Corneliu Rontescu

Alternative welding reconditioning solutions without post welding heat treatment of pressure vessel

In pressure vessels, working on high temperature and high pressure may appear some defects, cracks for example, which may lead to failure in operation. When these nonconformities are identified, after certain examination, testing and result interpretation, the decision taken is to repair or to replace the deteriorate component. In the current legislation its stipulated that any repair, alteration or modification to an item of pressurised equipment that was originally post-weld heat treated after welding (PWHT) should be post-weld heat treated again after repair, requirement that cannot always be respected. For that reason, worldwide, there were developed various welding repair techniques without PWHT, among we find the Half Bead Technique (HBT) and Controlled Deposition Technique (CDT). The paper presents the experimental results obtained by applying the welding reconditioning techniques HBT and CDT in order to restore as quickly as possible the pressure vessels made of 13CrMo4-5. The effects of these techniques upon the heat affected zone are analysed, the graphics of the hardness variation are drawn and the resulted structures are compared in the two cases.

The Ultrasonic Testing Methods for Special Braze Cladding

The present paper highlights the ultrasonic methods that can be used to detect the problems that can occur in special braze cladding. For this purpose, the sample production technology is described and the nonconformities that can arise during welding have been reviewed. The main nondestructive testing techniques are briefly presented motivating the chosen method for this study. Further, in the paper, the experimental procedure, materials and equipment used for welding are detailed. In the end, a comparison has been made between various parameters resulted from the nondestructive ultrasonic investigation. A validation for the presented method has been made through destructive examination by electron microscopy.

Ultrasound Methods for Evaluation the Quality of Welded Plastics

The article presents the way that could be evaluated feasible nondestructively with ultrasounds the plastics pipe type materials. The necessity of this study was discussed considering multiple uses of plastics’ welded joints especially in demanding fields such as natural gas transportation arteries. The main objectives were: developing a theoretical reference model of ultrasonic wave propagation through material, i.e. changing the acoustic parameters, determining reflections’ amplitudes on grid interface and bottom samples and experimentally verify the feasibility of the theoretical model developed. The methodology used consisted in studying the propagation of ultrasound waves of different frequencies and amplifications, in normal incidence, to the surface of 12 samples welded plastic pipe type, using pulse-echo technique with the functioning transducer in mode transceiver. With the obtained results we aimed to identify the sample with the highest quality of the welded joint (complete fusion) by drawing the amplitudes variation in the weld area and its bottom. For the best quality sample it was studied the amplitudes variation reflected on the same areas, on the entire circumference of the pipe (from 10 to 10 degrees) in order to establish the limits where the acoustic response in amplitude can evolve in reality for the piece without defect.

Qualitative and quantitative comparisons on reconditioning by welding of crankshafts from auto industry

One of the goals of modern society is represented by reducing the cost for the maintenance of cars. One of the pieces that break down most often on the engine block is the crankshaft, in various areas of it. Due to the fact that the price of a crankshaft is very high, specialists seek solutions for repairing and not replacing them. In this study, it is presented a comparison in terms of hardness obtained at recovering the counterweight by welding by using two methods of welding, WIG and SMAW through various techniques: normal, WTO, lateral depositing.

The effect of reconditioning techniques by welding on the quality of deposits on crankshafts, case study SMAW

Currently, we are searching for a range of solutions for repairing the crankshafts that had snapped during operation. The paper deals with the extension of the two methods for reconditioning by welding in the energy industry in the field of repairing the crankshafts in the automotive industry. The results obtained through the application of methods for reconditioning Weld Toe Tempering Technique and filling layers of sidings, which was used as a welding procedure SMAW. Qualitative and quantitative comparisons between the results of the two methods based on the criterion of rigidity are carried out.

Experimental Study towards Heterogeneous Welded Joint, Case Study: Welding Joint of Carbon Steel S235JR + AR with Stainless Steel 316L

In manufacturing industry there are many applications for the permanent joint of components of different shapes, but they are also very different in terms of chemical composition and structure [1, 2]. This paper is trying to find technological solutions of assembling by welding of two steels with totally different chemical composition, i.e. carbon steel S235JR + AR and austenitic stainless 316L. The process used for making the heterogeneous joint was Metal Inert Gas (MIG) with flux cored wire, numerically coded 137. The paper presents the effects of welding technology, through heat input, such as hardness. Variations of hardness values determined in the joint areas are presented, as well as the chemical composition of the welded joint obtained using the flux cored wire T 23 12 LPM 1/C1, according to EN ISO 17633 - A.

Software Application for Welding Processes and Control Optimization

Currently, when design engineering ensures operational security by fully taking into account reliability studies, it is of primary importance to have an encompassing understanding of the welding processes and all implicit problems that may arise, not only during their implementation phase but also after completion, in order to be able to avoid material losses. It is also necessary to have a full understanding of the imperfections that may occur in welded joints, their causes and the impact they can have on the operating endurance of the products, in order to be able to accurately determine if a product meets the required quality criteria. Thus, the development of software applications which can provide information regarding welding processes may be an important achievement for the education and industry. The software application presented in this paper provides information on the description of welding processes, welding parameters selection and calculation, types of materials and their classification in groups, as well as information about the types of imperfections, their causes, limits of acceptability and non-destructive examination methods for welded joints.