Steel – specified (& recycled) more than any other metal
Steel is the metal alloy produced from iron (Fe) when the Carbon (C) content is < 2%. Iron ore is an abundant natural resource found in concentrations up to 70% purity. The recipe for steel also includes smelted iron, limestone and coke to create new “primary” steel. The basic oxygen furnace (BOF) remains the primary mill “technology” that produces over 60% of the World’s steel supply. At the end of it’s useful life, steel is collected, reduced to scrap, remelted, cast and rolled into new products thanks to the lower energy requirements of the electric-arc furnace (EAF) that can use 100% steel scrap or highly concentrated direct-reduced-iron (DRI).
- iron is an abundant natural resource with richest deposits in: Australia, Brazil, South Africa
- metals smelted from high-purity ores reduce the overall impact
- high purity of iron ore, limestone, & coal gives steel a low carbon footprint
- high strength-to-weight ratio, low thermal movement, and ability to be easily formed
- steel is typically the low-cost architectural-metal
- Unlimited color & texture possibilities
The best metal roof, facade, gutter, flashing & trim applications deserve the highest quality metal: copper, zinc, & stainless steel for the appropriate applications create long-term solutions. But if the initial cost, carbon footprint or limited color selection is an issue, color-coated steel may be your best material choice.
- steel grades typically produced according to ASTM A1008 (cold-rolled steel) provides a wide range of steel alloy chemistry & physical properties. The most important metal property is yield strength which can be customized at the mill to optimize the steel for specific applications:
- Custom low-yield “foldable” steel similar to EDDS (Grade 23). Ideal for DLSS/ mechanical-lock roofing panels & where superior “crafted” roofing details are required (*see below).
- Custom high-yield “foldable” steel similar to a Structural Grade 30. Ideal for roof drainage components requiring tight seams with moderate stiffness (downspouts, elbows, etc.)
- Commercial Grade (CS, type B) & Structural Grade 33 for tile-effect panel profiles or mild formability
- Structural Grade Grade 40 & Gr50 are popular for snap-seam/ snap-lock standing-seam profiles and structural standing-seam profiles spanning open framing.
- Structural Grade 80 for very thin steel thickness (28 ga. or less), added stiffness or for dent resistance.
- corrosion protection of steel is applied by a continuous hot-dipped galvanizing bath. While zinc’ sacrificial nature helps protect the steel in most applications, alternative strategies that include large quantities of aluminum assisted by Silicon, Magnesium or both have gained market share for organic paint coatings. The thin metallic-coating beneath prepainted steel is typically one of the following:
- Galvanizing ASTM A653 100% Zn
- AlZn alloy
- Galvalume® ASTM A792 55% Al + 43.5% Zn + 1.5% Si
- ZINCALUME® ASTM A792 55% Al + 43.5% Zn + 1.5% Si
- Aluzinc® ASTM A792 55% Al + 43.4% Zn + 1.6% Si
- ZnAlMg alloy
- SuperDyma™ ASTM A1046 85.8% Zn + 11% Al + 3% Mg + 0.2 Si (ZalMag)
- ZAM® ASTM A1046 91% Zn + 6% Al + 3% Mg
- Magnelis® EN 10346 93.5% Zn + 3.5% Al + 3% Mg
- pretreatment of the the metallic-coated steel surface is necessary to maximize the adhesion of teh paint system. Application of a various types of thin organic coating (TOC) which traditionally have included chemicals that pose a risk to humans and the environmental are now coming under greater scrutiny:
- conversion coatings zinc phosphate, chromate-free, ??ask-your supplier
- primer epoxy, polyester, urethane
- coil-coated paint systems: PVDF, Urethane, Polyester, SMP, PVC/ Plastisol, BT (bio-content) resins
- clear-coat metallic-coated steel: Acrylic
Why Nordic-quality Steel from SSAB?
- Transparency – Mill-Certs confirm steel quality testing … and the mill location – Architects can SPECIFY
- undergound mines in Northern Sweden with very low phosphorus produces “clean” steel
- mid-size mill with quality reputation with significant assets & employees in Nordic countries & USA
- Eco-initiatives: low-impact plants, CO2-free steel R&D, Cr-free pretreatment, bio-based paint
- Product specific EPD from SSAB: download the GreenCoat EPD.
* foldable steel bridges the gap between the natural metals that are very malleable and tradition mild carbon-steel that is better suited for snap-seam panels applications rather than architectural double-lock standing seam profiles (1″ & 1.5″ seam heights). A softer steel with virtually no “spring back”, GreenCoat PLX Pro BT allows better seam folding and crafted detail execution that helps the installer create a higher quality steel roof and reduced demand for sealant. In addition, all PLX foldable steel also has a heavy G115 galvanizing layer for added protection below the paint.
Find more GreenCoat product information at: www.ssab.us/GreenCoat
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