High Content Alloy Research Articles

Manufacture and Application of High Nitrogen Steels

A high alloy content and new ways of manufacturing brought about high nitrogen steels (HNS) with 0.3 to 3% of nitrogen. Nitrogen in solid solution is used to improve the corrosion resistance of stainless steels, and stable nitride precipitates enhance the hot strength of hot work tool steels and creep resistant steels. A number of new HNS is used commercially, others are tested in different applications. This holds also true for martensitic or austenitic high nitrogen cases on stainless steels

Solidification and microstructure of a high alloy stainless steel

The steel considered in the present work can be classified as a 6Mo austenitic stainless steel, which has a much higher corrosion resistance than many other commercially available stainless steels. However, because of macrosegregation during solidification of ingot casting, the high alloy content in the steel, especially Mo, N, C, enhances precipitation of intermetallic phases such asa phase. Such precipitation mainly occurs in the center of the material and has normally no significant effect on mechanical properties or surface corrosion resistance. The introduction of modern production methods such as continuous casting of slabs for stainless sheet production has reduced the macrosegregation tendency and related precipitation. However, the microsegregation in a small scale may be enhanced as the higher cooling rate prevents the diffusion in the solidified region. In the present work, the continuous casting solidification process was simulated in a laboratory gradient

Mechanical properties of a rapidly solidified AlSiNiMn alloy

A promising new aluminium alloy made by rapid solidification processing (RSP) has high Si, Ni, and Mn contents. This RS alloy is promising for use as dynamically loaded automotive parts at temperatures up to about 250 °C. This is mostly attributed to the low coefficient of thermal expansion α; the high stiffness, fatigue strength, thermal stability and tensile properties are also important features. Experimental data presented herein focus on the microstructure of the as-cast and as-extruded RS material and on the physical and mechanical properties of extrusions and forgings. Compared with conventionally cast aluminium-silicon alloys, the RS alloy shows improved properties at both room and elevated temperatures. This is due to the refined microstructure (particles less than 5 μm), the high alloy contents and the novel metastable phases. The properties and easy formability of the cost effective RS-Al alloys are promising with respect to commercialization and market competitiveness in the near future.

Hall-Petch Basis for Assessing Alloy Strengthening

AbstractThe Hall-Petch relation σ = σo + kl−½, provides for the separate consideration of friction stress strengthening within the polycrystal grain volumes through σo and grain boundary strengthening through the product of the microstructural stress intensity k and the reciprocal square root of the grain diameter l Smaller grain diameters are normally obtained at higher alloy contents as illustrated for yield strength results reported for different face-centered-cubic Al-Mg alloys. Results on Al-Li alloy give an interesting example of substantial grain boundary strengthening that is associated with reduced ductility of the material. More complete results reported for the Cu-Al system, allow an evaluation of the strengthening component dependencies on alloy composition, in particular, connecting with a predicted square root of grain boundary obstacle stress in k. The much studied Cu-Zn alloys bring out subtle changes in σo and k

Plastic deformation instability in copper alloys

A systematic investigation was made of the temperature and velocity conditions for the appearance of stepwise deformation in copper alloys with a high alloying content (the Portevin-Le Chatelier effect) and the deformation mechanics of crystalline materials was analyzed from the viewpoint of an emsemble of dislocations. A mathematical model of the Portevin-Le Chatelier effect was constructed, based on general ideas concerning the behavior of dislocations and their interaction with alloying elements, and from the viewpoint of the theory of oscillations, taking into account the rigidity of the test-piece-machine system. Mechanical tests were performed on copperalloy test pieces in the temperature range 20–400°C. A characteristic feature found for the oscillation modes was that the peak-to-peak value Δσ was independent of ɛ and that there was a plateau with a weak dependence σ(ɛ) at the upper σ level. The dependences of the oscillation period on the temperature and the given plastic deformation velocity were in good agreement with experiment.

ガス・メタル・アーク溶接における鋼溶接金属の機械的性質について （第３報） 極低酸素鋼溶接金属の機械的性質について

In an oxidizing gas welding atmosphere of argon-based Ar-CO2-O2 gas mixture, weldings were carried out, using a popular Fe-Si-Mn electrode wire (YGW 12) and rolled steel for welded structure (SM 400B). Mechanical properties such as ultimate tensile strength and Charpy impact property for the extremely low oxygen steel weld metal which oxygen level is 0.001-0.025 mass/ have been investigated.The ultimate tensile strength seems to be governed principally by alloy content of weld metal, and small amount of oxygen in weld metal has only a minor effect on the ultimate tensile strength. The higher alloy content, the higher the ultimate tensile strength. The extremely low oxygen steel weld metal has greater tensile property, because of limited amount of oxidation losses of alloying elements such as carbon, silicon and manganese. The Charpy toughness of steel weld metal has been affected by the oxygen content in weld metal. High toughness obtained in two oxygen levels, one is 0.04-0.05 mass% oxygen which is well-known peak and the other is less than 0.002 mass% oxygen. It is very important that the Charpy impact property has been improved in the extremely low oxygen steel weld metal which oxygen level is less than 0.002 mass%.

Corrosion‐resistant special steels for flue gas desulphurisation plants

AbstractA Flue Gas Desulphurisation system is a chemical plant‐using materials which have proven their reliability in the chemical industry. Stainless steels with high alloy contents are a good choice, offering advantages such as corrosion resistance, thermal stability, weldability and easy access for inspection.Of importance are the alloying elements molybdenum and nitrogen. A number of steel grades have been developed or modified specially for FGD systems, depending on the corrosive environment.A new high alloyed steel is described, along with recommendations for welding.

Stainless steel in the 90's

This paper surveys the present development of stainless steels. It is found that the continuous improvement of the performance of existing steels and the development of new steels to a large extent depend on new processing technologies. The trends in the development of new stainless steels are discussed. The following directions were found to be prevalent, (i) steels with less impurities, (ii) more highly alloyed stainless steels, (iii) new duplex stainless steels, both towards higher alloy contents and towards moderate alloying and high cost-efficiency, and (iv) nitrogen alloying. Finally the prospects for future developments of the stainless steels are assessed, as well as the possible re-standardization of stainless steel base grades in the European harmonization program.

JESSOP TYPE 317L, 317L PLUS

Abstract JESSOPTYPE 317L and 317L Plus are low-carbon austenitic stainless steels with somewhat higher alloy content than AISI type 316L. This gives them superior corrosion resistance in difficult environments as well as higher elevated temperature strength characteristics. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: SS-502. Producer or source: Jessop Steel Company.

Cutting tool wear of laser-surface-melted high speed steels

A continuous wave CO 2 gas laser, operating at a power of 800 W, was used to surface melt the rake and clearance faces of AISI M2 and M35 single-point lathe tools. The tool bits were then tempered at 560 °C for 2 h. The melt depths ranged from 600 to 800 μm. The surface-melted layers were subsequently ground down to 200–250 μm. A 20 h.p. engine lathe was used to turn an AISI 4142 steel workpiece using both conventionally heat-treated and laser-surface-melted tools. The results indicated that the tool life of laser-treated M2 steel was 200%–500% higher than that of conventionally hardened tools when the tool life criterion was catastrophic failure. For M35 steel, the tool life of a laser-melted tool was 20%–125% higher than that of a conventionally hardened tool when the tool life criterion was based upon flank wear (to reach a distance of 0.30 mm). The reduction in tool wear due to laser surface melting was explained as being because of the high alloy content of martensite, the fine austenite grain size and the fine dispersion of carbides, all of which resulted in high hardness, good toughness and a low coefficient of friction at the tool-chip interface.

Electrochemical investigation of lead-calcium alloys in sulphuric acid

The hydrogen evolution reaction from, and the cycle life (Pb /ar PbSO 4) of, a series of lead-calcium alloys (0 - 0.2 wt.% Ca) in sulphuric acid hav The exchange current density and Tafel slope for the H.R.E. increase with Ca content up to 0.05 wt.% then decrease to a value approaching that of pure The observed results are explained by: (i) preferential adsorption of calcium ions at the electrode surface; (ii) incorporation of Ca, to form a supersaturated solution, with alloys containing < 0.075 wt.% Ca; (iii) formation of an insoluble, non-conducting layer of calcium sulphate on the high content alloy.

A quantitative study of preporcelain soldered connector strength with palladium-based porcelain bonding alloys

I n the making of multiple unit fixed prostheses, individual segments must be joined at some stage, either by casting the metal framework as one piece or by soldering the individual units. The soldering method has the advantage of permitting each individual retainer to be fitted to the abutment instead of fitting the entire prosthesis to multiple abutment teeth. To avoid exposing glazed porcelain to soldering investment and the soldering procedure, preporcelain soldering is preferred by some to postporcelain soldering. Recently, new compositions of dental porcelain bonding alloys were introduced. They are palladium-based, noble, and are comparatively low in cost. Their nobility is derived from the 75% to 85% palladium in their composition, with the addition of gold or platinum that yields a total of 80% to 90% noble metals. Smaller amounts of cobalt, gallium, indium, copper, and silicon are added to improve oxide formation for porcelain bonding, regulate the melting range, to improve strength, and for castability. The purpose of this study is to quantitatively evaluate the preporcelain soldered connector tensile strength of noble palladium-based alloys with conventional soldering procedures. Many investigations have evaluated soldered connectors. In 1975 Stade et al.’ found that the method of soldering was more significant to connector strength than gap width. Other investigators reported that nonnoble alloys cannot be consistently and adequately soldered.2-4 In an extensive two-part study Staffanou et a1.5 concluded that various combinations of precious, semiprecious, and base metal alloys could be successfully soldered. Barnard et a1.6 observed that a large excess of flux was necessary for soldering base metal alloy. Rasmussen et al.’ reported that preceramic soldered connectors with a high noble alloy content decreased in strength with increasing gap width. However, no investigation has focused on the soldered connectors of noble palladiumbased porcelain bonding alloys.

Résistance à la corrosion des fontes alliées

Owing to their relatively high alloy content, alloy cast irons often exhibit a high degree of corrosion resistance in many mediums. Nevertheless, it is necessary to know which kind of iron can be used in a definite medium. It seemed, therefore, interesting to collect information on this subject. It is the purpose of our paper.A large addition of nickel to cast iron produces materials with stable austenitic matrix which, being more noble than the matrix of unalloyed grey irons, gives very good corrosion resistance in most applications.High-chromium irons also have good corrosion-resistant properties due to the superficial formation of an impervious chromium oxide film. So, these irons are most useful in mediums containing a large supply of oxygen or oxidizing agents.The corrosion resistance developed by high-silicon alloys is due to the formation of a corrosion-resistant film containing a large amount of silica. These irons can withstand attacks from a very wide range of mediums, indeed few ions can penetrate this silica film.

Process–Structure Relationship of Extrusions Produced from Rapidly Solidified Al–Mg–Mn Powders

Cold compacts have been prepared from Al–Mg–Mn rapidly solidified powders containing 7, 12, and 15 wt-%Mg. The compacts were subsequently extruded using a wide range of temperature compensated strain rates. Despite their high alloy content, each of these powder alloys could be extruded with relative ease. It is the fine nature of the powder state which assists the extrusion of these alloys which are inherently difficult to fabricate in the cast state. The mode of deformation is shown to occur by dynamic recrystallization. The subsequent microstructure is of a fine grain size and is shown to be related to the processing conditions. A relation-ship between the high temperature flow stress and the extruded structure is also indicated. Observations of the powder microstructure are reported. It is shown that the original powder structure is completely transformed during the extrusion process. PM/0364

Laboratory evidence of the use of metal tools at Machu Picchu (Peru) and environs

An interpretation of use-wear marks on metal artifacts is developed from the principles of metal cutting and brittle fracture and applied to surficial markings and microstructural damage on bronze tools from Machu Picchu and environs. Most of the tools have blunt edges, relatively low tin contents, and were not work hardened before use; they appear to have been designed for work that involved breaking chips from hard, brittle material. Use-wear marks on these tools are interpreted as due to sliding contacts and impacts with rock. One tool with a relatively sharp edge has a higher alloy content than those with blunt edges and has been work hardened; it appears to have been designed for cutting wood and use-wear markings suggest it was so used. A long bronze bar carries markings that suggest use by stonemasons. Many of the tools are broken and study of their microstructures shows that the bronze used has poor mechanical properties because of porosity and bands of sulphide inclusions.

EASTERN STAINLESS TYPE 309S

Abstract EASTERN STAINLESS TYPE 309S is a heat-resisting grade of stainless steel. Because of its high alloy content, it resists scaling up to 2000 F. It also has good tensile and creep properties and elevated temperatures. Type 309S has good ductility and malleability; therefore, difficult shapes and structures can be fabricated easily and it can be machined readily. It can be welded easily and gives strong, ductile welds. Some of its many applications are annealing boxes, boiler baffles, dryers, furnace parts, heat exchangers and oil-refining equipment. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as creep. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: SS-441. Producer or source: Eastern Stainless Steel Company.

Corrosion behaviour of Ni‐Resist cast irons

Owing to their relatively high alloy content, Ni‐Resist austenitic irons exhibit a higher degree of corrosion/erosion resistance than ordinary cast irons or cast carbon steels in all environments. The influence of the nickel alloying addition increases the “nobility” of Ni‐Resist, placing it in the galvanic table between the nickel‐free ferrous metals and copper‐base alloys such as gunmetal and aluminium bronze. Ni‐Resist irons vary in alloy content, to meet specific requirements, and are produced with both flake‐graphite and spheroid‐graphite structures. Practical experience indicates that in most applications the corrosion resistance of an SG Ni‐Resist iron is similar or superior to the corresponding flake‐graphite grade.

Properties of powder and cast R6M5K5 high-speed steel

1. In powder R6M5K5 steel the primary carbide phase is MC carbide and in cast M6C. 2. The high alloy content of the solid solution and the dispersion of the carbide phase in powder R6M5K5 steel provides its increased red hardness and, consequently, better cutting properties.

Intergranular corrosion of high purity austenitic stainless steel containing silicon additions

The intergranular corrosion of high purity austenitic stainless steels was studied. Steels containing less than 500 ppm total impurities were doped with various amounts of silicon and solution treated before testing. Potentio-dynamic anodic polarization curves and fixed potential measurements were used with optical and scanning electron microscopy to study the corrosion morphology in these alloys. Between 1.1 and 1.5 V with respect to a saturated calomel electrode (SCE) intergranular corrosion took place in the silicon-doped steels. Silicon concentrations in the range 100–4800 ppm caused susceptibility to both intergranular and surface attack. The high purity base alloy (50 ppm) and high silicon content (4.15 wt.%) steels were immune to intergranular and surface attack. The transpassive current density (between 1.1 and 1.5 V (SCE)) was found to increase with increasing amounts of silicon.

Influence of martensite carbon content on the cyclic properties of dual-phase steel

A series of FeMnC alloys was quenched from 760° and 820°C. This treatment produced dual-phase microstructures in which the carbon contents of the martensite and ferrite phases were held constant while the percent martensite varied. The monotomic and cyclic properties of these steels were determined and the major influence on mechanical properties was found to be the percentage of martensite; both monotonic and cyclic stress levels increase linearly with martensite content. Carbon content of the phases also appears to play a role, particularly for cyclic properties. At constant martensite contents higher carbon levels result in better fatigue properties. Thus dual-phase steels with a higher alloy content (therefore able to be more slowly cooled resulting in higher carbon bearing martensite) may be preferable for cyclic applications.