Norma PN-72/H-84035 Structural alloy steels intended for the production of particularly loaded equipment – Grades
The PN-72/H-84035 standard was a Polish technical standard published on December 1, 1972, covering alloy structural steels intended for the manufacture of equipment subjected to high loads. The steels covered by this standard were used in sectors requiring exceptional material strength, such as the aerospace, automotive, and machinery industries, where maintaining high resistance to variable loads and abrasion was crucial.
Standard PN-72/H-84035 scope and specification
The standard covered grades of structural alloy steels intended for carburizing and heat treatment . These steels were smelted using advanced metallurgical processes, such as open-hearth furnaces, electric furnaces, oxygen furnaces, electroslag furnaces, and slag refining processes. The goal of these advanced methods was to achieve the highest possible chemical purity and structural homogeneity of the material, thereby increasing its strength and reliability in demanding technical applications.
The scope of the standard included products supplied in the form of:
- rolled and forged bars,
- ingots and semi-finished products,
- forgings,
- sheets, strips, pipes,
- cold drawn products.
These steels were intended for heat treatment to improve mechanical properties such as hardness, tensile strength, fracture and abrasion resistance, as well as to increase fatigue life.
Standard PN-72/H-84035 – examples of steel grades
- 12H2N4A – Chromium-nickel case-hardening steel, used for heavily loaded parts requiring high surface hardness and good core ductility.
- 20H2N4A – Chromium-nickel case-hardened steel, used in gear parts and mechanisms requiring high core strength and abrasion resistance.
- 30HN2MFA – Chromium-nickel-molybdenum-vanadium steel for heat treatment, used in the arms and aviation industries for heavily loaded parts such as shafts and axles.
- 30H2N2M – Chromium-nickel-molybdenum steel, used in aircraft and automotive structures requiring high surface hardness and fatigue resistance
- 18H2N4WA / 18H2N4MA– Chromium-nickel-tungsten steel with high hardness and strength after carburization. Characterized by good resistance to abrasion and variable loads. Used in the production of gears, crankshafts, transmissions, and machine components requiring exceptional surface durability.
- 12HN3A – A chromium-nickel steel designed for medium-diameter components, well suited for heat treatment. It is used in the automotive and aerospace industries, primarily for parts requiring high core strength, such as drive shafts and camshafts.
- 30HGSNA – Chromium-manganese-silicon-nickel steel, used in the aerospace and engineering industries. Characterized by high ductility, excellent fatigue resistance, and good hardenability, it is used in aircraft structural components and machinery subjected to high dynamic loads.
- 30HGSA – A chromium-manganese-silicon steel with properties similar to 30HGSNA, but without the addition of nickel. Used in load-bearing structures, springs, and shafts exposed to high dynamic loads. It is characterized by good weldability and fracture resistance.
- 38HNM – A chromium-nickel-molybdenum steel for heat treatment, characterized by high strength and core hardness. Used in components subjected to heavy loads, such as drive shafts, gears, and turbine components.
- 40HN2MA – Chromium-nickel-molybdenum-aluminum steel, used in structures requiring high resistance to abrasion and dynamic fatigue. It is used in the aerospace industry and in military equipment components.
- 20HN3A – A case-hardened chrome-nickel steel designed for machine parts that require a hard surface and a strong core, such as pins, gears, and worms.
- 18HGT – Chromium-manganese-titanium steel, used mainly in the automotive industry for the production of transmission components and suspension systems, characterized by increased abrasion resistance.
Each of these steel grades was developed for specific applications where resistance to variable loads, hardenability and the ability to operate in difficult mechanical and environmental conditions are key.
Quality standard PN-72/H-84035
The PN-72/H-84035 standard was considered very stringent, resulting from high requirements for chemical purity, compositional accuracy, and minimum mechanical parameters. The steels described in this standard were characterized by excellent strength properties, making them ideal for applications in critical structures where material reliability was crucial.
Standards from this period often placed a greater emphasis on quality than later European standards, which were partially relaxed to harmonize international requirements. Older standards were more stringent in terms of minimum tensile strength, hardness, and alloying element content.
Withdrawal of the standard and introduction of newer standards
The PN-72/H-84035 standard was officially withdrawn on December 17, 2012, as part of the process of harmonizing Polish standards with European standards introduced by the CEN Technical Committee (European Committee for Standardization). It was replaced by the following standards:
- EN 10084 – concerning carburizing steel,
- PN-EN 10083-1+A1:1999 – concerning steel for thermal improvement.
The new standards introduced a more unified approach, covering a wider range of steel grades and emphasizing material availability across Europe. However, they were often less stringent in terms of mechanical parameters and chemical purity control, which can be perceived as a compromise between quality and international material availability.
The PN-72/H-84035 standard was exceptionally precise and rigorous in terms of quality control for structural steels, making it indispensable in demanding industrial applications. Although it has been withdrawn in favor of more uniform European standards, it is still used as a reference point in some industries due to its high technical standards. In practice, many companies still use the requirements of this standard in their internal technical specifications, especially where material safety and reliability are key.