Correction to: On the effects of austenite phase transformation on welding residual stresses in non-load carrying longitudinal welds

A Correction to this paper has been published: 10.1007/s40194-021-01141-z

Homogenization of 7075 and 7049 Aluminium Alloys Intended for Extrusion Welding

During the extrusion of aluminum alloys profiles using porthole dies, the temperature of the material in the welding chamber is one of crucial parameters determining the quality of longitudinal welds. In order to extend the permissible temperature range, the billets intended for this process should be characterized by the maximum attainable solidus temperature. Within the present work, the homogenization of AlZnMgCu alloys DC-cast (Direct Chill-cast) billets was investigated, with the aim of solidus temperature maximization. Conditions of soaking and cooling stages were analyzed. The materials were homogenized in laboratory conditions, and the microstructural effects were evaluated on the basis of DSC (Differential Scanning Calorimetry) tests and SEM/EDS (Scanning Electron Microscopy/Energy-Dispersive Spectroscopy) investigations. For all examined alloys, the unequilibrium low-melting microstructure components were dissolved during soaking, which led to the significant solidus temperature increase, in comparison to the as-cast state. The values within the range of 525–548 °C were obtained. In the case of alloy with highest Cu concentration, the application of two-step soaking was necessary. In order to take advantage of the high solidus temperature obtained after soaking, the cooling rate from homogenization must be controlled, and the effective cooling manner is strongly dependent on alloy composition. For high-Cu alloy, the solidus decreased, despite the fast cooling and the careful billets preheating being necessary.

Inspection Case Analysis of Natural Gas Manifold in a High Acid Gas Field

Natural gas manifold is one of the key production facilities in gas field. It is used to buffer, collect and distribute natural gas in natural gas station. In the gas gathering terminal station of a high acid gas field, one of the manifolds had cracks and leakage on the surface of longitudinal welds when it ran for less than 100 hours. Several tests had been carried out of the failure weld seam. Test results analyses and theoretical analysis show that the cracking may cause by weld defects and propagated rapidly based on the mechanism of hydrogen blisters and HIC. In order to verify the conclusion of the analyses and ensure the safe operation of the gas field, an overall inspection of all the natural gas manifolds in the gas field had been carried out. The inspection results proved that there were manufacturing defects in the weld of all the manifolds in this gas field. The natural gas manifold has great influence on the safe operation of natural gas field. The poor working condition of the manifold may lead to failure and even endanger the safety of production. The case analysis in this paper provides a reference for the manifold inspection and ensures the safe operation of the gas field.

Analysis of Ultimate Load-Carrying Capacity of Combined Connection with Bolts and Welds

In this paper, load-carrying and deformation capacity of tension lap splices that have both welds and bolts acting in the same shear plane are studied using numerical method. The failure criterion of bolts and welds are given based on the finite element calculation and compared with existing experiment results, it shows that the established numerical model is correct and reliable. The strength of longitudinal welds and the bearing capacity of the high-strength bolts before slipping can be fully used in the combined joints, the bolts and welds fail almost simultaneously. The deformation of welds in combined connections is less uniform than its’ deformation in welded joints as the welds fails, and it causes the deformation of welds as failure is larger in combined connections than in welded connections. The deformation capacity of the combined joint are slightly increased contrasted with bolts joint and welds joint because of the interplay of bolts and welds acting in the same shear plane. The strengths of welds and bolts performed in combined connections can reach 0.95 and the deformation of combined connection is increased at least 1.10 times as the welds connection or the bolts connection.