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PRACTICAL WELDING LETTER, Issue #007 -- Electro Slag Welding, Titanium Filler Metal, Casting, Health February 29, 2004 |
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| We hope you will find this Letter interesting and useful. Let us know what you think of it. Practical Issues, Creative Solutions
This publication brings to the readers practical answers -----------------------------------------------------------------------
You are urged to pass-along this publication to your ----------------------------------------------------------------------- Date: March 2004 - Practical Welding Letter - Issue No. 07
------------------------TABLE of CONTENTS---------------------------
1 - Introduction 2 - Article: Electro Slag Welding 3 - How to do it well: Stainless to Mild Steel welding 4 - Filler Metal: Selection of Titanium Alloys 5 - Online Press: recent Welding and related Articles 6 - Terms and Definitions Reminder 7 - Article: Between Casting and Welding 8 - Site Updating 9 - Short Items 10 - Explorations: beyond the Welder 11 - Contribution: Welding Effects on Health 12 - Correspondence: a few Comments 13 - Bulletin Board Unsubscribe link ----------------------------------------------------------------------- 1 - Introduction This issue of Practical Welding Letter is the first one now distributed to more than 700 subscribers. This encouraging fact is not reflected in active interest and participation of readers, with very few welcomed exceptions. We have added in the Site a new page on Adhesive Bonding: although different from Welding, this joining process has gained increasing importance for attaching metals to themselves and to ceramics or composite materials. It is one more tool in store for special occasions when other methods fail to meet requirements. Electro Slag Welding is a mature process for quite important projects. Following development studies aimed at solving problems of inconsistence and limited properties, the method is by now well accepted and successfully applied. Welding dissimilar materials may be a challenge. Quite a number of questions were asked on how to weld Mild to Stainless Steel: a few hints are proposed and more will be added in the future if requested. The section on Filler Metals is devoted here to Titanium Alloys: the potential uses of Titanium should grow in time. Better be ready, by exploring types and properties. A reminder on Health was requested by a worried reader. Every welder should be instructed on how best to protect his/her health while welding happily around. We provide a few links. If anyone wishes to contribute ideas or comments, you are welcome. Other sections follow as usual. We think that the valuable Gifts made available by Sitesell may contribute to a change of attitude of many readers regarding their own qualities and capacities. It is a mine of benefits. We would like to encourage everybody to take advantage of these offers, because and despite the fact that they come at no cost to you. And as usually we urge you to let us have your feedback, click here. ----------------------------------------------------------------------- 2 - Article: Electro Slag Welding One of the highest weld deposition rates achievable for thick plates is supplied by Electro Slag Welding. This single pass process is quite specialized as it requires suitable equipment and controlled procedures to give its outstanding benefit in a well defined niche of applications. Therefore it is not much known or spread in the general purpose industrial welding community except where researched or used. The process is being employed essentially for welding low carbon steels, although, with appropriate precautions, it can now be applied also to higher mechanical properties structural steels. The minimum thickness for practical application is about 25 mm (1 inch) but occasional use has been made for thinner plates. The maximum is open, provided sufficient energy can be supplied: welding is known to have been applied to plates up to 300 mm (12 inches) thick, but that may not be the absolute maximum realized. The heat for melting the surfaces of the base material plates is supplied by a mass of continuously heated molten slag confined between those surfaces and special molds called shoes or dams, usually made of copper, water cooled or not, that are put in place before starting. In fact this welding process is similar, for certain aspects, to a casting process known as Electro Slag Remelting (ESR) used for refining the material of cast ingots by the action of specially formulated slags on the molten base material. The electric energy necessary to sustain the process is provided through consumable electrodes. The slag is heated by its resistance to the passage of an electric current and is constantly kept molten. The power supply is usually of direct current constant voltage type. The electrode wire is guided in the weld pool through an insulated consumable guide tube. The functions of the slag are to develop and provide the heat necessary for melting of the consumable electrodes and of the abutting surfaces of the plates to be welded, (and all of the waste heat that is lost to the environment), and to protect the molten metallic material from oxidation. Except from the starting stages when an arc is struck between electrode and base material, much as it is done in Submerged Arc Welding, as soon as an initial mass of slag is molten the arc is extinguished and resistive heating takes place. Welding proceeds in the vertical direction as the molten pool, kept by gravity at the bottom of the prepared cavity, slowly moves up along the joint, leaving in its wake a solidified progressive weld. Special provisions are needed to provide an initial sump space, where to melt the starting mass of flux, proper attachments to keep in place the copper shoes, and run off tabs to end the weld at the top of the joint. Some of the flux has to be continuously added in the correct quantity to keep almost constant the depth of the molten flux. As a result of quality and reliability problems in early produced joints, and of questionably low impact properties, the Federal Highway Administration of the United States Department of Transportation initiated a long term sponsored research to determine ways and procedures capable of producing acceptable welds suitable of being used for critical joints in bridges. The outcome of this effort was an improved process called Narrow Gap Improved Electro Slag Welding (NGI-ESW) and the removal of the moratorium on the application of the process that had been issued a few years before. A short memorandum in pdf. format can be downloaded by clicking here. -----------------------------------------------------------------------
3 - How to do it well: Stainless to Mild Steel welding Q: Is it possible to arc weld Stainless Steel to Mild Steel? A: Yes, Austenitic Stainless Steel is currently welded to Mild Steel, with certain precautions. First, the Stainless should be of a composition not susceptible to sensitization otherwise its corrosion resistance properties will result impaired by welding. (See on this problem the article on Welding Stainless Steels in the Welding Advisers Site, Click here.) Second, especially if the mild steel element is thick, it is customary to weld on top of it a layer of stainless (Type 309 or type 312) or of high nickel filler metal: this procedure is called buttering. The final welding thus occurs between two stainless surfaces. ----------------------------------------------------------------------- 4 - Filler Metal: Selection of Titanium Alloys Titanium can be as strong as steel but much lighter, its density being only about 60% of that of iron base materials. Titanium base metal is selected for its outstanding resistance to corrosion in marine and industrial harsh environments. It is the material of choice for its superior strength to weight ratio (specific strength) in somewhat elevated temperature ranges up to 600 0C, as the lightest material suitable to stand demanding load conditions under heat in compressor parts of aero turbine engines. It is suitable for continuous service at cryogenic temperatures, without embrittlement. And, being biocompatible, it has been used successfully for surgical implants and medical implements. As you probably know, an Overview on Welding Titanium is given in the page in our Welding Advisers Site available by clicking here. In this Article we propose to add a few hints on the Selection of Titanium Filler Wires while stressing again the most important contamination issues that risk to compromise the results of welding if not taken care of properly. You may remember that the accepted Classification of these electrodes and wires is given in For the majority of applications, the most common alloys of widespread use are the following:
Both materials above are alpha titanium alloys, readily weldable. Other Titanium alloys can be selected from the list of ASTM specified alloys, for special properties or exceptional corrosion resistance. Titanium and its alloys are not usually welded to dissimilar metals because they develop brittle intermetallic phases, except maybe with specialized techniques and with reduced properties. Titanium however can be welded successfully to Zirconium, Niobium (also known as Columbium) and Tantalum. Despite the diffused belief that Titanium is difficult to weld, because of its extreme susceptibility to contamination, it is one of the easiest materials to be welded, much more than some steels which can develop weld cracking. A work area reserved for Titanium welding should be set apart, with special provisions to avoid contamination of welded joints, either from particulate matter from current industrial operations, or by moisture and air drafts. The processes using filler metal, which are applied the most to welding Titanium alloys are Gas Tungsten Arc Welding (GTAW) also known as Tig (Tungsten Inert Gas), Plasma Arc Welding (PAW), which is a variant of the above, and Gas Metal Arc Welding (GMAW) also known as Mig (Metal Inert Gas). The first is usually accomplished with Direct Current power supply, with Straight Polarity, meaning that the electrode is connected to the negative contact. The last one is preferably performed with Direct Current but with Reverse Polarity, with electrode positive. With Tungsten electrodes one must strike the arc by using high frequency superposed current, avoiding contact between electrode and base metal, to prevent contamination of the weld. Protective atmosphere is usually provided by Argon or Helium inert gases, the second one or mixtures of the two being selected when a hotter arc with higher voltage is required. Titanium molten metal should be effectively protected from air contamination, either by enclosing it in an inert gas filled closed compartment, or by providing ample supply of protective gas. When welding outside an enclosure one should provide a uniform trailing non turbulent flow of protective gas on the adjacent material, on the underside of the root and along the trailing part of the weld bead, while at temperatures higher than 427 0C (800 0F). Insufficient shielding will make itself noticeable by the color assumed by contaminated material. Unalloyed Titanium and all the alpha-Titanium alloys are easily weldable. Cleaning of Titanium metal is most important to assure sound welds. It is performed by first eliminating all traces of paint, soil, organic oils or greases, with non-chlorinated solvents, and then by mechanical or chemical means to remove all traces of oxide layers. The selection of suitable Filler Material depends on the process to be applied and on the base material to be welded, of which one should know the type of metallurgical structure. While it is customary to match the composition of filler metal to that of the base material, it may be preferable to provide additional ductility by selecting a commercial pure filler wire instead of an alloyed one, if the reduced strength obtained is still acceptable. The weldability of Titanium alloys is based on toughness and ductility of weld metal. Unalloyed Titanium is usually welded in the annealed condition in preference to the cold worked condition. Then in general a certain increase in the strength of the weld is to be expected, along with a decrease in ductility. Titanium Filler Metals The following Table I lists some of the most useful Titanium Alloy Filler Metals, indicating the AWS established designation and the chemical composition.
Notes: Titanium Remainder It is generally recommended to use the lowest heat input that still provides the weld dimensions and properties required. The welding conditions should be verified by destructively testing weld samples to examine weld internal geometry and absence of defects, and when required to test mechanical properties. Welding Qualification may be required by applicable Codes. Preheating is not generally required except that if low ambient temperature causes moisture to condense on the metal, it is good practice to preheat mildly to remove humidity.
Bend Test A classic bend test to assess weld ductility is performed on welded sheet test pieces with the weld bead across the bend axis. Acceptable ductility is demonstrated when a 180 degrees bend of the test piece can be performed without developing cracks, around a mandrel of radius equal to the thickness of the sheet metal times the bend factor reported in the following Table, for different ASTM Grades.
Stress Relieving It is usual to perform Stress Relieving on Titanium Alloy weldments. The treatment prevents cracking and stress corrosion, and is beneficial in improving fatigue resistance. Time and temperature should be critically controlled to avoid grain growth and impairing of impact properties. Occasionally, for certain special alloys, welding may cause aging and embrittlement, unless followed by full annealing: testing should be performed in cases of doubt or for exceptional requirements. ----------------------------------------------------------------------- 5 - Online press: Recent Welding and related Articles New materials and new techniques are developed to meet new tasks and new challenges. Read on the Welding Journal on Aluminum Shipbuilding. Click here. In the fiftieth anniversary of the launching of the first nuclear submarine, the Nautilus, an article on the official ASME magazine recounts the story of Nuclear Navy. As of September 2006, the issue of January 2004 is now available online to ASME members only. Readers interested in the story should look for this magazine in a library. Quality in Production Welding is the title of this article dealing with troubleshooting the causes that produce porosity in welds. It appears in The World of Welding, a quarterly publication of the Hobart Institute of Welding Technology. Check with http://www.welding.org/ Selecting the best out of Shielding Gas supply Methods can be tough, if the basic elements are not known. Read on the parameters that make the choice Efficient. Click here. In GTAW, the refractory electrode plays a vital part in the success of the operation. An article on Selecting the Right Tungsten electrode for Aluminum Welding gives important clues. Read it by clicking here. ----------------------------------------------------------------------- 6 - Terms and Definitions Reminder Note: Following the addition in the Site of a new page on Adhesive Bonding (Click here to see it), we propose here a few Terms and Definitions pertaining to this subject. Adhesion: The state in which two surfaces are held together by attractive chemical forces developed by an interposed adhesive. Adhesive: a substance capable of holding together materials by surface attachment. Binder: A component of an adhesive substance generating the forces which hold together two elements. Bond Strength: The force required to break an adhesive joint. The type of stressing must be indicated (tensile, shear etc.). Catalyst: A substance which changes the rate of reaction of a chemical process. Cleavage Strength: A force directed so that it tends to separate the adhesive bonded surfaces by pulling at an angle from the joint plane. Cohesion: The force keeping together the particles of an adhesive. Cross Link: The nature of internal bonds developed by chemical reaction tying together one molecule of adhesive to another. Cure: The change of physical properties of an adhesive brought about by a chemical reaction, heating or radiation, with or without pressure, to develop adhesive forces. Hardener: a substance added to an adhesive to initiate or control a curing reaction. Peel Strength: the force required to separate two adherent surfaces by peeling them away from the joint. Polymer: A complex of high molecular weight formed by the reaction of simpler molecules that combine under suitable conditions. Polymerization: A chemical reaction in which simple molecules are linked together to form large molecules. Shear Strength: The strength of a bond stressed in shear, parallel to the plane of joint. Working Life: The period of time when a prepared adhesive is suitable to be applied, before curing. ----------------------------------------------------------------------- 7 - Between Casting and Welding A few of the important facts that set Casting successfully apart from other manufacturing technologies are summarized in the following. One of the first arts known to mankind from the dawn of civilization at far distant emplacements on earth, Casting is still a modern production method of sophisticated articles, presenting unique benefits unrivaled by competing techniques:
Molding is the art of preparing forms or cavities in appropriate materials, into which molten metal is poured to produce castings. The description of the techniques used is common to most materials, but procedures must be adapted to the different physical conditions prevailing in each case. Most important among these is shrinkage allowance, that is a dimensional correction used to compensate for the contraction of liquid metal in cooling, which is different for every castable material. Sand molding is the process of building the required cavity by pressing sand of useful characteristics suitably prepared, that is combined with a binder, around a pattern (usually made in wood) which reproduces the form of the desired cast object. The mold is divided into two frames or flasks, called the cope (the top side) and the drag (the bottom side), along a parting plane which permits the separation of the two parts, for removing the pattern. The mold must include channels, called sprues, runners, gates and risers, through which the molten metal will flow from the funnel to the cavity. The sand mold, which is green (as prepared) or fired (cured) according to the application, must resist the weight, erosion and deformation by molten metal and present a certain permeability to gases developing in the process, to let them out without trapping them into the cast part. For hollow cast parts, or for those including contours or passages, the mold must include a separately prepared core, reproducing the form of the free space to be left within the casting. The core is firmly held in place in the mold before casting, and removed after solidification, that is after completion of the casting process, along with all the mass of sand that is now discarded, and possibly reused after further conditioning. Cast irons are alloys of iron, carbon (1.7 to 4.5%) and silicon (1 to 3%) in which more carbon is present that can be retained in solid solution in austenite at the eutectic temperature. In gray iron the carbon in excess precipitates as graphite flakes. Gray iron is the most widely used and the least expensive of all cast metals. Usually the matrix structure is pearlitic. It is easily obtained even in intricate patterns, and it is selected when its mechanical properties are adequate. Different types can be specified, each one best adapted to specific applications within reasonable cost ranges. Composition and heat treatments can be modified to best suite the application involved. Minimum section obtainable and hardness depend also on pattern configuration and on pouring conditions: therefore it is not practical to give numbers for general reference. Wear resistance is elevated and can be made exceptional if needed. One of the most appreciated characteristics of cast iron is its high damping capacity, meaning its ability to absorb vibrations, which makes it a natural choice for machine tool bases and industrial equipment. Gray cast iron is readily machinable. It is also quite resistant to fatigue fracture, if the range of stressing is selected carefully. In general cast iron strength in compression is higher than in tension, dictating a clear preference for practical applications. Cast iron can be sensitive to shock, fracturing without appreciable deformation: this means that the ductility of cast irons is relatively low. Cast iron cannot be wrought and it is not malleable at any temperature. Iron castings can be readily welded either for assembling complex structures from simpler components or for repair. However a few provisions must be put in place to obtain successful results. More on this subject can be found in the page on welding Cast Iron in our Site, by clicking here. ----------------------------------------------------------------------- 8 - Site Updating 8.1 - Plasmatron is a nice name. It is also an interesting development of a new concept of Russian origin. It consists in a power supply and a cutting torch making plasma out of water and whose flame reaches 8000 0C. For brazing it is suggested to put some vodka (or alcohol) in the water, no kidding. A short reference was added to the page on Cutting. Click here. Readers having tested this Plasmatron are invited to share their impressions with our Audience. Write us by clicking here. 8.2 - The Page of the Month this time is about Adhesive Bonding. We agree that it is not Welding but it helps to get parts stick together in a different way, with certain Advantages and some Limitations, provided curing processes and type selection are properly taken care of. You can find it by clicking here. 8.3 - Are there any other interesting subjects you think are fit for dedicating them a page in the Site? Let us know, write a short note and e-mail it. Click here. ----------------------------------------------------------------------- 9 - Short Items 9.1 - Welding Duplex Stainless Steel. Duplex means double and, when referred to Stainless Steel, it indicates that the matrix is a mix in about equal proportions, of two kinds of metallographic structures called by metallurgists ferrite and austenite. Compositions are identified with reference to the Unified Numbering System. These are Stainless Steels with quite a substantial proportion of Chromium, the main ingredient for imparting stainless properties, and additional balanced quantities of Nickel, Molybdenum, Copper and sometimes Nitrogen. The base is obviously Iron. Carbon is kept low as are also Sulfur and Phosphorus. The main properties are improved corrosion resistance and mechanical properties (up to twice as strong), when compared with regular austenitic stainless steels. Other important differences are thermal conductivity and thermal expansion, midway between those of carbon and austenitic stainless steels. Although weldability of Duplex steels is good, attention should be devoted to sensitivity to degradation of properties, due to excessive time at heat. An important precaution is to limit as much as possible holding time at intermediate temperature, between 300 and 980 0C. Filler metals are chosen either with matching compositions or overalloyed with slight excess of nickel to promote more austenitic structure. Thorough documentation is recommended before starting a project and full qualification following procedure development, to assure acceptable properties in the complex structures that benefit most of the use of Duplex Stainless Steels. 9.2 - Shot Peening. As a surface treatment, shot peening is used to provide cold working by inducing compression stresses on a metallic surface. The residual stresses, deriving from welding or from any other operation can thus be modified. In particular shot peening may be used on high alloy or tool steels, on the still hot weld beads, to reduce shrinkage stresses to avoid the formation of shrinkage cracks. The operation is performed under controlled conditions in special equipment capable of directing a stream of shot at high velocity to impinge on the surface to be treated through suitable hoses and nozzles. The cumulative surface deformation effectively produces a more favorable stress condition capable of withstanding the tendency to crack from shrinkage or fatigue. 9.3 - Root pass in pipes with AWS E6010 electrodes: AWS A5.1 E6010 electrodes used with DCRP, electrode positive for shielded metal arc welding are a popular selection for providing a deep penetration arc suitable for all position welding. As such they meet requirements for welding the root pass in pipes in fixed position and, when properly applied, they provide radiographically acceptable welds with good mechanical properties. The main constituent of the shielding flux is cellulose, which produces a protective gas of relatively high moisture content. This electrode type is therefore not suitable whenever low hydrogen is required. These electrodes are fast freeze and the limited amount of slag is easily removed. A relatively high weld deposition rate can be achieved. 9.4 - AWS E7010: This is an all position welding electrode with cellulosic cover, suitable for welding high strength pipe. Recommended for X46, X52 and X56 grade pipe. It can produce radiographic quality welds. Useful when welding in vertical down position permitting deep penetration when proper keyhole is maintained. 9.5 - AWS E7018: For structural welding AWS A5.1 E7018 electrode is often selected. It runs easier than AWS E6010, providing higher mechanical properties. It is a low hydrogen electrode requiring careful storage, and oven drying before use when picking up moisture. E7018 can be almost dragged along the joint. Deposition rate is less than for E6010. Suitable for structural joints in low alloy steel, piping, construction equipment and boiler code applications. 9.6 - API 5L grade X65: For pipes of the above grade, if using Shielded Metal Arc Welding, electrodes of type E6010 or E7010 can be used for the root pass with Direct Current Reverse Polarity, Electrode Positive. Typically the vertical down position is selected. Low Preheating may or may not be required, depending on the thickness and on ambient temperature. The potential for higher weld deposition rate of continuous Gas Metal Arc Welding should be considered, either with solid or with Flux Cored wire. These processes however require expertise for establishing optimum parameters in order to obtain consistently acceptable results. 9.7 - Ultrasonic Testing: Non destructive weld testing techniques that use ultrasonic excitation and probing of internal features dependent on acoustic impedance changes, are extremely informative and useful. Unfortunately one needs generally highly specialized technicians who know how to use the instruments and how to interpret the signals. However for highly repetitive inspection work on well defined joint configurations, it is possible to build special transducers suitable for a single job: in this case the process can be designed to be performed by unskilled inspectors, mostly the welders themselves, who will obtain immediately a pass/fail answer to the test. 9.8 - Flash welding: Two pieces of metal clamped in separate fixtures capable of transmitting an electric current are brought together under a potential difference. The current flowing in the gap produces arcing or flashing that heats the abutting ends. As soon as the heat so developed is sufficient, the parts are brought by force in intimate contact, resulting in upsetting and welding. The process is ended by flash removal. Except for the obvious difference in the source of heating, the process is similar to friction welding. It is suitable and used therefore to weld frames, that do not present the symmetry required for friction welding. It is essentially a mass production method whose operators need not be skilled in the process, once all parameters are selected and fixed. 9.9 - Resistance Brazing: In properly prepared joints, a foil of suitable brazing alloy is interposed between abutting surfaces. The joint is heated by the passage of an electric current through electrodes under pressure, much as it is done in resistance welding. The heat melts the brazing alloy but not the metals to be joined, and a brazed joint is formed. The brazed area can be many times that of corresponding spot welds, so that the strength can be suited to the requirements. The process is mostly used with copper or brass parts, but also other materials have been successfully resistance brazed. 9.10 - Stud welding: An arc welding process used to attach fastener elements to metal bodies. The arc is generated between the fastener and the body under proper conditions, and then, once the temperature is right, the two are forced together until welding is completed. The process permits secure attachment of fasteners from one side, it is rapid and efficient, and does not need skilled workforce. The fasteners to be welded are clamped in a special stud gun and presented to the surface so that the automatic welding cycle is performed once a trigger is depressed. A suitable Direct Current power supply is used. ----------------------------------------------------------------------- 10 - Explorations: Beyond the Welder The International Titanium Association can be reached at: The Aluminum Association, Inc. displays a Site at: The American Zinc Association publishes information material and distributes downloadable educational zinc videos at: The International Magnesium Association is found at: The Lead Development Association International is available at: ----------------------------------------------------------------------- 11 - Contribution: Welding Effects on Health One of our readers took the initiative to suggest that PWL provide some information on the effects of the welding environment on the Health and wellbeing of Welders. We were previously informed by another reader of litigation in court connected with welders claiming to have had their health impaired due to poor conditions in the welding workplace. We think that anyone involved in welding should be aware of the occupational hazards that pertain to the trade. And anyone involved in Welding Education and Training should alert the students of health risks and preventive measures. Also we think that all responsible employers should at minimum comply with the requirements of the authorities charged with the protection of welders' health. It should be noted that some of the issues may not be clear cut, in that eventual outcome may become evident only a long time after exposure, so that it may be difficult to prove the relation of cause and effect between certain endangering factors and perceived results. Furthermore there are questions of statistical relevance that may complicate litigations more, or of personal habit (like smoking) that may aggravate a health situation. We present hereafter a few references dealing with Health Hazards for people involved with Welding.
http://www.afscme.org/health/faq-weld.htm http://www.osha.gov/SLTC/weldingcuttingbrazing/index.html http://www.osha.gov/doc/outreachtraining/htmlfiles/weldhlth.html http://www.usace.army.mil/inet/usace-docs/eng-manuals/em385-1-1/c-10.pdf http://www.msha.gov/illness_prevention/healthtopics/HHICM10.HTM http://www.sorm.state.tx.us/VolumeThree/2Chapter6/32615.htm http://erd.dli.state.mt.us/safetyhealth/brochures/safetyhealthhazards.pdf http://www.twi.co.uk/professional/protected/band_3/jk30.html http://www.rmis.rmfamily.com/sites/safetweldi.php (this facility requires a paid subscription) A book from http://www.sipreports.com/y1204.html Health Hazards in Welding (US $ 130) ----------------------------------------------------------------------- 12 - Correspondence: a few Comments 12.1 - An irate correspondent complained that he could not find what he was looking for in the Site, although he had the impression that the item had been promised to him in another page. He therefore reached the conclusion that the site is misleading. I am sorry for the above conclusion that I believe is not exact. I can assure everybody that I have no intention to mislead. It should be appreciated that, although quite a lot of information is packed into the Site, it cannot compete with a Welding Encyclopedia. I accept that there are some not answered problems. There may also be issues of navigation, the reader not being sure where to find what he/she looks for, and giving up too soon. That is why I propose to interested readers to send in their questions so that a specific answer can be addressed to them in response. If any other person thinks that he or she was induced to believe by some incautious affirmation in one page that the answer will be found in another page where it could not be located, I would like to know, to correct the impression or to provide the answer, whatever the case may be. Please feel free to express your comments on how you would like to see enhanced the Site's usefulness. 12.2 - Most of the questions are incomplete. Readers should understand that without knowing the details or requirements of their application it is quite difficult to get an idea of the problem. ----------------------------------------------------------------------- 13 - Bulletin Board 13.1 - We received a kind notice from one of our correspondents advising on: The 15th Rolling Conference The Conference will be held at Hotel Colonial, San Nicolas, Argentina, on November 2nd to 5th, 2004. Please feel free to contact: 13.2 - Please note that in the first week of March, I will be absent from work and unable to answer immediately to your questions. Nothing is going to be lost though. All correspondence will be answered a week later, I am sorry for any inconvenience. 13.3 - In past issues we already offered to interested readers the benefits proposed by SiteSell, the small but very successful firm that helps us build and maintain our Site. If you are open to new ideas and if you are not scared to explore around, the following links should appeal to you: we strongly recommend that you dedicate some time to see for yourself how you could profit from their innovative way to help regular people, with no previous experience, to make their mark. Start your exploration. Look for real proofs. Click here. And if you want to get at no cost a useful Manual for learning how to write successfully for the Net, you are urged to click here, and you will land on a page wherefrom you can download the book. -----------------------------------------------------------------------
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