scholarly journals Effect of the heat treatment mode of high chrome iron rolling mills on chrome redistribution in the stress field

2021 ◽  
pp. 113
Author(s):  
Olena Popova ◽  
Nataliia Lalazarova ◽  
Оlga Afanasieva
Keyword(s):  
Heat Treatment ◽  
Residual Stresses ◽  
Cooling Rate ◽  
Uniform Distribution ◽  
Temperature Difference ◽  
Thermal Stresses ◽  
Stress Gradient ◽  
Working Layer ◽  
Heating And Cooling ◽  
Uneven Heating

Heat treatment is an important stage in the technology of rolling rolls, due to the fact that the thermal stresses that occur during rapid or uneven heating summing up with the rather high residual stresses after casting, create a risk of cracking. Goal. The aim is improving the quality of rolling rolls by varying the modes of heat treatment. Therefore, it is important to assess the level of thermal stress. Method. Evaluation of thermal stresses arising in heating and cooling in the heat treatment process that summing up to the relatively high residual stresses after casting, creates the risk of fractures. The profile of the distribution of chromium in the cross section of the working layer at each time under the action of the stress gradient that occurs during heat treatment of the roll is obtained by calculation. Results To ensure a minimum temperature difference between the surface and the core, it is necessary to reduce the heating and cooling rate, as well as increase the duration of exposure at a given temperature. Reducing the cooling rate from 17 to 3.7°C/h decreases the temperature difference at the surface and in the center of the roll and the intensity of thermal stresses from 29 to 7 MPa. It is established that the rate of heating and cooling should not exceed 10– 15° C/h, and exposure to annealing should be at least 5–7 hours. Scientific novelty. The modes of heat treatment of rolling rolls with a high-chromium cast iron working layer are designed by estimating the level of thermal stresses. The profile of distribution of chromium after various modes of heat treatment is calculated analytically and its mode at which the most uniform distribution of chromium on section of a working layer remains is offered. Practical significance. The developed technique allows to calculate analytically the profile of distribution of chromium after various modes of heat treatment and to choose such a mode at which the most uniform distribution of chromium remains on the section of a working layer.

The Welding Process as a Local Issue with Global Consequences

2014 ◽  
Vol 969 ◽  
pp. 340-344 ◽  
Author(s):  
Mohamad Al Ali
Keyword(s):  
Residual Stresses ◽  
High Temperatures ◽  
Research Program ◽  
Local Stability ◽  
Thermal Stresses ◽  
Welding Process ◽  
Plastic Strains ◽  
Heating And Cooling ◽  
Uneven Heating ◽  
Transient Thermal

The welding process causes transient thermal stresses and non-continuous plastic strains around the weld due to the induced high temperatures. Uneven heating and cooling during the welding process cause a residual stresses in the welded member. The paper deals with the local influence of welding process and its global consequences at the creation and final redistribution of welding stresses. The paper also presents a verification of Modified empirical formulae, developed by the author, using experimental results of research program oriented to the effects of welding stresses and beams local stability [1, 2 and 3].

Residual Stresses in Elastoplastic Bending of Round Bar

2019 ◽  
Vol 946 ◽  
pp. 862-867 ◽  
Author(s):  
Vladimir N. Shinkin
Keyword(s):  
Residual Stresses ◽  
Heating And Cooling ◽  
Steel Bar ◽  
Hardening Modulus ◽  
Mechanical And Physical Properties ◽  
Metal Products ◽  
Weld Area ◽  
Uneven Heating ◽  
Temperature Heating ◽  
Elastoplastic Bending

Elastoplastic deformation on the presses and high-temperature heating of the steel sheet cause the large residual stresses in the sheet’s and bar’s wall. The technological operations of the obtaining of metal products, their shape and linear dimensions strongly affect on the distribution within the metal and the maximum values of residual stresses. The uneven cooling of various parts of the sheet and bar, obtained by bending, stamping and forging, also leads to the large residual stresses inside the metal. The greatest residual stresses occur in the weld area, where there is a strong heterogeneity of mechanical and physical properties of the metal due to uneven heating and cooling. Below the new analytical method for calculating of the residual stresses of a round steel bar in the elastoplastic bending is obtained. This method takes into account the diameter of the bar, as well as the modulus of elasticity, the yield strength and the hardening modulus of steel’s bar.

The Influence of Heating/Cooling Rate on Transformation Temperatures of Co-Base Alloy

2014 ◽  
Vol 782 ◽  
pp. 453-456
Author(s):  
Jana Dobrovská ◽  
Bedřich Smetana ◽  
Hana Francová ◽  
Zdenĕk Jonšta
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Cooling Rate ◽  
Base Alloy ◽  
Transformation Temperatures ◽  
X Ray ◽  
Heating And Cooling ◽  
The Individual ◽  
Dispersive Analyser ◽  
Scanning Electron

Thepaper deals with an experimental measurement of the transformation temperatures of Co-base alloy. Temperatures were determined by means of DTA-method during controlled heating and cooling. The samples in an as-received state were analysed at heating/cooling rates of 2, 5, 10 and 20 °C/min with the use of the equipment Setaram SETSYS 18TM (DTA-method). The samples after various heat treatments were analysed at heating/cooling rate of 5 °C/min by Setaram SETSYS 18TM (DTA-method). On the basis of evaluation of the results the influence of heating/cooling rate on shift of the transformation temperatures was determined. The influence of heat treatment on shift of the transformation temperatures was also studied. The samples in an as-received state and the samples after heat treatment were alsosubjected to the phase analysis by scanning electron microscopy using the microscope JEOL JSM-6490LV equipped with an energy dispersive analyser EDAX (EDS INCA x-act). The individual phases were identified by semi-quantitative X-ray microanalysis.

Development of Plastic Zones during the Thermal Cycle of Welding

2013 ◽  
Vol 586 ◽  
pp. 11-14 ◽  
Author(s):  
Mohamad Al Ali ◽  
Michal Tomko ◽  
Ivo Demjan
Keyword(s):  
Bearing Capacity ◽  
High Temperatures ◽  
Thermal Cycle ◽  
Thermal Stresses ◽  
Welding Process ◽  
Plastic Strains ◽  
Heating And Cooling ◽  
Plastic Zones ◽  
Uneven Heating ◽  
Transient Thermal

The high temperatures induced during the welding process cause transient thermal stresses and non-continuous plastic strains around the weld. Uneven heating and cooling processes together with these plastic strains result in residual (welding) stresses, [1]. This paper deals with the development of plastic zones, related to welding stresses and their effects on the bearing capacity from a Civil-engineering perspective.

Finite Element Modelling of 5- and 8-Pass Ferritic Steel Welds Using Phase Transformation Material Models

2011 ◽  
Author(s):  
David Z. L. Hodgson ◽  
Christopher M. Gill ◽  
Benjamin M. E. Pellereau ◽  
Paul R. Hurrell ◽  
John Francis
Keyword(s):  
Finite Element ◽  
Phase Transformation ◽  
Stress Field ◽  
Residual Stresses ◽  
Weld Metal ◽  
Cooling Rate ◽  
Pressure Vessel Steel ◽  
Material Models ◽  
Cooling Rates ◽  
Heating And Cooling

The modelling of welds is desirable to predict the distortion of components during manufacture, the position and magnitude of peak residual stresses and to predict metallurgical effects in specific regions. Welds are a complex modelling problem requiring both thermal and structural solutions. This has lead to the development of several weld-specific simulation packages and codes for finite element (FE) analysis. This paper describes the application of phase transformation material models to ferritic groove weld test specimens. These specimens were manufactured from SA508 Grade 3 Class 1 pressure vessel steel plates 200×150×20 mm with SD3 1Ni 1/4Mo weld metal deposited in a groove 10 mm deep. The fifth weld pass in both specimens had two stop-starts introduced to investigate their effect on the residual stress field. The first stop linearly ramped the torch power down before backtracking and continuing the bead. The second stop had the torch abruptly switched off before restarting in the same location. The residual stresses in these specimens were measured using Neutron Diffraction (ND) which has been compared with the FE predictions. The FE modelling used a decoupled thermo-mechanical approach. The VFT-CTSP weld simulation package was used for the thermal analysis and Abaqus 6.8-3 for the mechanical analysis using the VFT UMAT-WELD user subroutine with phase transformation material properties. The thermal results appear to be consistent with the thermocouple traces recorded during manufacture of the plates. The simulated thermocouple temperature peaks are within 10% of manufacturing peaks. The simulated heating and cooling rates closely follow the manufacturing heating and cooling rates. The stresses calculated appear to be similar to the ND results measured on the specimen plates though some suspected errors have to be taken into account. The predicted stress field in the weld bead has a discontinuity as the material within the model changes from SA508 to SD3. This is to be expected due to the slightly different Young’s modulii of the two materials. This effect is present in the FE results due to the inability to model the metal mixing that occurs at the fusion boundary. The ND results were continuous across the fusion zone (FZ) and heat-affected zone (HAZ). The phases predicted appear to be similar to those expected for welds of this type. The martensite formation in the weld metal is consistent with the cooling rates experienced at the stop-start locations. The ramped stop-start had the lower cooling rate and therefore less martensite forms while the abrupt stop-start had a higher cooling rate which produces a larger amount of martensite. The subsequent remelting caused by passes six-eight removes the effects of the stop-start features in the eight-pass plate in the FE predictions.

Effect of Heat Treatment Parameters on Mechanical Properties of Medium Carbon Steel

2020 ◽  
Vol 22 (4) ◽  
pp. 909-918 ◽  
Author(s):  
M. M. Blaoui ◽  
M. Zemri ◽  
A. Brahami
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Cooling Rate ◽  
Heating Rate ◽  
Physical And Mechanical Properties ◽  
Medium Carbon Steel ◽  
Holding Time ◽  
Austenitization Temperature ◽  
Heating And Cooling ◽  
Heat Treated

AbstractEngineering materials, mostly steel, are heat treated under controlled sequence of heating and cooling to alter their physical and mechanical properties to meet desired engineering applications. This paper presents a study of the influence of austenitization temperature, cooling rate, holding time and heating rate during the heat treatment on microstructure and mechanical properties (tensile strength, yield strength, elongation and hardness) of the C45 steel. Specimens undergoing different heat treatment lead to various mechanical properties which were determined using standard methods. Microstructural evolution was investigated by scanning electron microscopy (SEM). The results revealed that microstructure and hardenability of the C45 steel depends on cooling rate, austenitization temperature, holding time and heating rate.

scholarly journals Analysis of Thermal Stresses and Strains Developing during the Heat Treatment of Windmill Shaft

2017 ◽  
Vol 62 (2) ◽  
pp. 459-471 ◽  
Author(s):  
A. Cebo-Rudnicka ◽  
Z. Malinowski ◽  
T. Telejko
Keyword(s):  
Heat Treatment ◽  
Stress Field ◽  
Thermal Stresses ◽  
Stress Fields ◽  
Axially Symmetric ◽  
The Finite Element Method ◽  
Temperature Changes ◽  
Incremental Method ◽  
Heating And Cooling ◽  
The Mathematical Model

AbstractIn the paper the results of evaluation of the temperature and stress fields during four cycles of the heat treatment process of the windmill shaft has been presented. The temperature field has been calculated from the solution to the heat conduction equation over the whole heat treatment cycles of the windmill shaft. To calculate the stress field an incremental method has been used. The relations between stresses and strains have been described by Prandtl-Reuss equation for the elastic-plastic body. In order to determine the changes in the temperature and stress fields during heat treatment of the windmill shaft self-developed software utilizing the Finite Element Method has been used. This software can also be used to calculate temperature changes and stress field in ingots and other axially symmetric products. In the mathematical model of heating and cooling of the shaft maximum values of the strains have been determined, which allowed to avoid the crack formation. The critical values of strains have been determined by using modified Rice and Tracy criterion.

Transient and Residual Stresses in Heat-Treated Plates

1958 ◽  
Vol 25 (4) ◽  
pp. 459-465
Author(s):  
H. G. Landau ◽  
J. H. Weiner
Keyword(s):  
Stress Distribution ◽  
Residual Stresses ◽  
Cooling Rate ◽  
Thermal Stresses ◽  
Heated Plate ◽  
Perfectly Plastic ◽  
Heat Treated ◽  
The Face ◽  
Elastic Perfectly Plastic

Abstract Equations are given for determining transient and residual thermal stresses in a heat-treated plate. The material of the plate is assumed to be elastic, perfectly plastic. The temperature is assumed uniform on any plane parallel to the faces of the plate but can vary arbitrarily in the direction normal to the face and in time. The stress distribution during the unloading period is determined exactly without the simplifying assumption of simultaneous unloading. Application is made to the determination of stresses during cooling of a uniformly heated plate. The stress-distribution sequence and residual stresses are calculated for several values of cooling rate and yield stress.

scholarly journals Investigation of the influence of heat treatment modes of experimental steels for new generation railway rails on mechanical properties

2020 ◽  
pp. 247-255
Author(s):  
A.I. Babachenko ◽  
R.V. Podolskyi ◽  
G.A. Kononenko ◽  
Е.А. Safronova
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Cooling Rate ◽  
Operational Reliability ◽  
Operating Conditions ◽  
Railway Track ◽  
Controlled Cooling ◽  
Furnace Heating ◽  
Heating And Cooling ◽  
Cooling Media

The safety of railway transport depends on the quality of the metal, the efficiency of the technology for manufacturing rails and wheelsets, and the operating conditions of the railway track. The operational durability of rails is largely determined by the structural state and mechanical properties of the metal of the rail elements. On the basis of a comparative analysis of various methods and modes of treatment of railway rails, it was found that one of the ways to increase the operational reliability of rails can be the optimization of methods for heating and cooling the metal when implementing the modes of their heat treatment. A study of the microstructure of steel laboratory melts up to 10 kg, melted under the conditions of the IHM NASU (the symbol of which is PCT), after furnace heating with cooling the blanks for tensile specimens (55x12x12mm) in various cooling media: in calm air, under a ventilator, blowing with compressor air in water with a temperature of 80˚С. It is found that at cooling rate 5,1˚С / s (cooling air compressor) is obtained a homogeneous structure of fine pearlite with a hardness of the metal at the level of foreign standards. On the basis of technical sources, it has been established that volumetric furnace heating followed by immersion of the test specimens made of steel with 0,84%С, 0,44% Si, 0,95% Mn into an environment providing the metal with a controlled cooling rate of ≈5.1˚C / s contributes to the formation of a lamellar pearlite structure with a hardness of 415 HB. It was found that the use of furnace heating leads to the production of homogeneous austenite in the volume of the samples under study.

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