Oblique Y-groove cracking test of the welding cold cracking susceptibility of domestic X-70 pipeline steel

“Gas Transmitting From West to East Project“ is significant.it should ensure the welding quality and safety of pipeline.The task is very arduous to guarantee the quality of the projcet in the condition of long line.complex weather and geolgy features.in this paper,the welding cold cracking susceptibility of domestic X-70 pipeline steel adopted by the project, which is one of the most interesting questions of welding quality about petrol pipeline,was studied by means of oblique Ygroove cracking test.The crack ration of surface and section was tested under the conditions of different welding materials and preheat temperature.The thickness of plate stell was 14.7mm and 10.3mm.The results reveal that X-70 pipeline steel has good crack resistance.The research has important value for the construction of large-scale pipeline engineering and the application of domestic X-70 pipeline steel.     

Effect of pressure on solidification cracking susceptibility of Al–Si alloys

ABSTRACT

An approach was developed to calculate the crack susceptibility under various levels of pressure, and the corresponding numerical method was presented. The binary Al–Si alloy system was selected for study because the effect of high pressure on its phase diagram has been reported. The results showed a higher pressure can lead to a higher crack susceptibility and shift the most crack susceptible composition to higher solute contents. It was found a higher pressure can increase the effect of back diffusion on the solidification path and hence the crack susceptibility. This study provides a new understanding of the effect of pressure on solidification cracking susceptibility and can be a relevant starting point for studying solidification cracking under high pressures.     

Stress corrosion cracking of α–β brass in chloride containing waters

Abstract

Slow straining of an α–β brass in aqueous solutions with various concentrations of chloride ion has been used to ascertain the effects of potential, pH, and chloride content on the susceptibility to stress corrosion cracking. The ductility is at a minimum with 55 ppm Cl present and increases at higher concentrations, where dezincification effects become more significant. Anodic polarization increases the ductility loss but the effects are again complicated at high potentials by greater dezincification. The strqjn rate dependence of the embrittlement results in a ductility minimum at 2 × 10^?6. The results are assessed in terms of various cracking mechanisms but seem to be most consistent with a mechanism involving the rupture of a surfacefilm of CU₂O that forms on the alloy in the critical potential range.     

Effect of pre-deformation on the stress corrosion cracking susceptibility of aluminum alloy 2519

The effects of pre-deformation and strain rate on the stress corrosion cracking （SCC） behavior of aluminum alloy 2519 in air and in 3.5% NaCI water solution were investigated by means of slow strain rate tension （SSRT）, scanning electron microscopy （SEM）, and transmission electron microscopy （TEM）. The results indicate that the alloy is susceptible to SCC in 3.5% NaCI water solution and not in air. At the same pre-deformation, the alloy is more susceptible to SCC at 1.33 × 10^-5 s^-1 than at 6.66 × 10^-5 s^-1. Moreover, it is more susceptible to SCC at free pre-deformation than at 10% pre-deformation at the same strain rate. The number of 0 precipitated along the grain boundaries is reduced and distributed discontinuously, at the same time, the precipitate-free zones （PFZ） become narrow and the susceptibility to stress corrosion cracking is reduced after 10% pre-deformation.     

The effect of solidification behaviour of austenitic stainless steel on the solidification cracking susceptibility

0Introduction Oneofthemainproblemsinweldingausteniticstain lesssteelsishotcracking[1,2].Inweldingofsingle phase austeniticstainlesssteels,thetendencyofhotcrackingis moreserious[3].Inordertopreventhotcrackingofthis kindofmaterial,itwasattemptedtogaintwo p…     

Effect of high-temperature pre-precipitation on mechanical properties and stress corrosion cracking of Al-Zn-Mg alloys

1　INTRODUCTIONMediumandhighstrengthAl Zn Mgseriesaluminumalloysarethe primaryweldingstructurematerialsofaerocrafts ,transportationvehiclesandmilitaryequipments[1,2 ] ,duetoitsbetterweldabilityandexcellenttechnologicalproperty .Buttheexten siveutilizationofthesealloysishamperedbyitspoorstresscorrosioncracking (SCC)resistance[3,4 ] .Ac cordingly ,manystudieshavebeenconcernedwithsuchaproblemashowtoimprovestresscorrosionre sistanceofAl Zn Mgalloyswithnon deterioratedstrength[3,58] .Atpres…     

Hydrogen-increased dezincification layer-induced stress and susceptibility to stress corrosion cracking of brass

1　INTRODUCTIONDuringstresscorrosioncracking (SCC )con trolledbyanodicdissolution ,apassivefilmordezinci ficationlayerformsonthesurface[1] .Experimentalresultsexhibitedthatafoilofα Tiorbrasswithoneendfixedandanothersideprotectedwithaprotectivelayerformedonitwasconcaveduringcorrosioninamethanolandanammoniasolutions ,respective ly[2 ,3] .Thismeansthatatensilestressexistsontheinterfacebetweenthepassivefilmordezincificationlayerandthematrix [2 ,3] .Extensiveexperimentsshowedthatthedependenc…     

Passivity breakdown and stress corrosion cracking of α-brass in sodium nitrate solutions

The anodic behaviour and SCC susceptibility of pure copper and four α-brasses of different zinc alloy concentration in a 1 M NaNO₃ solution was studied by means of potentiodynamic polarisation curves and constant potential slow strain rate experiments. SCC was exclusively observed when the potential was equal to or higher than a certain critical value (E_c) at which pitting initiated under slow dynamic straining. It is concluded that the same SCC mechanism should be operating during SCC of copper and α-brasses in sodium nitrate, sodium nitrite and copper (II) nitrate solutions.     

Oxygen-induced intergranular cracking of a Ni-base alloy at elevated temperatures—an example of dynamic embrittlement

The brittle intergranular cracking of Alloy 718 at temperatures between 550 and 650°C and at oxygen pressures from atmospheric to 10⁻⁵ torr has been studied by the use of single-edge-notched specimens loaded in pure bending at fixed displacement. The cracking rate was calculated from the load relaxation and a compliance–calibration curve. Rates in the range 10⁻⁹ to 10⁻⁵ m/s were observed, depending on temperature and oxygen pressure. The phenomenon appears similar to the oxygen effects observed by others in cyclic loading and also to the dynamic embrittlement observed in other materials and environments. The mechanism recently modeled for dynamic embrittlement can be applied here directly, and the special characteristics of polycrystalline (as opposed to bicrystalline) behavior, as well as the effects of varying the oxygen pressure, can be explained.     

Stress-corrosion cracking of aged AlCuMg alloys in NaCl solution

Pitting potentials and stress corrosion life-times of AlCuMg alloys (mainly 2024 alloy) with various ageing structures have been measured in a de-aerated 1M NaCl solution under conditions of controlled potential. The aged alloy, which has the higher susceptibility to stress-corrosion cracking, showed two pitting potentials corresponding to pitting at the grain boundaries and within the grains. The susceptibility of the alloys to intergranular stress-corrosion cracking occurred at potentials above the pitting potential of the grain boundaries. The intergranular stress-corrosion cracking is caused not by the dissolution of the grain boundary precipitates (S phase) but by the pitting dissolution of the solute-denuded zones along the grain boundaries. Aspects of SCC in the alloys are similar to those in the Al-4%Cu alloy without Mg.     

Mechanism of hot cracking in the heat affected zone of repair welds. Repair weld cracking of service‐exposed HP‐modified heat‐resisting cast alloys (3rd report)

For several decades it has been possible to observe a tendency to light structures, particularly when they are destined to develop power and movement by consuming energy, especially when this energy derives from conventional fuel (petroleum derivates).

Lighter means of transport permit savings on fuel consumption and contribute to the environmental protection due to the reduction of greenhouse gases. The first approach in this direction had been the utilization of innovative materials able to offer further improved mechanical strength.

Nevertheless, this way presents natural limits depending on the loss of rigidity, hence excessive deformability even in the elastic field. This fact leads to the necessity to add stiffeners and reinforcing elements, but this at the same time means increase again the heaviness. Under these conditions more complex structural solutions step forward as the ‘sandwich’-structures manufacturable in a modular way provided with remarkable versatility in terms of design and choice of material. In the 1990s a European research project named ‘Sandwich’ financed by the European Union had given a significant contribution to the industrialization of structural solutions, which present a high level of innovations using aforementioned structures.

The present work proposes a preliminary study and several results of an investigation, which has as the main subject the production of innovative structural sandwich panels, in other words hybrid-sandwich panels in steel-aluminium assembled using two different joining technologies as laser and FSW, which can successively be connected as well to steel structures as to aluminium ones.     

Effect of scandium and titanium–boron on grain refinement and hot cracking of aluminium alloy 7108

Abstract

The effect of scandium and titanium–boron (Tibor) additions on the solidification behaviour of castings and welds of aluminium alloy 7108 has been investigated. A circular patch test was adopted to evaluate the effects of these elements on the hot cracking suscepti bility of welds made on cast coupons treated with different grain refiner additions. It was observed that grain size, as well as cracking susceptibility, decreased with increasing amounts of scandium and that hot cracking was completely eliminated at scandium additions above 0·25 wt-%. A more pronounced grain refining effect in welds was observed with Tibor and, in addition, no hot cracking was observed with Tibor additions as low as 0·02 wt-%Ti (0·004 wt-%B). Castings, however, were more effectively grain refined with scandium, achieving a finer grain size than with Tibor.     

Evaluation of solidification cracking susceptibility of Fe–18Mn–0·6C steel welds

Solidification cracking susceptibilities of high Mn steel welds were evaluated in the present study. A longitudinal Varestraint technique was utilised to assess the solidification cracking behaviours of the fusion zone. High Mn steel welds were more susceptible to solidification cracking than 304 and 202 austenitic stainless steel welds, however, they were less susceptible than 310S austenitic stainless steel welds. Extensive segregations of Mn and C took place at the dendritic and grain boundaries in the weld metal, and accordingly contributed to the increase of the hot cracking susceptibility of high Mn steel by the enlargement of solidification temperature range. Further, continuous γ-(Fe,Mn)₃C eutectic phases formed at 1090°C along the grain boundary primarily resulted in the increase of solidification cracking sensitivity in high Mn steel.     

Microstructure,cracking behavior and control of Al-Fe-V-Si alloy produced by selective laser melting

Selective laser melting(SLM) technology based on atomized powder was used to fabricate Al-8.5Fe-1.3V-1.7Si(wt%) alloy parts.The microstructure and crack characterization of SLM samples fabricated at various conditions were presented.Results show that the cracks appear periodically along the building direction,initiate preferably at the outer edges of the as-built samples and propagated along the remelting border zone(RBZ) into deposited layers.Solid-phase cracking is proposed according to the fr...     

Preparation and performance of rare earth Zr catalyst for reforming waste plastics cracking product

1　ＩＮＴＲＯＤＵＣＴＩＯＮＡｓａｓｏｌｕｔｉｏｎｆｏｒ“ｗｈｉｔｅｐｏｌｌｕｔｉｏｎ” ,ｐｒｏｄｕｃｔｉｏｎｏｆｆｕｅｌｏｉｌｂｙｃｒａｃｋｉｎｇｗａｓｔｅｐｌａｓｔｉｃｈａｓｂｅｅｎｐａｉｄｍｕｃｈｍｏｒｅａｔｔｅｎｔｉｏｎ .Ａｌｏｔｏｆｓｔｕｄｉｅｓｏｎｗａｓｔｅｐｌａｓｔｉｃｃｒａｃｋｉｎｇｐｒｏｃｅｓｓａｎｄｆａｃｉｌｉｔｙｈａｖｅｂｅｅｎｃｏｎｄｕｃｔｅｄ ,ｂｕｔｎｏｔｓｏｍｕｃｈｏｎｔｈｅｒｅｌａｔｅｄｃａｔａｌｙｓｔ.Ｔｈｅｃａｔａｌｙｓｔｓｕｓｅｄｉｎｔｈｅｗａｓｔｅｐｌａｓｔｉ…     

Research of stress corrosion cracking of T225NG titanium alloy in loop water of high temperature and high pressure

Double cantilever beam （DCB） specimens were used to research the stress corrosion cracking of T225NG titanium alloy in loop water of high temperature and high pressure. DCB specimens were forced pre-stress, put into high pressure ataoclave , and the stress corrosion and crack expansion of specimens were observed and measured in 500 h, 1 000 h and 2000 h respectively. The results show that small expansion occurred along the direction of pre-cracking. According to calculation, the speed of cracking expansion is lower than 10 -9 m/s in 500 h and the value of K ISCC /KI is higher than 0. 75, which proves that T225NG has an excellent corrosion resistance in loop water. The main reason is that there is an oxide film on the surface of specimens. According to the analysis of energy dispersive spectroscopy （EDS） and X-ray diffraction （ XRD ） , the oxide film consists of TiO2. Therefore, the oxide film at the crack tip impedes the hydrogen separating out from the cathode to penetrate into titanium alloy and resists hydrogen embrittlement.