It is a kind of metal alloy made of steel combined with other metals, such as nickel, chromium, and copper, which has been one of the greatest inventions in the history of mankind. In spite of its versatility in a wide range of applications, stainless steel is unlike any other material in the market. Its diverse range of grades allows it to accommodate a wide variety of applications across many different industries, making it a great choice.
Here are 7 things to consider while choosing the right stainless steel grade:
1. Welding requirements
Not all grades of stainless steel are weldable. Depending upon certain grades, welding can lead to problems such as intergranular corrosion, hot cracking, and stress corrosion cracking. In case your products need welding, you need to choose stainless steel grade that is weldable. Austenitic stainless steel grades such as 304L, and 347 ce be used for welding due to lower carbon levels. Ferritic stainless steels such as grade 430 or grade 439 are also readily weldable. Martensitic stainless is generally not suitable for welding. Extra care needs to be taken when welding stainless steel to ensure that the mechanical properties of the metal are not compromised during the welding process.
2. Corrosion resistance
Though stainless is known to have corrosion resistance, various grades of stainless steel have varying levels of corrosion resistance. Austenitic stainless steel like Grade 304 and 316 is the most sought-after for corrosion resistance because of high amounts of chromium and molybdenum, respectively. Ferritic stainless steels and martensitic are generally more affordable than austenitic stainless steel because they have less nickel and sometimes less chromium than austenitic stainless steels, which can result in a loss of corrosion resistance. They are suitable for applications that involve the indoor use of stainless steel as this limits exposure to weather and other corrosive elements.
3. Need of machining
Most grades of stainless steel can be machined, however, it is very susceptible to hardening. The machining process must be optimized to work at a rate that helps alleviate this issue, and the tools used for machining must also be kept in good working condition. Similar to carbon steels, sulfur can be added to increase machinability; grade 303 is an example of this. It is very similar to grade 304 except that sulfur has been added to it for machining purposes. Grade 416 is an example of ferritic stainless steel with added sulfur.
4. Heat treatment
If the stainless steel is going to be subjected to heat it is imperative to know how the product properties will be affected. Grade 440C and 17-4 PH, are heat-treatable stainless steels.
5. Strength
The quality of stainless steel depends on various factors and one of the most important factors to consider while selecting stainless steel is strength. The strength varies from varies between different grades. Martensitic stainless steels, like grade 440C, and precipitation-hardened stainless steels, like grades 17-4 PH and 15-5 PH have the best strength. Austenitic stainless steel comes second on the scale of strength. Duplex stainless steels can provide ferritic stainless steel properties while still maintaining ductility and toughness close to austenitic stainless steels.
6. Good Formability
If the application of stainless steel castings requires good formability, an austenitic grade such as 304 or a ferritic grade such as 430 is the best. Martensitic groups of stainless steel tend to be brittle and are not readily formable.
7. Cost-effectiveness
In order to choose a good stainless steel grade all the above considerations, are important but the most important one is cost-effectiveness. Your industry needs to have stainless steel applications that are profitable, match your intended environment, and have high performance for the long term. Though most grades of stainless steel require negligible maintenance, you still need to account for it depending upon the harsh, cold, or corrosive environment it is expected to work in.
What is Ferritic Stainless Steel?
A grade of stainless steel alloy known as ferritic steel contains 12% or more chromium in comparison to other grades of stainless steel. Ferritic steel differs from other forms of stainless steel in two essential aspects: the molecular grain structure as well as the chemical composition.
In reality, ferritic stainless steel can be defined as a straight chromium non-hardenable class of stainless alloys that have a chromium content of between 10.5% to 30%, and a carbon content of less than 0.20 percent.
In addition to not being hardenable by heat treatment, ferritic stainless steels are substantially harder after cold rolling. Ferritic stainless steels include:
- Grade 409: Automotive exhaust systems and heat exchangers
- Grade 416: Axles, shafts, and fasteners
- Grade 430: Food Industry and Appliances
- Grade 439: Automotive exhaust systems components
Austenitic Stainless Steels:
A face-centered cubic (FCC) steel or iron alloy with this type of structure is called austenite. It was named after Sir William Chandler Roberts-Austen, an Englishman who studied metal properties.
As the name implies, the word austenite refers to a face-centered cubic (FCC) structure found in iron alloys and steel alloys that have this type of structure. It was named after Sir William Chandler Roberts-Austen, an English scientist who studied the physical properties of metal during the 1800scategory is known for unsurpassed strength and formability and that it can not be hardened by heat treatment.
Grades of Austenitic stainless steel
- Grade 303: Fasteners, fittings, gears
- Grade 304: General-purpose austenitic stainless steel
- Grade 304L: Grade 304 applications that require welding
- Grade 309: Applications involving elevated temperatures
- Grade 316: Chemical applications
- Grade 316L: Grade 316 applications that require welding
Martensitic Stainless Steels:
In addition to having a high carbon content, Martensitic stainless steels contain between 12 and 18% Cr. They have moderate corrosion resistance and poor weldability, but can be hardened through heat treatment. The reason for this is they are used in knife blades and spring. It is also known that Martensitic stainless steels are used when corrosion resistance and/or oxidation resistance are required in conjunction with either high strength at low temperatures or creep resistance at elevated temperatures.
Grades for Martensitic stainless steels
- Grade 410: General purpose martensitic stainless steel
- Grade 440C: Bearings, knives, and other wear-resistant applications
Precipitation Hardened Stainless Steels:
Precipitation hardenable (PH) stainless steel alloys are one of the most common types of stainless steel alloys in use today, yet they are often not as well known as austenitic and ferritic steel alloys. While some people refer to the five types of stainless steel in fact, others may only mention four: the two already mentioned above, plus martensitic and duplex alloys. Precipitation hardening is left off the list since it does not fall under the category of stainless steel.
It is not hard to understand why austenitic and ferritic alloys are the most widely used alloys when it comes to commercial stainless steel applications today since they account for 95% of all commercial stainless steel applications. Why is a precipitation hardening so often overlooked in the industry today? We will discuss the material’s positive attributes as well as how precipitation hardening is accomplished in today’s post. Additionally, we will give you a brief overview of some of the most popular applications and the industries where you will find them the most commonly used. It is not hard to understand why austenitic and ferritic alloys are the most widely used alloys when it comes to commercial stainless steel applications today since they account for 95% of all commercial stainless steel applications. Why is a precipitation hardening so often overlooked in the industry today? We will discuss the material’s positive attributes as well as how precipitation hardening is accomplished in today’s post. Additionally, we will give you a brief overview of some of the most popular applications and the industries where you will find them the most commonly used.
Precipitation hardenable (PH) stainless steel Grades
- 17-4 PH: Aerospace, nuclear, defense, and chemical applications
- 15-5 PH: Valves, fittings, and fasteners
What to consider when choosing a stainless steel grade
It is important to consider several factors when choosing a stainless steel grade for a particular application. The following are some key considerations:
- There is no doubt that stainless steel is corrosion-resistant, but different grades have varying levels of resistance to different types of corrosion. It is important to select a material grade that is resistant to the environment the material will be exposed to (e.g. saltwater, acidic and alkaline solutions, high temperatures) and to consider how the material will be exposed to those conditions.
- Strength and hardness: Stainless steel is available in a variety of strengths and hardnesses. Select a grade that offers appropriate strength and hardness for the load the material will have to bear.
- Processing requirements: Some grades of stainless steel are easier to weld, machine, or form than others. Identify the fabrication or processing methods that will be used on the material, and choose a grade that meets their requirements.
- The cost of stainless steel varies depending on the grade and quantity ordered. Identify a grade that provides the necessary performance characteristics at a reasonable cost based on the project’s budget.
- Stainless steel is often used in architectural and decorative applications where appearance is important. Choose a grade that will achieve the desired finish (e.g. brushed or polished).
- Some stainless steel grades may not be readily available in certain sizes or forms. Check whether the desired size and form are available for the material.
- Regulatory compliance: Some applications may require compliance with regulatory standards, such as those pertaining to food contact or medical devices. Select a grade that meets the requirements of the applicable regulations.
Choosing a stainless steel grade should be based on a careful evaluation of the specific application requirements and a thorough understanding of the properties and characteristics of different grades.
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