Steel material properties - Steelconstruction. From Steelconstruction. The properties of structural steel result from both its chemical composition and its method of manufacture , including processing during fabrication. Product standards define the limits for composition, quality and performance and these limits are used or presumed by structural designers. This article reviews the principal properties that are of interest to the designer and indicates the relevant standards for particular products. Specification of steelwork is covered in a separate article. Weldability is determined by the chemical content of the alloy, which is governed by limits in the product standard. ![]() DIMENSIONS FOR HOT ROLLED STEEL BEAM, COLUMN, CHANNEL AND ANGLE SECTIONS. 4-2 alro.com Weight Leg Leg Thickness (per ft.) 1/2 1/2 1/8.38 5/8 5/8 1/8.48 3/4 3/4. CHAPTER 1 PROPERTIES OF STRUCTURAL STEELS AND EFFECTS OF STEELMAKING AND FABRICATION Roger L. Brockenbrough & Associates, Inc. We stock, distribute and add value to Steel Coil Durability depends on the particular alloy type - ordinary carbon steel, weathering steel or stainless steel . While the major constituent of steel is iron, the addition of very small quantities of other elements can have a marked effect upon the properties of the steel. The strength of steel can be increased by the addition of alloys such as manganese, niobium and vanadium. However, these alloy additions can also adversely affect other properties, such as ductility , toughness and weldability . The chemical composition for each steel specification is therefore carefully balanced and tested during its production to ensure that the appropriate properties are achieved. The manufacturing process may involve combinations of heat treatment and mechanical working that are of critical importance to the performance of the steel. The more steel is rolled, the stronger it becomes. This effect is apparent in the material standards, which tend to specify reducing levels of yield strength with increasing material thickness. Steel that is then allowed to cool naturally is termed 'as- rolled' material. Normalizing takes place when as- rolled material is heated back up to approximately 9. This process refines the grain size and improves the mechanical properties, specifically toughness. Normalized- rolled is a process where the temperature is above 9. This has a similar effect on the properties as normalizing, but it eliminates the extra process of reheating the material. Normalized and normalized- rolled steels have an 'N' designation. Therefore, higher strength steels require improved toughness and ductility, which can be achieved only with low carbon clean steels and by maximizing grain refinement. The implementation of the thermomechanical rolling process (TMR) is an efficient way to achieve this. Greater force is required to roll the steel at these lower temperatures, and the properties are retained unless reheated above 6. Thermomechanically rolled steel has an 'M' designation. It is rapidly cooled or 'quenched' to produce steel with high strength and hardness, but low toughness. The toughness is restored by reheating it to 6. Quenched and tempered steels have a 'Q' designation. It is frequently used in conjunction with tempering which is a second stage heat treatment to temperatures below the austenitizing range. The effect of tempering is to soften previously hardened structures and make them tougher and more ductile. ASTM Steel Channel Section Properties various sizes ranging C3 - C15 ASTM A36 channel is one of the most widely used carbon steels in industry. This essential tool for steel designers, presents section properties and member capacities in tabular form to BS 5950 -1 : 2000, and includes: Dimensions and static parameters of American Standard Steel Channels. In European Standards for structural carbon steels (including weathering steel ), the primary designation relates to the yield strength, e. S3. 55 steel is a structural steel with a specified minimum yield strength of 3. N/mm. The minimum UTS is relevant to some aspects of design. Designers should note that yield strength reduces with increasing plate or section thickness (thinner material is worked more than thick material and working increases the strength). For the two most common grades of steel used in UK, the specified minimum yield strengths and the minimum tensile strength are shown in table below for steels to BS EN 1. Minimum values of yield strength and tensile strength are specified in the relevant product standard BS EN 1. The stress- strain relationship does not have the clear distinction of a yield point and stainless steel 'yield' strengths for stainless steel are generally quoted in terms of a proof strength defined for a particular offset permanent strain (conventionally the 0. Austenitic steels have a lower yield strength than commonly used carbon steels; duplex steels have a higher yield strength than common carbon steels. For both austenitic and duplex stainless steels, the ratio of ultimate strength to yield strength is greater than for carbon steels. In steel these imperfections take the form of very small cracks. If the steel is insufficiently tough, the 'crack' can propagate rapidly, without plastic deformation and result in a 'brittle fracture'. The risk of brittle fracture increases with thickness, tensile stress, stress raisers and at colder temperatures. The toughness of steel and its ability to resist brittle fracture are dependent on a number of factors that should be considered at the specification stage. A convenient measure of toughness is the Charpy V- notch impact test - see image on the right. This test measures the impact energy required to break a small notched specimen, at a specified temperature, by a single impact blow from a pendulum. For non- alloy structural steels the designations of the subgrades are JR, J0, J2 and K2. For fine grain steels and quenched and tempered steels (which are generally tougher, with higher impact energy) different designations are used. A summary of the toughness designations is given in the table below. The rules relate the exposure temperature, stress level etc, to a 'limiting thickness' for each sub- grade of steel. Guidance on selection of an appropriate sub- grade is given in ED0. The designer relies on ductility for a number of aspects of design, including redistribution of stress at the ultimate limit state, bolt group design, reduced risk of fatigue crack propagation and in the fabrication processes of welding, bending and straightening. The various standards for the grades of steel in the above table insist on a minimum value for ductility so the design assumptions are valid and if these are specified correctly the designer can be assured of their adequate performance. However, welding involves locally melting the steel, which subsequently cools. The cooling can be quite fast because the surrounding material, e. This can lead to hardening of the 'heat affected zone' (HAZ) and to reduced toughness. The greater the thickness of material, the greater the reduction of toughness. This susceptibility can be expressed as the 'Carbon Equivalent Value' (CEV), and the various product standards for carbon steels standard give expressions for determining this value. Although special corrosion resistant steels are available these are not normally used in building construction. The exception to this is weathering steel . The type and degree of coating protection required depends on the degree of exposure, location, design life, etc. In many cases, under internal dry situations no corrosion protection coatings are required other than appropriate fire protection. Detailed information on the corrosion protection of structural steel is available. No protective coating is needed. It is extensively used in the UK for bridges and has been used externally on some buildings. It is also used for architectural features and sculptural structures such as the Angel of the North. Suitable grades for exposure in typical environments are given below. The most important difference is in the shape of the stress- strain curve. While carbon steel typically exhibits linear elastic behaviour up to the yield stress and a plateau before strain hardening is encountered, stainless steel has a more rounded response with no well- defined yield stress. Therefore, stainless steel 'yield' strengths are generally defined for a particular offset permanent strain (conventionally the 0. The curves shown are representative of the range of material likely to be supplied and should not be used in design. For cold rolled and hot rolled strip, the specified strengths are 1. Materials within brackets might be considered if some moderate corrosion is acceptable. Accumulation of corrosive pollutants and chlorides will be higher in sheltered locations; hence it might be necessary to choose a recommended grade from the next higher corrosion class. Technical delivery conditions for non- alloy structural steels, BSI.^ NA to BS EN 1. A1: 2. 01. 4, UK National Annex to Eurocode 3: Design of steel structures General rules and rules for buildings, BSI^ BS EN 1. Hot finished structural hollow sections of non- alloy and fine grain steels. Technical delivery requirements, BSI. Technical delivery conditions. BSI^ BS EN 1. 99. Eurocode 3: Design of steel structures. General rules - Supplementary rules for cold- formed members and sheeting, BSI.^ 6. BS EN 1. 99. 3- 1- 4: 2. A1: 2. 01. 5 Eurocode 3. Design of steel structures. Supplementary rules for stainless steels, BSI^ BS EN 1. Stainless steels. List of stainless steels, BSI^ BS EN 1. Eurocode 3. Design of steel structures. Material toughness and through- thickness properties, BSI. BSI^ 1. 0. 0. 10. BS EN 1. 00. 88- 4: 2. Stainless steels. Technical delivery conditions for sheet/plate and strip of corrosion resisting steels for construction purposes, BSI.
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