Understanding Ferritic Stainless: A Comprehensive Guide

Ferritic stainless steel accounts for one of the most exceptional materials in contemporary industries because of its superior properties like strength, corrosion resistance, and low cost. This ferrous alloy is found in numerous applications, from automotive exhaust systems to kitchen equipment. But what differentiates ferritic stainless steel from other types? And why is it so commonly used in so many different fields? This article aims to cover everything that concerns ferritic stainless steel, including its main characteristics, uses, advantages, and disadvantages. For manufacturers, engineers, or anyone who is concerned with material science, this article will broaden their horizons regarding the importance of ferritic stainless steel.

What is Ferritic Stainless Steel, and How Does It Differ from Other Types?

Ferritic stainless steel contains between 10.5 to 30% chromium and little to no nickel, making it predominantly composed of iron and chromium. Ferritic grades, unlike austenitic stainless steel, have a body centered cubic (BCC) crystal structure, which is what allows them to have higher resistance to stress corrosion cracking and better thermal conductivity.

Ferritic stainless steel is also magnet and possesses corrosion resistance, though limited, is greatly favorable in automotive components, industrial machinery, and household appliances. Thermally stable and less expensive to produce due to low nickel percentages, half of its appeal comes from being more economical compared to other types of stainless steel. Unfortunately, it is less formable and weldable which changes with austenitic grades.

Composition and Chemical Composition of Ferritic Stainless

The base element of ferritic stainless steels is primarily iron with chromium content averaging between 10.5 % and 30%. The corrosion resistance of the material is obtained in the specific chromium concentration mentioned. Other elements like molybdenum, aluminum, and titanium may further enhance some properties such as strength oxidation resistant or stability but in very small proportions. Ferritic stainless steel is different from the other grades because it has almost negligible or no nickel content. This leads to lower expenses and unique structural features of the material.

Comparison with Austenitic and Martensitic Grades

Stainless steels, including Austenitic, Martensitic, and Ferritic, possess distinct traits that are intricately linked to their uses because of differences in metallurgical design and alloy composition.

Austenitic Stainless Steels have the most remarkable corrosion resistance, ductility, and formability. They are composed primarily of iron, chromium (16-26%), and nickel (6-22%). In addition, they include small quantities of molybdenum for enhanced resistance to pitting and crevice corrosion, especially in chloride environments. This grade is structurally stable from cryogenic temperatures to over 1500 degrees Fahrenheit (815 degrees Celsius), making it excellent for food processing, chemical plants, and marine industries. Notable features of austenitic steels include their non-magnetic nature, which sets them apart from the majority of other grades. Popular subgrades consist of 304 and 316, which are optimized for distinct corrosive environments, with 316 being a more dominant chloride-resistant grade because of 2-3% molybdenum addition.

Compared to austenitic steels, Martensitic Stainless Steels are magnetic and differ in their exceptional strength and hardness obtained through tempering. While possessing lower chromium content (12-18%) and trace amounts of nickel, these steels exhibit lower corrosion resistance but are superior in toughness and wear resistance. Martensitic grades 410 and 420 are employed in the manufacturing of surgical instruments, turbine blades, and industrial tools, where resistance to cutting, machining, or impact is essential. These steels can be heat treated to achieve a Rockwell hardness of over 58 HRC.

The trade-offs of both these austenitic and martensitic grades are noticeably different from that of the more economical stainless ferritic steels which have a focus on corrosion resistance and stability. Ferritic steels are relatively cheap and made of nickel and chromium (10.5% – 30%) which makes them moderately corrosion resistant, but extreme temperatures or harsh corrosive environments can easily damage them. These cheaper grades are especially useful in making automotive parts like exhaust systems and appliances because they possess relatively good magnetic properties.

With the knowledge of these types of steels, industries can provide exact specifications to be met in terms of mechanical properties, corrosion resistance, and cost, ultimately increasing efficiency. There is still work done to make these categories more precise with newer designs of alloys in order to provide better-tailored solutions to different industrial applications.

Applications and Uses of Ferritic Stainless Steel

Ferritic stainless steels are preferred in multiple sectors because of their economical pricing, formability, and resistance to corrosion. These are their main applications and uses:

Automotive Industry

For parts like the exhaust system, ferritic grades are widely claimed in the automotive industry:

• Exhaust systems: Grades like 409 and 439 are used in oxidized or heated situations.
• Fuel Systems: Fuel tanks and pipelines often require these grade’s fuel-resistant metals.
• Structural components: To comply with efficiency standards, ferritic grades meet strength and are lightweight.

Appliances and Household Goods

• Ferritic grades like 430 are preferred for washing machines and dishwasher appliances because of their aesthetic view along with hardware corrosion.
• Ferritic steels can withstand high temperatures, and does not deform significantly, which is why it is used in cooking equipment and oven liners.

Construction and Architecture

• Cladding and roofing, along with other armor fabrication, have weather-resistant benefits with the use of ferritic stainless steel.
• Other architectural constructions that require high-strength and low maintenance are made out of durable and mildly corrosive high-strength ferritic grades.

Industrial Equipment 

• Due to their good thermal conductivity, these heat exchangers are used in power plants or chemical processes, and they have corrosion-resistant properties.
• These grades are often used in mildly corrosive storage tanks and containers.

Energy & Power Generation

• Ferralsitic stainless steel’s high strength at elevated temperatures makes it useful for solar water heaters and heat collectors.
• Its high-temperature performance is also leveraged by components of fossil-fuel power plants such as boiler systems.

Food and Beverage Industry

• Farralitic stainless steels, especially grade 430, are inert which makes them favorable in food contact. Used in fermentation tanks, food-grade containers, and other processing machining.

Other Applications

• Elevator interiors and decorative panels are fabricated from ferritic steel due to their aesthetic sheen.
• Used in electrical applications where magnetic properties are needed, such as the core in transformers.
• Strength and corrosion protection are combined in ferritic stainless steel for use in automated teller machines (ATMs) and vending machines.

These examples, both diverse and critical, highlight the development of technology in the industries and underscore the need to advance the alloy composition of ferritic stainless steels to meet growing needs.

How Does Heat Treatment Affect Ferritic Steel?

Importance of Anneal in Ferritic Grades

During the processing of ferritic stainless steels, annealing plays an important role because it adjusts internal strains while restoring ductility and refining the microstructure. With controlled heating and cooling, the material is annealed to ensure uniformity in mechanical properties alongside maximum formability. This treatment is also essential to re-establish an optimal crystalline structure, thus enhancing corrosion resistance and making it ideal for high-performance applications. Practices geared towards proper annealing are critical in achieving the desired consistency and toughness in ferritic grades.

Impact on Mechanical Properties

Metals, especially ferritic grades, tend to lose their strength as internal stress is relieved, resulting in softer metals. This makes the metal easier to work with and boosts its overall efficiency for various applications. The annealing process leads to the key mechanical changes listed below:

• Reduction in Hardness: The toughness of a material is determined by measuring the material’s hardness, and annealing processes lead to softening of the material. For example, ferritic grades can have their hardness values drop from 250 HV to 150 HV with the correct temperature and time of the annealing process.
• Improved Ductility: Another notable change in ductility is the increase in elongation percent. For instance, in a cold-worked stat, a metal can have 10% of an elongation value, and after annealing, that value can increase to 25% or more.
• Stress Relief: Internal stresses created by machining parts and forming them are removed. This prevents warping or undesired breaking of the material when it is being used.
• Tensile Strength Adjustment: Tensile strength does decrease, but stays in acceptable range. For example, after annealing, depending on the conditions, a toughness value of 500 MPa could drop to 400MPa.
• Improvement of Corrosion Resistance: During the annealing process, as the crystalline structure is reformed, it helps to further decrease weak areas which enhances the materials resistance to corrosion.

These modifications highlight the great significance of annealing in adjusting mechanical properties while maintaining specific engineering standards and material dependability.

Influence on Grain Structure

Similar to other treatments of metallic materials, annealing alters grain structure and affects the resulting mechanical properties and microstructure homogeneity. During the heating phase of annealing, grains boundaries transform with increasing atomic movements, enabling rearrangement of defects, like dislocations. The subsequent cooling phase either leads to grain growth or recrystallization depending on the parameters of the thermal cycle.

Recent studies suggest that carbon steels undergo significant recrystallization annealed at temperatures between 600°C and 800°C, resulting in finer equiaxed grains that uniformly distribute stress and make them more ductile. Empirical data supports this claim as the measured average grain size was found to decrease from roughly 50 μm in the as-cast condition to 15 μm post-annealing under certain conditions, which is clear evidence of grain refinement.

More detailed studies reveal the effect of controlled annealing of aluminum alloys is the formation of higher density of High Angle Grain Boundaries (HAGBs). This structural evolution is believed to lead to higher formability by reducing strain localization. For stainless steels, it was found that slow cooling annealing is beneficial in reducing grain coarsening while retaining good intergranular corrosion resistance.

In summary, the effect of annealing on grain structure is controlled by the material composition, soak time and cooling rate. The mechanical properties of the material and its applicability will need to be ascertained in order to optimize these factors.

Why Do Ferritic Stainless Steel Grades Offer Corrosion Resistance?

Role of Chromium Content

It is chromium that accounts for the corrosion resistance in the ferritic grades of stainless steel. When chromium is exposed to oxygen, it reacts to form a thin and stable chromium oxide on the steel surface. This leads to passive film formation. This film shields the steel from further oxidation while protecting it from corrosive conditions. Approximately 11 to 12 percent chromium content is needed in the steel to maintain reasonable corrosion resistance. In more oxygen-aggressive environments, higher chromium content will enable even further passive film resistance. The long-term operability of various environments is made sustainable due to the self-repairing feature of the passive film.

Effects of Molybdenum and Nickel

As nickel and molybdenum are considered the most important alloying constituents in stainless steel, their incorporation into the steel improves the corrosion resistance and the mechanical properties, as well as their performance at extreme service conditions. Molybdenum is recognized to enhance resistance to pitting and crevice corrosion, which is especially important in chloride-laden environments. This makes molybdenum indispensable in marine applications as well as chemical processing industries. Type 316 stainless steel, which contains 2-3% molybdenum, shows strikingly better resistance compared to molybdenum deficient grades like Type 304.

On the other hand, nickel is also important because it aids in the stabilization of the austenitic structure of stainless steels and enables good formability, weldability, and toughness at a wider range of temperatures. In addition, the corrosion resistance in acidic and reducing environments is further improved with high nickel content. Stainless steels with 8-10% nickel, such as Type 304 and Type 316, perform well in inhibitive environments containing sulfuric or phosphoric acids. Duplex and super-duplex stainless steels take advantage of the corrosion resistance achieved by both molybdenum and nickel, as well as their outstanding mechanical strength.

Research shows that increasing molybdenum content by up to 1 percent in stainless steel improves pitting resistance in chloride solutions by nearly 40 percent. In the same manner, 8 percent or greater proportional nickel aids in the retention of austenitic stability while also improving tensile strength at cryogenic temperatures. Together, these elements are critical in allowing molybdenum stainless steels to satisfy stringent requirements in diverse industries like energy, transportation, or even infrastructure while ensuring safety and reliability in extreme operating conditions.

Comparing Corrosion Resistance with Austenitic Stainless Steel

The corrosion resistance of stainless steel grades 304 and 316 is much better because of their increased chromium and nickel percentage. For example, Grade 316 stainless steel is more resistant to pitting and crevice corrosion because of the additional molybdenum content of 2-3%. These types of pitting and crevice corrosion are often found in the presence of chlorides, which affect marine and chemical processing industries. Clinical studies demonstrate that 316 stainless steel is more suited to withstand pitting at chloride concentrations of around 1,000 ppm, which renders it favorable in hostile coastal and industrial scenarios.

Moreover, the passive oxide layer generated by the chromium content in austenitic stainless steel acts as a powerful shield against general corrosion. Tests conducted in controlled environments show that alloys with 18% chromium and 8% nickel, like Grade 304, are enduring in less hostile environments over time, but tend to underperform in highly acidic or chloride-laden environments, susceptible to localized corrosion.

Austenitic alloys are superior to other stainless steel varieties like ferritic or martensitic grades in both uniform corrosion resistance as well maintaining mechanical properties at elevated and ultra-low temperatures, including cryogenic regions. This makes austenitic alloys especially useful in the oil and gas industry, which sustains extreme environmental conditions with different corrosive agents such as sulfuric acids and saline waters, which require reliable and durable alloys. In addition, the ongoing optimization of alloys, including duplex and super austenitic steels, seeks to further expand the limits of corrosion resistance to guarantee functionality in harsher environments.

Can Ferritic Stainless Steels Crack Easily?

Understanding Crack Formation in Ferritic Grades

In comparison to other types, such as the austenitic grades, crack formation in ferritic stainless steels is much less common due to their lower vulnerability to stress corrosion cracking. Nevertheless, these steels possess the ability to crack under particular conditions, such as exposure to extreme stresses in combination with hostile environments and hydrogen and chloride-rich ones. Improper heat treatment or welding processes can also increase the risk of cracking due to the weakening of the grain boundaries. To reduce these risks, there is a need to follow the prescribed guidelines pertaining to fabrication and select the right alloy composition that will be suited for the target application.

Preventive Measures During Weld Processes

A few practical guidelines must be taken into account in order to preserve ferritic stainless steels throughout their welding processes:

Preheat and PWHT

• Appropriate preheat, which usually falls within the range of 150°C to 300°C, depending on the alloy grade, can help in decreasing the risk of cracking by minimizing the development of thermal gradients. PWHT is used to relieve the residual stresses after the material has been welded and restore its mechanical properties. PWHT procedures have been shown to reduce the effects of hydrogen cracking by fifty percent PWHT.

Control of Heat Input

• Too much heat input during welding can lead to coarser grains and greatly reduced toughness in the HEAT-AFFECTED ZONE (HAZ). The optimal heat input is determined on the basis of the material thickness and the welding techniques employed. For ferritic stainless steels, an input range of 1-1.5 kJ/mm should be maintained for the best quality and integrity of the weld structure.

Use of Low-Hydrogen Consumables

• Hydrogen is a very important factor behind weld cracking. Low-hydrogen or hydrogen controlled filler materials can be very effective in reducing the amount of hydrogen that is absorbed during the welding process. Studies suggest that low-hydrogen electrodes significantly lower delayed cracking in environments that are prone to chloride.

Gas Shielding Approach

• Using the right shielding gas is essential to avoid oxidation while providing contour stability of the weld pool. An Ar-He or Ar-H2 mixture is neutral for ferritic stainless steels and will produce desirable beads with minimal spatter.

Correct Joint Design

• Stress concentration is mitigated through careful weld joint preparation. Inclusion and incomplete fusion defects that would weaken the weld are unlikely with well-designed joints with decent edge preparation and root gaps.

Welding Surface Cleanness

• The presence of oil, grease, or even moisture on a surface can lead to contamination of the weld pool which leads to defects. Appropriate solvents or mechanical approach to clean the surface will ensure a clean welder surface area and minimizes risks.

Ferritic stainless steels can have their welds enhanced in reliability and durability by following these approaches. In addition to these, compliance with defined standards AWS D1.6/D1.6M or ISO 3834 reveal additional information to ensure quality and safety during welding operations.

Comparative Analysis with Martensitic Stainless Steels

Just like the ferritic stainless steel, martensitic stainless steels are also iron alloys. However, they are very different with respect to their composition, microstructure and application. One major difference stems from carbon content; martensitic grades have more carbon, between 0.1% to 1.2%, while ferritic grades have less than 0.1%. The increased carbon content for martensitic steels allows the development of a martensitic microstructure by quenching and tempering processes, which increases hardness and strength.

Considering mechanical properties, martensitic stainless steels have higher tensile and yield strength; for instance, types 410 or 420 have a tensile strength of 500 to 1,400 MPa. These types of steel are useful in manufacturing cutlery blades, turbine blades, and valves, which need resistance to wear. In contrast, strength levels for ferritic stainless steels are modest, usually between 350 to 600 MPa, but can withstand corrosive environments that are not aggressive.

Resistant corrosion is yet another remarkable mark of distinction. While martensitic grades are inherently stainless, their chromium levels (commonly found between 12-18%) are relatively lower than that of ferritic grades, and the existence of high carbon renders them more vulnerable to pitting and crevice corrosion, especially in chloride-containing regions. Ferritic steels, with chromium percentages usually from 10.5% to 30%, are more resistant to corrosion, especially during oxidation and mild reduction phases.

Resistance to weldability poses a particular problem in martensitic grades as they are prone to the creation of hard and brittle welds as a result of rapid cooling rates, causing welds to transform to martensite. Mandatory preheating and post-weld treatments are often necessary to mitigate cracking or loss of strength. Although not as amenable as austenitic stainless steels, Ferritic stainless steels are easier to weld compared to martensitic steels, and an as-welded state requires less stringent heat treatment conditions, assuming proper welding practices are followed.

In terms of thermal performance, martensitic grades lag behind ferritic stainless steels when it comes to thermal conductivity and low thermal expansion. As a result, ferritic stainless steels are beneficial for use in automotive exhaust pipes and heat exchangers. Conversely, situations where high strength, low wear, and robust resistance to extremes of temperature are less of an issue, martensitic steels are more desirable.

In essence, the choice of either type of stainless steel, ferritic or martensitic, comes down to how their specific characteristics, such as strength, corrosion resistance, weldability, and thermal properties, meet application requirements. For instance, while a cutting tool is best served with a ferritic grade 440C due to its unbeatable hardness, a grade 430 might be more appropriate for ornamental or functional components that resist corrosion.

What are the Popular Ferritic Stainless Steel Grades and Their Properties?

Overview of Standard Ferritic Grades

Ferritic stainless steels consist of a wide variety of alloys with high chromium content and minimum carbon content. These grades are organized according to their functionality, with each alloy fulfilling certain functional needs. A brief outline of widely known ferritic stainless steel grades, along with their key features, is presented below:

Grade 409

• Chromium Content: ~10.5-11.75%.
• Key Features: Cost effective option for car exhaust systems; has favorable oxidation and corrosion resistance at high temperatures.
• Applications: Mufflers, automotive parts, and non-critical corrosion-resistant structures.

Grade 410S

• Chromium Content: ~11.5-13.5%.
• Key Features: Better welded joint performance along with increased impact toughness relative to 410 and lowered hardenability resulting in less chances of cracking.
• Applications: General hardware products, furnace parts, and heat exchangers.

Grade 430

• Chromium Content: ~16-18%.
• Key Features: Excellent formability good corrosion resistance, and retention of surface finish.
• Applications: Cladding, kitchen appliances, and trim components for the automotive industry.

Grade 434

• Chromium Content: ~16-18% (added with molybdenum).
• Key Features: Better resistance to pitting and crevice corrosion owing to the addition of molybdenum.
• Applications: Chemical processing equipment, marine applications, and automotive exhaust systems.

Grade 436 

• Chromium Content: ~16-18% (added with controlled molybdenum and titanium).
• Key Features: Enhanced forming characteristics and better resistance to stress corrosion cracking.
• Applications: Furnace linings, automotive trim, and sink units.

Grade 444

• Chromium Content: ~17.5-19.5% (Alongside Molybdenum).
• Key Features: Resists chloride corrosion exceptionally and is thus usable in aggressive surrounding conditions.
• Applications: Equipment for solar water systems, water heaters, and food processing.

Distinct grades are designed to fulfill particular industrial requirements and provide different combinations of strength, workability, and toughness to corrosion. Selecting a ferritic grade requires having a clear picture of the operational environment and the mechanical stresses to be encountered.

Key Mechanical Properties of Ferritic Steels

Ferritic stainless steels are well known for their unique mechanical properties which are applicable in different industries. Listed below are some important mechanical properties of ferritic steels:

Tensile Strength  

• The tensile strength of ferritic stainless steels varies within the bound of 380 to 620 MPa for different grades and compositions. For example, Grade 430, which is a commonly referred grade, has a typical tensile strength of around 450 MG. Thus, these materials are able to sustain considerable amounts of stress and tension.

Yield Strength  

• Ferritic steels have yield strength from 205 up to 450 MPa, providing some resistance to deformation when loaded. Improved grades such as 444 provide higher yield strengths. These values are very useful for structures that require a lot of strength.

Elongation at Break  

• Ferritic stainless steels have elongation values, which normally are range from 20 to 30 percent. These moderate levels of ductility offer reasonable not being too soft for many forming and fabrication processes.

Hardness (Brinell or Rockwell)  

• Ferritic steels, depending on grade and heat treatment, generally possess Brinell hardness numbers of 150 -200 HB. This gives them a reasonable level of hardness and good durability for different difficult working environments.

Thermal Conductivity

• At room temperature, ferritic stainless steel’s thermal conductivity value ranges from 25-30 W/(m·K), which is higher than austenitic steels | austenitic steels’ thermal conductivity is lower. The improved values in thermal conductivity is useful in automotive parts such as heat exchangers and exhaust systems.

Coefficient of Thermal Expansion

• Compared to their austenitic counterparts, these steels have a lower thermal expansion coefficient (~10-11 x 10^-6 /°C), which enables higher dimensional stability with changes in temperature.

Impact Resistance

• Compared to austenitic grades, impact resistance in ferritic stainless steels is lower. However, their performance at room and elevated temperatures is adequate for most standard applications. In the designs, considerations of toughness at sub-zero temperatures due to bcc (body-centered cubic) crystal structure need to be acknowledged.

With such properties, these steels are usable in most demanding applications alongside corrosion resistance which enables engineering design flexibility while taking valiables such as mechanical performance and environment into account.

Exploring Grades of Ferritic Stainless Steel, such as 430

Due to its reasonable costs and remarkable resistance to corrosion, Type 430 is one of the most used ferritic stainless steels. It is recognized for the following properties:

Corrosion Resistance

• Type 430 stainless steel has decent anti-corrosive properties in mildly corrosive surroundings and is well suited for kitchen devices and decorative trims because it withstands food chemicals as well as oxidizing agents.

Formability and Weldability

• This grade can be readily welded with ordinary methods and it is easily formed into different shapes, although post weld annealing may be necessary to preserve desirable ductility.

Thermal conductivity

• In comparison to austenitic grades, Type 430 has greater thermal conductivity and is beneficial in applications that require thermal transfer, such as heat exchangers.

Applications

• Typical uses include household appliances, automotive trim, and architectural cladding, where aesthetic appearance and moderate corrosion resistance are essential.

Considering how Type 430 provides such a favorable balance of performance and cost efficiency, it is able to be utilized in numerous industrial and consumer-oriented applications.

Frequently Asked Questions (FAQs)

Q: What is ferritic stainless steel?

A: A Ferritic stainless steel is an alloy of stainless steel which mainly contains ferrite, which is a phase of iron. Unlike austenitic stainless steel, Ferritic stainless steel is less expensive because it contains little to no nickel. In addition, it has a magnetic characteristic, and it is known to be resistant to corrosion.

Q: What are the properties of ferritic stainless steel?

A: Good formability and strength, excellent resistance to corrosion, especially for outdoor structures, are some of the properties of ferritic stainless steel. Furthermore, these steels possess body centered cubic structure which makes them suitable for certain applications because of their magnetic nature.

Q: How does ferritic stainless steel differ from austenitic stainless steel?

A: Ferritic stainless steels contain very small percentage or no nickel, making them cheaper in comparison to Austenitic stainless steels. In addition, Ferritic and austenitic steels have differing crystal structures. While ferritic steels have a cubic structure, austenitic steels have a face-centered cubic structure. These differences affect their formability and strength characteristics.

Q: What are common applications for ferritic stainless steel?

A: The good corrosion resistance and formability properties of ferritic stainless steels make them useful in automotive exhaust systems, kitchen utensils, and architectural trim. They are further employed in low-cost environments where high nickel content is not required.

Q: How many types of ferritic stainless steel are there?

A: There are several types of ferritic stainless steel alloys classified into different grades based on their composition and ferritic content. Common ferritic grades are derived from the classification of the American Iron and Steel Institute, which include group 2 and group 4 ferritic steels, both of which possess unique characteristics for specific applications.

Q: What characterizes ferritic stainless steel in terms of composition?

A: The chromium content of ferritic stainless steels is what characterizes them, which varies in percentage from 10.5%-30% with little to no nickel, which is what distinguishes them from other forms of stainless. Their magnetic properties because of lower amounts of nickel and cost-effectiveness are what make these steels popular.

Q: How effective are ferritic stainless steels for high-temperature applications?

A: Although ferritic stainless steels have good corrosion resistance, they are not recommended for use on temperatures exceeding 600 degrees celcius because of the risks posed by embrittlement. Nonetheless, specific ferritic grades can function adequately in moderate temperature settings.

Q: Is it easy to weld ferritic stainless steel?

A: Ferritic stainless steel is weldable, but as with other types of weldable metals, it may involve some grain growth and welding crack challenges. Preheat and proper filler metals will yield better results. The formability of these steels also impacts how weldable these steels are.

Q: What makes ferritic stainless steel lower in price than the other types of stainless steel?

A:  The primary reason why ferritic stainless steels are less expensive is their low nickel content. Since nickel is costly, having little or no nickel in the alloy improves the cost efficiency. In addition, ferritic steels are useful for many applications because of their reasonable cost without significant sacrifice of cadmium corrosion resistance, so these alloys are economical.

Reference Sources

1. The Corrosion Resistance of AISI 442 and AISI 446 Ferritic Stainless Steels as Support to PEMWE Bipolar Plates

• Authors: M. Dan et al.
• Published in: Materials Volume 16 2023
• Key Findings: 
• Both AISI 442 and AISI 446 have similar corrosion resistance; however, AISI 446 has a more noble corrosion potential and performs better during potentiostatic stress tests.
• For AISI 446, the current density during polarization at 2 V vs SHE is much less than the current density for AISI 442.
• AISI 446 intercrystalline and pitting corrosion sensitivity is not detected and thus confirms the outstanding corrosion resistance of AISI 446.
• Methodology:
• Electrochemical corrosion tests are performed to determine the effectiveness of the materials.
• Surface morphology was characterized, and the chemical composition of the surface layer was analyzed with EDX energy dispersion (Dan et al., 2023).

2. The Effect of the Filler Material on Microstructural and Mechanical Properties of 430 Ferritic Stainless Steel Welded Joints

• Authors: G. Shanmugasundar et al.
• Published in: Materials Volume 16 2023
• Key Findings: 
• The filler material selection (310 austenitic vs. 410 ferritic) strongly influences the dilution percentage, microstructure, microhardness, and tensile properties of the welded joint.
• Compared to the 310 filler, the 410 filler provided better mechanical properties with its ferritic microstructure for martensite and austenite.
• Methodology: 
• Tungsten Inert Gas (TIG) welding was used to create butt joints, and the effects of different filler materials were analyzed through microstructural and mechanical property assessments(Shanmugasundar et al., 2023).

3. Effects of Initial Microstructure on the Low-Temperature Plasma Nitriding of Ferritic Stainless Steel 

• Authors: Lingze Li et al.
• Published In: Coatings, 2022
• The Key Findings: 
• The characteristics of the nitrided layer on ferritic stainless steel are highly dependent on the initial microstructure.
• The best performance after low-temperature plasma nitriding was observed in ferritic stainless steel that underwent solid solution and annealing treatment.
• The nitrided layer achieved a hardness above 1832 HV0.1.
• Methodology: 
• Ferritic stainless steels were subjected to low-temperature plasma nitriding, and then the microstructure and other characteristics were analyzed using optical and scanning electron microscopy (Li et al., 2022).

4. New Developments in Ferritic Stainless Steel Capable of Withstanding High Temperatures

• Authors: Yang Zhao et al.
• Published In: Tungsten, Volume 5, 2022.
• Key Findings: 
• The paper highlights new developments in the area of stainless steel ferritic containing alloys, paying closer attention to their uses and behavior at high temperatures.
• Methodology: 
• The author attempts to gather existing sources on the topic while pointing out significant milestones that were achieved and what still needs to be done(Zhao et al., 2022, pp. 467–480).

5. Use of Artificial Neural Networks in Modeling the Chemical Composition of Ferritic Stainless Steel

• Author: R. Honysz
• Published In: Metals, Volume 11, 2021
• Key Findings: 
• The study investigates the feasibility of determining the chemical structure of ferritic stainless steels using their mechanical properties as input parameters for artificial neural networks.
• The data accurately predicts the amounts of alloying elements present in stainless steel.
• Methodology:
• Different types of artificial neural networks, such as radial basis function networks and multilayer perceptrons, were used to establish the correlation of the mechanical properties with the chemical makeup of the alloy(Honysz, 2021, p. 724).

6. Stainless steel

7. Steel

8. Alloy