UNI standards for steel materials

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Introduction to UNI Steel Standards

The Review of UNI Standards for steel consists of three comprehensive volumes containing formally approved UNI standard classifications, guides, practices, specifications, test methods, terminology, and related materials including proposals. These standards have been developed to ensure consistency and quality in steel production and application across various industries.

The UNI standards encompass a wide range of steel materials, including carbon and alloy steels, plates for boilers and pressure vessels, sheets and strips, high-strength low-alloy steels, heat-treatable steels, hot and cold-rolled plates for cold forming, and spring steels. Each standard provides detailed requirements for specific applications, ensuring that steel materials meet the necessary quality and performance criteria.

Steel Pipe and Tube Specifications

UNI standards cover various types of steel pipes and tubes designed for specific applications. These include pipes for high-temperature service, ordinary use, and special applications such as fire protection. The specifications for steel tubes detail standard requirements for:

• Boiler and superheater tubes
• General service tubes
• Steel tubes in refinery service
• Heat exchanger and condenser tubes
• Mechanical tubing
• Structural tubing

These standards ensure that steel pipes and tubes possess the necessary properties for their intended applications, contributing to safety and reliability in various industrial settings.

Classification of UNI Steel Standards

The UNI standards for steel materials are organized into three main groups:

• Group of standards for structural and constructional steels
• Group of standards for tool steels
• Group of standards for stainless and heat resisting steels

For each standard, the following information is typically provided:

• Standard number and year
• Grade
• Chemical composition
• Mechanical properties (yield point, tensile strength, notch toughness)

When relevant, additional information may include steel type, manufacturing method, plate thickness, heat treatment procedures, and other specialized data.

Structural and Constructional Steel Standards

The UNI standards for structural and constructional steels cover a wide range of applications, from bearing steels to railway components and pressure vessels.

Table 1. Group of standards for structural and constructional steels

Standard Number	Last Version	Description
UNI 3097	1975	Ball and roller bearing steels
UNI 3160	1983	Wear-resisting sand casting
UNI 3545	1980	Spring steels
UNI 3608	1983	Steel casting
UNI 4010	1975	High strength castings
UNI 4838	1980	Free-cutting steels
UNI 5462	1964	Seamless tubes
UNI 5598	1971	Wire rod for drawing
UNI 5571	1966	Chain steels
UNI 5949	1967	Seamless tubes with low temperature impact test
UNI 6102	1990	Railway tyre
UNI 6328-92		Rails
UNI 6358-90		Railway tyre
UNI 6363	1984	Welded and seamless tubes for water mains
UNI 6403	1986	Tubes for use in motor vehicles
UNI 6551	1969	Steel for axles
UNI 6786	1971	Steel for axles
UNI 6787	1971	Steel for axles
UNI 6860	1971	Wheel centres (cast)
UNI 7064	1982	Strip for springs
UNI 7065	1972	Strip
UNI 7091	1972	Welded tubes
UNI 7176	1973	Steel for axles
UNI 7316	1974	Cast exposed to pressure
UNI 7317	1974	Castings tough at subzero subject to pressure
UNI 7356	1974	Steels for bolts nuts and rivets
UNI 7382	1975	Hot rolled special steel
UNI 7464	1975	Wheel centres (cast)
UNI 7660	1977	Steels for pressure vessels
UNI 7729	1984	Seamless tubes
UNI 7730	1977	Hollow bars for machining
UNI 7746	1977	Forged steels
UNI 7806	1979	Hollow sections (cold-rolled)
UNI 7810	1973	Hollow sections (cold-rolled)
UNI 7846	1978	Cementation steels
UNI 7847	1979	Steels for superficial hardening
UNI 8077	1980	Nitriding steels
UNI 8373	1982	Hot rolled finished products
UNI 8550	1984	Case hardening steels
UNI 8551	1984	Steels for superficial hardening
UNI 8552	1984	Nitriding steels
UNI 8788	1985	Cementation steels
UNI 8863	1987	Tubes
UNI 8890	1987	Steels for cold forming
UNI 8893	1986	Strip for springs
UNI 8913	1987	Welded tubes
UNI EN 10025	1994	Non alloy steels
UNI EN 10028-2	1992	Flat products for pressure purpose (elevated temperatures)
UNI EN 10028-3	1992	Flat products for pressure purpose (weldable fine grain steels, normalized)
UNI EN 10083-1	1991	Heat-treatable steels
UNI EN 10083-2	1991	Heat-treatable steels
UNI EN 10130	1991	Cold rolled flat products cold forming
UNI EN 10207	1991	Steels for simple pressure vessels
UNI 6904-71	1971	Seamless tubes
UNI 7500-75	1975	Steels for pressure vessels
UNI 7737-77	1977	Steel castings
UNI 8317-81	1981	Plates sheet and strip
UNI 8366-82	1982	Strips for springs

Tool Steel Standards

Tool steels have specific requirements due to their application in cutting, forming, and shaping other materials.

Table 2. Group of standards for tool steels

Standard Number	Description
UNI 29 55-82	Tool steels

Stainless and Heat-Resisting Steel Standards

Stainless and heat-resisting steels are crucial for applications involving corrosive environments or high-temperature service conditions.

Table 3. Group of standards for stainless and heat-resisting steels

Standard Number	Description
UNI 3159-83	Heat resisting sand castings
UNI 3161-83	Heat resisting sand castings
UNI 3992-75	Steels for internal combustion engine valves
UNI 6900-71	Stainless and heat resisting steels
UNI 6901-71	Stainless and heat resisting steels (semifinished products)