Common Mistakes Made When Handling Stainless Steel

3 Common Mistakes Made When Handling Stainless Steel

Producing components with stainless steel is a smart choice for durability and product longevity because of its natural oxide protection layer. However, warping, corrosion, or even metallurgical changes can occur if best practices are not used.
Metalworkers new to stainless, or even experienced welders and fabricators in a hurry, need to pay close attention to proper stainless steel handling techniques and procedures to maintain the integrity of the metal and keep the final product in-spec.
Find out why introducing surface contaminants is one of the riskiest blunders in handling stainless steel and how to avoid this and other mistakes during stainless steel fabrication.

1. Metallurgical Changes

How it happens:
• The Heat Affected Zone (HAZ) during the welding or thermal cutting process is larger on stainless steel because of lower thermal diffusivity (4.2 mm2/s) compared to other metals
• This can lead to a change in grade (austenitic stainless steel turning martensitic, more brittle and harder) or heated metal becomes weaker
Cutting Options:
In his article on HAZ, Andrea Bustreo notes the four types of cutting and factors that should be noted in employing them during stainless steel fabrication.
• Shearing, manual cutting and waterjet cutting do not provoke a HAZ because they do not overheat the sheet metal.
• Laser cutting generates the smallest HAZ among all thermal cutting techniques because it applies heat on a very small area.
• Plasma cutting generates an intermediate HAZ because the plasma pulse is wider than a laser beam. Higher currents allow for a higher cutting speed, reducing the duration of exposure and the width of the HAZ.
• Oxyacetylene cutting generates the widest HAZ of all thermal cutting systems because of the intense heat, slow speed, and wide flames.
Weld Decay:
Intense localized heat from welding can result in the depletion of chromium in the base metal around the weld. This change in the metal makes it sensitive to corrosion. ASM International published a paper listing these options for controlling stainless steel sensitization.

• A postweld high-temperature anneal and quench to redissolve the chromium at grain boundaries, and hinder chromium carbide formation on cooling.
• A low-carbon grade of stainless steel (e.g., 304L or 316L) to avoid carbide formation.
• A stabilized grade of stainless steel containing titanium (alloy 321) or niobium (alloy 327), which preferentially form carbides and leave chromium in solution.
• A high-chromium alloy (e.g., alloy 310)

2. Distortion

How it happens:
Stainless steel’s low thermal conductivity and high expansion rate make it an easy target for distortion during welding
Welding Tips:

• Use lowest amperage possible without jeopardizing the weld quality
• Control interpass temperatures
• Use controlled tack welding, clamping jigs, or a copper backing plate

3. Introducing Surface Contaminants

How it happens:
• Iron filings and other environmental contaminants come in contact with stainless steel
• Grease on hands, chalk, and other items introduced during handling can contaminate the surface
• Both of these can lead to localized corrosion
Avoiding Surface contamination:
• Use an abrasive designed for stainless steel grinding, blending, and deburring

• Keep stainless steel abrasive products separate from other abrasives used on different metals. Never use an abrasive product that has been used on a different type of metal
• Store stainless steel separately from carbon steel and other metals
• Keep stainless steel in packaging and protected from the elements as long as possible
• Remove adhesives used in transport from the stainless steel: these can harden and cause crevice corrosion on the site

Proper welding and cutting techniques, awareness of the HAZ, and adherence to good quality control and anti-contamination measures will give you an in-spec, well-finished stainless steel product. Make sure that you and your team read this article to keep common stainless steel fabrication mistakes at bay.
To learn more about stainless steel fabrication, download your copy of A Metalworker’s Guide to Stainless Steel.
How To Protect Stainless Steel From Rust And Corrosion
#1 You might be knowing that water or moisture content in the air is the enemy of stainless objects when it comes to rusting or corrosion. This is because the oxygen present in the water or moisture will combine with the iron present in the stainless steel and reacts with it to form iron oxide. Thus, you can see that the substances that have iron content in it can easily form iron oxide. To protect the stainless steel substances, you must always keep them dry and away from moisturized air. You can even install a dehumidifier to keep the air dry and remove moisture from the air. Keeping the objects clean will help the substances to be away from the dirt and mud that usually comes with moisture in it.
#2 You Must Not Let The Stainless Steel Develop Any Sort Of Scratches:
When the stainless steel develops scratch on the surface or any sort of crack (even minor), it will expose the underlying metal to moisture content and hold water. Due to the scratches and the cracks, the iron present in the stainless steel comes in contact with moisture or water and starts rusting. Usually, the manufacturing industries are making use of cold-rolled steel because it does not trap water or moisture and keeps the metallic surfaces durable.
#3 You Can Passivate The Stainless Steel To Protect It From Rust And Corrosion:
This is another important way in which you can protect stainless steel from rust and corrosion. Passivating the stainless steel material is performed by altering the metal’s surface with an extremely thin layer of chromium. The technicians choose chromium because it has high resistance to moisture, and thus it becomes the ideal choice when it comes to protecting metallic surfaces from rust or corrosion. When you regularly passivate the stainless steel, it will help in keeping the material as it is for a long period without it developing rust or corrosion.
#4 Powder Coating The Stainless Steel Products:
You Must Keep The Stainless Steel Material Clean and Dry:
Although stainless steel is highly resistant to corrosion, it is not entirely corrosion proof. A good way to safeguard stainless steel objects, which are exposed to the exterior elements, is by the method of powder coating. In this method, a fine layer of dry powder is applied to the surface electrostatically. This is followed by setting this paint layer with heat. This method provides both color and rust protection to the stainless steel objects.
#5 You Must Regularly Maintain Stainless Steel:
When you are regularly keeping the stainless steel objects or materials properly maintained, there are fewer chances that it will develop rust or corrosion. You need to ensure that whenever the metallic surfaces are getting damaged or developing cracks; you fix them as soon as possible.
Summary:
Although stainless steel is an alloy when it continuously comes into contact with moisture or water, it will definitely be prone to developing rust and corrosion. You can follow the aforementioned ways to keep the stainless steel protected from rust and corrosion for a long period, and you will not have to compromise with the quality of the stainless steel. If you are successful in keeping the stainless steel protected from rust and corrosion, you will never have to worry about the quality of the object.

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Which is better? 304 vs 316 Stainless Steel

Common stainless steels

The two most common stainless steel grades are 304 and 316. The key difference is the addition of molybdenum, an alloy which drastically enhances corrosion resistance, especially for more saline or chloride-exposed environments.
316 stainless steel contains molybdenum. 304 stainless steel does not.
For outdoor furnishings like rails and bollards, stainless steel is an ideal corrosion-resistant material, but it will only withstand long-term exposure if the grade is appropriate for its environment. 304 is an economical and practical choice for most environments, but it doesn’t have the chloride resistance of 316. The slightly higher price point of 316 is well worth it in areas with high chloride exposure, especially near the ocean or by heavily salted roadways. Each application for stainless steel has unique demands and needs a stainless steel that’s up to the task.
Other common consumer stainless steels include 410 and 430.

304 Stainless Steel

304 stainless steel is the most common form of stainless steel used around the world, due to its excellent corrosion resistance and value. It contains between 16 and 24 percent chromium and up to 35 percent nickel, as well as small amounts of carbon and manganese.
The most common form of 304 stainless steel is 18-8 (18/8) stainless steel, which contains 18 percent chromium and 8 percent nickel.
304 stainless steel is the most common form of stainless steel used around the world due to excellent corrosion resistance and value.
304 can withstand corrosion from most oxidizing acids. That durability makes 304 easy to sanitize, and therefore ideal for kitchen and food applications. It is also common in buildings, décor, and site furnishings.
304 stainless steel does have one weakness: it is susceptible to corrosion from chloride solutions, or from saline environments like the coast. Chloride ions can create localized areas of corrosion, called “pitting,” which can spread beneath protective chromium barriers to compromise internal structures. Solutions with as little as 25 ppm of sodium chloride can begin to have a corrosive effect.

Common uses for 304 stainless steel:

• Storage tanks
• Fasteners and finishing hardware (screws, nuts, bolts, plates, handles)
• Pots and pans
• Residential sinks and sink parts
• Indoor architectural/decorative hardware (panels, sculptures, sconces)
• Equipment tubing
• Residential appliances

316 Stainless Steel

316 grade is the second-most common form of stainless steel. It has almost the same physical and mechanical properties as 304 stainless steel, and contains a similar material make-up. The key difference is that 316 stainless steel incorporates about 2 to 3 percent molybdenum. The addition increases corrosion resistance, particularly against chlorides and other industrial solvents.

316 stainless steel has additional molybdenum that gives it resistance to chlorides and other processing chemicals.

316 stainless steel is commonly used in many industrial applications involving processing chemicals, as well as high-saline environments such as coastal regions and outdoor areas where de-icing salts are common. Due to its non-reactive qualities, 316 stainless steel is also used in the manufacture of medical surgical instruments.

Alternative 300-series grades can contain up to 7 percent molybdenum. They provide even better chloride resistance, but such heavy-duty resistance is only necessary in industrial or high concentration exposure conditions.

Common uses for 316 stainless steel:

• Industrial equipment as used in:
Pharmaceutical manufacturing
Chemical manufacturing
• Industrial and chemical transportation
• Pressure vessels
• Cisterns and pipes for chemical applications
• Medical equipment where non-surgical steel
• Marine equipment
• Outdoor site furnishings
• Commercial kitchens
• Food production and processing in saline environments
• Commercial appliance

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Stainless steel is one of the most widely used metals

Stainless steel is one of the most widely used metals for construction materials. Due to its strength, versatility, and recyclability, stainless steel is the go-to metal choice for a variety of projects including architecture, landscaping, interior construction, and engineering.
In this article, we’ll discuss what stainless steel is used for, what it’s made of, types of stainless steel (focusing on the 300 and 400-grade series), and the many cost benefits when choosing your construction materials.

WHAT IS STAINLESS STEEL USED FOR?

Stainless steel is used in hundreds of industries including domestic, architectural, transport, medical, food and drink, and pharmaceutical. Its durability and strength make it ideal for everything from surgical instruments to industrial piping.
There are few industries where you won’t find stainless steel, and it is by far the most popular non-magnetic material option in commercial construction.

WHAT IS STAINLESS STEEL MADE OF?

Stainless steel is a low-carbon steel alloy containing an average of 18% chromium along with varying amounts of silicon and manganese. Chromium gives the steel its durability by hardening and increasing its corrosion resistance in high-heat or oxygenated environments. In some grades, nickel and molybdenum are also present to further increase corrosion resistance.

WHAT ARE THE TYPES OF STAINLESS STEEL?

Stainless steel is divided into five primary categories — all of which come in a variety of grades. The most popular are the 300 and 400 series. The five basic types of stainless steel are:

• Ferritic: Chromium-based with less than 0.10% carbon. Limited in use.
• Austenitic: The most common type of stainless steel with the addition of nickel, manganese, and nitrogen to increase weldability and formability.
• Martensitic: Similar to ferritic, but with a higher carbon concentration. It has high strength but lacks the corrosion resistance of austenitic steel.
• Duplex: Approximately 50% ferritic and 50% austenitic. It’s known for its high strength and resistance but is fragile during welding.
• Precipitation Hardening (PH): Comparable to austenitic steels given extremely high strength, with the additions of copper, niobium, and aluminum over an ‘aging’ heat treatment.

THE 300 SERIES

The 300 series is made of austenitic steel and offers versatility, corrosion resistance, strength, and extreme temperature resistance.
The most popular grade of the 300 series is Grade 304. Grade 304 is also known as 18/8 due to its composition of 18% chromium and 8% nickel. In addition to the standard benefits of austenitic steel, Grade 304 also showcases recyclability, long life, aesthetic appeal, substantial hygiene, and low maintenance. It also has a low-carbon version known as 304L.
Common uses of Grade 304 include refrigerators, dishwashers, and food processing equipment. It’s also found in chemical containers, heat transfer plates, and construction tools.

THE 400 SERIES

The 400 series is made of ferritic and martensitic stainless steel, with the additions of carbon, chromium, and manganese. It also boasts high strength and wear resistance.
The most popular grade of the 400 series is Grade 410. Grade 410 contains 11.5% chromium which makes it extremely strong following heat treatment. This grade is also magnetic when hardened, making it suitable for certain jobs the 300 series cannot do. Grade 410 also tends to be cheaper than Grade 304 due to its low alloy content.
Grade 410 is primarily used in the automobile industry and in part making for refineries and gas and steam components.

WHAT ARE THE COST BENEFITS OF STAINLESS STEEL?
Stainless steel will have a larger initial cost than lesser quality material. However, it’s been shown to have a lower cost over time than other materials due to its superior durability, corrosion resistance, heat resistance, tensile strength, and hygienic benefits.

CORROSION RESISTANCE
When chromium is added to stainless steel during the manufacturing process, it combines with oxygen in the air to create a thin protective film over the metal. This film can repair itself if damaged and allows stainless steel to resist corrosion, rust, water stains, and general wear. Any item you construct with stainless steel will have a longer shelf life than items made with inferior, corroding material

TEMPERATURE RESISTANCE

Depending on the grade, certain types of stainless steel can resist scaling and maintain strength at extremely high temperatures. Other varieties of stainless steel are designed to survive long-term cryogenic temperatures.
While not all grades show the same temperature resistance, there is stainless steel to meet the needs of nearly any environment.

TENSILE STRENGTH

All grades of stainless steel have extreme tensile strength. Both cold-hardened and heat-treated stainless are relatively lightweight despite their strength and durability. All grades have high shock resistance and can endure heavy loads.

HYGIENIC BENEFITS

Thanks to its chemical makeup, stainless steel naturally rejects the growth of bacteria and other pathogens. It’s also extremely easy to clean with a basic wipe down and an all-purpose cleaner. If you’re looking to go the extra mile, you can follow it up with an optional polish too. All the methods above make stainless steel a long-term and low-maintenance solution for hospital-grade tools, cutlery, pharmaceuticals, and other sanitary purposes.

Use these basic tests to identify meatal
Different metals come in a selection of grades, and pure metals are typically combined with supplementary elements to create a variety of alloys. But grade refers not only to the composition of your metal (i.e., its chemical makeup) but also to how your metal was manufactured and its mechanical properties. Of course, if you’re ordering a metal, this information is on the packaging. But what if you’re working with metals you aren’t familiar with?
There are seven common testing methods for determining the alloy composition of a certain metal. These tests are a great way to gain insight into your metal when you don’t have access to higher-end tools.
Even if you have access to XRFs (X-ray Fluorescence Analyzers) or LIBS (Laser-Induced Breakdown Spectroscopy), we recommend starting with these basic tests to narrow down your options and make more informed testing decisions.

1. Surface Appearance Test: The surface appearance test looks at any colors and marks on the surface of the metal. This test is not the most specific, but it can narrow down your metal options so that you know which follow-up tests will be the most beneficial.

One of the easiest determinations you make with a surface appearance test is in the oxidation levels. If you have to scrape away rust to see the original color of the metal, you’ll be able to compare the color of the oxidation with the color of the original metal and gain insight into the level of iron.

2. Spark Test: The spark test creates sparks from the metal by grinding it against a wheel. The length, color, and form of the sparks can indicate the family of metal. We’ll go deeper into the spark test for steel alloys below.

3. Chip Test: The chip test looks at the fragility and structure of a metal by using a chisel to break off a small piece. The size of the chip, the texture of the edges, and the smoothness of the chip itself can give great insight into the type of metal you’re dealing with.

4. Magnet Test: Perhaps the simplest of the tests, the magnet test determines whether or not a metal is magnetic by holding it to a magnet. It’s worth noting, however, that some stainless steels are not magnetic, so it’s not always a foolproof test on its own.

5. Torch Test: The torch test looks at the consistency of a metal once it’s melted, in addition to how fast that melting occurred. Depending on what you’re constructing, this is a crucial test, as it determines whether your metal is safe to use for your project.

6. Chemical Test: The chemical test is not applicable to all metals, but it is very useful in identifying steels, magnesium, and aluminum. Small amounts of phosphoric acid will show bubbling on low-chromium stainless steels, and silver nitrate will leave a black residue on magnesium (but not on aluminum).

7. Hardness Test: The hardness test (commonly referred to as the Rockwell Hardness Test) looks at the strength of a metal against a material trying to imprint against it. Each metal has a specific hardness number assigned to it, which corresponds to the level of impression. This makes the hardness test one of the most accurate metal identifiers.

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