scholarly journals Problems Accompanying Repairs of Chemical Equipment

2020 ◽  
pp. 13-19
Author(s):  
Edmund Tasak ◽  
Aneta Ziewiec
Keyword(s):  
Heat Treatment ◽  
High Temperature ◽  
Welded Joints ◽  
Chemical Equipment ◽  
Treatment Processes ◽  
Welding Technology ◽  
Long Time ◽  
Formation Of Cracks

The paper presents problems experienced during repairs of structures operated at high temperature for a long time. Research-related TOFD method-based ultrasonic tests revealed indications implying the presence of unacceptable imperfections in welded joints. Attempted repairs involving the use of welding methods proved ineffective as the welding and heat treatment processes resulted in the formation of cracks. The tests and analysis of the above-named issue revealed that the reason for repair-related problems lay in relaxation cracks triggered by excessively high stresses in the joints and improper parameters of heat treatment to which the steel of the boiler was subjected. The welding technology developed as a result of the study enabled the performance of the proper repair of related equipment and made it possible to re-start the production.

scholarly journals The Assessment of Selected Properties of Welded Joints in High-Strength Steels

2020 ◽  
pp. 73-79
Author(s):  
Lechosław Tuz
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Welded Joints ◽  
Heat Input ◽  
Structural Changes ◽  
High Strength Steels ◽  
High Strength ◽  
High Quality ◽  
Treatment Processes ◽  
Welding Processes

The use of technologically advanced structural materials entails the necessity of adjusting typical welding processes to special requirements resulting from the limited weldability of certain material groups. Difficulties obtaining high-quality joints may be the consequence of deteriorated mechanical properties and structural changes in materials (beyond requirements of related standards). One of the aforementioned materials is steel characterised by a guaranteed yield point of 1300 MPa, where high strength is obtained through the addition of slight amounts of carbide-forming elements and the application of complex heat treatment processes. A heat input during welding may worsen the aforesaid properties not only in the weld but also in the adjacent material. The tests discussed in the article revealed that the crucial area was that heated below a temperature of 600°C, where the hardness of the material decreased from approximately 520 HV to 330 HV.

scholarly journals Hőkezelési folyamat számítógépes modellezése

2009 ◽  
Vol 4 (1) ◽  
pp. 117-123
Author(s):  
Zoltán Fabulya ◽  
György Hampel
Keyword(s):  
Heat Treatment ◽  
Computer Simulation ◽  
Energy Consumption ◽  
Specific Energy Consumption ◽  
Time Span ◽  
Fuel Gas ◽  
Environment Management ◽  
Treatment Processes ◽  
Long Time ◽  
Canned Meat

The heat treatment of cans, particularly canned meat, is a process with a big energy need, since the cans need sterilization, a heat treatment with a long time span around 120°C with the use of fuel gas in big quantity. The reduction of the use of the natural resources is the challenge in our days which appears in the new system approach of the environment management, the principle of sustainable development. That is to say, let us produce the same amount of products with less energy consumption, or more amounts with less specific energy consumption. The heat treatment is used to avert microbiological danger. The operation regulation has to be defined in a way which produces a microbiologically reliable product, but does not harm its organoleptic peculiarities, substance, taste and flavour because of the oversized treatment. In the interest of safety we have to define the extent and the time span of the heat effect leading to the destruction of the microbiological pathogens with the use of engineering calculations, modelling and computer simulation. We also have to secure the observance of the regulations obtained this way for the sake of the higher quality and the less resource utilization. This observance ability is answered with the help of our developed model for the computer simulation of heat treatment processes.

High-Temperature Heat-Treatment of the Welded Joints of Du300 Austenitic Pipelines at 900°C

Atomic Energy ◽  
2014 ◽  
Vol 116 (6) ◽  
pp. 382-386
Author(s):  
A. N. Romanov ◽  
S. V. Evropin ◽  
A. G. Derzhavin ◽  
A. V. Tutukin ◽  
D. A. Ognerubov
Keyword(s):  
Heat Treatment ◽  
High Temperature ◽  
Welded Joints ◽  
High Temperature Heat Treatment ◽  
Temperature Heat ◽  
Temperature Heat Treatment

Effects of Different Heat Treatment Conditions on Fatigue Behavior of AA7075 Alloy

2013 ◽  
Vol 32 (4) ◽  
pp. 345-351 ◽  
Author(s):  
Avni Fakioglu ◽  
Dursun Özyürek ◽  
Ramazan Yilmaz
Keyword(s):  
Heat Treatment ◽  
High Temperature ◽  
Fatigue Strength ◽  
Artificial Aging ◽  
Fatigue Behavior ◽  
Experimental Studies ◽  
Fatigue Tests ◽  
Treatment Processes ◽  
Solution Treated ◽  
Xrd Techniques

AbstractIn this study, the effect of different heat treatment processes applied to AA7075 alloys on the fatigue behavior was examined. The processes applied to AA7075 aluminum included annealing (O), high temperature pre-precipitating (HTPP), artificial aging (T6), retrogression and re-aging (RRA). The annealing heat treatment was performed for 2 hours at 500°C and samples were cooled in the furnace. In the artificial aging (T6) process, after the samples were solution treated for 2 hours at 500°C, they were quenched at room temperature and aged for 24 hours at 120°C. In the retrogression and re-aging process, samples were solution treated for 1 hour at 220°C after the T6 process and then re-aged for 24 hours at 120°C. In the high temperature pre-precipitating, pre-precipitates were formed for 30 minutes at 450°C and then, it was aged for 24 hours at 120°C. All samples were characterized through the scanning electron microscope (SEM + EDS), hardness measurements and X-ray difraction (XRD) techniques. At the end of experimental studies, SEM and EDS examinations XRD results revealed that η (MgZn2) phase formed in the microstructure following the HTTP, RRA and T6 heat treatment processes. As a result of the fatigue tests, the highest fatigue strength was measured in samples treated with artificial aging (T6), the lowest fatigue strength was measured in the annealed (O) samples.

scholarly journals INVESTIGATION OF THE MUTUAL INFLUENCE OF WELDING TECHNOLOGY AND HEAT TREATMENT OF WELDED JOINTS MADE OF DISSIMILAR GRADES OF STEEL

2021 ◽  
pp. 83-87
Author(s):  
M. V. Efimov ◽  
N. A. Kidalov ◽  
N. I. Gabelchenko ◽  
D. O. Aliev ◽  
L. S. Semenova
Keyword(s):  
Heat Treatment ◽  
Welded Joints ◽  
Welded Joint ◽  
Mutual Influence ◽  
Heat Resistant ◽  
Welding Technology ◽  
Dissimilar Steels ◽  
Welding Processes

The work is devoted to the study of welding and heat treatment modes of dissimilar steels: low-alloyed manganese-silicon and heat-resistant chromium-molybdenum to ensure the strength of the welded joint in accordance with the requirements of the current NTD. To achieve this goal, special welding processes were developed, which consist in changing the geometry of the preparation of the edges of the welded joints and tightening the tolerance for the temperature limits of heat treatment. The presented measures make it possible to ensure the mechanical and operational properties of welded joints at the required level.

Microstructural characterization of plasma-processed Ti-Al metal matrix composites

1989 ◽  
Vol 47 ◽  
pp. 552-553
Author(s):  
M. G. Burke ◽  
M. N. Gungor ◽  
M. A. Burke
Keyword(s):  
High Temperature ◽  
Titanium Aluminide ◽  
Plasma Processing ◽  
Microstructural Characterization ◽  
High Temperature Strength ◽  
Matrix Composites ◽  
Intermetallic Matrix ◽  
Long Time ◽  
Strength And Stiffness ◽  
Intermetallic Matrix Composites

Intermetallic matrix composites are candidates for ultrahigh temperature service when light weight and high temperature strength and stiffness are required. Recent efforts to produce intermetallic matrix composites have focused on the titanium aluminide (TiAl) system with various ceramic reinforcements. In order to optimize the composition and processing of these composites it is necessary to evaluate the range of structures that can be produced in these materials and to identify the characteristics of the optimum structures. Normally, TiAl materials are difficult to process and, thus, examination of a suitable range of structures would not be feasible. However, plasma processing offers a novel method for producing composites from difficult to process component materials. By melting one or more of the component materials in a plasma and controlling deposition onto a cooled substrate, a range of structures can be produced and the method is highly suited to examining experimental composite systems. Moreover, because plasma processing involves rapid melting and very rapid cooling can be induced in the deposited composite, it is expected that processing method can avoid some of the problems, such as interfacial degradation, that are associated with the relatively long time, high temperature exposures that are induced by conventional processing methods.

High-Temperature Instability of A Cr2Nb-Nb(Cr) Microlaminate Composite

1996 ◽  
Vol 54 ◽  
pp. 374-375
Author(s):  
M. Larsen ◽  
R.G. Rowe ◽  
D.W. Skelly
Keyword(s):  
Heat Treatment ◽  
Solid Solution ◽  
High Temperature ◽  
Elevated Temperatures ◽  
Aircraft Engine ◽  
Lattice Parameter ◽  
Microstructural Stability ◽  
Elevated Temperature Strength ◽  
Cross Sectional ◽  
Bcc Structure

Microlaminate composites consisting of alternating layers of a high temperature intermetallic compound for elevated temperature strength and a ductile refractory metal for toughening may have uses in aircraft engine turbines. Microstructural stability at elevated temperatures is a crucial requirement for these composites. A microlaminate composite consisting of alternating layers of Cr2Nb and Nb(Cr) was produced by vapor phase deposition. The stability of the layers at elevated temperatures was investigated by cross-sectional TEM.The as-deposited composite consists of layers of a Nb(Cr) solid solution with a composition in atomic percent of 91% Nb and 9% Cr. It has a bcc structure with highly elongated grains. Alternating with this Nb(Cr) layer is the Cr2Nb layer. However, this layer has deposited as a fine grain Cr(Nb) solid solution with a metastable bcc structure and a lattice parameter about half way between that of pure Nb and pure Cr. The atomic composition of this layer is 60% Cr and 40% Nb. The interface between the layers in the as-deposited condition appears very flat (figure 1). After a two hour, 1200 °C heat treatment, the metastable Cr(Nb) layer transforms to the Cr2Nb phase with the C15 cubic structure. Grain coarsening occurs in the Nb(Cr) layer and the interface between the layers roughen. The roughening of the interface is a prelude to an instability of the interface at higher heat treatment temperatures with perturbations of the Cr2Nb grains penetrating into the Nb(Cr) layer.

INFLUENCE THE QUENCHING AND TEMPERING ON THE MICROSTRUCTURE, MECHANICAL PROPERTIES AND SURFACE ROUGHNESS, OF MEDIUM CARBON STEEL

2018 ◽  
Vol 18 (1) ◽  
pp. 125-135
Author(s):  
Sattar H A Alfatlawi
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Surface Roughness ◽  
Carbon Steel ◽  
Cold Water ◽  
Medium Carbon Steel ◽  
Medium Carbon ◽  
Heating And Cooling ◽  
Treatment Processes ◽  
Quenching And Tempering

One of ways to improve properties of materials without changing the product shape toobtain the desired engineering applications is heating and cooling under effect of controlledsequence of heat treatment. The main aim of this study was to investigate the effect ofheating and cooling on the surface roughness, microstructure and some selected propertiessuch as the hardness and impact strength of Medium Carbon Steel which treated at differenttypes of heat treatment processes. Heat treatment achieved in this work was respectively,heating, quenching and tempering. The specimens were heated to 850°C and left for 45minutes inside the furnace as a holding time at that temperature, then quenching process wasperformed in four types of quenching media (still air, cold water (2°C), oil and polymersolution), respectively. Thereafter, the samples were tempered at 200°C, 400°C, and 600°Cwith one hour as a soaking time for each temperature, then were all cooled by still air. Whenthe heat treatment process was completed, the surface roughness, hardness, impact strengthand microstructure tests were performed. The results showed a change and clearimprovement of surface roughness, mechanical properties and microstructure afterquenching was achieved, as well as the change that took place due to the increasingtoughness and ductility by reducing of brittleness of samples.

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