemicals from M/s Henkel Chembond
13 Testing of mech properties ASTM - A 924 / A 924M
14 Microstructure design Galume Structure consists of two layers of Al-Zn ovelay coat and containing intermetallic / alloy layer. Al gives barrier protection and Zn given sacrificial Galvanic protection to the steal substrate
15 Resistance to corrosion - Salt spray life Min Hrs (ASTM B 117) 1000 HRS corrosion 5 % (max) for Acrylic coated
16 Heat resistance and heat reflectivity properties Due to bright surface & find spangles excellent heat reflectivity up to 315 c. & due to high Aluminium content, Galume has heat (oxidizing) resistance up to > 320 c without discoloration and without impalrment of its alloy coating
17 Proudct certification All products are accompained with MTC
 
Here are the advantages of Galvalume roofing sheets:
• Durable and strong
• One of the most thermally efficient roofing materials available today
• Superior corrosion resistance
• Attractive
• Available from an extensive network of suppliers
• A deterrent against intruders
• Excellent resistance to impact from hail
• Excellent flexibility in design, can be curved, for truly individual designs
• Flexibility of design allows for both traditional straight roof sheeting as well as innovative curved roofing designs
• Easy maintenance
• Weather tight and secure when installed to manufacturer's specifications.
 
Recommended Roof Pitch
After extensive research, study and tests, the bureau of Indian Standards has recommended roof pitch of 18.3 degrees as best suited and optimal for all Indian conditions. We subscribe to standardization process. However, designers are free to choose slope of their choice keeping factors like heat dissipation, operational requirements, energy conservation and environmental factors in mind. Profile is suitable for adaptation to slope as designed.
 
Recommended Thickness
• Al-Zn alloy coated steel (550 MPa): 0.50 mm TCT
• Pre - painted galvanized steel (240 MPa): 0.60 mm TCT
• Pre - painted Al-Zn alloy coated steel (550 MPa): 0.50 mm TCT
• BHP Galvalume: 0.5 mm
• PPGI : 0.6 mm
 
Available Lengths
• Standard lengths 2 m, 2.5 m, and 3 m.
• A-la-carte lengths 300 mm to 15m. Lengths above 7 m will however require special transportation.
• Lengths beyond 12 m require special trailers that may not be easily available.