Hot-Rolled Steel Bars and Shapes

To reveal the energy consumption characteristics of a steel bar and all-lightweight shale ceramsite concrete (ALWSCC), focusing on hot rolled crescent ribbed bars (CRB) and hot rolled plain steel bars (PSB), a series of pull-out tests were carried out. The bonding failure modes, the contribution of the ribs to bond-slip failure and the energy consumption characteristics were analyzed based on the curves of pull-out load F-slip displacement S and energy consumption W–slip displacement S. Results show that the splitting failure is the main failure of the CRB specimen, and the pulling out failure is the main failure of the PSB one. The ratio of the total energy dissipation of splitting failure to that of the pulling out failure is less than 30%. The mechanical bite force between CRB and concrete contributes more than 95% to the bond strength. The pull-out force is divided into four stages, such as the chemical adhesive force stage (elastic and micro-elastic strain stage), the common-effect stage of mechanical bearing force and static frictional force (plastic development stage), and the frictional force stage (crushed stage). The new design is proposed to guarantee the ductility of the reinforced concrete structure, which is based on the bond-slip energy consumption rather than the traditional strength design. The conclusions provide a reference to the reinforced concrete practice.

Residual mechanical behavior of (SD 500) hot rolled TMT reinforcing steel bars after elevated temperatures

The anisotropy of bulk formability in hot-rolled AISI 1040 steel bars has been evaluated using upset and bend tests in longitudinal, circumferential, and radial directions. The index of workability is improved approximately 65 pct by aligning the critical tensile stresses parallel to inclusion plane and elongation (longitudinal direction). The lowest workability is attained in the radial direction where tensile stresses are perpendicular to the plane of inclusions. In the circumferential direction, tensile stresses are parallel to the plane of inclusions, though perpendicular to inclusion elongation, leading to intermediate workability. Tensile ductilities in the principal directions are compared with the three workability levels. Tension fracture data agree with the forming limit line in the radial direction. In the other directions, however, the tension test progressively overestimates workability as the workability level increases.

The study took five samples of screw-thread steel III, i.e. HRB400 steel bar of different diameters: 10mm, 12mm, 16mm, 20mm and 25mm; and conducted contrast experiments of their mechanical properties and components. The 600 sets of data collected from the experiments were processed by multivariate regression analysis of mechanical properties and components by diameter with MATLAB. The result showed that differentHRB400 screw-thread steel bars have different components with the mechanical properties meeting the standard of GB1499.2-2007 [1] part 2 steel for reinforced concrete hot rolled ribbed steel bar, which has a guidance function to scientific research in universities and production in enterprises.

Hot forging of steel bars is the technique employed to produce many critical automotive components such as connecting rods and stabilizer bars. These parts typically need subsequent heat treatment to obtain the necessary properties. Microalloying adds very small amounts of certain elements to steel to improve mechanical properties, particularly strength and hardness. The new types of bar products obtainable through microalloying are outlined. These steels are both hot-rolled and cold-finished bar products. By using microalloyed (columbium or vanadium) hot-rolled bars in hot forging applications, the need for subsequent heat treatment of the as-forged parts can be eliminated in many situations. Furthermore, after cold forming or cold finishing, mechanical properties previously unobtainable using the standard grade are possible. In many situations this increased strengthening potential permits the steel user to select a lower priced bar which has the desirable properties.

Two 25 x 40 mm (1 x 1.5 in.) AISI 4150 hot-rolled steel bars that cracked during heat treatment were examined to determine whether the heat treating procedure had contributed to the failure. Metallographic examination of a cross section taken through the fracture revealed an oxide coating on both sides of the fracture surface. The oxide was also found on the top and bottom sides of the sample. Sawcut sides of the bar did not exhibit the oxide layer The presence of the oxide in the fracture, combined with its absence on all exterior surfaces, indicated that the fracture occurred as a result of an oxide seam in the original material rather than from oxide from heat treating. Nondestructive testing prior to machining and heat treatment was recommended.

Numerical study on upgrading beam-column connections in steel framed buildings for progressive collapse mitigation

Duration of Impact of Two Spheres.---The Hertz theory was verified by experiments with brass and cast-iron spheres of 3.8 and 7.6 cm. diameter respectively, using a condenser discharge method of measuring short time intervals which gave accurate results for intervals of the order of ${10}^{\ensuremath{-}4}$ second.Duration of Impact of Bars.---Experiments with hot-rolled steel bars, 2.86 cm. in diameter and 16 to 62 cm. long, prove that the compressional wave theory is inadequate since the duration of impact was found to be a function of the initial velocity and to be proportional not to the first power of the length of the shorter bar but more nearly to the two-fifths power. Moreover, the fundamental assumption of the compressional wave theory was shown to be wrong by means of a model in which the wave velocity was slow enough to be observed. A theoretical expression was then derived on the basis of certain assumptions as to the distribution of pressure and its variation with the displacement of the center of mass of the colliding body, which agrees in general with the experimental results.

Surface wrinkle defect of carbon steel in the hot bar rolling process

<div class="htmlview paragraph">High strength fasteners and cold forgings are typically produced from carbon or low alloy steel. While the final components usually exhibit adequate mechanical properties such as strength, toughness and fatigue resistance, the cost of producing components using these conventional steels is unattractively high. A large portion of these costs originate in the nature of the steel chosen for fabrication. The cumulative cost of total material-related processing, e.g. spheroidize annealing required before cold forging plus that of the QT and stress relieving heat treatments following cold forging, renders the total process rather cost ineffective. An ideal steel for cost-effective cold forging must exhibit the following characteristics: (i) Good bulk formability in the hot rolled bar or rod form, (ii) Should be capable of generating high strengths during the cold forging process, and (iii) Should retain good toughness in the final component. A new steel for high strength cold forging applications, which has the characteristics of the ideal steel, has been developed by The Basic Metals Processing Research Institute of University of Pittsburgh. This new microalloyed steel, called BHS-1, exhibits a multiphase microstructure which, can be developed during controlled hot processing of bar or rod. Laboratory and industrial trials have shown that this new steel is capable of attaining very high strengths, ductilities, notch toughness and fatigue resistances in a variety of applications and is a viable cost-effective substitute for conventional QT steels.</div>

The deformation behaviour of a hot rolled micro-alloyed steel bar of grade 38MnVS6 was examined using an FEM model during the initial passes in a blooming mill, as a function of three different pass schedules, roll groove depth, collar taper angle and corner radius. The simulations predicted the effective strain penetration, load, torque, fish tail billet end shapes, and metal flow behaviour at a chosen temperature, mill rpm and draft. The model predictions were validated for typical groove geometry and a typical pass schedule. Lower collar taper angle, lower corner radius and higher depth of groove in hot rolling enabled achievement of higher strain penetration, higher mill load and lower fish tail formation. The present study establishes the capability of the model to improve the internal quality of the rolled billet as measured by effective strain which was corroborated to the rolled bar macrostructure and microstructure. The model enables yield improvement by the choice of draft to minimise fish tail losses. The surface quality is improved by the ability to avoid fin formation that occurs at certain conditions of rolling. Thus, the groove geometry, roll pass schedule and rolling mill parameters and temperature can be optimised for best product quality and yield.

It is important to avoid buckling during low-cycle fatigue testing. The buckling load is dependent on the specimen shape, material properties, and the testing machine. In the present investigation of hourglass-shaped specimens the importance of the diameter to radius of curvature is examined. Diameters of 5 and 7 mm are examined with a ratio of radius of curvature to diameter of 4, 6, and 8. The machine used is an Instron 8800 with elongated rods for a climate chamber. This leads to a reduced stiffness of the machine during compression testing. A finite element model (in Abaqus) is developed to identify the critical buckling force. For hourglass-shaped specimens, buckling means onset of sideways movement, without a drop in the applied load which is typical for conventional Euler buckling. The onset of sideways movement is identified experimentally by analysis of the data from extensometer and the load cell. This model is verified by experiments and fits within 0.6 to − 11% depending on the specimen diameter and diameter to radius of curvature ratio. The smallest deviations are obtained for the 7-mm-diameter specimen with deviation varying from 0.6 to − 3.3% between the model and the experiments. The current investigation is done with a commercially available hot rolled structural steel bar of Ø16 mm.

Cold-finished steel bars are carbon and alloy steel bar products (round, square, hexagonal, flat, or special shapes) that are produced by cold finishing previous hot-wrought bars. by means of cold drawing, cold forming, turning, grinding, or polishing (singly or in combination) to yield straight lengths or coils that are uniform throughout their length. Cold-finished bars fall into five classifications: cold-drawn bars; turned and polished bars; cold-drawn, ground, and polished bars; turned, ground, and polished bars; cold-drawn, turned, ground, and polished bars. Different size tolerances are applicable to cold-finished products, depending on shape, carbon content, and heat treatment. When used to identify cold-finished steel bars, the various quality descriptors are indicative of many characteristics, such as degree of internal soundness, relative uniformity of chemical composition, and relative freedom from detrimental surface imperfections. Cold drawing significantly increases machinability, tensile and yield strengths of steel bars. Two special die-drawing processes have been developed to give improved properties over those offered by standard drawing practices. These processes are cold drawing using heavier-than-normal drafts, followed by stress relieving; and drawing at elevated temperatures.

Experimental study on mechanical properties of corroded stainless-clad bimetallic steel bars

Hot rolling processes have been extensively used to produce round bars by reducing the cross‐sectional area of continuously cast steel. The current trend toward increasing productivity often requires a more aggressive reduction per pass. Establishing safe and optimized hot rolling parameters must be determined to avoid damage while deforming the specific steel composition. Understanding the damage mechanism during the metal forming process is vital for product quality. Herein, a combined experimental and simulation approach is developed to track the evolution potential damage during hot bar rolling. Hot tension tests are conducted on as‐cast vanadium microalloyed 15V38 steel at different hot rolling temperatures and strain rate conditions to develop Johnson–Cook‐type material model. A thermomechanical finite element model is developed to simulate potential damage trends in a 12‐pass square‐to‐round and 8‐pass round‐to‐round standard industrial hot rolling process, employing damage criteria. Results are illustrated by creating a damage map at each rolling pass to determine the critical hot rolling conditions for damage initiation. Several parametric studies are also performed to illustrate the application of the suggested methodology for hot rolling process optimization. Results show that the probability of the damage initiation is higher at higher pass reductions and lower temperatures.