Showing papers on "Weldability published in 2002"

Laser Transmission Welding of Semi-Crystalline Thermoplastics—Part I: Optical Characterization of Nylon Based Plastics

Abstract: Optimization of welding for thermoplastic parts strongly depends on the material properties, part design, as well as the welding operating technology conditions. Laser transmission welding requires...

Weldability of High Nitrogen Stainless Steel

Abstract: The purpose of this paper is to give a short survey of nitrogen influence on stainless steel welds. The review are covers: the levels of nitrogen in weld metal, the influence of nitrogen on stainless steel weld metal characteristics such as weld defects, corrosion resistance and mechanical properties. High nitrogen steel welding must consider the risk of nitrogen escape from the weld pool. Avoiding nitrogen losses may be accomplished by controlling shielding gas, welding parameters and compositions of filler metal. The increase of nitrogen in the weld metal decreases in the δ ferrite content. The reduction of δ ferrite in austenitic weld metals will result in an increase in the solidification cracking susceptibility. However, the role of nitrogen in affecting the solidification cracking susceptibility of fully austenitic weld metals is unclear. Nitrogen addition increases the pitting corrosion resistance in weld metals whereas decreases resistance to stress corrosion cracking because of δ ferrite reduction. Nitrogen also improves mechanical properties in weld metals. However, the presence of nitrides may be detrimental to the mechanical properties in stainless steel welds.

Pulsed Nd:YAG laser welding of copper using oxygenated assist gases

Abstract: The effects of using oxygenated assist gases on the weldability and weld properties of Nd:YAG, pulsed laser welds in copper (Cu) have been evaluated. It was found that the effective absorptivity of the Cu increased as the oxygen content of the Ar assist gas was increased. This facilitated laser welding of Cu at much lower laser powers and increased weld penetration. The use of oxygenated assist gas promoted nucleation and growth of submicroscopic oxide particles within the weld metal. These particles dispersion-strengthened the weld metal, thereby increasing both weld metal hardness and strength. However, when O2 concentrations in the assist gas were greater than 90 pct, weld metal embrittlement due to excessive volume fractions of oxides was observed. The use of oxygenated assist gas also led to excessive cold lapping and poor bead quality. The bead quality was improved, however, by ramping-down the laser power before terminating each pulse.

The influence of minor elements on the weldability of an INCONEL 718-type superalloy

Abstract: The effect of the minor elements C, B, and P on the weldability of the INCONEL 718 alloy was studied. Wrought alloys containing systematic additions of the three minor elements were evaluated by thermal simulation and by electron-beam welding. The ductility recovery temperature from the thermal simulation experiments and the microfissuring behavior in the heat-affected zone (HAZ) of the electron-beam samples were used to evaluate the effect of minor elements on weldability.

Ni-base heat resistant alloy and welded joint thereof

Abstract: A Ni-base heat resistant alloy excellent in weldability and strength at elevated temperatures and suited for use in manufacturing cracking furnace tubes and reformer furnace tubes to be used in ethylene plants as well as a welded joint therefor is provided. The alloy of the invention is a Ni-base heat-resistant alloy, which comprises C: not more than 0.1%, Si: not more than 2%, Mn: not more than 2%, P: not more than 0.025%, S: not more than 0.005%, N: not more than 0.04%, Cr: 10 to 30%, Al: 2.1 to less than 4.5%, and Mo: 2.5 to 15% or W: 2.5 to 9% or Mo and W: 2.5 to 15% in total, and satisfies the relation (1) given below: (104Si+1980P+1980S+9Al+15Ti+11Nb+1.8W+11600B)≦{1.1(240−20000S−1900P−30Al−10Ti−9W+17000B) (1) In the welded joint of the invention, both of the base metal and weld metal are made of the alloy having the above composition, and the ST value of the weld metal as calculated according to the following formula (2) or (3) is larger by not less than 3 than the ST value of the base metal: in the case of Ti≦4C; ST−Mo+1.5W+100Ti (2) in the case of Ti>4C; ST=Mo+1.5W+400C (3).

Chromium Nitride Precipitation Behavior in Weld Heat-affected Zone of High Nitrogen Stainless Steel

Abstract: High nitrogen stainless steels (HNS) containing about 1 mass% (%) nitrogen without adding Mn were manufactured by pressurized electro-slag remelting method. The chromium nitride precipitation behaviors at the weld heat-affected zone (HAZ) of HNS with different compositions were investigated. We also evaluated the localized corrosion resistance of the welded joints. The nitride precipitates were identified as Cr 2 N containing a small amount of Mo and Fe by TEM/EDS analyses. Tme-temperature-precipitation curves of some HNS were obtained. It was found that for 23Cr-4Ni-2Mo-1 N steel, aging for 2 s in the temperature range between 1 173 K and 1 373 K caused Cr 2 N precipitation and decreased the critical pitting corrosion temperature (CPT) in the 6% FeCl 3 solution. Precipitation was delayed to 4 s by decreasing the nitrogen content from 1 to 0.8 % and was further slightly delayed to over 5 s by adding the pre-deformation followed by the thermal treatment of 23Cr-4Ni-2Mo-0.8N steel. Precipitation at the HAZ was accelerated by a continuous thermal cycle test compared to the prediction based on the additivity rule, and that the existence of a ferritic phase affected acceleration was estimated. Joints welded by laser and minimum heat input conditioned plasma arc welding showed a 348 K CPT in a 6 % FeCl 3 solution and no crevice corrosion occurred at 308 K in artificial seawater. The CPT dropped notably against holding time above 1 073 K at the HAZ. The CPT drop was slightly relieved by decreasing nitrogen content in the base metal from 1 to 0.8 %.

Rotary friction welding of an Fe3Al based ODS alloy

Abstract: An Fe 3 Al based oxide dispersion strengthened (ODS) alloy is under consideration for possible use as tubes in advanced heat exchangers, and it is necessary to investigate methods of joining the alloy to itself, and to Haynes 230 alloy. Previous experience on iron aluminides has shown them to be weldable by several processes, but it is known that fusion processes invariably lead to a loss of the Y 2 O 3 oxide dispersion which is an essential feature of ODS alloys. Therefore, solid state processes offer a potential advantage, and in this work continuous drive rotary friction welding has been investigated as a method to join the Fe 3 Al ODS alloy in both the recrystallized and unrecrystallized condition. Trials were also undertaken to join both recrystallised and unrecrystallized material to Haynes 230 alloy. All welds were made in 15-mm diameter material, using a conventional continuous drive rotary friction welding machine. Welds were evaluated initially using tensile tests, and detailed metallographic observations of the grain size, and the nature of the solid state interface between the materials. It was found possible to make high quality welds containing no flaws for a variety of welding conditions. The microstructural condition of the Fe 3 Al ODS alloy had no apparent influence on weldability, and no difficulty was encountered in making the dissimilar metal joints. The results obtained are discussed in terms of the microstructures obtained, and are compared with other studies on joining iron aluminides and ODS alloys.

Thermally stable aluminum-lithium alloy 1424 for application in welded fuselage

Abstract: Sheets of Al – Li alloy 1424 have high fracture toughness and diminished rate of fatigue crack growth, high corrosion resistance, and excellent weldability. The chemical composition and the regime of the hardening heat treatment of alloy 1424 are shown to provide good thermal stability of the sheets with respect to fracture toughness (K c f) and growth rate of fatigue cracks (GRFC) after a hold of up to 3000 h at 85°C. These characteristics decrease only after a hold of 4000 h and only in the L – T direction. The suggested process for manufacturing sheets diminishes the anisotropy of the strength characteristics and the elongation due to the formation of a partially recrystallized structure.

Weldability and Microstructural Aspects of Shielded Metal Arc Welded HSLA-100 Steel Plates

Abstract: HSLA-100 steel with 14 mm thickness in quenched and tempered condition was shielded metal arc welded (SMAW) with 2 kJ/mm heat input using basic flux coated filler rods without any pre or post welding heat treatments. The steel was found to be welded satisfactorily in this condition without developing any defect. Optical microscopy studies revealed typical cast dendritic structure in the weld metal and coarse bainite in grain-coarsened area of the heat-affected zone (HAZ). Transmission electron microscopy (TEM) study confirmed incidence of mixed structure of martensite laths and bainite in weld metal, while, it was mainly of bainite laths in HAZ with evidence of martensite–austenite (M–A) constituent and massive ferrite. The yield strength (YS), ultimate tensile strength (UTS) and Charpy V-notch (CVN) impact energy of the weld metal (YS-695 MPa, UTS-842 MPa and CVN-105 J at –50°C) and HAZ (YS-790 MPa, UTS-891 MPa and CVN-130 J at –50°C) were found satisfactory although HAZ properties were inferior to the base metal properties. The hardening of HAZ was not very significant in this steel under the present welding condition.

Improvement of weldability of TRIP steels by use of in‐situ pre‐ and post‐heat treatments

Abstract: Low alloy TRIP-aided steels are very interesting for the automotive industry as they combine both a high strength and an excellent formability. Though the actually developed TRIP steels can be considered as low alloyed when compared to the first generations of steels exhibiting TRIP effect, due to their chemical composition, they still exhibit a quite high carbon equivalent. This is particularly detrimental for the weldability of those materials. After solidification, welds are very hard and can show a brittle behaviour. The hardness of the heat affected zone of the welds can even exceed 500HV and cold cracking phenomena is prone to occur. In the automotive industry, spot welding is the main joining process. During spot welding of TRIP steels, the interface between the plates can act like a notch and promote fracture of the weld. This is particularly dangerous when brittle welds are submitted to peel stresses. The aim of the paper is to demonstrate that a careful choice of the process parameters can significantly improve the resistance of the welds. The selection of the welding cycle parameters is far from being an easy task as many different parameters are involved. Therefore, a design of experiment methodology (DOE) was chosen to optimise the welding cycle for a cold-rolled TRIP steel with a tensile strength above 700 MPa. Mechanical properties of the welds were significantly improved by use of pre- and post-heat treatments. Those improved welding cycles were realised without excessive extension of the total weld cycle on a conventional spot welding machine. This means that the optimised welds can be obtained in the existing production lines without any additional investment or significant decrease in productivity.

Weldability characteristics of shielded metal arc welded high strength quenched and tempered plates

Abstract: High strength, quench and tempered (Q&T) plates having yield strength of a minimum of 670 MPa and conforming to SA 517 Gr. F specification were successfully developed at Rourkela Steel Plant in plates up to 40 mm thickness. The plates are used extensively for the fabrication of impellers, penstocks, excavators, dumpers, and raw material handling devices, where welding is an important processing step. SA 517 Gr. F plates, characterized by a relatively high carbon equivalent (CE: ∼0.6) and alloyed with Ni, Cr, Mo, Cu, and V, are susceptible to a crack-sensitive microstructure and cold cracking during welding. In view of the above, the present study investigated the weldability properties of 20 mm thick plates using the shielded metal arc welding (SMAW) process. Implant and elastic restraint cracking (ERC) tests were carried out to assess the cold cracking resistance of the weld joint under different welding conditions. Preheat of 100 °C, partial or full rebake, and a heat input of 14.9 to 15.4 KJ/cm resulted in static fatigue limit (SFL) values well in excess of the minimum specified yield strength (MSYS) of 670 MPa and a critical restraint intensity (K cr) value of 34,650 MPa, indicating adequate cold cracking resistance. Lamellar tear tests conducted using full thickness plates at heat input levels ranging from 9.7 to 14.4 KJ/cm and weld restraint loads (WRL) of 510 to 685 MPa showed no incidence of lamellar tear upon visual, ultrasonic, and four-section macroexamination. The weld joint, based on optimized welding parameters, exhibited adequate tensile strength (812.4 MPa) and low temperature impact toughness 88.3 and 63.4 J (9.2 and 6.6 kg-m) at −40 °C for weld metal (WM), and heat-affected zone (HAZ) properties, respectively. The crack tip opening displacement (CTOD) values of WM and HAZ (0.40 and 0.36 mm, respectively) were superior to that of the parent metal (0.29 mm), indicating adequate resistance of weld joint to brittle fracture. It was concluded that the weld joint conforms to the requirements of SA 517 Gr. F specification and ensures a high integrity of the fabricated products.

Aluminum-lithium alloys with scandium

Abstract: Aluminum-lithium alloys with diminished density and high crack resistance characteristics are widely used in aircraft. Scandium additives to this alloy improve the strength properties and considerably enhance the weldability.

Development of 18Cr-9Ni-W-Nb-V-N Austenitic Stainless Steel Tube for Thermal Power Boilers

Abstract: An 18Cr-9Ni-W-Nb-V-N austenitic stainless steel tube for thermal power boilers has been newly developed. The high temperature mechanical properties and corrosion resistance of the steel were investigated. The creep rupture strength of the developed steel is about 1.5 times as high as that of SUS347HTB, and is almost the same as that of Ka-SUS310J2TB at 650°C. This excellent creep strength of the steel is mainly due to solid solution strengthening by tungsten and nitrogen, and precipitation strengthening by nitrides of niobium and vanadium. The carbon content of the steel is reduced to 0.03% to improve intergranular corrosion resistance. The steam oxidation resistance and the high temperature corrosion resistance of the tube are almost the same as those of SUS347HTB. Weldability of the developed steel is superior to that of SUS304HTB and SUS310TB. Thus the developed steel is suitable for use as a material for superheater and reheater tubes of thermal power boilers.

Possible Use of New Materials for High Pressure Linepipe Construction: An Opening on X100 Grade Steel

Abstract: The increasing needs of natural gas, foreseen for the next years, makes more and more important the type of transportation chosen, both from strategic and economic point of view. The most important gas markets will be Northern America, Europe, Asia and Russia but the demand shall be fulfilled also by emerging producers as Kazakhstan, Turkmenistan and Eastern Siberia that at the moment are developing their resources in order to be competitive on Gas market. In this way producers and customers will be placed at greater and greater distances implying realization of complex gas transportation pipeline network, when use of LNG tankers is impossible or uneconomic. On the base of these considerations in 1997 began a feasibility study on X100 steel, given that, comparing different design approaches, it has been observed that consistent savings could be obtained by means of using high grade steel and high pressure linepipes. In this multi-sponsored project (Eni group, European Community of steel and Carbon, CSM, Corus and Europipe) CSM and Corus group were involved in the laboratory and full-scale pipes testing, Europipe was the pipes producer and Snam Rete Gas was involved in field weldability and technical coordination. No technical breakthrough, but only improvements in the existing expertise were involved in the X100 production; consequently, the production window is very narrow. However optimized steelmaking practices and processes enabled the material to reach the desired properties: strength, toughness and weldability. This paper is intended to present the general results arising from this project, in terms of steel properties (chemical composition, mechanical properties), ductile and brittle fracture resistance (results of full scale burst tests, West Jefferson tests) and field weldability, but above all the know-how stored till now on high grade steel and its possible use from a Gas company and a Pipe maker point of view.Copyright © 2002 by ASME

Filler metal selection for welding a high nitrogen stainless steel

Abstract: Cromanite is a high-strength austenitic stainless steel that contains approximately 19% chromium, 10% manganese, and 0.5% nitrogen. It can be welded successfully, but due to the high nitrogen content of the base metal, precautions have to be taken to ensure sound welds with the desired combination of properties. Although no matching filler metals are currently available, Cromanite can be welded using a range of commercially available stainless steel welding consumables. E307 stainless steel, the filler metal currently recommended for joining Cromanite, produces welds with mechanical properties that are generally inferior to those of the base metal. In wear applications, these lower strength welds would probably be acceptable, but in applications where full use is made of the high strength of Cromanite, welds with matching strength levels would be required. In this investigation, two welding consumables, ER2209 (a duplex austenitic-ferritic stainless steel) and 15CrMn (an austenitic-manganese hardfacing wire), were evaluated as substitutes for E307. When used to join Cromanite, 15CrMn produced welds displaying severe nitrogen-induced porosity, and this consumable is therefore not recommended. ER2209, however, outperformed E307, producing sound porosity-free welds with excellent mechanical properties, including high ductility and strength levels exceeding the minimum limits specified for Cromanite.

Galvanized, high tensile strength, hot rolled steel sheet having excellent weldability, production method therefor and working method therefor

Abstract: PROBLEM TO BE SOLVED: To provide a galvanized, high tensile strength, hot rolled steel sheet which is suitable for producing a product having a complicated cross-sectional shape such as automobile parts by pressing and also has excellent weldability, and to provide a production method therefor. SOLUTION: The galvanized, high tensile strength, hot rolled steel sheet comprises, by weight, 0.01 to 0.1% C, ≤0.3% Si, 0.2 to 2.0% Mn, ≤0.04% P, ≤0.02% S, ≤0.1% Al, ≤0.006% N and 0.03 to 0.2% Ti, also one or more kinds of metals selected from ≤0.5% Mo and ≤1.0% W, and the balance substantially Fe, wherein, by weight %, 4.8C+4.2Si+0.4Mn+2Ti≤2.5 is satisfied. The steel sheet has a structure mainly made up of a ferrite single phase, and in which precipitates of <10 nm containing Ti and one or more kinds of metals selected from Mo and W are dispersed in the ranges satisfying, by atomic ratio, (Mo+ W)/(Ti+Mo+W)≥0.2. COPYRIGHT: (C)2004,JPO

Gas tungsten arc welding studies on similar and dissimilar combinations of Al-Zn-Mg alloy RDE 40 and Al-Li alloy 1441

Abstract: The present study is concerned with gas tungsten arc welding of two high strength aluminium alloys, namely, an Al-Zn-Mg alloy (RDE 40) and an Al-Li based alloy of Russian grade 1441. One of the critical requirements of these two alloys is that they should be weldable. In the present work, weldability aspects of these alloys were studied in terms of solidification cracking tendency, microstructure, tensile properties, and microhardness across the welds. These studies were extended to dissimilar welds between RDE 40 and 1441 produced via conventional gas tungsten arc (GTA) welding as well as pulsed current GTA welding. It was found that RDE 40 welds were less sensitive to solidification cracking and weld metal porosity compared with 1441 alloy. The superior weldability of RDE 40 was related to the equiaxed nature of the fusion zone and a lower sensitivity to moisture pickup. It was possible to produce RDE 40-1441 welds without defects. Pulsed current welding of RDE 40 to 1441 showed improved mechani...

High-strength hot dip galvanized steel sheet having excellent adhesion property and weldability

Abstract: PROBLEM TO BE SOLVED: To provide a high-strength hot dip galvanized steel sheet having excellent adhesivity and weldability and a method for manufacturing the same. SOLUTION: A cold rolled steel sheet of a chemical composition containing, by weight %, 0.05 to 0.25% C, ≤0.1% P, ≤0.1% S, and ≤0.02% N, and containing one or ≥2 kinds selected from the group consisting of 0.5 to 3.0% Mn, 0.01 to 2.0% Si, and 0.01 to 2.0% Al at ≤4.0% in total is used as a base metal. The steel sheet is provided with plating films containing, by weight %, 0.50 to 7.0% Fe, containing 5 to 90vol% Fe-Zn alloy phase developing at the boundary of the plating film/the base metal and consisting of the balance substantially an η phase. COPYRIGHT: (C)2004,JPO

A New 5xxx Series Alloy Developed for Automotive Applications

Abstract: The Aluminium-magnesium or 5xxx alloys in sheet form have been considered for some time to be the most appropriate choice for vehicle structures as they offer attractive combinations of formability, strength, weldability and corrosion resistance.

Cast steel composition for railway components

Abstract: A high strength steel alloy for use in manufacturing railway car components. The alloy has a chemical composition that meets the industry required specifications for B grade steel and exhibits better mechanical properties, such as higher yield and tensile strengths. Secondary benefits of the inventive steel alloy include enhanced weldability and improved fatigue resistance.

Steel having excellent high temperature strength and its production method

Abstract: PROBLEM TO BE SOLVED: To provide high tensile strength steel having excellent high temperature strength, good weldability and toughness, and to provide its production method. SOLUTION: This steel has a composition containing, by mass, =30 N/mm2 through age-precipitating treatment performed at 600 deg.C. If required, specified amounts of Cr, Mo, B, Mg, Ca and rare earth metals are contained as well. In its production method, steel is reheated at 1,000 to 1,250 deg.C, rolled at a cumulative draft of >=30% at =750 deg.C and subsequently subjected to accelerated cooling from 700 to 400 deg.C, or to the hot rolling. Then, the steel is reheated at the Ac3 to 950 deg.C and thereafter subjected to accelerated cooling.

Laser Weldability of Aluminum Alloys.

Abstract: This study was performed with the objective of producing sound laser weld beads in aluminum alloys. CO 2 and YAG laser weldability of aluminum alloys was investigated in terms of penetration and porosity formation. Deeplypenetrated welds were easily formed in alloys with a considerable content of Mg, Li or/and Zn in an inert shielding gas, and deep penetration was obtained in any alloy welded with a CO 2 laser beam in a nitrogen shielding gas. Welding phenomena, keyhole behavior, and the formation mechanism and preventive remedies for bubble formation and porosity were examined by observation through high-speed video cameras and the x-ray transmission imaging system. It was especially revealed that many bubbles were chiefly generated from a keyhole tip, resulting in the formation of porosity. Porosity formation tendency was interpreted in terms of keyhole stability, vapor ejection direction and melt flows depending mainly upon the welding speed It was also found that a melt flow in vacuum was different from that in general welding at low speeds in Ar or He gas, and consequently no porosity formation was attributed to no bubble generation. The size and number of pores could become smaller and be reduced at low welding speeds under the negative pressure achieved by a newly developed tornado nozzle.

Progress on Welding of High Nitrogen Alloyed Austenitic Stainless Steels

Abstract: Stainless steels are often ranked regarding the capability of their chemical composition to achieve a certain pitting resistance. This paper focuses on the weldability of nitrogen alloyed austenitic/superaustenitic stainless steels. In addition, chemical composition, corrosion and mechanical properties together with some common applications are presented. The Pitting Resistant Equivalent number PRE, shows the relative effect of Cr, Mo, N and sometimes W on the pitting corrosion resistance. Based on the PRE level, the steels are divided into three groups. For each group the following topics are covered: chemical composition; mechanical and corrosion properties; applications; weldability (general; processes; filler materials; joint properties). This review is not concerned with the 200 series (UNS S20000 series) high manganese, high nitrogen stainless steels.

Gas shielded arc welding wire for low alloy steel excellent in hydrochloric acid resistance and sulfuric acid resistance, and gas shielded arc welding method using same

Abstract: PROBLEM TO BE SOLVED: To provide a gas shielded arc welding steel wire which is excellent in corrosion resistance, is securable a satisfactory weldability, and can form a weld metal part excellent in strength and toughness on impact with respect to the welding wire which is used for welding a sulfuric acid dewpoint corrosion resistant steel capable of obtaining excellent corrosion resistance under the environment of concentrated sulfuric acid and concentrated hydrochloric acid, and to provide a welding method using the wire. SOLUTION: the steel wire for gas shielded arc welding excellent in resistances to hydrochloric acid and sulfuric acid contains C of 0.02 to 0.2 %, Si of 0.2 to 1.5 %, Mn of 0.5 to 2.5 %, P of 0.03 % or less, S of 0.02 % or less, O of 0.003 to 0.05 %, Sb of 0.01 to 0.2 %, and Ni of 0.1 to 1 % in mass % to the whole of wire mass. Moreover, the residuals are of Fe and inevitable impurities. An arc welding is performed in an atmosphere of gaseous CO 2 , mixed gas of CO 2 and Ar, etc. using the wire. COPYRIGHT: (C)2004,JPO

Introduction to Austenitic Stainless Steels

Abstract: The family of austenitic stainless steels has a wide variety of grades precisely tailored for specific applications such as household and community equipment, transport, food industry, industrial equipment, chemical and power engineering, cryogenics, and building industry. The optimum choice of the grades would depend on service needs and this would require a clear understanding of the metallurgical parameters, which control the microstructure and thus the mechanical properties, formability and corrosion resistance. This chapter, in brief, deals with the physical metallurgy, welding metallurgy, and physical and mechanical properties of austenitic stainless steels. In the physical metallurgy of stainless steels the tendency of alloying elements to form different phases, the transformation of austenite to martensite during cooling or straining, hardening processes and formation of intermetallic phases, have been discussed. The influence of chemical composition, and temperature on the various physical properties of austenitic stainless steel such as coefficient ofexpansion, thermal conductivity and magnetic permeability is highlighted. Variation in mechanical properties, such as tensile, fatigue and creep strengths of austenitic stainless steels with temperature, composition and microstructure has been discussed. The mechanisms to strengthen the austenitic stainless steels by appropriate thermo-mechanical treatments, grain refinement etc. have also been addressed. Austenitic stainless steels lend themselves remarkably to deep drawing and cold rolling, where their work-hardening characteristics enable high strength levels to be attained. Weldability is excellent, and welds, which do not transform to martensite during air-cooling, have mechanical properties similar to base metal.

Weldability of Galvannealed Interstitial Free Steel

Abstract: A series of interstitial free steel strips were subjected to different annealing treatments after being galvanized by immersion. Samples from these strips were cut and various tests were carried out on them. The coating was studied by optical and scanning electron microscopy, analysis of the X-ray spectra was conducted on the samples while being observed in the latter equipment. Resistance to powdering of the coating was studied by means of V-bend testing. Spot resistance welding tests were conducted by varying the current supplied by the machine, different geometrical parameters and the resistance of the welded joint were evaluated. It was found that the amount of powdering of the coating increased as the amount of Γ phase augmented, as well as with the increment in coating thickness. The mechanical strength of welded strips was found to improve with the increment in welding current, up to the point where expulsion of material was occurred.