Assessing Mottled Indications when Digitally Radiographing Austenitic Stainless Steel Welds

When radiographing an austenitic stainless steel weld with an appreciable weld deposit size, selecting a low radiographic kilovoltage (keV) can contribute to producing a radiographic indication that is not an imperfection. The contributors to this mottled condition are both radiographical and metallurgical. Electrons from low keV can diffract or absorb when penetrating through the dendritic grain structure of a weld. The increase in keV, or using gamma ray–equivalent isotopes, produces a marked change in electron output and penetration in material.

APPLICATION OF WC GRAINS BY DEPOSITION BRAZING

The article describes problems of hard depositional brazing of wolfram-carbide grains in various matrixes. Especially iron and nickel base matrix on base material from constructional carbon steel. The experimental part was brazed by oxyacetylene flame (method 912 according to EN ISO 4063). The major goals of the experiment were to describe the technological procedure of hard depositional brazing of this specific part. Consequently, were proved wolfram-carbide deposit on two test coupons. These test coupons were metallographically and qualitatively evaluated. The advantage of wolfram-carbide depositional brazing is a service life of deposit, that could be multiple higher, than standard weld deposit with carbon, chromium and vanadium filler material. The advantage is also costly because this kind of braze is cheaper than hard surfacing filler material. This specific application of the wolfram-carbide layer is one of the hardest coatings that could be by flame brazing technology performed. Usage of this application is for example in the mining, woodcutting industry, where it is necessary to improve abrasion and resistance, service life, and guaranteed durability or hardness for cutting tools.

Properties of a thick-section narrow-gap gas tungsten arc weld of cast Haynes 282

A 50.8-mm-deep gas tungsten arc weld was made with matching filler metal in cast Haynes 282 alloy. The narrow-gap joint was filled with 104 weld beads. Visual and dye-penetrant inspection of cross-weld specimens indicated that the cast base metal contained numerous casting defects. No visible indications of physical defects were found in the weld deposit. The weld heat-affected zone was characterized by microcracking and localized recrystallization. The cause of the cracking could not be determined. Hardness testing showed that a softened region in the as-welded heat-affected zone was nearly eliminated by post-weld heat treatment. Tensile testing up to 816 °C showed that cross-weld specimen strengths ranged from 57 to 79% of the cast base metal tensile strength. The stress-rupture strengths of cross-weld specimens are within 20% of base metal reference data. Failures of both tensile and stress-rupture specimens occurred in the base metal.

Hardfacing of Copper

The article discusses the primary issues of the hardfacing of copper elements exposed to intense abrasive wear, gas-abrasive wear at high temperature and in contact with liquid metal. In addition, the article presents test results concerning the surfacing of copper grade M1 performed using a self-shielded flux-cored wire providing weld deposit Fe14 and plasma powder surfacing performed using powder providing weld deposit Ni3 (in accordance with EN 14700).

Effect of Groove Designs on Residual Stress and Transverse Shrinkage in GMAW and PGMAW of A333 Seamless Steel Pipes

The effectiveness of weld joints primarily depends on the fusion of base metal, minimum heat-affected zone (HAZ) and lesser residual stresses. The severity of thermomechanical effects e.g. weld shrinkages and residual stresses is significantly minimized by narrow gap welding technique over the traditional welding. This work describes the welding of A333 Grade 3 steel pipes by the application of GMAW and PGMAW techniques. The analysis is made to capture the effects of groove designs on residual stress and transverse shrinkage. The process parameters used for the analysis are voltage, current and welding speed. In this work, narrow groove design using PGMAW process is capable of reducing the number of passes and area of weld deposit by 35–40% by volume. In PGMAW, decrement in residual stresses is observed with a narrow groove compared to conventional V groove technique. The results are validated by metallurgical and mechanical investigation of welded joints. This work will help other researchers to understand the effect of narrow gap welding using an optimum number of passes for thick pipes.

Researches on the Welding Behaviour of Two Brands of High-Alloy and High-Efficiency Electrodes Used to Charge High Wear Parts

The research performed and presented in this paper, aims to verify the welding behavior of electrodes developed experimentally, as well as the possibility of their use in production. A group of two electrodes produced by Bohler Company, Gridur 24 and B.M.N were taken as reference, in order to compare them in terms of the mechanical properties of the deposited metal, with the experimentally developed electrodes EICr12Fe and EIMn13SiFe. They were made determinations of the chemical composition of the deposited metal with the two types of electrodes, measurements regarding the hardness of the metal deposited, comparative determinations of the structure of the weld deposit, and of the welding penetration, determinations of the deposition yield and verification of the welding behavior.

Effect of Laser Parameters on Processing of Biodegradable Magnesium Alloy WE43 via Selective Laser Melting Method

The global aim of the theme of magnesium alloy processing by the selective laser melting technology is to enable printing of replacements into the human body. By combining the advantages of WE43 magnesium alloy and additive manufacturing, it is possible to print support structures that have very similar properties to human bones. However, printing magnesium alloy parts is very difficult, and the printing strategies are still under development. Knowledge of weld deposit behaviour is needed to design a complex printing strategy and still missing. The main aim of the manuscript is the find a stable process window and identify the dependence of the weld deposit shape and properties on the laser power and scanning speed. The range of the tested parameters was 100–400 W and 100–800 mm/s for laser power and scanning speed. The profilometry and light microscopy were used to verify the continuity and shape evaluation. The microhardness and EDX analysis were used for the detailed view of the weld deposit. The manuscript specifies the weld deposit dimensions, their changes depending on laser power and scanning speed, and the continuity of the weld tracks. The stable weld deposits are made by the energy density of 5.5–12 J/mm2. Thin walls were also created by layering welds to determine the surface roughness scattering (Ra 35–60) for various settings of laser power and scanning speed.

THE CORROSION AND WEAR RESISTANCE OF LASER AND MAG WELD DEPOSITS

The paper focuses on the possibility of HPDC molds restoration for aluminium casting by laser and MAG weld cladding with a welding wire of the same grade like the base material. A chemical analysis of the weld deposits showed a decrease in the content of some elements in the MAG deposit due to the higher thermal input to the weld bath. The lower heat input of laser welding has resulted in a higher incidence of fusion defects lack between the weld deposit and the base material. Thermal conditions during welding affected hardness of weld deposits and their abrasive resistance as well. The resistance of materials against dissolution when immersed in AlSi8Cu3 alloy was similar for both deposits and the base metal.

Development of welding fluxes for hardfacing based on the mineral raw materials of the far eastern region

This paper presents the results of the research aimed at the creation of the ilmenite-fluorite welding flux using mineral raw materials of the Far Eastern region. The authors have performed thermodynamic calculation based analysis of the possible physical and chemical processes in the slag system. The experimental research we have conducted resulted in the mathematical dependencies that allow selecting flux components that would ensure the desired properties of the hard facing surfaces formed. Experimental overlay welding sessions were performed to determine the welding-technological characteristics and properties of the welded deposit. The results of the research show that the flux, consisting of 50 % of the mineral components extracted in the Far Eastern region and of 50 % of the standard flux АN22 is basic (В = 1.46) and has a low oxygenation capacity (А = 0.22). This facilitates reduction processes in the slag bath and, as a consequence of, results in obtaining high quality weld deposit. High level mechanical and performance properties of the coatings formed is maintained due to the reduction of alloying elements and possible formation of carbides (CrFe)7C3 or (CrFe)23C6, alloyed cementite (CrFe)7C3 and other substances. As an example, overlay welding under AN22PK-DMS flux produces the maximum content of chrome in the welded deposit of 12 – 15 %, and the maximum content of manganese of 6 %.