Hot Metal Rolling Research Articles

3D characterization of splits in tested fracture mechanics specimens using X-ray computed tomography

Splits are delaminations that may appear perpendicular to the crack plane during fracture toughness tests of certain materials, such as hot-rolled metal alloys. X-ray computed tomography (CT) was used to conduct a 3D analysis of the geometrical and morphological characteristics of the splits in SE(B) specimens machined from a DH36 steel. Tomograms and 3D reconstructions of the CT results were compared with high-resolution images obtained through optical microscopy (OM) and scanning electron microscopy (SEM). Quantitative and qualitative comparisons revealed a good agreement between the results, validating the split characterization by CT. It was discussed whether characterizing the splits just by the routinary fracture surface observation conducted in fracture mechanics specimens can hide important phenomena such as plane changes, branching, and interactions between delaminations. On the other hand, CT enables an accurate and comprehensive characterization of the morphological and geometrical attributes of splits. Contrasts between the analysis and characteristics of deformed and undeformed splits were made. Finally, the limitations and challenges of the 3D split characterization by CT were also discussed, exploring experimental and image processing issues. These findings emphasize that a more thorough understanding of the internal structure of splits can be achieved by applying CT analysis, contrasting with traditional fracture surface examination. This study highlights the relevance of CT in revealing hidden complexities within the internal structure of specimens with splits.

Study on Nanofluid Boundary Layer Flow Over A Stretching Surface by Spectral Collocation Method

The method of Spectral collocation is used to analyze the flowing Nano fluid layer in contact with a stretching surface for comprehensive information and thus to have its utility in industrial activities like the production of glass fibers, petroleum refining, hot rolling of metals, metal spinning etc. The spectral collocation model incorporates thermophoresis and Brownian motion phenomena to describe the fluid flow, fluid concentration and temperature profiles. A similarity solution has been presented for the governing equations of fluid momentum, concentration and temperature. The computational results are the function of Prandtl number (Pr), Lewis number (Le), thermophoresis and Brownian motion phenomena. The engineering quantities like thermophoresis parameter (Nt), Brownian motion parameter (Nb), buoyancy-ratio parameter (Nr) and reduced Nusselt number (Nu) and reduced Sherwood number (Sh) have tabulated corresponding to Prandtl number (Pr) and Lewis number (Le). The results of the current study thrown light on fluid velocity and heat transfer rates in the boundary layer. The numerous industrial products and manufacturing processes of superior quality can be exercised with the current studies.

Methods for Studying the Structural State of Continuously Cast Slabs and the Hot-Rolled Metal Produced at the Casting and Rolling Complex

Methods for Studying the Structural State of Continuously Cast Slabs and the Hot-Rolled Metal Produced at the Casting and Rolling Complex

Effect of Cr/Mn segregation on pearlite—martensite banded structure of high carbon bearing steel

The effect of Cr/Mn segregation on the abnormal banded structure of high carbon bearing steel was studied by reheating and hot rolling. With the use of an optical microscope, scanning electron microscope, transmission electron microscope, and electron probe microanalyzer, the segregation characteristics of alloying elements in cast billet and their relationship with hot-rolled plate banded structure were revealed. The formation causes of an abnormal banded structure and the elimination methods were analyzed. Results indicate the serious positive segregation of C, Cr, and Mn alloy elements in the billet. Even distribution of Cr/Mn elements could not be achieved after 10 h of heat preservation at 1200°C, and the spacing of the element aggregation area increased, but the segregation index of alloy elements decreased. Obvious alloying element segregation characteristics are present in the banded structure of the hot-rolled plate. This distinct white band is composed of martensitic phases. The formation of this abnormal pearlite—martensite banded structure is due to the interaction between the undercooled austenite transformation behavior of hot-rolled metal and the segregation of its alloying elements. Under the air cooling after rolling, controlling the segregation index of alloy elements can reduce or eliminate the abnormal banded structure.

Improvement of Technology for Producing Rolled Sheet from Continuously Cast Steel Slabs. Part 1. Experimental Study of Casting Using a Pressure Submersible Nozzle

It is proposed to use a new submersible nozzle with eccentric apertures in order to improve continuously-cast slab quality. Calculations show that up to 38% of the heat of steel overheating is removed in the upper part of the crystallizer. The number of equiaxed crystals increases by several factors with an increase in crystallization rate. Pilot plant approval of advanced continuous casting of low-carbon and low-alloy steels makes it possible to improve hot rolled metal strength and toughness. Forecasting low-carbon steel sheet ultimate strength and relative elongation is conducted using known experimental equations. Rolled steel quality is evaluated from slabs selected from eight melts. The slab sulfur content obtained using a nozzle with eccentric apertures is somewhat higher than in slabs cast through existing nozzles.

Comprehensive Temperature Control of a Hot Metal Rolling Thickness Measurement System

The work is devoted to the development of integrated thermostating subsystem of a high-precision system for measuring the thickness of hot metal rolling. The developed thermostatting subsystem includes active and passive modules, which ensured thermostability of the measuring modules at the level of 0.5 degrees in a hot metallurgical workshop. Thermal stabilization made it possible to ensure high accuracy in measuring the thickness of hot metal rolling in a hot metallurgical production workshop.

Application of System Analysis for Technological Processes Investigation

System analysis is used as the effective way for design and modification of different kinds of technical systems. Application of system analysis to any technological process allows to present the links between input and output parameters which makes it possible to analyze its effectiveness and effect on the process for manufacturing of the object with necessary level of quality. The paper presents results of system analysis application for multioperational technological processes. The main aim of hot rolling process is manufacturing the hot rolled metal sheet with definite geometrical parameters which are necessary for further cold rolling process. The scheme of hot rolling operation with its input and output links is presented. The obtained results can be used for mathematical modeling of hot rolling operation. It is shown the application of system analysis for technological process of coating on the example of vacuum ion-plasma coating process. Because of existence of operated, noncontrolled, and indignant parameters of the coating process application of system analysis is the effective way for structural analysis of this technical system. It is proposed to supplement system analysis with function-oriented analysis. This approach can state the links between properties of the object which are sufficient for its application and technological parameters of the manufacturing technological process.

Technology Development for Producing Hot-Rolled Sheet Steel from Continuous-Casted Slab

To improve the quality of continuous-casted slabs and to reduce the cost of the produced rolled steel by ₽258 per ton, a resource-saving technology and submerged casting nozzle with eccentric holes are proposed. The experimental industrial tests of this technology for low-carbon and low-alloyed steel show an increase in the strength and toughness of the obtained hot-rolled metal. The results of the economic calculations at casting of 1.5 million tons of slabs and production of hot-rolled steel from them are provided. The computations of the ultimate strength and relative elongation of sheet steel were performed using well-known equations. The physical simulation results of sheet rolling in the finishing group of NShS and subsequent cooling establish the laws of metal structure formation.

Study of rollers thermal state at hot rolling of long products profiles at 370/150 mill of OJSC “Belorussky steel-works – UKKh “Belorusskaya metallurgical company”

In the rolling production, rolls with box passes are widely used, which is explained by the best gripping ability and high draw ratio. However, along with these advantages, there are significant drawbacks - the formation of an erosion net along the bottom of the pass and side cracks on the side outlets, since hot rolling of metals and alloys is accompanied by intense wear of the working rollers and welding fixtures, which happens due to exposure to high temperatures and stresses. Therefore, the task of elaboration of rational temperature regime to provide not only stable mill operation, but also high rollers endurance, is rather actual and requires its solution. It is very important to follow the today’s trend to increase continuous mills rolling speed, which will result in still heavier temperature conditions of rollers operation. Results of the study of the rolling process main technological parameters influence on the formation of erosion net across the bottom of the pass presented, as well as magnitude and nature of the distribution of thermal cyclic stresses along the surface layers of the bottom of pass. Study of the thermal state of roughing stands rollers of OJSC “Belorussky steel-works” 370/150 continuous wire-rod mill show, that comparing with intermediate and finished stands rollers they subject more to thermo-cyclic destruction of passes surface, but not to mechanical one. As a result of the computer simulation new data obtained on the character and peculiarities of dynamics of surface thermal state of rollers passes. The possibilities to reduce thermal cyclic stresses by improving the cooling regime of the rolls shown. Using the simulation by the finite elements method, the study of the dynamics of heating and stress state of the surface and subsurface layers of the pass bottom was accomplished. Based on the analysis results of numerical experiments and analytical calculations, isotherms of the surface layers of the bottom of the pass were compiled to select the optimal cooling mode. The data obtained can be used to control the cooling systems of roughing stands rollers of continuous section and pipe hot rolling mills.

Formation of Indices of Flatness and of Cross Section Geometry of Hot-Rolled Metal at 2000 Rolling Mill of NLMK

The geometric indices of both finished rolled metal and its semi-finished products, intended for subsequent treatment, are perhaps the most important from the perspective of the evaluation of the consumer quality of hot-rolled mill products. The survey information is presented, which makes it possible to evaluate the direction of activity and the operating results of engineering and technological personnel of the hot-rolled mill-producing department and related services of NLMK in this direction for the past two decades.

Influence of various welding methods on the structure and properties of welded austenite steel joints with nitrogen content ~ 0,5%

The analysis of literature data on the weldability of nitrogen-containing austenitic steels with high equilibrium nitrogen concentrations (0.4-0.6) is performed, and the results of studies of the structure and phase composition and mechanical properties are given for Cr-Mn-Ni-Mo-N welded joints with nitrogen concentration ~ 0.5% obtained by laser welding (for thin sheet metal) and argon arc and manual arc welding (for hot rolled metal with a thickness of up to 20 mm)

Structure and properties of 17G1S-U low-carbon pipe steel microalloyed by boron

The results of analysis of the influence of boron microalloying on structure and properties of 17G1S-U pipe steel are given in the paper. Studies of metal structure were performed by electron microscopy and local X-ray spectral analysis. It has been established that metal containing 0.006 % of boron is characterized by an increased volume concentration to 0.029 % of oxide (OS) and oxysulfide (OSB) inclusions, whose content in metal without boron reaches 0.006 %. Separate sulphide inclusions (CB), whose concentration does not exceed 0.004 % against 0.029 % in a metal without boron, containing 0.01 % S is practically absent in the metal with boron containing 0.003 % S. The microalloying of pipe steel by boron has ensured the preferential formation of small nonmetallic inclusions, evenly distributed in the volume of metal. The proportion of nonmetallic inclusions with size less than 2 (rm is 76.1 %, whereas in steel without boron it is only 58.5 %. In this case, large nonmetallic inclusions of more than 10 rm are practically absent in the sample with boron. Their share does not exceed 0.6 %, which is 22 times less than their amount in the sample without boron. The structure of the sample without boron consists mainly of ferrite and a small amount of perlite, and the sample with boron is represented by a dispersed ferritic-bainitic structure. Increasing the microhardness of both ferrite and pearlite 80 and 100 HV10, respectively, is observed by adding boron to steel. The mechanical properties of 10 mm hot rolled metal from boron-containing 17G1S-U pipe steel are characterized by increased strength properties with preservation of plastic characteristics, due to the formation of predominantly small nonmetallic inclusions and a finely dispersed ferritic-bainitic structure. The absolute values of the yield stress and the time resistance of pipe steel containing in mass %: 0.006 B and 0.003 S are achieved without heat treatment at 585 and 685 MPa, respectively, and meet the X80 strength class, while retaining sufficiently high plastic characteristics. The pipe steel without boron containing 0.01 % of S belongs to the X70 strength class and is characterized by tensile strength lowered to 540 and 610 MPa and a temporary resistance, respectively.

Diagnostic and Automatic Adjustment Algorithms for a Non-Destructive Statistical Monitoring System for the Mechanical Properties of Hot-Rolled Metal Stock

This paper discusses the algorithms used for diagnostics and automatic adjustment of the parameters for non-destructive monitoring of the properties of rolled metal at the Vyksa Production Site. We describe the results obtained, in addition to the levels of monitoring for the status of the certification system.

Development of a Process for Manufacturing a 29N26KKhBTYu-VI Precision Alloy

A full technique of production of a 29N26KKhBTYu-VI precision alloy is developed and implemented. A 500-kg ingot has been melted in Russia for the first time. This ingot is used to form an experimental batch of forged billets 90 mm in diameter and to fabricate hot-rolled metal billets 20 and 30 mm in diameter. The temperature–time deformation conditions, including data on the ductility of the alloy at the deformation temperature and the technological parameters of each processing stage, are studied. A comprehensive metallographic investigation of the alloy is performed.

Steel Alloy Hot Roll Simulations and Through-Thickness Variation Using Dislocation Density-Based Modeling

Different roll pass reduction schedules have different effects on the through-thickness properties of hot-rolled metal slabs. In order to assess or improve a reduction schedule using the finite element method, a material model is required that captures the relevant deformation mechanisms and physics. The model should also report relevant field quantities to assess variations in material state through the thickness of a simulated rolled metal slab. In this paper, a dislocation density-based material model with recrystallization is presented and calibrated on the material response of a high-strength low-alloy steel. The model has the ability to replicate and predict material response to a fair degree thanks to the physically motivated mechanisms it is built on. An example study is also presented to illustrate the possible effect different reduction schedules could have on the through-thickness material state and the ability to assess these effects based on finite element simulations.

Heat-treatment of clad steel plate for application of hull structure

Clad steel plate has good corrosion resistance and mechanical properties arising from the hot rolling of dissimilar metals, such as carbon steel and stainless steel. However, it is difficult to simultaneously achieve good corrosion resistance from the cladding metal (stainless steel) and good mechanical properties from the base metal (carbon steel) because the different steels display opposite behaviours during the heat treatment process. Proper material selection and heat-treatment conditions are necessary for fabricating clad steel plates for application in the hulls of ships. In this study, the optimal heat-treatment conditions for maximizing the corrosion resistance of the metal (S32750) and the mechanical properties of the base metal (EH40) were investigated on the laboratory scale. The quenching and tempering method employing water quenching after treatment at 1080°C for 1h/in and air cooling after treatment at 550°C for ~1–2h was more effective than normalized heat treatment. The characteristics of the fabricated clad steel plate were evaluated using the selected heat treatment conditions.

Quality Control system for a hot-rolled metal surface

The modern ideas about of quality of products are based on the principle of the absolute satisfaction of requirements of recommendations of the buyer. A presence of surface defects of steel-smelting and rolling origin is peculiar to the production of hot-rolling mill. The automatic surface inspection system (ASIS) includes two digital line video cameras for the filming of the upper and lower surfaces of the flat bar, block of illumination of the upper and lower surfaces of the flat bar, computer equipment. A system that secures 100 % control of the surface of rolled metal (of the upper and lower side) detects automatically and classifies the sheet defects in the real time mode was mounted in the domestic practice in the first time in 2003 on hot rolling mill 2000 JSC «Novolipetsk Iron & Steel Corporation» (NISC). The whole assortment of the mill 2000 was divided for the five groups by the outward appearance of the surface. The works on the identification of defects of hot-rolled metal and widening of data base of knowledge of ASIS were continued after the carrying out of guarantee tests. More than 10 thousand images of defects were added to the data base during the year.

클래드강 적용을 위한 선급용 강재의 열처리 특성 평가

Abstract Clad steel has good corrosion resistance and mechanical properties arising from the hot rolling of dissimilar metals, such as carbon steel and stainless steel. However both good corrosion resistance from the cladding plate material(stainless steel) and mechanical properties from the base plate material (carbon steel) are difficult to obtain because the different steels display opposite behaviors during the cladding process. In order to make clad steel for application in the hulls of ships, proper materials selection and heat-treatment conditions are necessary. In this study, mechanical properties of base plate materials with different chemical composition were evaluated according to heat condition of cladding plate material.

High temperature fatigue tests and crack growth in 40CrMoV13.9 notched components

The present paper addresses experimentally the high temperature fatigue of 40CrMoV13.9 steel and the effect of surface roughness on fatigue strength and crack initiation. The 40CrMoV13.9 steel is widely used in different engineering high temperature applications among which hotrolling of metals, where, in order to assure a constant temperature, the rolls are provided with cooling channels. These are the most stressed zone of the rolls where cracks systematically initiate. In order to completely characterize the high temperature behaviour of this steel, firstly uniaxial-tension load controlled fatigue tests have been conducted at different temperatures up to 650°C. Two geometries are considered: plain specimens and plates weakened by symmetric V-notches. Subsequently, with the aim to investigate the influence of the cooling channels roughness on the high temperature behaviour and the cracks initiation, uniaxial-tension load controlled fatigue tests have been conducted on plate with central hole at the service temperature of 650°C varying the surface roughness. After a brief review of the recent literature, the experimental procedure is described in detail and the new data from un-notched and notched specimens are summarized in terms of stress range, at the considered temperatures. Finally, fatigue data from un-notched and notched specimens are re-analysed by means of the mean value of the Strain Energy Density (SED) approach extended at high temperature.

Influence of surface roughness on high temperature fatigue strength and cracks initiation in 40CrMoV13.9 notched components

The present paper addresses experimentally the high temperature fatigue of 40CrMoV13.9 steel and the effect of surface roughness on fatigue strength and cracks initiation.The 40CrMoV13.9 steel considered here is widely used in different engineering high temperature applications among which hot-rolling of metals, where, in order to assure a constant temperature, the rolls are provided with cooling channels. These are the most stressed zone of the rolls where cracks initiate systematically.In order to completely characterize the high temperature behaviour of this steel, firstly uniaxial-tension load controlled fatigue tests have been conducted at different temperatures up to 650°C. Two geometries are considered: plain specimens and plates weakened by symmetric V-notches, with opening angle and tip radius being equal to 90° and 1mm, respectively. Subsequently, with the aim to investigate the influence of the cooling channels roughness on the high temperature behaviour and the cracks initiation, uniaxial-tension load controlled fatigue tests have been conducted on plate with central hole at the service temperature of 650°C, varying the surface roughness.After a brief review of the recent literature, the experimental procedure is described in detail and the new data from un-notched and notched specimens are summarized in terms of stress range, at the considered temperatures.Finally, fatigue data from un-notched and notched specimens are re-analyzed by means of the mean value of the Strain Energy Density (SED) extended at high temperature.