Stainless steel and titanium alloy are commonly used metals in many industrial applications. These two metals are naturally beautiful and have their own qualities and strengths. Unless you go deep into their chemical and structural qualities, the difference between steel and titanium may not be discernible. This article introduces stainless steel and titanium and their pros and cons, as well as the differences between them, to help you learn more about the fundamentals of each metal.
Table of Contents
What is Stainless Steel?
In metallurgy, stainless steel is a category of highly alloyed steel designed to provide high corrosion resistance with at least 10.5% chromium by mass, with or without additional alloying elements, and a maximum of 1.2% carbon by mass. It is steel mixed with one or more elements to modify its properties. Alloying is the process of combining more than one metal.
Stainless steels, commonly known as inox steels or inox from the French inoxydable (inoxidizable), are steel alloys that are very well known for their corrosion resistance that rises with rising chromium content. The chromium in the alloy forms a thin, impervious oxide film in an oxidizing atmosphere, which protects the surface from corrosion. Nickel is another alloying ingredient in certain stainless steel to increase corrosion protection. Carbon is used to strengthen and harden the metal.
5 Types of Stainless Steel
Stainless Steel can be divided into five different types. These include:
- Ferritic stainless Steels
- Austenitic Stainless Steels
- Martensitic Stainless Steels
- Duplex Stainless Steels
- PH Stainless Steels
Ferritic Stainless Steels
Ferritic stainless steels have around 10.5 to 30% chromium, low carbon (C<0.08%), and no nickel. They are referred to as ferritic alloys because they have principally ferritic microstructures at all temperatures and cannot be hardened by heat treatment and quenching. While certain ferritic grades include molybdenum (up to 4.00%), chromium is the major metallic alloying ingredient. Furthermore, they have relatively low high-temperature strength. Ferritic steels are selected for their resistance to stress corrosion cracking, making them an appealing option to substitute austenitic stainless steels in applications of chloride-induced SCC. The AISI 400-series of stainless steels includes a significant number of ferritic steels. Some varieties, like the 430 stainless steel, have great resistance to corrosion and high heat tolerance.
430 Stainless Steel
430 stainless steel is a versatile steel with excellent corrosion resistance. It possesses higher thermal conductivity than austenite, a lower thermal expansion coefficient than austenite, heat fatigue resistance, the inclusion of the stabilizing element titanium, and strong weld mechanical properties. 430 stainless steel is utilized in building ornamentation, fuel burner components, household appliances, and home appliance parts.
430F is a steel grade that adds free-cutting performance to 430 steel. It is primarily used to manufacture automated lathes, bolts, and nuts. 430LX is an alloy in which Ti or Nb is added to 430 steel to reduce C content and improve processing and welding performance and primarily used for hot water tanks, hot water supply systems, sanitary appliances, home appliances, durable appliances, bicycle flywheels, and other applications.
Austenitic Stainless Steels
Austenitic stainless steels have a Cr content ranging from 16 to 25% and can also include nitrogen in the solution, both of which contribute to their relatively strong corrosion resistance. Austenitic stainless steels offer the highest corrosion resistance of any stainless steel, as well as exceptional cryogenic characteristics and high-temperature strength. They have a nonmagnetic face-centered cubic (fcc) microstructure and are readily welded. This austenite crystalline structure is obtained with adequate amounts of the austenite stabilizing elements: nickel, manganese, and nitrogen.
Although austenitic stainless steel cannot be hardened by heat treatment, it can be hardened to high strength levels while preserving desirable ductility and toughness. The most well-known grades of austenitic stainless steel are 304 stainless steel and 316 stainless steel, which offer exceptional resistance to various ambient conditions and numerous corrosive media.
304 Stainless Steel
In austenitic stainless steel, 304 stainless steel is particularly prevalent. It has a high nickel level that ranges between 8 and 10.5% by weight and a high chromium content of between 18 and 20% by weight. Manganese, silicon, and carbon are other important alloying ingredients. The rest of the chemical makeup is mostly iron. Because of the high levels of chromium and nickel, 304 stainless steel has good corrosion resistance. Common uses for 304 stainless steel include refrigerators and dishwashers, commercial food processing equipment, fasteners, piping, heat exchangers, and construction in situations that would corrode conventional carbon steel.
316 Stainless Steel
316 stainless steel, like 304, contains a high concentration of chromium and nickel. 316 also includes silicon, manganese, and carbon, with iron accounting for the bulk of the composition. The chemical makeup of 304 and 316 stainless steels differs significantly, with 316 containing a large quantity of molybdenum; often 2 to 3% by weight vs. merely negligible levels in 304. Because of the higher molybdenum concentration, grade 316 has greater corrosion resistance. Regarding austenitic stainless steel for maritime applications, 316 stainless steel is frequently regarded as one of the best options. 316 stainless steel is also often used in equipment for processing and storing chemicals, refineries, medical devices, and maritime environments, especially those with chlorides.
Martensitic Stainless Steels
Martensitic stainless steels, like ferritic steels, are based on chromium but have a greater carbon content of up to 1%. They have a chromium content of 12 to 14%, a molybdenum content of 0.2 to 1%, and usually no nickel. Because they contain more carbon, they can be hardened and tempered like carbon and low-alloy steels. They have moderate corrosion resistance and are robust, strong, and slightly brittle. In contrast to austenitic stainless steel, they are magnetic, and a non-destructive test utilizing the magnetic particle inspection method can be performed on them. Typical products include cutlery and surgical instruments.
Duplex Stainless Steels
As their name implies, Duplex stainless steels are a mixture of two of the most common alloy kinds. They feature a mixed microstructure of austenite and ferrite to produce a 50/50 blend, while the ratio may be 40/60 in commercial alloys. Their corrosion resistance is comparable to that of austenitic stainless steel. Still, their stress-corrosion resistance (particularly to chloride stress corrosion cracking), tensile strength, and yield strength (about twice that of austenitic stainless steels) are typically greater. Carbon is preserved to a very low level (C<0.03%) in duplex stainless steel. Their chromium level varies from 21.00 to 26.00%. Their nickel content ranges from 3.50 to 8.00%, and molybdenum may be included in these alloys (up to 4.50% ). Toughness and ductility are often intermediate between those of austenitic and ferritic grades.
Based on their ability to resist corrosion, duplex grades are classified into three sub-groups: standard duplex, super-duplex, and lean duplex. Compared to conventional austenitic steels, super-duplex steels offer greater strength and resistance to all types of corrosion. Marine applications, petrochemical plants, desalination plants, heat exchangers, and papermaking are all common usages. The oil and gas sector is the major customer today, and it has pushed for more corrosion-resistant grades, resulting in the wide use of super-duplex steels.
PH Stainless Steels
PH stainless steels (precipitation-hardening stainless steels) contain around 17% chromium and 4% nickel, providing an optimal combination of martensitic and austenitic properties. They are noted for their capacity to develop high strength with heat treatment, similar to martensitic grades, and they also have the corrosion resistance of austenitic stainless steels. Even at high temperatures, these alloys maintain their strength and corrosion resistance, making them good for use in aerospace.
Precipitation-hardening stainless steels have high tensile strengths due to a heat treatment technique that results in precipitation hardening of a martensitic or austenitic matrix. Hardening is accomplished by incorporating one or more elements: copper, aluminum, titanium, niobium, and molybdenum. They typically are the best combination of high strength, toughness, and corrosion resistance of all the available stainless steel grades.
To learn more about Stainless steel technical properties, please check the Stainless Steel Grade Chart – Technical Properties.pdf
What is Titanium?
Titanium is a silver-colored, shiny transition metal with a low density of 4.506 g/cm3 and a melting point of 1,668 ℃. The two most useful properties of titanium are corrosion resistance and the highest strength-to-density ratio against any metal. Titanium is 30 % stronger than steel but nearly 43 % lighter, and 60 % heavier than aluminum but twice as strong.
Titanium has a relatively low thermal expansion coefficient and fairly hardness, although not as hard as some heat-treated steel, is nonmagnetic, does not exhibit a ductile-brittle transition, and has good biocompatibility and a poor conductor of heat and electricity. However, oxygen and nitrogen are absorbed by titanium rapidly at temperatures above 500 ℃, which leads to potential embrittlement problems.
Titanium is important for many high-performance applications, including aircraft, vehicle engines, luxury marine equipment, medical parts, and industrial machinery.
Typical Grades of Pure Titanium
#1 Grade 1
Grade 1 is the first of four commercially pure titanium grades. It is the most pliable and ductile of this pure titanium. It has the greatest formability, the best corrosion resistance, and the highest impact toughness.
Because of these characteristics, Grade 1 titanium plate and tubing is the preferred material for any application requiring ease of formability. These are some examples:
- Chemical processing
- Anodes with dimensional stability
- Medical industry
- Marine industry
- Automotive parts
- Structure of an aircraft
#2 Grade 2
Because of its diverse usage and extensive availability, grade 2 titanium is known as the “workhorse” of the commercially pure titanium industry. Many of its properties are similar to those of Grade 1 titanium, however, it is significantly stronger. Both are equally resistant to corrosion.
This alloy has excellent weldability, strength, ductility, and formability. As a result, Grade 2 titanium bars and sheets are the preferred choices for a wide range of applications:
- Power generation
- Medical industry
- Processing of hydrocarbons
- Marine industry
- Shrouds for exhaust pipes
- Desalination of aircraft skin
- Chemical processing
- Chlorate production
#3 Grade 3
This grade is the least frequently used of the commercially pure titanium grades, yet it does not reduce its value. Grade 3 is stronger than Grades 1 and 2, has similar ductility and is slightly less formable than its predecessors – yet it has greater mechanical properties.
Grade 3 is used in applications that need moderate strength and significant corrosion resistance. These are some examples:
- Structures used in aviation
- Chemical processing
- Medical industry
- Marine industry
#4 Grade 4
Grade 4 titanium is the strongest of the four commercially pure titanium grades. It is also well-known for its high corrosion resistance, formability, and weldability.
Despite its traditional use in the following industrial applications, Grade 4 titanium has lately found a niche as medical grade titanium. It is required in applications requiring high strength:
- Airframe parts
- Cryogenic vessels
- Heat exchangers
- CPI equipment
- Tubing for condensers
- Surgical equipment
- Pickling baskets
Titanium alloys have excellent mechanical and exploitation properties such as high strength-to-density ratio, high corrosion resistance, high fatigue and cracking resistance, and ability to withstand moderately high temperatures without creeping, which have been widely used in aerospace industries as structural materials for supersonic aircraft and spacecraft and non-aerospace sections such as military, automotive, and sporting goods.
Due to being biocompatible, nontoxic, and not rejected by the human body, titanium alloys are also very popular in medical applications, including surgical implements and implants like joint replacement, which can last up to 20 years.
Typical Alloys of Titanium
#1 Grade 7
Grade 7 is mechanically and physically equal to Grade 2, except for including the interstitial element palladium, which transforms it into an alloy. Grade 7 titanium alloy is the most corrosion-resistant of all titanium alloys, with good weldability and fabricability. It is more corrosion-resistant in reducing acids.
Grade 7 is often used in chemical processes and parts of the production lines.
#2 Grade 11
Grade 11 is identical to Grade 1, except for a trace of palladium added to improve corrosion resistance. This corrosion resistance is important for preventing crevice erosion and lowering acid levels in chloride environments.
Other advantageous characteristics include high ductility, cold formability, reliable strength, impact toughness, and weldability. This alloy is suitable for the same titanium applications as Grade 1, particularly if corrosion is a problem, such as:
- Chemical production
- Chlorate manufacturing
- Applications in the sea
#3 Grade 12
For its exceptional weldability, grade 12 titanium is an excellent titanium alloy. It is a long-lasting alloy with a lot of strength at high temperatures. Grade 12 titanium has properties identical to 300 series stainless steel.
This alloy can be hot or cold manufactured by the press brake, hydropress, stretch, or drop hammer methods. Because of its capacity to be molded in many forms, it is valuable in a wide range of applications. The exceptional corrosion resistance of this alloy makes it important to equipment manufacturers where crevice corrosion is an issue. Grade 12 is suitable for the following industries and applications:
- Heat exchangers and shells
- Hydrometallurgical applications
- Chemical manufacturing at high temperatures
- Marine and airfare components
You can find more titanium alloys on the wiki: Titanium alloy on wiki.
Stainless Steel vs. Titanium: What Are Their Differences?
Titanium and stainless steel are widely employed in various consumer and industrial applications. What is the difference between stainless steel and titanium? Titanium and stainless steel have distinct properties that set them apart from one another. We shall compare titanium and stainless steel, utilizing different properties for ease of comprehension.
The composition of the elements can be utilized to distinguish titanium from stainless steel. Commercially pure titanium, generally speaking, comprises a range of elements such as nitrogen, hydrogen, oxygen, carbon, iron, and nickel. Titanium is the primary element, with other elements ranging in percentage from 0.013% to 0.5%.
Stainless steel, on the other hand, is made up of various elements, including at least 10.5% chromium and additional elements, with percentage compositions ranging from 0.03% to more than 1.00%. The chromium component in stainless steel aids in corrosion prevention and offers heat resistance. These elements are aluminum, silicon, sulfur, nickel, selenium, molybdenum, nitrogen, titanium, copper, and niobium.
A material’s hardness is a comparative measure that defines the material’s response to etching, deformation, scratching, or denting over its surface. This measurement is generally done with indenter machines, which come in multiple types based on the material’s strength. The Brinell hardness test is used by makers and consumers of high-strength materials.
While stainless steel’s Brinell hardness varies widely depending on alloy composition and heat treatment, it is generally tougher than titanium. Titanium, on the other hand, deforms quickly when indented or scraped. To circumvent this, titanium generates an oxide layer known as the titanium oxide layer, which forms an extremely hard surface that resists the most penetrating pressures.
The capacity of a material to continue to function without requiring excessive repair or maintenance during its half-life is an indicator of the material’s durability. Because of their superior characteristics, titanium and stainless steel are both long-lasting. Titanium is about 3 to 4 times stronger than stainless steel. This allows titanium to have a lifespan that is increased by several generations.
Elasticity is a measure of a material’s flexibility. In other words, it evaluates how easily a material can be bent or warped without distortion. The normal elasticity of stainless steel is 200 GPa, whereas titanium’s is 115 GPa. Because most of its alloys are more elastic, stainless steel often beats titanium in this area. Again, more flexibility makes it easier to mill stainless steel and make different parts. This is an important quality because it directly affects the cost of processing.
A material’s ultimate tensile strength is the maximum on the engineering stress-strain curve. It is the greatest stress that a material in tension can withstand. Most of the time, ultimate tensile strength is abbreviated as tensile “strength” or “the ultimate.” Stainless steel has a greater ultimate tensile strength than titanium.
The important point to remember here is that while stainless steel has greater overall strength, titanium has greater strength per unit mass. As a result, stainless steel is often the best choice if overall strength is the major driver of an application selection. If weight is of primary importance, titanium may be a better alternative.
A material’s yield stress or yield strength is the stress at which it distorts. The yield strength of stainless steel 304L is 210 MPa, compared to 1100 MPa for Ti-6AI-4V (Titanium grade). As seen by the elasticity differential, titanium is harder to produce yet has a higher strength per unit of mass.
Also, titanium is biocompatible, while stainless steel is not. Because of this, titanium is a great choice for a wide range of medical uses.
One notable distinction between titanium and stainless steel is their weight. Titanium has a high strength-to-weight ratio, allowing it to deliver about the same level of strength as stainless steel at 40% of the weight.
As a result, titanium is essential for applications requiring minimal weight and maximum strength. This is why titanium is useful in airplane components and other weight-sensitive applications. On the other hand, steel is useful for car frames and other things, but it is often hard to make things lighter.
Titanium is more costly than stainless steel in terms of pricing. As a result, titanium becomes more expensive for some industries, like buildings, where huge volumes are required. If cost is a big factor, stainless steel may be better than titanium if both are good enough.
Stainless steel is a reasonably priced option. It is easier to manufacture since there is no scarcity of iron or carbon on earth. Furthermore, there are no sophisticated processing requirements for stainless steel. Stainless steel prices, on the other hand, vary greatly due to the sheer number of options. A carbon and iron alloy would be the least costly. Those constructed from chromium, zinc, or titanium would be more expensive.
Stainless steel and titanium have different applications. Stainless steel is ideal for architecture, paper, pulp and biomass conversion, chemical and petrochemical processing, food and beverage, energy, firearms, automobiles, the medical industry, and 3D printing. On the other hand, titanium is perfect for aerospace, consumer applications, jewelry, the medical industry, and nuclear waste storage.
Stainless Steel vs. Titanium: Which One to Choose?
Both stainless steel and titanium have distinct properties that make one or the other more appropriate for your specific needs. Knowing the pros and cons of both metals will assist you in making your decision. Below are their advantages and disadvantages.
Advantages of Stainless Steel
- Low price and is readily available.
- High strength and durability.
- Excellent corrosion resistance.
- Excellent mechanical properties.
- Sustainability and environmentally friendly.
- High strength and superior durability.
- Stainless steel is recyclable.
- Easy to customize.
- Stainless steel equipment is easy to clean.
Disadvantages of Stainless Steel
- The strength gets lower at high temperatures.
- Difficult to weld or fabricate.
- Stainless steel equipment is very heavy.
Advantages of Titanium
- Amazing corrosion resistance.
- High-melting point and withstand high temperatures.
- High strength and lightweight.
- Non-toxic, widely used in the medical industry.
- Good biocompatibility.
Disadvantages of Titanium
- Expensive cost.
- Low elasticity and is readily deformed.
- Difficult in extracting, casting, and processing.
The main distinction between the two materials is that titanium is an element while stainless steel is an alloy. Titanium’s properties occur naturally in the metal. On the other hand, stainless steel is a metal alloy of chromium, iron, nickel, and other things.
Because of these differences, the properties of both metals may differ from each other, making them both viable possibilities. We recommend that you select the one that suits your application best.
Thank you for reading our article. We hope it can help you better understand the differences between titanium and stainless steel so that you can pick the right material for your project. If you need metal parts and are seeking rapid prototyping services, LEADRP is a good choice because we’re committed to producing high-quality parts and prototypes at affordable prices and with a short lead time.