Rolling Heat Research Articles

Hot rolling of powder-in-tube Li-doped Bi(2212) tapes

Powder-in-tube Li-doped Bi(2212) tapes with high critical currents have been obtained by a hot rolling process. Hot rolling was accomplished in the final rolling stage after partial melting by preheating the rolls with infrared heaters to various temperatures ranging from 300/spl deg/C to 410/spl deg/C and then rolling the tapes directly from a 750/spl deg/C furnace. T/sub c/ decreased after hot rolling and final heat treatment. Microstructural analysis shows improved grain alignment with increased hot rolling temperature. Due to the small thermal capacities of these Ag-clad BSCCO tapes, as well as the difference in temperature between the rolls and the furnace, the remnant liquid phase that termed from partial melting was melted during the 750/spl deg/C preheat and subsequently formed a glassy phase upon contact with the heated rolls. The amount of glassy phase was reduced with increasing roll temperature. Results show that the enhancement of J/sub c/ was due to an improvement of grain alignment and reduction in the amount of secondary phases. >

Protection of titanium-alloy ingots from gas saturation on heating

Coating compositions have been developed for protection of titanium alloys from gas saturation in lengthy ingot heating for rolling at 1200°C. As a coating base, 82 and 72+80 glass enamels were employed. Chasov Yar clay, aluminum oxide, metallic aluminum, and sodium tripolyphosphate were used as the mill additives for providing high protection and good coating adhesion to the ingots. Sulfite liquor, water glass, and carboxymethylcellulose were taken as binding components. In all cases, the laborious stage of preliminary ingot metallization has been eliminated.

Rolling of Ni-based alloy (57Ni-15Cr 16Mo-3W) billets

In Wakayama steel works of SMI, carbon steel and stainless steel billets are rolled by 2-stand 2-high reversing blooming mill.Ni-based alloy (57Ni-15Cr-16Mo-3W) billets have been produced by hot forging because of its high deformation resistance (from 3.5 t ingot to finished bar dia. 253 mm). Recently hot rolling of the alloy became possible. Two-heat rolling is used. The relatively low soaking temperature (1 230 °C) is applied for the first rolling to prevent a hot tear formation by a grain boundary remelting of the ingot due to segregation. After the first heat rolling, the intermediate bar is reheated at 1 250 °C to assure lower deformation resistance for the final rolling.Pass design and schedule are improved to reduce the amount of deformation at the final stages. The second bloomer housing design is modified to reduce stress concentration and to allow higher rolling load application.

High-strength rolled sections with structural anisotropy

The article investigates the properties of high-strength sections .for building structures. It examines theinfluence of structural anisotropy on the operational properties of profiles of steel St3ps strengthened fromthe rolling heat on a high-speed mill. It is shown that the use of such rolled sections in industo, is promising.

Heat fluxes and roll circulations over the western Gulf Stream during an intense cold-air outbreak

Turbulence and heat fluxes in the marine atmospheric boundary layer (MABL) for the roll vortex regime, observed during the Genesis of Atlantic Lows Experiment (GALE) over the western Gulf Stream, have been studied. The spectral analysis suggests that cloud streets (roll vortices) are vertically organized convection in the MABL having the same roll scale for both the cloud layer and subcloud layer, and that the roll spacing is about three times the MABL depth. The roll circulations contribute significantly to the sensible (temperature) and latent heat (moisture) fluxes with importance increasing upward. Near the MABL top, these fluxes are primarily due to roll vortices which transfer both sensible heat and moisture upward in the lower half of the convective MABL. Near the MABL top, the roll circulations transfer sensible heat downward and moisture upward in the clear thermal-street region, but roll vortices influenced by evaporative cooling can transfer sensible heat upward and moisture downward in the cloud-street region. Near the cloud-top, the upward buoyancy flux due to evaporative cooling is highly related to the roll circulations near the inversion. For the lower half of the MABL, the normalized temperature flux decreases upward more rapidly than the humidity flux, which is mainly because potential temperature (θ) increases slightly upward while humidity (q) decreases slightly upward above the unstable surface layer. The gradient production (associated with the θ gradient) is a source for the temperature flux in the unstable surface layer but changes to a sink in the mixed layer, while the gradient production (associated with the q gradient) acts as a source for the humidity flux in both the unstable surface and mixed layers. The results suggest that the entrainment at the MABL top might affect the budgets of temperature and humidity fluxes in the lower MABL, but not in the unstable surface layer.

Thermoplastic working with cyclic phase recrystallizations during production of plate steel

The cycles of repeated plastic working with cyclic phase recrystallization developed make it possible to form from the rolling heat the optimum structure and properties in plates in the stage of imparting to the plate the necessary shape and dimensions, that is, directly in the hot rolling process.

Pseudoeutectoid in low-carbon unalloyed steel

1. Refinement of hot-rolled type St3sp steel contributes to the strengthening (for example, by 120 N/mm2). The resilience (by 10 J/cm2) and the fiber portion in the fracture (by 20%) are simultaneously increased in this case. 2. The presence in the structure of a pseudoeutectoid, whose amount ranges from 40 to 60%, depending on the regime, assumes decisive significances in the formulation of properties of low-carbon unalloyed steel after quenching from the rolling heat. 3. Quenching from the rolling heat promotes the strengthening of steel St3sp (by 60–80%), but simultaneously gives rise to loss of resilience due to a reduction in the work of crack initiation.

Technical fundamentals of the hardening and tempering of heavy forms of rolled product

The fundamentals of the hardening and tempering of heavy forms of rolled product are evaluated and compared from the points of view of the efficiency of the processes and the effects of the process parameters and temperatures on the mechanical and structural properties of the product. Process directions taken to improve the combination of properties of the product and to reduce the negative influence of contamination by impurities of the former austenitic grain boundaries are assessed. The two production methods of heat treatment and thermal hardening of rolled steel, the classical method with separate heating and the method which uses the rolling heat directly in the rolling line, are compared for their efficiency and for their effects on the weldability and heat resistance of the steels. The influence of carbon content on the determination of the process parameters is discussed. Treatment regimes to improve the corrosion resistance of the product are also suggested.

Building glass made from wastes from ferrosilicon production

The production of ferrosilicon is accompanied by the formation of considerable amounts of dusts and sludges resulting, respectively, from the dry and wet scrubbing of gaseous wastes from the production process. In this paper the authors seek to establish the scope for utilizing these dusts and sludges as base materials for the production of industrial-grade glass. The glass formation ranges were investigated in the following systems: sludge-dolomite-soda, sludge-dust-dolomite-soda, and sludge-dust-soda. Results are presented on the workability under heat treatment and rolling conditions for each of these systems as well as the final phase properties obtained. Test processing of the systems in a furnace showed no evidence of harmful impurity release.

Magnetic properties of boron-silicon-iron alloys decarburized at the hot-band stage

Magnetic properties of boron-silicon-iron alloys with various amounts of carbon have been investigated by the measurement of magnetic induction at a magnetizing force of 800 Am−1. The amount of carbon was varied before and after hot rolling by adding carbon to the melts and by decarburization of hot bands at 700‡ C. Results show that high magnetic inductions are obtained from heats with 0.043 to 0.070 wt% carbon but that the heat with 0.024 wt% carbon does not result in high induction. Results also show that complete secondary recrystallization and high induction are obtained from heats whose hot bands have been decarburized to a level of 30 p.p.m. provided that the heat contained 0.043 to 0.070 wt% carbon during heating for hot rolling. From these results it can be said that carbon plays a significant role during heating for hot rolling in determining the texture and magnetic induction of boron-silicon-iron alloys.

Effects of decarburization and normalizing heat treatment in boron-silicon iron alloys

Effects of carbon content and various heat treatments on the secondary recrystallization in boronsilicon iron have been studied by measurement of induction at a magnetizing force of 800 A/m and examination of microstructures at various stages of sample preparation process. Carbon was varied before and after hot rolling by adding carbon to the melts and by oxide decarburization of hot bands at 700 °C. Results show that complete secondary recrystallization and high induction (1.92 Tesla) are obtained from heats whose hot bands have been decarburized at 700 °C to a level of 30 to 40 ppm provided the heats contained 0.039 to 0.049 wt Pct carbon during heating for hot rolling. From these facts and analysis of microstructures of cross-sectional area of specimens at various stages of process it can be said that one of the major roles that carbon plays is to introduce, through transformation of austenite, a nonuniform layer-like microstructure during hot rolling and during the normalizing heat treatment of the hot band. This structure continues to exist in the final cold rolled sheet and results in anisotropic growth of secondary grains, and plays a significant role in the secondary recrystallization of boron-silicon iron.

Porosity Associated With Insoluble Carbides in VIM-VAR AISI M-50 Steel and Its Probable Effects on Rolling Contact Fatigue

The influence on the heat treatment response and rolling contact fatigue behavior of thermomechanical processing (TMP) to refine grain and soluble carbide size was studied for VIM-VAR AISI M-50 steel. Material was processed by warm rolling and then given a final, hardening heat treatment. As-received material was also given the same final heat treatments to provide a comparison. Rolling contact fatigue testing indicates equivalence of the as-received (spheroidize-annealed) and TMP specimens evaluated. This is believed to result from inability of this TMP to refine insoluble carbides and also to the presence of porosity in both as-received and also the processed material. The porosity consists of voids at the ends of the insoluble carbides and does not appear to have been reported heretofore.

Hardening from the rolling heat of low-pearlite constructional steel microalloyed with niobium and vanadium

1. In direct hardening after controlled rolling with finishing at 780–800°C in low-pearlite steels there is formed a mixed structure with predominance of lath dislocation (packet) martensite, as the result of which the steel acquires high strength, ductility, and weldability. 2. As the result of direct hardening after controlled rolling from temperatures of the two-phase area in low-pearlite steel there are formed mixed bainitic-martensitic and ferritic-bainitic-martensitic structures providing after heat treatment using the optimum cycle a yield strength of 720 MPa with T50=−80°C. 3. After direct hardening from the rolling heat, low-pearlite steels acquire a stable dislocation structure which is sufficiently fully inherited in phase transformation by lath dislocation (packet) martensite or other structures with a lath morphology. 4. The formation of a limited quantity of nonmartensitic transformation products (hypoeutectic and acicular ferrite) does not cause a significant reduction in the combination of mechanical properties of hardened low-pearlite steels.

Mastery of a technology for quenching bimetallic slabs from rolling heat

Our plant has developed and introduced a technology for quenching bimetallic slabs with a stainless-steel cladding layer from rolling heat. Rolling is done on a 4500 plate mill with subsequent cooling of the slabs in a water bath located 70 m from the mill table. The base layer of the slabs consists of steels St3sp, 20K, 16GS, and 09G2S, while the cladding layer consists of steels 08Kh13, 10KhlSNIOT, 12KhlSNIOT, and 10KhI7NI3H2T in different combinations.

The Direct Powder-Rolling Process for Producing Thin Metal Strip

The direct powder-rolling process has the potential to provide strip/sheet/foil products from a wide variety of unique powder metallurgy alloys. Alloy powder particles are directly roll-compacted to form strip or sheet of near-final thickness. Subsequent heat treatment and rolling produces material which has properties equivalent to those of the ingot metallurgy (I/M) counterpart. Following a general review of the process, microstructures of powder and roll-compacted material, and their relationship to properties, are discussed.

Study of the mechanical properties of laminated composite materials given compatible heat treatment

Variation of the ratio of composite ultimate strength to the ultimate strength of the bonding or cladding layers (matrix) in relation to reinforcement volume concentration (reinforcing layer) is given in Fig. 1 for two composites. In one composite the volume ratio of the components was varied by cladding thickness (reinforcing layer thickness was almost constant), and in the other case by reinforcement volume. The composites differed somewhat according to the strength of the reinforcement (quenched steel VKS-1). As is apparent, for the first composite the dependence of strength on reinforcement volume coneentration is linear, almost coinciding with values calculated by the rule of additions based on ultimate strength of the starting materials; for the second composite this relationship deviated a little from linearity and the strength of the second composite compared with the first decreases more sharply with a single reinforcing layer of VKS-1 steel with varying strength [3]. The greater the strength of VKS-1 steel in a homogenous condition due to increased carbon content, then the greater is the level of strength reduction in the composite. The reason for this reduction is diffusion migration of carbon from the reinforcement into the cladding during high temperature heatLug in the form of hot rolling and subsequent heat treatment [3, 4]. Therefore, in comparing strength data it is necessary to compare this type of composite with an identical thickness of reinforcing layer. Using the calculation it is possible to estimate the level of composite strength reduction during technological operations. ofc/ofm

Energy Saving Considerations in Mass Induction Heating

Mass heating for rolling, forming, and forging applications normally involves large cross section and high tonnage. As a result of the extreme energy requirements, the current energy situation has created a totally new environment for process heating systems. More efficient induction heating processing techniques, equipment designs, and heating methods are discussed. Exploitation of current and new methods to provide supplemental induction heating to existing facilities as well as new installations will be covered in depth.

Quench-hardening reinforcement bars from rolling heat

Quench-hardening reinforcement bars from rolling heat

Hydrogen embrittlement of high-strength steel obtained by thermal hardening from rolling heat

Hydrogen embrittlement of high-strength steel obtained by thermal hardening from rolling heat

Precipitate morphology in MnS-AlN-inhibited high permeability grain oriented silicon steel

A transmission electron microscope study of precipitation in an MnS-AlN-inhibited 3% silicon steel is described. The effects of various hot rolled band heat treatments are related to precipitate morphologies developed by subsequent cold rolling and recrystallization in a decarburizing anneal. The hot rolled band heat treatments consisted of solutioning at 1120°C, air cooling to selected temperatures and quenching. Quenching at temperatures higher than about 650°C resulted in a uniformly distributed fine structure (approx. 100A) imaged by strain contrast and believed to be vacancy discs stabilized by carbon diffusion. The vacancy discs did not occur in hot rolled bands quenched from temperatures below 650°C. Cold rolled and recrystallized structures derived from high quench temperatures contained clusters of very fine precipitate particles. The clusters consisted mostly of spheroidal MnS particles with some angular AlN particles. The tendency for particle clustering decreased with decreasing quench temperature, and non-uniform coarsening of the MnS particles occurred both within clusters and from cluster to cluster. Quenching from 540°C and below resulted in essentially random particle distribution and in the more frequent occurrence of angular AlN particles. The absence of particle clusters in cold rolled and recrystallized structures corresponded approximately with the disappearance of vacancy discs as quench temperature was decreased in the original heat treatments.