Structural steels

EXAMINATION OF THE KINETICS OF MAGNETIC PROPERTIES IN TEMPERING STRUCTURAL STEELS WITH SPECIAL REFERENCE TO ACTIVE INSPECTION OF THEIR QUALITY by E.S. Gorkunov and I.n. Batuklitina, Vol. 23, No.3, pp. 177-183... 

Fig. 1 Beginning stage of pitting origin (hardened structural steel)...

Fig.7 Emission activity time trend (structural steel - loading 4000 MPa)...

Fig.9 Distribution of emission counts number in individual levels (structural steel) a) higher contact load (4000 MPa) b) lower contact load (2500 MPa).

Small batch retorts, heated electrically or hy combustion, are widely used as carburizing furnaces and are applicable also to chemic processes involving the heat treating of particulate sohds. These are mounted on a structural-steel base, complete with cyhnder, furnace, drive motor, burner, etc. Units are commercially av able in diameters from 0.24 to 1.25 m and lengths of 1 to 2 m. Continuous retorts with helical internal spirals are employed for metal-heat-treating purposes. Precise retention control is maintained in these operations. Standard diameters are 0.33, 0.5, and 0.67 m with effec tive lengths up... 

FIG. 14-79 Cost of trays in plate towers. Price includes tray deck, bubble caps, risers, downcomers, and structural-steel parts. The stainless steel designated is type 410 Peters and Timmerhaus, Plant Design and Economics for Cbemical Engineers, 4th ed., McGraw-Hill, New York, 1.9.91). 

Liquid-Metal Corrosion Liquid metals can also cause corrosion failures. The most damaging are liqmd metals which penetrate the metal along grain boundaries to cause catastrophic failure. Examples include mercury attack on aluminum alloys and attack of stainless steels by molten zinc or aluminum. A fairly common problem occurs when galvanized-structural-steel attachments are welded to stainless piping or eqmpment. In such cases it is mandatoty to remove the galvanizing completely from the area which will be heated above 260°C (500°F). 

Started to rise from the reaction, causing the vessel bottom head to fail at the weld seam. The force from the escaping gases propelled the tank into the ceiling and overhead structural steel. A small fire erupted which was quickly brought under control by the automatic sprinkler system. Even though the chemists had reviewed the chemistry and did not anticipate any problems, use testing could have identified this problem in the laboratory rather than the plant. 

Table 1.3 shows a rough breakdown of material prices. Materials for large-scale structural use - wood, cement and concrete, and structural steel - cost between UK 50 and UK 500 (US 75 and US 750) per tonne. There are many materials which have all the other properties required of a structural material - nickel or titanium, for example - but their use in this application is eliminated by their price. 

Basic construction Wood, concrete, structural steel UKE50-500 USS75-750... 

Cement and concrete are used in construction on an enormous scale, equalled only by structural steel, brick and wood. Cement is a mixture of a combination of lime (CaO), silica (SiOj) and alumina (AI2O3), which sets when mixed with water. Concrete is sand and stones (aggregate) held together by a cement. Table 15.4 summarises the most important facts. 

This stress is only a quarter of the yield stress of a typical structural steel, and the shaft therefore has an ample factor of safety against failure by plastic overload. 

The second failure mode to consider is fatigue. The drum will revolve about once every second, and each part of the shaft surface will go alternately into tension and compression. The maximum fatigue stress range (of 2 x 56 = 112 MPa) is, however, only a quarter of the fatigue limit for structural steel (Fig. 28.5) and the shaft should therefore last indefinitely. But what about the welds There are in fact a number of reasons for expecting them to have fatigue properties that are poorer than those of the parent steel (see Table 28.1). 

Figure 28.6 shows the fatigue properties of structural steel welds. The fatigue limit stress range of 120 MPa for the best class of weld is a good deal less than the limiting range of 440 MPa for the parent steel (Fig. 28.5). And the worst class of weld has a limiting range of only 32 MPa ...

Fig. 28.5. Fatigue data for a typical structural steel in dry air. Note that, if the fatigue stress range is less than 440 MPa (the fatigue limit] the component should last indefinitely. The data relate to a fatigue stress cycle with a zero mean stress, which is what we have in the case of our tail drum.

Almost all common metals and structural steels are liable to corrode in seawater. Regulations have to be followed in the proper choice of materials [16], In addition, there is a greater risk of corrosion in mixed constructions consisting of different metals on account of the good conductivity of seawater. The electrochemical series in seawater (see Table 2-4), the surface area rule [Eq. (2-44)] and the geometrical arrangement of the structural components serve to assess the possibility of bimetallic corrosion (see Section 2.2.4.2 and Ref. 17). Moreover the polarization resistances have considerable influence [see Eq. (2-43)]. The standards on bimetallic corrosion provide a survey [16,17]. 

Figure 4.18 Ductile to brittle transition diagram for a structural steel (Mager and Marschall, 1984)...

The load carried comprises approximately half the mass of the conveyor unit (50 9 kg), and half the mass of the items being conveyed at any one time. The mass of the items being conveyed on half of each conveyor unit fluctuates from 0 to 72 kg, approximately following a Normal distribution. The material specified for the hanger is hot rolled Grade 43C structural steel, which has a minimum yield strength SjVin = 275 MPa for a thickness t < 16 mm (BS 4360, 1990). 

Most turbomachinery is mounted on structural steel platforms sometimes referred to as base plates or skids. These platforms are then installed on a mass of concrete at the jobsite (either by direct grouting or mounting on sole plates) to become the machinery foundation. Platforms should always be considered as part of the foundation rather than as part of the machinery. 

The tube bundle is fabricated as a rigid structure to be handled as an individual assembly. Structural steel side members and tube supports are used for this purpose. Such supports are used beneath the bottom of the tubes to prevent the... 

An innovation is a direct-contact condenser mounted on the vapor body. A short piece of vertical pipe connects the vapor body with the condenser to minimize piping and pressure drop. This design also eliminates structural steel for support of a separate condenser. For cooling tower applications, the hotwell is elevated to permit gravity flow of water from the hotwell to the top of the cooling tower, thus eliminating the need for a pump. 

Mild steel (<0.25% carbon) is the most commonly used, readily welded construction material, and has the following typical mechanical properties (Grade 43A in BS4360 weldable structural steel) ... 

ME-O-JF 115 Electrical Design Requirements for Mechanical Equipment ME-0-JN400 Instruments Furnished with Packaged Equipment MD-0-JJOO3 Vendor Drawing and Data Submittal Requirements ME-O-JSO 10 General Specification for Structural Steel... 

Each of the three process lines is supported within a structural steel framework that is 20 m tall. Each line contains a number of vessels (reactors, flash drums, separa-... 

Bauschung,/. swelling, etc. (see bauschen) protuberance bulge crease (in fabrics). Bau-stabl, m. structural steel, -stein, m. building stone brick (. ) unit, -stoff, m. building material, structural material (Physiol.) nutrient, -stoffwechsel, m. constructive metabolism, anabolism. 

Form-sand, m. molding sand, -schwindung, /. shrinking, shrinkage, -stahl, m. structural steel profile steel, -stein, m. shaped brick (Lead) pipe stone, -stiiek, n. shaped part, -ton, m. molding clay. 

Steel. Steel shall conform to one of the applicable ASTM specifications referred to by applicable AISC specifications. Other steels not covered by these specifications may be used provided that the chemical and physical properties conform to the limits guaranteed by the steel manufacturer. Structural steel shapes having specified minimum yield less than 33,000 psi shall not be used. Certified mill test report or certified reports of tests made in accordance with ASTM A6 and the governing specification shall constitute evidence of conformity with one of the specifications listed. 

AISC specifications for the design fabrication and erection of structural steel for buildings shall govern the design of these steel structures (for AISC specifications, see the current edition of Steel Construction Manual of the American Institute of Steel Construction). Only Part I of the AISC manual, the portion commonly referred to as elastic design, shall be used in determining allowable unit stresses use of Part II, which is commonly referred to as plastic... 

Because of the effect of low temperatures on structural steel, it will be no use to change (decrease) the allowable unit stresses mentioned in the preceding paragraphs titled Allowable Stresses. Low temperature phenomena in steel are well established in principle. Structures to be used under extreme conditions should use special materials that have been, and are being, developed for this application. 

Structural Steels. Structures shall conform to sections of the AISC Specifications for the Design, Fabrication and Erection of Structural Steel Buildings."... 

Protection. Forged parts, rolled structural steel shapes and plates, and castings shall be cleaned, primed, and painted with a good commercial paint or other specified coating before shipment. Machined surfaces shall be protected with a suitable lubricant or compound. 

Plates, Shapes, and Bar Stock. Structural material used in the manufacture of main load carrying components of the equipment shall conform to applicable ASTM or API specifications covering steel shapes, plates, bars, or pipe, or a proprietary specification conforming to the minimum requirements of applicable ASTM or appropriate standard. Structural steel shapes having a specified minimum yield strength less than 33,000 psi, or steel pipe having a specified minimum yield strength less than 35,000 psi shall not be used. 

In many instances, adequate existing civil/stmctural or services installation information may not be available. Guessing the likely bearing capacity of floor slabs, foundations, structural steel or sub-slab ground, etc. can prove disastrous. Equally, assuming likely operational conditions for new installations can lead to embarrassing (and quite possibly dangerous) under-performance. The cheapest or quickest installation is not always the best or... 

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