Spring steel is widely used in several industries for applications that are subjected to cyclic loads.
But what exactly is spring steel? What are its properties? And what are the different types of spring steel?
Spring steel is the term used for grades of steel that offer a high yield strength and have the ability to withstand stress without permanent deformation. These steels are generally used for making springs, cords, blades, tools, etc. Spring steels are high in carbon along with traces of other elements.
This article provides a detailed guide on spring steels and helps you understand what sets them apart from other grades of steels, by going through their properties, types, and applications.
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Spring Steel: What makes it Different?
Spring steel is a name given to some highly durable grades of steel that can withstand extreme twisting or bending forces without permanent deformation.
Due to their high yield strength and elasticity, they can return to their original form, even after withstanding extreme forces.
Moreover, spring steel comprises alloying elements which add up to the total strength and ductility of the material.
It is typically made from high-carbon steel alloyed with elements like manganese, silicon, and chromium.
These steels undergo strain hardening through heat treatment or work hardening, which rearranges the molecular arrangement due to external forces and stresses, making the material stronger.
This step includes hot or cold rolling, annealing, tempering, normalizing, and quenching to remove brittleness and form a uniform material microstructure that results in higher strength and durability.
Properties of Spring Steel
Spring steel possesses multiple properties that render it suitable for several applications.
Spring steel is highly elastic, meaning it can return to its original orientation without any significant deformation, even after being subjected to extreme forces or stresses.
It has a high yield strength ratio greater than 85%, which is more than structural steel. This value indicates the ratio of the elastic limit to the tensile strength.
As a result, spring steel is suitable for applications involving repetitive or cyclic loading, like in the case of suspension systems of automobiles.
Due to its high carbon content and work hardening, spring steel possesses high strength, making it extremely durable.
Its tensile strength varies between 1250 and 2200 N/mm², depending on the spring steel grade.
This makes spring steel preferable for use in applications involving high loading or extreme stresses, like in heavy industrial machinery damping systems.
High Fatigue Resistance
A high fatigue resistance means that this steel can easily withstand repetitive or cyclic loading that is high in magnitude without significant deformation.
This particular aspect renders spring steel ideal for applications involving high fatigue loadings, such as valve springs or clutch plates.
Good Resistance to Wear
A good resistance to wear and tear means that this steel can easily withstand friction and abrasion due to surface contact for a prolonged period without significant damage.
This property makes it suitable for use in applications such as blades or cutting tools, where sharpness must be maintained over time.
Using spring steel would enhance the tool life and require less frequent maintenance or resharpening, thus cutting down maintenance costs.
Good Corrosion Resistance
Good corrosion resistance means that spring steel can withstand the rough environments of water and chemical applications without significant corrosion or rusting.
The alloying elements like chromium or nickel form a protective external layer on the steel, thus enhancing the corrosion resistance of the spring steel.
This aspect renders spring steel ideal for applications like anchor chains, winches, or hydraulic pumps.
Types of Spring Steel
Spring steel usually comprises carbon with a percentage of 0.3% to 1.5%, along with nickel-chromium or nickel-titanium alloys with a percentage varying between 1% to 3%.
Depending on their composition, there are different types of spring steel available in the metalworking industry.
High Carbon Spring Steel
|Type of Carbon spring steel||Carbon content|
|AISI 1070||0.65 to 0.75%|
|AISI 1074||0.70 to 0.80%|
High-carbon spring steel has various subcategories that possess varying percentages of carbon, with higher carbon content resulting in greater strength and hardness.
AISI 1050, 1070, 1074, and 1095 are the most commonly used grades of high-carbon spring steel.
Generally, AISI 1050 has a carbon composition of approximately 0.50%, AISI 1070 contains 0.65 to 0.75% carbon, AISI 1074 comprises 0.70 to 0.80% carbon, while AISI 1095 contains 0.90 to 1.03% carbon.
All these grades offer great durability and toughness, with AISI 1095 possessing the greatest strength and hardness.
These spring steels are commonly used for making cords for musical instruments, such as piano wire, guitar strings, etc.
Alloy Spring Steel
|Type of alloy spring steel||Characteristics|
|AISI 5160||Lowest tensile strength among the three|
|AISI 6150||Moderate yield strength|
|AISI 9254||Highest yield strength with low strain characteristics|
Alloy spring steel is usually classified based on strain, tensile strength, and yield strength.
It comprises small percentages of alloying elements like silicon and molybdenum as well.
AISI 5160, 6150, and 9254 are the most commonly used grades of alloy spring steel.
AISI 5160 contains 0.75 to 1% manganese with 0.7 to 0.9% chromium and has the lowest tensile and yield strength among these grades.
AISI 6150 possesses 0.7 to 0.9% manganese and 0.8 to 1.10% chromium, which provides it comparatively better yield strength than AISI 5160.
On the other hand, AISI 9254 comprises 0.6 to 0.8% manganese, 0.035% phosphorus, 0.04% sulfur, 1.2 to 1.6% silicon, and 0.6 to 0.8% chromium.
All these alloying elements provide AISI 9254 spring steel with the greatest tensile and yield strength of 1890 MPa and 1650 MPa, while having lower strain characteristics than the rest.
Stainless Spring Steel
Although stainless steel differs from typical spring steel, some grades of spring steel share the properties and composition of stainless steel.
The different grades of stainless spring steel are classified based on the varying nickel and chromium compositions.
AISI 301, 304, and 316 are the most commonly used stainless spring steel grades in the industry.
These grades offer high wear and corrosion resistance, with enhanced strength, and toughness.
Amongst these grades, AISI 301 and 304 have a higher yield strength but lower wear resistance than AISI 316 due to the presence of molybdenum.
Nickel Alloy Spring Steel
|Types of Nickel Alloy Spring Steel||Characteristics|
|Inconel 718||High strength and hardness|
|Inconel 625||Better corrosion resistance|
Nickel alloy spring steel’s grades are classified based on the varying nickel compositions and the associated mechanical properties.
Inconel 718 and 625 are common grades of nickel alloy spring steel that are used in the metalworking industry.
The Inconel 718 contains cobalt, which gives it high strength and hardness, whereas Inconel 625 comprises higher levels of chromium and molybdenum, giving it better corrosion resistance.
Copper Alloy Spring Steel
|Type of Copper alloy spring steel||Composition||Characteristic|
|Beryllium Copper||0.5% beryllium||High fatigue strength|
|Phosphor Bronze||0.5 to 11% tin||High conductivity|
Copper alloy spring steel’s grades are classified based on the varying copper compositions and the associated mechanical properties.
Beryllium copper and phosphor bronze are the most popular grades in use.
The beryllium copper grade comprises about 0.5 % beryllium along with minor amounts of cobalt and silicon, whereas phosphor bronze contains between 0.5 to 11 % tin with small amounts of phosphorus.
Beryllium copper has a much higher fatigue strength, but phosphor bronze has higher conductivity, making it ideal for conducting applications.
Chrome-Silicon Spring Steel
|Type of chrome-silicon spring steel||Properties|
|AISI 9260||Higher tensile strength|
|AISI 9254||Comparatively lower tensile strength|
Chrome silicon steel is classified based on mechanical properties like tensile strength, yield strength, and elongation.
AISI 9260 and 9254 are broadly used popular grades, with AISI 9260 possessing a higher percentage of silicon.
These grades have similar elongation characteristics, with AISI 9260 having a slightly higher tensile strength and AISI 9254 having a slightly greater yield strength.
Applications of Spring Steel
|Automobiles||Suspension systems/shock absorbers|
|Medical Industry||Medical devices like stretchers and surgical lights|
|Industrial Machinery||Damping systems, clutch springs, cutting tools, and blades|
|Consumer Goods||Locks, hinges, or utensils like pressure cookers|
High carbon and alloy spring steel are commonly used in automobile applications such as suspension systems and shock absorbers due to their high elasticity, strength, and fatigue resistance.
These properties enable this steel to withstand the heavy cyclic loading involved in suspension systems or shock absorber applications without deformation.
Due to its high elasticity, wear resistance, and durability, chrome silicon spring steel is widely used for medical applications, such as in stretchers and surgical lights.
These properties render this steel ideal for tolerating highly frequent cyclic loading without wear or deformation.
Alloy and oil-tempered spring steel are common in machinery-related applications like damping systems, clutch springs, cutting tools, and blades due to their high fatigue resistance, corrosion resistance, and high durability.
These aspects make this steel suitable for resisting corrosion, fatigue loading, and wear in machining applications.
Consumer goods often employ high carbon spring and stainless spring steel in numerous products like locks, hinges, and utensils like pressure cookers due to their visual appearance, high durability, and elasticity.
These aspects render this steel preferable for resisting cyclic loading, giving off a visually aesthetic look in consumer goods.
Spring Steel vs Stainless Steel
|Spring Steel||Stainless Steel|
|Higher percentage of carbon||Higher percentage of alloying elements|
|Stronger and tougher||Relatively lower strength|
|Higher elasticity||Relatively lower elasticity|
|Magnetic in nature||Non-magnetic in nature|
|Relatively lower corrosion resistance||Better corrosion resistance|
|Greater machinability||Lower machinability|
|Greater weldability||Lower weldability|
|Less visually aesthetic||More visually aesthetic|
Spring steel has a comparatively high carbon composition of 0.3 to 1.5% than stainless steel and small percentages of other alloying elements like manganese, silicon, and chromium.
Contrarily, stainless steel comprises around 10% chromium and other alloying elements like nickel, molybdenum, and titanium, with a lower carbon composition.
Generally, spring steel is stronger than stainless steel due to its higher carbon content and other alloying elements.
Spring steel is more elastic than stainless steel, which is ideal for fatigue-loading applications.
Stainless steel may deform or lose its original shape after being exposed to fatigue loading over a long time.
Spring steel is cheaper than stainless steel, making it a more feasible option for hobbyists.
Moreover, this aspect also makes spring steel preferable for bulk production applications.
Spring steel is magnetic due to the significant presence of magnetic alloying elements like manganese, whereas stainless steel is a non-magnetic metal.
This aspect makes spring steel useful for applications like magnetic latches or refrigerator doors.
Although spring steel is generally more vulnerable to corrosion than stainless steel, it can undergo plating techniques for enhanced protection.
Stainless steel does not require plating as it offers better corrosion resistance.
Generally, stainless steel is more difficult to machine due to its hardness, raising manufacturing costs and production times.
Spring steel is easier to weld due to its composition, as it has a higher carbon content that prevents brittleness.
Whereas, stainless steel contains chromium that reacts with carbon to form chromium carbides, resulting in cracking and consequent brittle fracture due to welding.
Spring steel has a relatively dull appearance compared to stainless steel’s shiny, smooth, shiny look, making it ideal for applications where visual aesthetics are a priority.
Spring steel is a type of steel that provides excellent yield strength and resistance to deformation, making it ideal for making springs, suspensions, and other applications that are subjected to cyclic loads.
Its high durability and cheap cost make it a consumer favorite, especially from a hobbyist and DIY perspective.
Although it provides excellent strength and durability at reasonable costs, stainless steel is preferable over spring steel for applications where corrosion resistance and lustrous appearance are preferable.
Frequently Asked Questions (FAQ)
What is the maximum temperature that spring steel can tolerate before deformation?
The maximum temperature that spring steel can tolerate before deformation is approximately 500°C (723K).
Can spring steel rust?
Yes, spring steel can rust over time as its major component is iron which oxidizes and rusts upon contact with air.
Is spring steel toxic?
No, spring steel is not toxic as it is free from any toxic materials in its composition, like lead, barium, or mercury.
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