Hello Again.

Blimey, it's February already, I guess the Northern part of the globe is looking forward to Spring, while down under here in OZ we are approaching the end of summer... just a few more weeks and we'll be into Autumn... great, it's my favourite part of the year, I don't do much in the foundry over the hot months, and like many others in OZ, I really look forward to the cooler part of the year, which means lots of melting and pouring.

A big welcome to the many new subscribers who have joined the ezine in the past month, we trust you will enjoy the articles and gain some knowledge along the way. Thank you also to all who have purchased the ebook package over the past few weeks, we truly appreciate your support, many new clients who want to learn about hobby casting dont just come from the US, Canada, Europe, South Africa,The UK, NZ or Australia, we also noticed a couple from Israel, and another from The United Arab Emirates, its good to see the home foundry activity is still happening over there in the middle east. There have been several people from Malaysia & a few from Japan come on board in the last few weeks.

If you are within an easy drive of other metal casters and you happen to get together every now and again for a weekend of fun and casting, then don’t be afraid to send in a short story and some pictures of your weekend of casting, so that other ezine readers can read about your weekend adventure.

I need metal casting related stories for the ezine, please consider sending in something, even if you think you cant write, we can work together to get it right, so what about it.
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Below you'll read a little about what happens to metal during annealing & re-crystal- lisation when metal is shaped or rolled, metal is a remarkable substance, it's structure and characteristic means that it can be manipulated in many ways to convert it into what ever quality of metal is required. You'll also read an overview of metal Alloys. And some tips to build your own moulding bench.

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 During cold rollling (above) metal becomes work hardened.

 

During a hot rolling process re-crystallisation can take place.

Annealing and re-crystallisation.

A cold-worked metal, that is, one that has been deformed without any application of heat, is in a state of considerable internal stress. During annealing, these stresses are re- moved, and the original ductility of the metal returns. The changes, which accompany an annealing process, occur in three stages.

01. The relief of stress.
As the temperature of the cold-worked metal is gradually raised, some of the internal stresses disappear, as atoms move through small distances into positions nearer equilibrium. At this stage, there is no alteration in the generally distorted appearance of the structure, and, indeed, the strength and hardness produced by cold working remain high. Nevertheless, some hard-drawn materials, such as 70-30 brass, are given a low-temperature anneal in order to relieve internal stresses, as this reduces their tendency towards 'season cracking' during service, i.e., the opening up of cracks along grain boundaries, due to the combined effects of internal stresses and surface corrosion.
Note: Almost all castings pulled from the sand mould have internal stresses of some kind, heat treatment will normalise the metal.

02. Re-crystallisation.
With a further increase in temperature, a point is reached where new crystals begin to grow from nuclei, which form within the structure of the existing distorted crystals. These nuclei are generally produced where internal stress is greatest, that is, at grain boundaries and on slip planes. As the new crystals grow they take up atoms from the old distorted crystals, which they gradually replace. Unlike the old crystals, which had become elongated in one direction by the cold-working process, these new crystals are small and equi-axed.

This phenomenon, known as re-crystallisation, is the principal method used to obtain a tough, fine-grained structure in most non-ferrous metals. The minimum temperature at which it will occur is called the re-crystallisation temperature for that metal, though it is not possible to determine this temperature precisely, because it varies with the amount of cold work to which the metal had been subjected before the annealing process. The more heavily the metal is cold-worked, the greater the internal stress, and the lower the temperature at which re-crystallisation will begin. Alloying, or the presence of impurities, raises the re-crystallisation temperature of a metal.

Metal                                       Re-crystallisation
                                                 temperature ('C)

Tungsten                                            1200
Nickel                                                 600
Pure iron                                            450
Copper                                               190
Aluminium                                          150
Zinc                                                     20

03. Grain growth.
If the annealing temperature is well above that for re-crystallisation of the metal, the new crystals will increase in size by absorbing each other cannibal fashion, until the resultant structure becomes relatively coarse-grained. This is undesirable, since a coarse grained material is generally less ductile than a fine-grained material of similar composition. Moreover, if the material is destined for deep drawing, coarse grain tends to disfigure a stretched surface by giving it a rough, rumpled appearance known as 'orange peel. Both the time and temperature of annealing must be controlled, in order to limit grain growth; though, temperature has a much greater influence than does time on grain growth.

Metal Alloys- A General Overview.

Most of our useful metals are soft and ductile when pure. Pure copper and pure alum- inium are admirable materials from which kettles, pots, pans and the like can be formed; whilst dead-mild steel which industrially is the nearest feasible approach to pure iron is widely used for the bodywork of motor cars, and countless other drawn or pressed com- ponents. Unfortunately, these pure metals, though ductile, are comparatively weak; and, whilst it is possible to increase their strengths by means of cold work processes, it is usually necessary to obtain still greater strength and hardness by alloying.

An alloy is a mixture of two or more metals, made with the object of improving the pro- perties of one of these metals, or, in some cases, producing new properties not pos- sessed by either of the metals in the pure state. For example, pure copper has a very low electrical resistance, and is therefore used as a conductor of electricity; but, with 40% nickel, an alloy, 'Constantan', with a relatively high electrical resistance is produced. Again, pure iron is a ductile though rather weak material; yet the addition of less than 0.5 % carbon will result in the exceedingly strong alloy we call steel. In this chapter we shall examine the internal structures of different types of alloy, and show to what extent the structures of these alloys influence their mechanical properties.

It is a general rule that, in order to produce a useful alloy, two metals must 'mix' with each other in the molten state. In some cases they do not; but, like oil and water, form two sep- arate layers in their containing vessel. Clearly, such metals are unlikely to form a useful alloy, and we must therefore begin with the assumption that the two metals do mix; that is, they completely dissolve in each other in the liquid state, to form a single homogeneous solution. Vast volumes have been written about the alloying of metals, to learn more about this fascinating subject, take a look in the metallurgy section of your local library.

The Hobby Foundry Moulding Bench - Tips To Build Your Own.
Article Classification: Workshop skills, welding & fabrication.

If you're going to spend a good part of your spare time working in your hobby foundry, then you'll need to have the best possible equipment & gear that  you can afford. And there is no need to go out and spend a small fortune, if you are resourceful you can build your own moulding bench.

If you have the ability to fabricate & weld steel, then the best way is to self-build, you can custom design & build a moulding bench exactly the way you want it.

And if you don't know how to fabricate and weld then building a moulding bench will provide a learning experience in basic fabrication and arc welding skills. It's not hard; it's a lot of fun, & quite rewarding when you  can complete worthwhile projects.

In the 3-Vol-foundry ebook, we illustrate a moulding bench constructed from re-cycled steel tube, 3/4" thick MDF board for bench top, it is mounted on casters for mobility. When the bench is not being used for making moulds it can be used for other purposes in the workshop. To protect the bench top, it is wise to clad the MDF with 16g or 18G sheet metal, preferably with a zinc or galvanised coating to prevent rust occurring, which will happen if you use green sand for moulding as it holds quite a bit moisture and will eventually corrode plain sheet metal.   

Moulding Bench Dimensions - What is the right height for you.

Most tables & benches are made to standard heights, these heights are determined from the size of the average human being... but what if you're not Average, you might be quite tall or very short, nothing is more uncomfortable than working at a bench that's not tuned to your height.

So think carefully when you construct your own moulding bench. You don't want to have to bend over the bench too far as this will give a back ache, make it too high, and you wont be able to carry out your moulding work properly. Measure the heights of various tables and benches around your house which are made to recommended table or bench
heights, try these out in an imaginary way, and then adjust slightly up or down to suit you and not anyone else, because you will be the one working on the bench.

A good way to see what bench height is best for you is to place your mould boxes on a normal table; imagine you are about to start work in your foundry. Make an assessment to see if the table is to high, or low, or perhaps it's just right, make an informed decision and then build your new moulding bench to suit you.

You will be spending a lot of time ramming and making sand moulds so make sure the bench height is the most comfortable possible. You should also think about storage areas underneath your moulding bench, design your bench to store your sand bins, moulding boxes, bottom boards, tins of parting powder, and other hand tools used in your hobby foundry. Moulding bench illustrations and measurements are provided in the 3-Volume hobby foundry ebook.

Home Made Hand Tools For Hobby Foundry Work.
Article Classification: Workshop Tools, welding & fabrication.

If you have been thinking about making a start in hobby foundry work in your home work- shop, you may be forgiven for thinking that the tools and equipment are going to cost you an arm and a leg, this need not be. Sure, you could trot off to the downtown industrial tools supplier and take home an arm full of expensive tools.

But if you take a good look at some of the tools, you'll discover that the design principles and fabrication could well be undertaken in the home workshop if you have metal fabri- cation skills and a reasonable amount of basic metal working equipment.

Take for instance "crucible lifting tongs", once you understand how these tools operate; you could quite easily make a set or two over a weekend. The basic design action ope- rates on the "scissor principle" but they don't cut anything, they are designed to "clamp securely" onto the crucible to lift it out of the furnace when the metal has melted.
Great caution needs to be taken while carrying out this operation, as one slip due to faulty or badly designed tongs, and you could have a disaster on your hands.

The best way to design and build a set of tongs is to copy a well made set, or to follow directions set out in a textbook or ebook downloaded from the net, a free how to build   crucible tongs guide book is provided in the ebook package at our web site.

Following are some of the most frequently used basic tools you'll need in the hobby foundry; Bench ramming moulders tool - Tube sprue cutter - turned wood sprues - slick & oval spoon - hand riddle or sand sieve - draw pins, screws & hooks - vent wire - rapping bar and spike - gate cutter - strike off bar. Sand carving tools (made from old hacksaw blades)

The tools mentioned above seem to be the ones that will be most used in your hobby foundry... and all of them can be home made if you have metal & wood working skills, it will take time and effort to make the tools required, but they wont cost you a red cent if you make them from scrap materials, and if you are like most hobbyists you will know where to "scrounge stuff".

You may have to experiment with different ideas before you arrive at the most satis- factory design, but you will learn a great deal about why things have to be made certain ways.

Do you own a wood lathe? Even a most basic machine will suffice in the home workshop, you could even make your own wood lathe if you were keen enough, I guarrantee there are tens of thousands of home made wood lathes sitting in hobby workshops the world over. A wood lathe will repay itself many times over when you start to make patterns for your hobby foundry.

Your bench-ramming tool can be quickly turned to shape on the wood lathe, in fact, while you're at it, make two or three of them in different shapes & sizes, they will all come in handy when ramming and moulding patterns of differing sizes, you could get away with a single tool, but you wont regret making extra sand ramming tools. 

Draw pins and spikes are used to remove timber patterns from sand moulds after the pattern has been rammed. The pattern will need to be carefully removed without dis- turbing any of the surrounding sand. Draw pins can easily be fabricated from long slender wood screws, and particleboard screws are ideal.  The easiest way to convert wood- screws into draw pins is to braze weld a short length of 1/4" dia mild steel rod onto the head of the screw...that is all you need to do... make a set of them in different lengths and using different gauge screws,  you should have the field covered as far as lifting pins or draw spikes go... simple isn't it.

Worn or blunt hacksaw blades are usually thrown in the bin, from now on you should save them, as many useful little hobby foundry tools can be made from old blades, quite often-
small sand carving tools can easily be made by grinding and shaping with a normal bench grinder. One of the best ways to make a mould vent tool is with a bicycle spoke, they are quite tensile in strength, and all you need is to form a point on one end, topped with a round wood handle on the other, and it's ready to go.

By being resourceful and thinking how you can use scrap materials, you should see now that there is absolutely no need to spend large  amounts of money to get the tools and things you need for your hobby. The more fabrication skills you have the better you will be
equipped to build all manner of tools and equipment at a very low cost.
Good Luck.

Industry News Snippets.
Plugging holes in light metal casting technology.
To read this article click on the link below.
http://www.uq.edu.au/news/index.html?article=2337

US aluminium casting may need to double capacity by 2015:
Thayer. http://metalsplace.com/metalsnews/?a=3719