Norma PN-74/H-84032 Spring steel - Species - is a Polish technical standard from 1974 that specifies requirements for spring steel used in the production of springs and other elastic elements. It focuses on the chemical composition, mechanical properties, and markings of these steels to ensure their appropriate quality and durability. PN-74/H-84032 was replaced by PN-EN 10089: 2003and then by PN-EN 10089: 2005.
The current standard is PN-EN 10089: 2005, which specifies the technical requirements for hot-rolled and heat-treated spring steels.
Standard PN-74/H-84032 – scope
The described Standard covers spring steels intended mainly for the production of elements with high elasticity and fatigue resistance, such as springs, springs, torsion bars and other components used in motor vehicles and industrial machines.
Standard PN-74/H-84032 – chemical composition
The chemical composition of steels specified in the standard includes carbon as the basic strengthening element and alloying additives such as:
- H chrome, improving hardenability and abrasion resistance.
- S silicon, increasing elasticity and hardness.
- G manganese, improving hardenability and strength.
- F vanadium, increasing fatigue resistance and durability of the material.
The number in the designation (e.g. 50HS) indicates the average carbon content in hundredths of a percent, meaning that 50HS contains approximately 0,50% carbon.
Mechanical properties
The standard specifies the mechanical properties of steel that must be met after heat treatment , including:
- Yield point – the minimum stress value after which the material undergoes permanent deformation.
- Tensile strength – the maximum force that a material can withstand before breaking.
- Hardness – given in HRC or HB units, defining the material’s resistance to penetration.
- Fatigue resistance – a key parameter for springs and leaf springs that are subject to repeated cyclic loading.
Heat treatment
The standard specifies requirements for heat treatment , including hardening and tempering , to achieve the optimal combination of hardness and elasticity of steel. This process includes:
- Hardening – heating to a specific temperature and then rapid cooling in a properly selected cooling medium.
- Letting go – reheating hardened steel to a suitably selected temperature to obtain the required combination of mechanical properties.
The combination of hardening and high tempering is referred to as quenching and tempering.
Designations and classification, steel grades according to the PN-74/H-84032 standard
Each steel grade in the PN-74/H-84032 standard has a designation consisting of a number and letters, where the number indicates the carbon content and the letters symbolize the main alloying elements. Examples:
1. Carbon spring steels
They are characterized by a high carbon content , which provides good hardness and elasticity after appropriate heat treatment, but does not provide the corrosion resistance characteristic of stainless steels. Unprotected carbon steel can, among other things, corrode uniformly.
- 65 – Spring steel with a carbon content of approximately 0,65%, used in the production of springs with medium strength requirements.
- 75 – Contains approximately 0,75% carbon. It is characterized by greater hardness and durability, suitable for springs subjected to higher loads.
- 85 – Spring steel with a high carbon content (approx. 0,85%), used in components requiring high elasticity, hardness and wear resistance.
2. Non-chrome spring steels
They do not contain chromium as the main alloying element, and in individual grades the important additions include manganese and silicon.
Manganese
- 65G – Manganese spring steel with approximately 0,65% coal and addition manganese. Abrasion-resistant, used in springs with high elasticity and dynamic loads.
Silicon
They contain silicon as the main alloying element, which influences, among other things, the elastic properties and behavior of the steel during heat treatment.
- 50S – Silicon steel with 0,50% carbon. Used in simple spring elements.
- 45S – Steel with a slightly lower carbon content (0,45%). Less hard, more flexible.
- 40S2 – Approximately 0,40% carbon and 2% silicon. High elasticity, used in lighter springs.
- 50S2 – 0,50% carbon and 2% silicon. Durable steel for springs exposed to medium loads.
- 55S2 – Increased carbon content (0,55%), harder, used in automotive springs and coil springs.
- 60S2 – 0,60% carbon, high hardness and abrasion resistance. Used in springs for large vehicles.
- 60S2A – Variety 60S2 with improved steel purity, used in railway springs and heavy machinery.
Manganese-silicon
- 60SG – Spring steel with the addition of manganese i silicon, 0,60% carbon. Very good elasticity and fatigue resistance.
3. Chrome spring steels
Chromium as an alloying addition primarily increases hardenability and influences hardness, strength, and wear resistance. It's important to remember that the mere presence of chromium in low-alloy spring steel does not guarantee the corrosion resistance of stainless steel.
Manganese-silicon-chromium
- 60SGH – Spring steel with the addition of manganese, silicon i chrome, with a carbon content of approximately 0,60%. Designed for high-strength and fatigue-resistant springs.
Chromium-manganese
- 50HG – Steel with 0,50% carbon, with the addition of chrome i manganeseIt is characterized by very good durability and is used in springs and suspension coils.
Chromium-silicon
- 50HS – Contains approximately 0,50% coal and accessories chrome i silicon. Used in heavily loaded springs and leaf springs.
Chrome-vanadium
- 50HF – Contains approximately 0,50% coal and chrome i vanadiumVanadium influences the microstructure and fatigue properties of steel. This grade is used, among other things, for heavily loaded springs, torsion bars, and leaf springs.
Each steel grade in the PN-74/H-84032 standard is designed for specific applications, from lightweight springs to heavily loaded springs and torsion bars. More information about the entire group can be found on the alloy structural steels – spring steels page.
Application
The steels described in the PN-74/H-84032 standard are used in the production of:
- car and railway springs,
- suspension springs in motor vehicles,
- springs used in industrial equipment,
- mechanical elements subjected to high dynamic loads.
For elastic elements, not only static strength is important, but also the material's behavior under repeated load changes. Surface condition, corrosion , surface defects, and improper heat treatment can affect the durability of a component operating under cyclic loading.
Changes and consequences of the norm
The PN-74/H-84032 standard was later replaced by standards consistent with the European system, including PN-EN 10089:2005 , which updated the requirements for the chemical composition, mechanical properties, and technical delivery conditions of spring steels. Other developed standards can be found in the list of PN, EN, ISO, DIN, ASTM, AISI, and other steel standards.