Stainless Steel 400 Series: Grades 410 & 416

Chapter 1: What is 400 Series Stainless Steel?

Series 400 stainless steels are high strength and wear resistant stainless steels due to their high carbon content. They are differentiated from austenitic stainless steels in that they have lower resistance to corrosion due to their high carbon content. Series 400 stainless steels have an 11% chromium and 1% magnesium content to go along with their higher carbon content. The combination of these alloys gives 400 series stainless steel its exceptional strength and wear resistance.

The use of series 400 stainless steel depends on several factors. It has a martensitic crystal structure and can be hardened and tempered through aging and heat treatment. Unlike other series of stainless steels, series 400 is known for its hardness, strength, and resistance to wear with grade 410 described as a general-purpose stainless steel while grade 416 is the first free machining stainless steel.

Grade 410 stainless steels have an 11.5% chromium content, which provides corrosion protection, a factor that can be enhanced by polishing, tempering, and hardening. It is referred to as a general-purpose stainless steel because of its ability to adapt to a wide range of applications. Common uses for grade 410 stainless steels are knife blades, scissors, kitchen tools, and firearm components.

Grade 416’s machinability partly comes from its sulfur and phosphorus content. Part of its popularity is due to its lower cost and easy accessibility. The tensile strength of grade 416 ranges between 510 MPa and 800 MPa with a hardness between 230 HB and 320 HB.

Chapter 2: How Series 400 Grades 410 and 416 are Made

Each type of stainless steel is engineered to have properties that make it ideal for specific applications. Series 400 has a higher carbon content to increase its strength and make it more resistant to wear, it is less resistant to corrosion and rust. As with all types of steel, series 400 is made from iron with a chromium content of 11% up to 27%, 1% of carbon, and 2.5% of nickel. Since the martensitic crystalline structure of series 400 varies, the strength and hardness of its different grades varies.

The Manufacturing of Stainless Steel Series 400

The first step in the manufacture of stainless steel series 400 is accumulating the appropriate materials for its mixture. Each of the elements for series 400 are chosen with the proper ratios to create series 400 properties. In many cases, ratios are on a range because of the potentiality of possible variances in the purity of the elements placed in the mix.

1. Melting – Once the proper combination of materials is collected, they are placed in a melting furnace that can take several different forms, which is determined by the type of energy used to power the furnace. Although gas and propane are available, many melting furnaces use electric power. To properly mix the various alloys, the furnace is heated to the melting point for each alloy, a process that can take between 8 and 12 hours. The melting process creates a molten mixture for the next step in the stainless steel manufacturing process.

   

   
   

2. Excess Carbon Removal – The carbon removal process is carefully monitored since the amount of carbon removed determines the type of series 400 stainless steel. The process for the removal of carbon is completed by vacuum oxygen decarburization (VOD) or argon oxygen decarburization (AOD) system. The careful regulation of this process is necessary since the amount of carbon influences the tensile strength and hardness of the stainless steel. Since series 400 stainless steel has a high carbon content, the regulation of carbon is a critical aspect of the manufacturing process.

   

   
   
3. Turning and Stirring – A critical factor regarding the quality of series 400 stainless steels is the even distribution of the different alloys to create a homogeneous mixture. To ensure the proper consistency, the mixture is put through a stirring and turning process, which has the additional effect of removing certain components from the mixture. The resulting outcome is a uniform molten combination of alloys that ensures the quality of the stainless steel.

4. Forming Stainless Steel Series 400 – The forming of the molten stainless steel involves putting the molten material through a casting process, which can be continuous or ingot casting. With continuous casting, the molten stainless steel is fed into a mold with the desired shape. It enters the mold through holes in the appropriate portions to fit the mold. Heat is removed by water that surrounds the mold, a process that solidifies the molten metal. The final forms can be bars, tubes, sheets, or specialized forms.

   

   
   
5. Annealing – Annealing helps the metal regain its grain structure before it is shaped any further. The stainless steel is heated and held at a critical temperature to reset the microstructure. During the process, the grains recrystallize and grow. Immediately after the grains recrystallize, they are cooled to avoid excess grain growth. The process of annealing may be repeated several times to achieve the necessary thickness. Prior to annealing, stainless steel series 400 has an austenitic grain structure. When it cools to room temperature, it transforms for a martensitic structure.

6. Cutting and Shaping – To prepare stainless steel for the final product for which it has been manufactured, it is cut and shaped such that it has the proper dimensions for the requirements of an application. The shaping and cutting processes take several forms and vary in accordance with the size and shape of the stainless steel billet. Metal shears, CNC machining, and laser cutting are some of the methods used to create the proper shape.

   

   
   

7. Surface Finishes – There are many types of finishes for stainless steel series 400, which is a process that is applied to stainless steel to increase its durability, corrosion resistance, smoothness, and grain pattern. Although finishes can enhance the appearance of stainless steel series 400, they can also add to improve performance, strength, reliability, and properties. Rolling, polishing, and blasting are finishing methods that affect how the stainless steel is produced, its thickness, surface, cleanliness, mechanical abrading.

The choice of surface finish is critical to how stainless steel series 400 meets the requirements of the application for which it is manufactured. Since series 400 stainless steels are mainly used for applications that require strength, they do not necessarily require an aesthetically appealing appearance. Due to its low resistance to corrosion, finishes are added to enhance the stainless steel’s ability to resist rust and corrosion, which includes certain types of coatings.

Stainless Steel Grade 410

The process for the manufacture of stainless steel grade 410 follows the same steps as those for stainless steel in general. In most cases, the molten form of grade 410 is formed into ingots that are heated and hot worked by forging, rolling, and extrusion. The shaped forms are annealed to improve their ductility and workability. The finishing processes used on grade 410 include hot rolling, cold rolling, and more annealing or heat treatments.

Additional finishing methods are used to improve the properties of stainless steel grade 410 and include various types of surface treatments. Grade 410 is heat treated at 750°C up to 820°C (1382°F up to 1508°F) and quenched using oil, water, or air. Since the metal is brittle after quenching, it is tempered to relieve its internal stress and improve its toughness and ductility.

Stainless Steel Grade 416

Stainless steel grade 416 is the first stainless steel grade that can be free machined. It is manufactured using the same process as that which is used for grade 410 and is a variation of grade 410 with a higher sulfur content to increase its machinability. Once grade 416 is formed into sheets, bars, rods, and pipes, it is hardened and polished to increase its resistance to corrosion. To increase its resistance to oxidation, it is heat treated at 760°C (1400°F).

Chapter 3: Stainless Steel Grade 410

Stainless steel grade 410 is one of the most popular forms for stainless steel and is referred to as a general use stainless steel due to its ability to be used in a wide range of applications. Aside from its easy availability and low cost, grade 410 is marginally machinable and formable. Its lower cost is due to the limited use of expensive alloys in its composition and manufacturing.

Like other grades of series 400 stainless steel, grade 410 has good resistance to corrosion, which can be enhanced through hardening, tempering, and polishing. The application of various treatments changes the properties of grade 410 especially its corrosion resistance. When properly treated, stainless steel grade 410 can be corrosion resistant in moist and wet environments and ones with mild chemicals. Regardless of the various treatments, grade 410 cannot be used in conditions where there is salt water or acidic chemicals.

The higher carbon content of stainless steel 410, at 0.1%, gives it its strength and reduces its ductility. Its 12% chromium content results in the formation of chromium carbide compounds that gives stainless steel 410 wear resistance and edge retention and is one of the reasons for its machinability. The blend of elements that combine to form stainless steel 410 gives it resistance to high temperature oxidation and scaling.

Stainless steel 410 can be cut, shaped, and formed due to being worked and quench hardened and tempered. Compared to stainless steels grades 304 and 316, stainless steel 410 is harder to machine, which is the reason 304 and 316 replace grade 410 for some applications.

Stainless steel grade 410 is an air hardening stainless steel that has to be preheated before welding and given an anneal before the weld cools, or the metal will harden and crack. It can be cold formed when annealed and hot formed at 750°C – 1150°C (1382°F – 2102°F). For less stressful forming processes such as bending, the preheating temperature can be substantially lower in the hundred-degree range. Although stainless steel grade 410 is machinable, it is normally annealed prior to the process and has to be put through decontamination and passivation after being machined.

The melting point of stainless steel 410 is 1495°C (2729°F) with a density of 7.65 g per cm³ (0.276 lb. per in³), specific gravity of 7.65, and modulus of elasticity in tension of 29x10⁶ psi or 200 GPa. Its tensile strength is 65,000 psi with a yield strength of 30,000 psi. On the Rockwell hardness scale, stainless steel 410 measures at HRB80, which is used to measure low carbon steels.

The martensite microstructure of grade 410 is a type of crystalline structure that has ferromagnetism. During heat treatment, the austenitic microstructure of grade 410 undergoes a transformation into a martensite microstructure, which gives the metal improved strength and hardness and its magnetic nature. This aspect of grade 410 makes it ideal for magnetic assemblies, magnetic sensors, and magnetic separators.

Chapter 4: Stainless Steel Grade 416

Stainless steel grade 416 has the highest machinability of all of the different stainless steels with a rating of 85%. The rating scale for machinability was established by the American Iron and Steel Institute (AISI) and is expressed as a percentage with carbon steel having a 100% rating, which means it is easy to machine. As the percentage for a metal moves below 100%, it is determined to be difficult to machine. Most stainless steels are in the 40% to 80% range.

Grade 416 is resistant to acids, alkalis, fresh water, and dry air but is less corrosion resistant than non-machinable stainless steels. In order to enhance the corrosion resistance of grade 416, it is hardened, which gives it a smooth surface. The hardening process for grade 416 involves heating the metal to 925°C up to 1010°C (1742°F up to 1850°F) followed by oil quenching and tempering.

In order to weld grade 416, the metal has to be preheated to 200°C up to 300°C (392°F up to 572°F), which is followed by annealing or stress relief. Grade 410 electrodes are ideal for the grade 416 welding process, and grade 309 filler rods can be used, as well.

Stainless steel grade 416 is the grade of stainless steel that is most often used for machining. The reason for the high machinability of grade 416 is its high sulfur content. In addition, grade 416 can be heat treated to further enhance its machinability, which gives it an improved machinability performance over austenitic 300 series stainless steels.

The machinability of all stainless steels is dependent on the elements and materials that are added. Many of the elements that are added to stainless steel increase its strength but make it difficult to machine, such as chromium, nickel, and molybdenum. The addition of sulfur increases the metal's machinability since it lowers the shear strength of inclusions that act as stress risers and weaken the steel. The lowered shear strength makes it possible for machined chips to break away from the work area more efficiently and helps avoid the build up of waste on the cutting tool, known as bird nesting. In addition to sulfur, other additives used to enhance machinability include selenium and calcium.

Chapter 5: Uses for Stainless Steel Grade 410

The applications for which stainless steel grade 410 is used require mild corrosion resistance, heat resistance, and strength. It is supplied to fabricators and manufacturers in sheets, bars, plates, rolled, and drawn. The type of form used by stainless steel product producers is dependent on the dimensions and specifications of their product. As with all series and grades of stainless steel, there are specialized types of stainless steel grade 410 that are engineered for certain types of applications.

AWS E410-16 Stainless Steel

AWS E410-16 are coated electrodes with a titania flux coating, which are used for welding and repairing stainless steel grades 410, 416, 420, and 431. It is a coated electrode with hardenability with exceptional strength and moderate resistance to corrosion with a tensile range of 700 Mpa up to 850 Mpa. AWS E410-16 has excellent rust resistance and can be hardened to a Rockwell hardness of 40 depending on the amount of carbon it contains. There is a wide assortment of applications for which AWS E410-16 is used including bolts, bushings, and various types of fasteners.

ER410 Stainless Steel

ER410, like AWSE410-16, is used to weld stainless steels and is used to weld overlays on carbon steels. It is used to weld stainless steels with a similar chemical composition and as an overlay for carbon steels to give them resistance against corrosion and abrasion. ER410 is a hardening filler metal that requires joints to be preheated to 176.7°C (350°F) prior to welding the joint.

Knife Blades

The various types of kitchen cutlery require a knife blade with strength, durability, and some resistance to corrosion. These factors are the reason that stainless steel grade 410 is used for the manufacturing of knives and flatware and for use in industrial food processing. The chromium content of grade 410 protects knife blades from the effects of the acidity of food and the corrosiveness of water. The heating process in the manufacture of grade 410 gives the knife blades their hardness and edge retention, which helps in their durability and longevity.

Stainless Steel 410S

Stainless steel 410S is a low carbon modification of stainless steel 410. The low carbon content and some alloy additions reduces austenite formations at high temperatures, which restricts the ability of stainless steel 410S from hardening. It remains soft and ductile after being rapidly cooled. The non-hardening characteristic prevents the steel from cracking when exposed to excessively high temperatures or welding. The ductility of stainless steel 410S makes it easy to form and shape and increases its viability for a wide range of applications from ore processing to plates and valves.

Gate Valves

Gate valves are used for fluids that flow in a straight line and require minimal restrictions. The composition and properties of the gate valve material is very important, since the range of liquids or gases widely vary and can affect the performance of the valve. High volume liquid and gas flow requires a gate valve with exceptional strength and corrosion resistance, which is the reason that stainless steel 410 is used in gate valve construction and is used in the manufacture of a variety of gate valves. The mechanical and physical properties of stainless steel 410 make it an ideal material for gate valves for the oil and gas, pharmaceutical, and waste water treatment industries.

Chapter 6: Uses for Stainless Steel Grade 416

Stainless steel grade 416 is a free machining stainless steel, which is a metal that allows small chips to break evenly during machining. The machining process can be completed continuously since the machined chips do not need to be removed, a factor that allows for longer run times and machining cycle times. Stainless steel 416 is normally used for parts and components that require extensive machining and corrosion resistance, such as electric motors, pumps, valves, screw machines, studs, and gears.

Many of the uses for stainless steel grade 416 are the same as those for grade 410 with the difference between the two being 416’s strength and toughness. A common use for stainless steel 416 is as fasteners due to its strength. In addition, it is used for cutlery and kitchenware, like grade 410. A unique use for grade 416 is as components for firearms.

Firearms

The use of grade 416 in the manufacture of firearms is due to its strength, resistance to rust, and resistance to heat. The main part of a firearm that is made of stainless steel is the barrel through which the fired projectile travels. It is included in the barrels of rifles, pistols, competitive rifles, and military weapons. In order to be approved for use in firearms, grade 416 is tested ultrasonically under the American Society of Testing and Materials (ASTM) stipulation 2375, which outlines the parameters for the ultrasonic test.

In addition to the barrels of firearms, grade 416 has been found to have the strength, endurance, and stability to perform as other aspects of firearms, such as triggers and firing pins. Any aspect of a weapon that requires constant and repetitive use is made of grade 416 stainless steel to ensure the safety of a weapon and its performance. The barrels of firearms made with grade 416 stainless steel have greater accuracy and are the reason competitive and target shooters prefer grade 416 barrels.

Springs

Springs are various sizes of wires that are wound in a helical fashion with each type of spring having a different and unique form to fit the requirements of an application. They have to be exceptionally durable and able to easily recover after being stressed or deformed. Stainless steel grade 416 is an ideal material that is used to form springs due to its strength, durability, machinability, and rust and corrosion resistance. The types of springs manufactured using stainless steel 416 include the full spectrum of springs with larger springs being the most common.

Chapter 7: Common Forms of Stainless Steel Grades 410 and 416

The various forms of stainless steel grades 410 and 416 are produced to meet the requirements of manufacturers and take several different shapes. During the manufacturing process, the molten stainless steel is formed into different shapes for shipment. Common forms used in the production of grades 410 and 416 are sheets, bars, plates, billets and ingots, or being cold drawn through a die to form a specialized shape.

Plates

Stainless steel plates have a similar structure to that of sheets with a greater thickness. Although both forms of stainless steel are in the form of thick flat pieces of metal, the differentiating factor between the two forms is their thickness with flat forms that have a thickness of 2 to 3 mm (0.079 in up to 0.12 in) being defined as plates. Plates are produced in the same way as sheets by having the material rolled through a mill.

Rods

Rods have a cylindrical shape and are used in their manufactured form as supports. They come in different diameters in accordance with the purpose for which they are manufactured. Rods also come in different lengths, a factor that makes them flexible enough to be used for the CNC process for producing screws and fasteners.

Bars

Bars are a unique form of stainless steel and take a wide assortment of shapes that include round, hexagonal, strips, and specialized ones for specific applications. They are hot or cold rolled to achieve the necessary hardness for an application. Bars can have complex profiles that have different cross-sectional shapes. This aspect of bars is one of the reasons for their wide use.

Sheets

Sheets are one of the more common forms of stainless steel that are used for shipping since they fit easily on pallets and can be loaded in stacks. Like the other forms of stainless steel, sheets come in a wide variety of sizes. They can be rectangular or square depending on the preference of the manufacturer. In the manufacturing process, sheets can be laser cut, stamped, bent, and deformed to fit the requirements of a product or application. They are seldom used in their original form and are normally reengineered by a mechanical process.

Billets and Ingots

Billets and ingots are another common form of stainless steel that are used for shipping and manufacturing. They are used in a wide array of manufacturing processes from casting to extrusion. The shapes of stainless steel billets are easy to manipulate and handle. They can be easily placed in furnaces to melt the metal for being injected into a casting mold.

Chapter 8: The Benefits of Stainless Steel Series 400

Series 400 stainless steel is known for its strength, hardness, and wear resistance and is used in applications for several industries. The list of uses for series 400 stainless steels includes simple cutlery and kitchen tools, industrial machinery, medical instruments, and petrochemical equipment. It has the necessary quality and performance that is demanded by manufacturers.

Alloys in the 400 series, such as grades 410 and 416, are versatile, dependable, and resilient and provide a cost effective and reliable metal to meet the needs of high stress applications. The wear and tear resistance of series 400 stainless steels makes them applicable for specialized and unique applications.

Cost Effective

The lower nickel content of series 400 stainless steels significantly affects its cost compared to other types of stainless steel. It is one of the reasons that series 400 is selected for so many applications.

Manufacturing

The ease of forming and shaping of series 400 makes it possible to quickly produce the metal. It is one of the easiest steels to produce compared to other forms of steel. The ability to form and shape series 400 is part of the reason for its wide usage.

Maintenance

Series 400 has similar strength compared to carbon steel but with rust and corrosion resistance, which makes it easier to maintain compared to carbon steels. While carbon steel requires the applications of coatings for protection from rust and corrosion, series 400 is naturally resistant.

Wear

One of the outstanding characteristics of series 400 stainless steels is their ability to endure wear and tear, which is unlike other forms of stainless steel. This aspect makes series 400 stainless steels long lasting and highly durable and makes it an option for applications that require strength and endurance.

Conclusion

• One of the distinguishing features of stainless steel series 400 is its manganese content, which is 1% higher than that of series 300 stainless steels.
• The strength and durability of stainless steel series 400 is due to its higher carbon content, which gives it a martensitic crystalline structure.
• The different forms of stainless steel series 400 includes plates, sheets, bars, and tubes that are formed and shaped to meet the requirements of manufacturers.
• The extra strength and durability of stainless steel 400 series increases its usefulness for stressful and demanding applications but lowers its resistance to corrosion and rusting compared to other forms of stainless steel.
• Stainless steel 410 is referred to as a general-purpose stainless steel that is used to produce components and parts that have to endure high stress.
• Stainless steel 416 is the first free machining stainless steel and has the highest machinability of all stainless steels. It has exceptional strength and resilience when hardened and tempered.