If you work in the steel industry, you understand that there are all sorts of varieties of steel used for a myriad of applications. Because of these varying applications and products, steel&#;s HARDNESS (as measured on the ROCKWELL SCALE) should fit the needs of the finished product. To find the best fit for the job, steel is generally categorized into four main grades of steel for buyers to purchase. These grades are determined by the overall hardness of the steel and manufacturers can select the grades based on which type of product and application the steel will be used for.
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Commercial Steel (CS/CQ)
Typical Rb range 40-65
Commercial Steel represents the most common quality of steel that is mainly used for flat applications. Buyers looking for steel that requires little to no draw or bend would consider commercial steel a good option. Drawability is essentially the formability or structural softness of steel. If you were to think of bending or shaping steel, the harder that steel is (or the higher the Rockwell) the sturdier the steel will be. Many commercial products used in the automotive and furniture industry are manufactured from commercial grade steel.
Drawing Steel (DS) Typical Rb range 35/50
As you&#;d imagine, drawing steel is regarded as having a higher drawability than commercial grades. Drawing steel is a softer steel that typically contains less than .05 percent carbon. If a customer&#;s product needed the ability to be moderately bent or shaped in the manufacturing process, then drawing would be a suitable choice.
Deep Drawing Steel (DDS) Typical Rb range 25/40
Deep drawing steel is reserved for fairly severe drawing applications. An example of deep drawing steel would be the softness of an aluminum can and how easily formable it is. The process of deep drawing is to radically draw into a sheet metal blank with a forming die through a fast and hard punch or hit made by a machine. This transforms the shape through material retention. The process is considered &#;deep drawing&#; when the depth of the part that&#;s drawn exceeds its diameter. Deep drawing steel should be used for these deep drawing applications.
Extra Deep Drawing Steel (EDDS) Typical Rb range 15/30
For the last of the four common steel grades, there is extra deep drawing steel. This grade is for really severe drawing applications. EDDS really only allows for the product to be hit with a one or two hit draw. If it is hit more than that, then issues will be had with splitting of the steel. This is why it&#;s important for customers not to order extra deep drawing steel if they will be sending it through several different hits because it will fail.
How Hascall Steel Determines the Grades
As stated above, the determining factor in identifying steel grades is hardness. Steel&#;s hardness is measured using the Rockwell scale; and the softer steels are represented by LOWER Rockwell numbers.
Rb&#;s are not the only determining factor of steel, chemistries, physicals, annealing cycles, etc. all play an important role in making various grades of steel. But a simple Rb test can help guide you in determining what you may need.
When Hascall Steel receives a shipment of steel from our suppliers, our own in-house laboratory accurately tests the mechanical properties to determine both the Rockwell and the tensile, yield, and elongation (TYE). This gives us trustworthy data, and allows us to confirm Rockwell results against our purchase order documents. Having an in-house lab at Hascall Steel is an advantage to us in our pursuit of knowing our material, and accurately matching our inventory to our customers grade requirements.
Stainless steel is a commonly used material in applications ranging from medical instruments or chemical storage to transport or power generation because of its high corrosion resistance, hygiene, and strength. While there are more than 3,500 grades of steel, not all stainless steel grades are created equally.
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With so many options, how can you ensure you&#;re selecting the appropriate grade for your specific needs?
To determine which grade of steel will uphold best in a given environment, think about the conditions your final product will face. Extremely low pH, high stresses and high temperatures, and crevice corrosion negatively impact stainless steel performance. Steels in the austenitic T3XX series, like the common types 316 and 304 alloys, retain their strength, toughness, and corrosion-resistant properties over the broadest temperature range.
Corrosion resistance is the main reason for choosing austenitic stainless grades. Type 316, with its molybdenum addition, even resists chloride ions found in marine and chemical processing applications. With any steel grade, high-quality structural design is the best defense against corrosion.
Next, consider these three top mechanical qualities:
Stainless steel contains 10&#;30% chromium as its alloying element, which is what helps it resist corrosion. The nickel addition in austenitic grades provides the highest toughness and ductility among stainless grades. Grades high in chromium, molybedenum, and nickel are the most resistant to corrosion.
Alloy content is not the only aspect to consider when choosing a grade of stainless steel; the material&#;s processing also affects the mechanical response. The duration of time steel is held at different temperatures as part of its cooling process, as well as the total speed at which it is cooled can affect its overall quality.
While the hardness of carbon steels can be increased by heat treatment, austenitic stainless is hardened by cold working operations like rolling, bending, swaging, or drawing at temperatures below the recrystallization temperature. Be aware that increased hardness by cold working operations decreases other properties like elongation and impact resistance.
Austenitic stainless steel is widely available in bar, wire, tube, pipe, sheet, and plate forms; Most products require additional forming or machining before they can be used for their specific application.
Stainless steel tubing, for instance, may need bending or coiling, re-drawing, machining, welding, or end forming. If your stainless steel will see machining processes like CNC machining, drilling, reaming, bevel cutting, chamfering, knurling, or threading, choose a machining rate that mitigates the risk of work hardening or select a &#;free-machining&#; grade containing sulfur.
When welding any stainless steel parts, embrittlement in the weld area is a top concern. Choose a lower carbon grade like 304, 304L, or 316L to reduce carbide formation.
Many designers choose stainless steel for its aesthetic appearance, whether that appearance is a shiny, electropolished &#;bright&#; finish, a dull &#;pickled&#; finish, a matte surface polished to a specific RMS, or a light-absorbing black oxide coating. Austenitic stainless steel grades can take any of these finishes plus the common addition of passivation.
Customers may also need certification for application-specific specifications. For instance, ASTM A213 and A249 should be used for boiler, superheater, and heat-exchanger tubes, while ASTM A908 should be used for hard-drawn austenitic stainless steel industrial needle tubing. There are more than 12,000 ASTM standards, and each addresses a specification so customers know the technical standards tested for chemical composition, heat treatment or temper, and other physical and mechanical attributes.
Although high-performing austenitic stainless steels are the most expensive stainless steels upfront, they are well worth the investment. Choosing a corrosion-resistant material well-suited to its application reduces maintenance, downtime, and replacement costs. Life-cycle costing methods can quantify current and future costs and create an &#;apples-to-apples&#; comparison of different materials.
At Eagle Stainless we can help you prioritize your material requirements and guide you toward choosing the perfect stainless steel grades for your application. With quality management certifications in place since , our commitment to quality is evident at every step of the process and designed to help you make the best steel selection for your industrial application.
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