Norma PN-74/H-84019 “Special unalloyed steels for heat treatment and surface hardening – Steel grades.”
The PN-74/H-84019 standard was a Polish standard for non-alloy steels intended for case-hardening and quenching. It was published in 1974 and was in force until its withdrawal in 2003. The PN-74/H-84019 standard was withdrawn on June 6, 2003, and replaced by the PN-EN 10083-1+A1:1999 standard , consistent with European standards, which introduced harmonized European requirements for steels for case-hardening and quenching. The PN-74/H-84019 standard was used in the engineering and automotive industries, where steel was used to manufacture parts requiring high elasticity and resistance to dynamic loads.
Scope of the PN-74/H-84019 standard
The PN-74/H-84019 standard defined technical requirements for the chemical composition, mechanical properties, and applications of unalloyed steels. It primarily concerned spring steel and heat-treatable steel, which were used in various industries.
Norma PN-74/H-84019 – The main parameters specified in the standard
- Chemical composition of steel:
- Mechanical Properties:
- The standard specified the minimum values of yield strength, tensile strength and hardness of steel after appropriate heat treatment.
- Usage:
- Production of spring elements such as:
- Clutch springs.
- Shock absorbers.
- Lightly loaded spring elements (e.g. up to 10 mm thick).
- Production of spring elements such as:
- Characteristics:
- Low alloy steel.
- Unwelded – not susceptible to welding.
- Low corrosion resistance.
The PN-74/H-84019 standard specified the requirements for the chemical composition and mechanical properties of various grades of non-alloy steel intended for surface hardening and heat treatment.
This standard distinguishes:
- 10 species case-hardening steel.
- 28 types of steel for normalization, thermal improvement and hardening surface.
Additionally, hardenability bands are given for 12 grades of surface hardening steel and their 24 varieties.
Examples of steel grade designations according to this standard consisted of two-digit numbers that indicated the approximate average carbon content in hundredths of a percent, e.g. 10, 15, 20, 25, 30, etc.
The letters after the numbers had the following meanings:
- G: steel with increased content manganese.
- A: steel with increased purity in the range phosphorus i sulfur.
- AA: steel with strict requirements regarding chemical composition.
- rs: steel with regulated sulfur content.
- h: steel with the required hardenability.
- H: steel with an increased lower hardness limit in relation to the required hardenability band.
- L: steel with a lower hardness limit than the required hardenability range.
The numbers after the letters, e.g. 4, 5, 15, indicated the distance from the sample face in millimeters.
The PN-74/H-84019 standard specified requirements for unalloyed steels intended for surface hardening and thermal improvement . The following steel grades were distinguished within this standard:
Case hardening steels: C10, C15, C20, C22, C25, C30, C35, C40, C45, C50
C10
Low-alloy steel coal, used primarily in structural components with low strength requirements. It is characterized by good ductility and cold workability. It has good weldability but low hardness after heat treatment.
C20
A low-carbon structural steel with moderate mechanical properties, used in the production of structural components requiring moderate strength. Easily machined and welded, it is used for shafts, axles, and bushings.
Steels for normalizing, heat treating and surface hardening: C22E, C25E, C30E, C35E, C40E, C45E, C50E, C55E, C60E, C22R, C25R, C30R, C35R, C40R, C45R, C50R, C55R, C60R, C35G, C40G, C45G, C50G, C55G, C60G, C45GA, C50GA, C55GA, C65 (spring steel)
C22
A low-carbon steel used for light-duty machine parts. It is characterized by good weldability and ductility, and is suitable for parts subject to limited heat treatment.
C45
A medium-carbon structural steel used in the production of high-strength machine parts, such as drive shafts, gears, and pins. It is heat-treatable, achieving good strength parameters after hardening and tempering.
C60E
High-carbon steel used in components subjected to high mechanical loads, such as springs, shafts, and hand tools. Requires appropriate heat treatment to achieve the desired mechanical properties.
C65
Spring steel High-strength alloy designed for the production of spring elements such as leaf springs, valve springs, and snap rings. It is characterized by good elasticity and resistance to deformation, but limited corrosion resistance.
The main chemical components of these steels are carbon and manganese, with a permissible phosphorus and sulfur content not exceeding 0,040%.