Optimization of the technology of cutting heavy-gage sheet metal by thermal method

The analysis of the influence of various technological solutions used in the thermal cutting of heavy-gage sheet metals to reduce the deformations of the resulting piece parts is given. It has been suggested to use a gas-oxygen cutting technology with packing sequence without localization of heat build-up. The effect of improving the efficiency and quality of production using the developed cutting technology is shown.

Digital twin of the process of thermal cutting of flat material into figured parts

The designing a digital twin of the process of the thermal cutting of sheet material using laser or gas equipment for its figure cutting is considered. The solution to the problem of optimizing the path of the cutting tool taking into account the thermal effects on the material to be cut is discussed. The solution of the problem of modeling the temperature change of the material to be cut is considered on the basis of a discrete - logical representation of information about the state of the technological system of sheet cutting. The results of a computational experiment are presented.

Edge Microstructure and Strength Gradient in Thermally Cut Ti-Alloyed Martensitic Steels

Recently developed Ti-alloyed martensitic steels are believed to exhibit higher wear resistance than traditionally quenched and tempered medium carbon steels. However, their properties may deteriorate during thermal cutting and welding as a result of microstructure tempering. This would present significant challenges for the metal fabrication industries. A decrease in strength and wear resistance associated with tempering should vary with steel composition, initial steel microstructure and properties, and cutting method. In this work, we investigated the effect of thermal cutting on the edge microstructure and properties in two alloyed plate steels containing 0.27C-0.40Ti and 0.39C-0.60Ti (wt.%) commercially rolled to 12 mm thickness. Three cutting methods were applied to each of the two plates: oxy-fuel, plasma and water-jet. Microstructure characterisation was carried out using optical and scanning electron microscopy. With an increase in thermal effect, from water-jet to plasma to oxy-fuel, the heat affected zone width increased and hardness decreased in both steels. However, the hardness profile from the cut edge to the base metal significantly varied with steel composition, particularly C and Ti contents. The dependence of grain structure and precipitation kinetics on steel composition, and cutting method, were thoroughly investigated and linked to the hardness profile variation. The obtained results will be used to optimise the technological parameters for cutting and welding of Ti-alloyed martensitic steels.

Modeling of heat propagation processes during thermal metal cutting, taking into account the main provisions of the theory of welding deformations and stresses

The article describes the features of applying the main provisions of the theory of welding deformations and stresses to the thermal cutting of metal. The above calculation formulas allow us to pre-evaluate the temperature deformations of the sheet edges during separation heat cutting, as well as the size and configuration of the temperature field, to take into account the thermal effect on the metal and determine the size of the zone of thermal influence. These equations are considered by the authors as a basis for the development of a method for calculating thermal deformations and stresses during thermal cutting of metal, taking into account the transverse and longitudinal distribution of temperature over the sheet section, the ambient temperature and interaction with it, the parameters of the geometry of the cut sheet and its stiffness, heat capacity, thermal conductivity and other temperature characteristics.

Influence of the Thermal Cutting Process on Cracking of Pearlitic Steels

The paper presents research results of the influence of heat input into high carbon rail steel during cutting processes on microstructure transformation and cracking. The massive block of steel prepared for rail rolling processes was cut and examined by nondestructive magnetic testing and destructive testing by microscopic examination and hardness measurements. The results show unfavorable microstructure changes where pearlite and transformed ledeburite were obtained. The effects of the presence of such microstructures are high hardness near to cutting surfaces (above 800 HV) and microcracks which grow into low hardness block cores during rolling and rail shaping.

Influence of competing notches on the fatigue strength of cut plate edges

Material fatigue is one of the elementary causes of damage in steel construction besides corrosion and abrasion. Design recommendations require that weld seams are placed in less stressed areas due to the crack-sensitive nature of the welded areas. As a result, unwelded areas of the components such as free cut plate edges gain technical and economic relevance as locations for potential fatigue cracks. In the metal processing industry, different thermal cutting processes are frequently used. During the process, unwanted boundary conditions can lead to undesired cuts in the component geometry during the cutting process. These process dysfunctions lead to incorrect components and to rejects. This article presents results of fatigue test data of oxy-fuel thermal cut edges of defect-free and faulty repair-welded samples to investigate the influence of competing notches on the cut edge. Specimens are made from construction steels S355N and S690Q of a 20-mm-thick plate. The presented data shows that the fatigue strength of the damaged cut edges can be recovered by the repair procedure and does not show any reduction of the fatigue strength due to the determined pores or other metallurgical notches of the repaired section.

The Evolution of Residual Stress in Rib-Diaphragm Joints of Orthotropic Steel Decks Subjected to Thermal Cutting and Welding

Residual stresses change the stress ratio of fluctuating stresses, hence seriously affect the fatigue life of orthotropic steel decks (OSDs) under traffic loading. Residual stress distributions near the U rib-diaphragm joints are very complicated and need to be investigated further. In this paper, a systematic method has been proposed for calculating the residual stress field in the joint of U rib and diaphragm due to thermal cutting and welding. Firstly, a mathematical model of cutting heat sources was established to predict the temperature field. Then, a numerical elastoplastic thermomechanical model was built to predict the residual stress evolutions in a diaphragm-rib joint through the whole fabrication process involving flame cutting and welding. Moreover, the simulated temperature contours at the fusion zone and the residual stress distributions in the rib-diaphragm joint were compared and verified against the experimental ones. The numerical results showed a great agreement with the experimental ones, indicating that the heat source model can be used to accurately predict the temperature field during flame cutting. Finally, the validated numerical model was utilized to conduct parametrical analyses on the effects of thermal processing rates, e.g., the cutting and welding speeds and on the residual stress distribution in the rib-diaphragm joint. The results indicate that a faster cutting speed and a slower welding speed can decrease the residual stress magnitude at the rib-diaphragm joints and reduce the high-stress zone near the diaphragm cutouts.

A Comparison Study on the Influence of Cutting Edge Hybrid Ultrasonic Thermal Technology versus Ultrasonic Cutting on Seatbelt Processing Quality

Research conducted aimed to compare the hybrid ultrasonic-thermal cutting technology with the classic thermal cutting one. The experimental program was carried out on the ISIM designed hybrid equipment, operating at a frequency of 35 KHz, with a cutting geometry of the ultrasonic horn - sonotrode and the thermal anvil designed specifically for the task at hand; the first phase of the experimental program was developed on the thermal cutting module, the second one was performed on the US-thermal hybrid module, both modules being part of the hybrid cutting equipment designed and patented by ISIM Timisoara. The research performed in this present paper, intends to highlight the benefits of the hybrid cutting technology when compared to classical thermal cutting, in order to process two types of materials with different specifications and dimensions. After visually inspection cut materials have been then compared with automotive seatbelt quality standard IATF - International Automotive Task Force 16949. Experiments highlighted that hybrid ultrasonic-thermal cutting process has a significant influence on the quality of processed materials when compared to classic thermal cutting process, which in some cases makes the materials unsuitable for use in the automotive industry. The paper further presents two types of technology data sets suitable for 2 types of materials and up to automotive industry requirements.