An in-process multi-feature data fusion nondestructive testing approach for wire arc additive manufacturing

Purpose The major problem that limits the widespread use of WAAM technology is the forming quality. However, most of the current research focuses on post-process detections that are time-consuming, expensive and destructive. This paper aims to achieve the on-line detection and classification of the common defects, including hump, deposition collapse, deviation, internal pore and surface slag inclusion. Design/methodology/approach This paper proposes an in-process multi-feature data fusion nondestructive testing method based on the temperature field of the WAAM process. A thermal imager is used to collect the temperature data of the deposition layer in real-time. Efficient processing methods are proposed in this paper, such as the temperature stack algorithm, width extraction algorithm and a classification model based on a residual neural network. Some features closely related to the forming quality were extracted, containing the profile image and width curve of the deposition layer and abnormal temperature features in longitudinal and cross-sections. These features are used to achieve the detection and classification of defects. Findings Thermal non-destructive testing is a potentially superior technology for in-process detection in the industrial field. Based on the temperature field, extracting the most relevant features of the defect information is crucial. This paper pushes current infrared (IR) monitoring methods toward real-time detection and proposes an in-process multi-feature data fusion non-destructive testing method based on the temperature field of the WAAM process. Originality/value In this paper, the single-layer and multi-layer WAAM samples are preset with various defects, such as hump, deposition collapse, deviation, pore and slag inclusion. A multi-feature nondestructive testing methodology is proposed to realize the in-process detection and classification of the defects. A temperature stack algorithm is proposed, which improves the detection accuracy of profile change and solves the problem of uneven temperature from arc striking to arc extinguishing. The combination of residual neural network greatly improves the accuracy and efficiency of detection.

IDENTIFIKASI CACAT LASAN FCAW PADA FONDASI MESIN KAPAL MENGGUNAKAN METODE ULTRASONIC TESTING

Ultrasonic testing is one of the non-destructive inspection methods for welding results. The ultrasonic testing method has several advantages, namely it can be used to analyze the position of the defect in the object, both the depth of the defect and the dimensions of the defect, and it is an environmentally friendly method. Physical defects that are in solid objects of course cannot be known from direct vision so it is necessary to carry out an inspection of an object to see whether or not there are defects that occur in solid objects. Ultrasonic testing of the results of FCAW welding on the foundation of the ship's engine. FCAW welding is applied to the foundation with two types of welding positions, namely the overhead position coded P1 and the horizontal position coded P2. The test was carried out using a wave frequency of 4 MHz and using a 0° probe for analysis of defects in the area around the weld metal and a 70° probe for analysis of the weld metal. The tests were carried out using the ASME section V and ASTM E164 standards as the standard for determining defects. The test results at the P1 welding position found two types of defects, namely incomplete fusion defects with five welding points with the longest defect length of 40mm and porosity defects with two points with the longest defect length of 30mm. While the results of ultrasonic testing at the P2 welding position found two types of defects, namely slag inclusion defects with a defect length of 35mm and incomplete penetration defects with a defect length of 20 mm. The conclusion of ultrasonic testing is that the difference in welding positions is that the welding position greatly affects the quality of the welding results. The defects resulting from the welding position also vary.

Numerical analysis of lost foam casting for large-caliber water meter shell

Large-caliber water meter shells are prone to shrinkage porosity, wrinkles, air entrapment, slag inclusion, and other defects during the lost foam casting process. Taking the vertical spiral wing WS-100 water meter as the research object, through the analysis of the structure of the water meter shell, the flow field and temperature field of the design of outer bottom injection-vertical pouring, outer bottom injection-horizontal pouring and inner bottom injection-horizontal pouring involved in the filling and solidification process are numerically simulated and solve analysis, respectively. The results showed that: when the inner bottom injection-horizontal pouring process was adopted, the filling process of the casting was stable, the isolated liquid phase area of the solidification process was relatively small, and the possibility of forming defects was less. The casting performance is excellent, and the numerical analysis is verified to be effective.

The effect of casting speed on slag-inclusion defects in 1050 × 200 mm ultra-low-carbon automobile steel slabs

The effect of casting speed on slag-inclusion defects in 1050 × 200 mm ultra-low-carbon automobile steel (UAS) slabs was studied by performing nail plate experiments and by monitoring the liquid level fluctuations during the continuous casting process. The number, location, length, and proportion of slag-inclusion defects in hot-rolled coils produced at different casting speeds were analyzed. The results showed that the defects in the hot-rolled coils were mainly owing to the mold protective slag. For the continuous casting speed of 1.6 m/min, the fraction of slag-inclusion defects was the lowest (at 5.3%), and the number of slag-inclusion defects was lower than for the other casting speeds. The length of slag inclusions was under 900 mm. Furthermore, the number of slag-inclusion defects on the upper and lower surfaces was smaller than those for the other casting speeds. At different casting speeds, slag-inclusion defects mainly existed within 100 mm of the edge on both surfaces of hot-rolled coil plates. The fluctuation within the 0–1 mm range was 98.1% for the casting speed of 1.6 m/min, indicating that the flow rate of molten steel on both sides of the nozzle was relatively stable, which helps to control slag-inclusion defects in hot-rolled coils.

Detection of slag inclusions using infrared thermal imagining system

Assuring high quality of welded joins is a vital task in many industrial branches also when joints are made manually. It is the case metal-arc welding with covered electrode. One of main imperfection, that can occur in this process is slag inclusion. In the paper an method for detection of slag inclusion in multipass manual welding is proposed and validated. The key idea of the method is that small temperature disturbances will be noticeable in consecutive cross-section of joint in the cooling pass. Temperature distribution weld face was measured with longwave infrared camera (LWIR). For consecutive cross-section made in IR representation of joint differences in mean temperature was calculated to assess the cooling rate directly after the elements were welded. It can be made because on each thermogram the whole joint is visible, thus position of electrode in time can be easily marked. Results of slag inclusion detection were compared with radiographic images of made joints. In the future additional studies will be performed in order to generalize proposed method to wider group of materials and for more complex welds.

Analisis Cacat Produk pada Proses Pengelasan Pipa Penstock (Studi Kasus: PT. XYZ)

Bidang hidromekanikal merupakan bidang yang cukup kompleks untuk digeluti sebagai bidang usaha. Objek dari studi kasus pada penelitian ini adalah perusahaan yang menjadi kontraktor bangunan hidromekanikal dan komponennya seperti bendungan, pintu air, dan lainnya dari mulai proses pembuatan atau produksi komponen, perakitan, pengujian hingga instalasi di lapangan. Dengan sistem produksi engineering to order pada perusahaan, rana kualitas produk cukup signifikan untuk memenuhi permintaan customer. Produk yang memiliki cacat (defect) memang ada beberapa yang dapat diperbaiki, tetapi hal itu membuat cost perusahaan bertambah banyak untuk pengerjaan ulang dan membutuhkan waktu produksi lebih lama. Dari hal ini dapat diketahui pentingnya perbaikan dan pengendalian kualitas pada produk yang dihasilkan oleh perusahaan. Penelitian ini bertujuan untuk mengetahui penyebab terjadinya cacat pada proses pipa penstock. Mengidentifikasi, mengukur, dan menganalisis penyebab terjadinya cacat pada pengelasan proses pipa penstock dan Mengetahui improvement apa yang dibutuhkan perusahaan untuk meningkatkan kualitas pengelasan pipa penstock. Metode yang digunakan dalam penelitian ini adalah Six Sigma di mana metode ini berfokus terhadap permasalahan kualitas produk dan dapat digunakan untuk dapat melakukan perbaikan pada proses produksi dan dapat menanggulangi terjadinya cacat produk. Dari hasil penelitian didapatkan bahwa cacat las yang paling signifikan terdapat pada pipa penstock adalah porosity dan slag inclusion dengan persentase kumulatifnya sebesar 98,5%. Didapatkan pula nilai sigma dengan DPMO sebesar 73.430,49 adalah 2,951 σ. Rekomendasi untuk dapat menanggulangi cacat produk dibuat untuk dapat menanggulangi agar cacat produk yang ada nantinya dapat diminimasi.

Pipe metal and welded connection defect repair by cladding

Cladding repair is the one of the most simple and least expensive repair technologies. It refers to both permanent and temporary repair methods. It reduces work costs and time of repair works while retaining the quality required by the statutory requirements. With the help of cladding repair, a significant number of defects of corrosion-mechanical origin can be eliminated. The problem of improving this technology is of utmost importance. The purpose of the present research is to develop the technology for effective and safe cladding repair of such defects as corrosion damages of pipe metal and such welded connection defects as incomplete groove filling, undercut, pores, strikes, slag inclusion. The following problems were solved to reach this goal: research of thermal cycles in the course of cladding, research of cladding modes, development of multipass repair technology, determination of allowable defect parameters, and detection of methods for optimal quality control of repaired areas. The specialists performed testing of full-scale pipe samples and circular joint of pipes, imitating the surface defects after cladding repair. The test results did not reveal the damage of metal and welded connection areas. Cladding repair allows recovering bearing capacity of pipeline to design level. This technology can be used in the works on shutdown pipelines and on pipelines under operation.

Virtual study of conditions for occurrence of non-metallic inclusions under consumable-electrode multiple-pass welding of pipe-lines

The causal factors for the occurrence of non-metallic inclusions in the form of slags, complex oxides and sulfi des under multi-pass arc welding analyzed. It is assumed that lack of fusion in interlayers and slag inclusions are formed on the surface of the beads of previous passes if slag residues in craters exist arising from short interruptions of arc burning, or lack of fusion at bevelled edges. The virtual study is carried out using physical and mathematical model, the features of which are fi xing the level of the melt at the solidifi ed front of the weldpool and introducing into it description of non-metallic inclusions fi lling cavities in the surface crater or lack of fusion at the side face of the groove. The results of numerical simulation of the remelting process of slag residues in different welding modes and with different sizes of slag inclusion are presented. It is shown that, with signifi cant depth of craters or lack of fusion, comparable with the thickness of the deposited layer, it is diffi cult to create conditions for their rise to the surface of the weldpool even at the maximum permissible arc current.

The Interfacial Characterization and Performance of Cu/Al-Conductive Heads Processed by Explosion Welding, Cold Pressure Welding, and Solid-Liquid Casting

The Cu/Al composites conductive head is widely used in hydrometallurgy as the core component of cathode plate. Its conductive properties directly affect the power consumption, and the bonding strength and corrosion resistance determine the conductive head service life. The Cu/Al conductive head prepared by explosion welding, cold pressure welding, and solid-liquid casting methods were investigated in this paper. The interface microstructure and compositions were examined by scanning electron microscope and X-ray energy dispersive spectrometry. The bonding strength, interface conductivity, and the corrosion resistance of three types of joints were characterized. The Cu/Al bonding interface produced by explosive welding presented a wavy-like morphology with typical defects and many of brittle compounds. A micro-interlocking effect was caused by the sawtooth structures on the cold pressure welding interface, and there was no typical metallurgical reaction on the interface. The Cu/Al bonding interface prepared by solid-liquid casting consisted mainly of an Al-Cu eutectic microstructure (Al2Cu+Al) and partial white slag inclusion. The thickness of the interface transition layer was about 200–250 µm, with defects such as holes, cracks, and unwelded areas. The conductivity, interfacial bonding strength, and corrosion resistance of the conductive head prepared by explosive welding were superior to the other two.