By Karen Knapstein
You will get efficient and thoughtful service from Hunter Special Steel Co., Ltd.
If you don’t know what to ask for, odds are you won’t get what you need. Asking the right questions is the first step in getting the coil you need to fill your customers’ orders to their satisfaction. Coil width and thickness are two of the most obvious factors that affect metal forming. They influence the quality of the final product, the performance of the machine, and the amount of sale-able material you can get out of a coil. 3GM Territory Manager Adam Buck, who has 15 years of experience in metal roofing manufacturing and sales, shares his insights about metal coil size and thickness.
Adam explains the standard coil widths for different gauges: “The industry standard width for 29 ga. coil is 40.875”. Some people will order that material in 41” because they want to make the underlap and overlap on their metal panel a little bit wider.” However, he estimates more than 99% of what people use to make 29 ga. ag panel and residential panel is 40.875” wide.
The thicker 26 ga. material, commonly used to make R panel or PBR panel, comes in 41.” and 43”-wide coil.
Users should be cautioned: The wider material won’t fit through all machines. The width tolerance is the difference between the lower and upper limit dimensions that a roll former will accept. The guides in the roll forming machine will determine that tolerance.
“A lot of people want an ag panel rib height of 7/8” but want it in 26 ga. but they don’t want to pay a processing company to slice the material down,” Adam explains. “So they often ask if the 26 ga. material will run through an ag panel line. The answer to that is ‘Some do, some don’t.’ It depends on the guides in the machine.” Roll formers need to measure the guides to see if the larger coil will work in their machine.
You can count on the consistency of the coil width if you buy from a reputable supplier. Adam says if you order a coil 40 7/8” wide, it will be 40 7/8” wide — but there could be a very small variation (+/- 1/16”). If it does vary a little bit, you may have to adjust the guides on your machine to make sure their overlap stays long enough for the panel to lap properly. “You can’t really steal from the overlap side of the panel; you must steal from the underlap side when you’re adjusting your machine,” he continues. “There’s very little extra material to play with.”
When addressing coil thickness, the main thing Adam stresses is the yield — the weight per linear foot (pounds/foot). The pounds per foot is the weight of 1’ of a specific width of coil (i.e. 40.875” x 1’). “A lot of people in the industry get caught up in the decimal thickness,” he explains. “The common thicknesses in the industry are .”, .”, .”, .”, .”, .”, and .”. Thicknesses from . to . material are all 29 ga. product. On the steel service center side of things, when you’re purchasing coil from mills you’re buying by the pound. Our customers are typically buying it by the foot.”
He gives one example of why the reason yield matters so much: “I was at customer’s place and he had some . material on his floor. If I order that thickness I would expect to get a target yield of about 2.04 pounds/foot. I checked all the coil tags, and what I found is the coils weighed anywhere from 1.92 pounds/foot to 2.05 pounds/foot. What that shows is just because a coil tag says . thickness it doesn’t mean the yield corresponds with the thickness of the material. If the coil tag says it’s . thickness and it weighs 1.92 pounds/foot, it’s actually not . thickness. The yield is what tells me what the thickness is.”
“Tell me what you want it to weigh per foot and that’s what I’ll make sure it weighs,” he continues.
3GM supplies roll formers with a lot of 29 ga. coil. “When I’m qualifying a customer, the customer usually says they’re looking for 29 ga. .” material. My next question is: What do you want that to weight per foot? The customers don’t request a yield, but in the backs of their minds they have a yield that they’re trying to hit. But they never communicate that unless they’re asked.”
Gauge is a guide — not a hard and fast measure. “If the customer wants material that’s 2.02 pounds/ foot and I send him 1.92 pounds/foot, he’s not actually getting the material that he wants because he’s not going to hit the yield that he has in mind,” explains Adam. “A lot of people get caught up on decimal thickness. For me, as a coil supplier, the decimal thickness is a guide but it doesn’t really mean a whole lot. I like to get down to the specifics: the yield and what it weighs per foot. So if I know a guy is looking for 2.04 pounds/foot, I know what yield they’re looking for specifically.”
Adam continues: “With most mills, if you order .” thickness, for the most part it’s going to be a heavier 29 ga. product, say 2.04-2.05 pounds/foot. But I’ve seen on occasions where it’s definitely not, like the example I gave earlier.”
Understanding thickness terminology will help you get the material that will give you the yields you need. “Minimal thickness” is thickness that will be greater than or equal to the target thickness. “Nominal thickness” can be equal to, thicker or thinner than the target thickness. For example, when you ask for .” minimal thickness, the coil will always be at least .”. If you ask for .” nominal thickness, it may measure anywhere from .” to .” from coil to coil. Nominal thickness is thickness that can vary the most; it may be plus, minus or equal to the target thickness.
“The industry as a whole typically goes with minimal thickness,” Adam says, “but you do see a little bit of nominal thickness out in the market. Minimal definitely provides a more consistent product.”
The consistency of the thickness can vary from mill to mill. “Mills have their own quirks, and some mills have it dialed in better than others,” he says. “Some mills you see a lot of variance.
We try to stick with mills that really dial in their product. We don’t want to see a whole lot of switching back and forth between thicknesses when we’re sending customers product. We want to provide a great quality product that’s very, very consistent. Whether they’re buying it today or buying it six months from now, it should be about the same.”
There are a few tips and tricks to mitigate coil and width variances. Regarding thickness variances, he advises that when switching coils, if going from .” material to .”, you may have to back the guides off by a thousandth. Or vice versa, you might have to tighten it down a thousandth if you’re running it a little bit thinner.
“If the material is too thick and you roll form it without adjusting your machine, you could scar your panel and/or peel the paint off the material. As the material goes thicker, you have to back off the dies in order to produce a thicker product.”
Dealing with width variance can be a bit more tricky. For example, say a customer orders 40 7/8”, he roll forms the product and the overlap isn’t long enough. That means the coil isn’t wide enough. So he has to “borrow” material from the underlap side to put on the overlap side. “He might not have enough underlap left,” explains Adam. “That material is going to be tough to use. You can use it for trim or you can try to find a happy medium and use a very small underlap. The underlap is so important because that’s a purlin-bearing leg — it adds strength and rigidity to the panel. If both sides were overlaps, it would be a really flimsy product regardless of the gauge. Rigidity is important.”
Adam assures that roll formers usually have very few problems with thickness and width. “Most of the steel mills — internationally and domestically — have it dialed in pretty good in a construction product they know what needs to get into customers’ hands to roll form a great product.”
Buying quality coil is a critical step in running a profitable roll forming business. When something goes wrong, it can jeopardize your profitability. Keeping accurate records is cheap insurance in protecting that profitability. The importance of keeping accurate records can’t be overstated. If one of your customers comes back with a complaint, you need to be able to tell your supplier specific details about the materials. “The first question we ask on the service side is what coil tag or coil number it came off of,” Adam explains. No matter who your service center/supplier is, they will ask for this information. They can’t make any an assumption about which coil is the problem; they have to provide the mill with specific, factual information in order to process a claim. Adam says once they have the specific information, then they can go back and look at the mill certifications and quality control reports released by the mills in order to track warranty claims.
Clear communication with your coil supplier is important. When you process coil into panels and trims, you need to know the profit margin on each coil. If the material you are using isn’t sellable/usable, your profits won’t end up where you need them to be. RF
About 3GM Steel
Here are the 10 most frequently asked questions about GI coils:
A GI (Galvanized Iron) Coil Is A Type Of Steel Coil That Has Been Coated With A Layer Of Zinc Through A Process Called Galvanization. This Coating Helps To Protect The Underlying Steel From Corrosion, Making The GI Coil More Durable And Long-Lasting Compared To Untreated Steel Coils. GI Coils Are Commonly Used In A Variety Of Applications Including Construction, Automotive Manufacturing, Appliances, And General Engineering. They Are Known For Their Strength, Corrosion Resistance, And Affordability, Making Them A Popular Choice In Many Industries.
2. What Are The Advantages Of Using GI Coils?
Galvanized iron (GI) coils offer 8 advantages, making them popular in various industries:
1. Corrosion Resistance
2. Longevity
3. Strength and Toughness
4. Versatility
5. Cost-Effectiveness
6. Aesthetic Appeal
7. Recyclability
8. Protection for Base Metal
Overall, the advantages of using GI coils make them a preferred choice for a wide range of applications, including construction, automotive manufacturing, appliances, agricultural equipment, and more.
3. How Are GI Coils Manufactured?
GI (Galvanized Iron) coils are manufactured through a process called hot-dip galvanizing. Here's 7 general of the process:
The resulting GI coils are highly corrosion-resistant and are commonly used in a wide range of applications, including construction, automotive, and manufacturing industries.
Galvanized Iron (GI) coils find applications across various industries due to their corrosion resistance and durability. Some of the industries that typically use GI coils include:
Galvanized Iron (GI) coils are available in different grades, which are typically categorized based on the thickness of the zinc coating applied to the steel substrate. The most common grades of GI coils include:
1. SGCC (DX51D):
This is one of the most widely used grades of GI coils. SGCC stands for "Hot-Dip Galvanized Steel Sheet and Coil", and DX51D is the European equivalent. These coils have a standard zinc coating thickness and are suitable for general applications in various industries.
2. SGCD (DX52D)
SGCD or DX52D grade GI coils have a higher zinc coating thickness compared to SGCC/DX51D coils. They offer improved corrosion resistance and are often used in environments with higher levels of moisture or exposure to corrosive elements.
3. SGCE (DX53D)
SGCE or DX53D grade GI coils have an even higher zinc coating thickness than SGCD/DX52D coils. These coils provide enhanced corrosion protection and are suitable for applications where extended durability is required, such as in coastal areas or harsh industrial environments.
4. SGCF (DX54D):
SGCF or DX54D grade GI coils have the highest zinc coating thickness among the commonly available grades. These coils offer superior corrosion resistance and are suitable for demanding applications where maximum protection against corrosion is essential, such as in marine environments or chemical processing plants.
If you want to learn more, please visit our website Galvanized Steel Coil Manufacturers.
It's important to note that the specific grades and designations may vary slightly depending on regional standards and specifications. Additionally, there may be other specialized grades of GI coils available for specific applications or industries, but the ones mentioned above are the most commonly used grades in general industrial and commercial applications.
The standard sizes and dimensions of Galvanized Iron (GI) coils can vary depending on the manufacturer, region, and specific requirements of the customer. However, there are some common size ranges that are widely available:
GI coils typically come in widths ranging from 600mm to mm (approximately 24 inches to 59 inches). The choice of width depends on factors such as the intended application, machinery constraints, and transportation considerations.
The thickness of GI coils can vary from as thin as 0.12mm to as thick as 4.0mm (approximately 0. inches to 0.157 inches). The specific thickness required depends on the strength and durability requirements of the application.
The weight of GI coils can range from a few hundred kilograms to several metric tons, depending on the width, thickness, and length of the coil. Common coil weights range from 3 to 15 metric tons (approximately to pounds).
The inner diameter of GI coils typically ranges from 508mm to 610mm (approximately 20 inches to 24 inches). This inner diameter is standardized to fit various types of coil handling and processing equipment.
The outer diameter of GI coils can vary depending on factors such as coil width, thickness, and weight. However, common outer diameters range from mm to mm (approximately 39 inches to 79 inches).
GI coils are usually supplied in continuous lengths, with typical coil lengths ranging from mm to mm (approximately 39 inches to 118 inches). However, longer or custom lengths may be available upon request.
It's important to note that these dimensions are general guidelines, and actual sizes may vary depending on the specific specifications provided by the customer or the manufacturing capabilities of the supplier. Additionally, GI coils can be cut to custom lengths or slit to narrower widths to meet the requirements of different applications.
GI coils have superior corrosion resistance compared to other types of steel coils. This is because they are coated with a layer of zinc, which acts as a sacrificial anode, protecting the underlying steel from rust and corrosion. This makes GI coils ideal for outdoor or humid environments where corrosion is a concern.
The galvanization process adds an extra layer of protection to GI coils, making them more durable compared to other types of steel coils. They are less likely to rust or corrode over time, resulting in a longer lifespan.
While GI coils may be slightly more expensive upfront due to the galvanization process, they are generally more cost-effective in the long run because of their extended lifespan and reduced maintenance requirements. They may require less frequent replacement or repair compared to other types of steel coils.
GI coils typically have similar strength characteristics to other types of steel coils of comparable thickness. The galvanization process does not significantly alter the mechanical properties of the steel, so GI coils retain their strength and structural integrity.
GI coils have a characteristic shiny, metallic appearance due to the zinc coating. This can be desirable for certain applications where aesthetics are important. However, for applications where appearance is not a concern, other types of steel coils may be preferred.
Overall, GI coils offer excellent corrosion resistance, durability, and cost-effectiveness compared to other types of steel coils, making them a popular choice for a wide range of applications, including roofing, automotive, construction, and manufacturing.
The process of galvanizing GI coils involves several steps:
The steel coils are cleaned to remove any surface contaminants such as oil, grease, or dirt. This is typically done using a chemical cleaning process or by immersing the coils in a degreasing solution.
The coils are then immersed in a pickling solution, usually an acidic bath such as hydrochloric acid or sulfuric acid. This removes any remaining oxides and mill scale from the surface of the steel, preparing it for the galvanizing process.
After Pickling, The Coils Are Rinsed To Remove Any Residual Pickling Solution And Then Immersed In A Flux Solution. The Flux Helps To Prevent Oxidation Of The Steel Surface Before It Is Galvanized And Promotes The Adhesion Of The Zinc Coating.
The prepared steel coils are passed through a bath of molten zinc at temperatures typically around 450°C (850°F). The coils are carefully submerged in the zinc bath, ensuring that the entire surface is coated with a layer of molten zinc. This process is known as hot-dip galvanizing.
Once the steel coils have been galvanized, they are removed from the zinc bath and allowed to cool in the open air or by quenching in water. This solidifies the zinc coating and ensures that it adheres firmly to the surface of the steel.
After cooling, the galvanized GI coils may undergo further processing such as skin-pass rolling or tension leveling to improve surface finish and flatness. They may also be cut to size and coil-wound for shipment to customers.
The galvanizing process creates a durable, corrosion-resistant coating of zinc on the surface of the steel coils, providing long-lasting protection against rust and corrosion in a variety of environments.
The lifespan of GI (Galvanized Iron) coils can vary depending on factors such as the thickness of the zinc coating, the environmental conditions they are exposed to, and the quality of the galvanizing process. However, in general, GI coils are known for their durability and long lifespan.
Under normal conditions, where they are not subjected to extreme corrosion or mechanical damage, GI coils can last for several decades. It's not uncommon for properly galvanized GI coils to remain corrosion-free and structurally sound for 20 to 50 years or even longer.
Factors that can affect the lifespan of GI coils include exposure to corrosive environments such as coastal areas with high salt content in the air, industrial environments with chemical pollutants, or frequent exposure to moisture and harsh weather conditions.
Regular maintenance, such as periodic inspections for damage or signs of corrosion, can help extend the lifespan of GI coils. Additionally, applying protective coatings or sealants as needed can provide extra protection against corrosion and prolong the lifespan of the coils.
Overall, GI coils are valued for their longevity and resistance to corrosion, making them a popular choice for a wide range of applications where durability and reliability are important.
Several factors can influence the price of GI (Galvanized Iron) coils:
The price of GI coils is heavily influenced by the cost of raw materials, primarily steel and zinc. Fluctuations in the prices of these materials due to factors such as supply and demand, tariffs, and currency exchange rates can impact the overall cost of GI coils.
The process of galvanizing involves several steps, including surface preparation, pickling, fluxing, and hot-dip galvanizing. The cost of these processes, including labor, energy, and overheads, can affect the price of GI coils.
3. Zinc Coating Thickness:
The thickness of the zinc coating applied to GI coils can vary depending on the desired level of corrosion resistance and durability. Thicker coatings require more zinc and may result in higher production costs, which can influence the price of GI coils.
Like any commodity, the price of GI coils is influenced by supply and demand dynamics in the market. Increased demand for GI coils, particularly during periods of high construction activity or infrastructure development, can drive prices higher.
GI coils manufactured to higher quality standards or certifications may command a premium price due to their superior performance and reliability. Customers may be willing to pay more for GI coils that meet specific industry standards or regulatory requirements.
The cost of transporting GI coils from the manufacturing facility to the customer's location can impact the overall price. Factors such as distance, mode of transportation, and fuel prices can influence transportation costs and, consequently, the final price of GI coils.
Economic conditions, trade policies, and geopolitical events can also affect the price of GI coils. Trade tariffs, sanctions, or changes in government regulations can lead to fluctuations in prices or supply chain disruptions.
Overall, the price of GI coils is influenced by a combination of factors related to raw materials, manufacturing processes, market dynamics, quality standards, and external economic and political factors. Understanding these factors can help manufacturers, suppliers, and customers make informed decisions regarding the purchase and sale of GI coils.
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If you are looking for more details, kindly visit advantages of pickled and oiled steel.