Posted tagged ‘metal’

AUTOMOBILE ENGINES

September 10, 2011

The working of an automobile engine follows the same principle as an internal combustion engine. Air, from outside, enters the engine through the air cleaner and reaches the throttle plate.
The pedal in your car is the control for the amount of air that you would want to be taken in, and you control it by pressing on this gas pedal.
The air is then distributed through the intake manifold of the cylinders.

At some point fuel is injected into the air stream, and the mixture vaporizes and is drawn into the cylinders as they start their intake stroke.

This way, when the cylinder has reached its bottom, it has drawn in sufficient mixture. As it moves up, compressing the mixture, the spark plug ignites the mixture, and as the powerful gas formed expands, it pushes the cylinder to the bottom with the cylinder once again drawing in the mixture.

In designing automobile engines, you need to be a specialist in automobile engineering.
The consideration that is taken while designing such an engine is whether it should be a carburetor or a diesel one. carburetor engines are most commonly found in passenger cars and low capacity trucks, while trucks with a capacity over two tons are fitted with diesel engines, including dump trucks, trailer tractors and bus.

Increasingly the medium and low-capacity vehicles are being fitted with diesel engines, since the fuel consumption of these engines are 30% to 50% lower than the carburetor engines.
Diesel engines not only cost more, but maintenance is much more expensive than the other type of engine. Diesels require more metal parts per kilowatt.
The critical parts of diesel engines are made of alloy steel, and the fuel injection system is much more expensive than carburetor engines.

However, the cost of manufacturing carburetor engines has increased with the use of higher mechanical grade components, considering the thermal loads of the material used. At the same time the use of high alloys and increase in production costs have contributed to the higher price of such engines.

There is a sharp rise in using aluminum alloys in design of carburetor engines in passenger cars, and with the use of high octane petrol, the cost of operation of these cars have come down extensively. Using alloy steel in constructing the engine body and other parts of the engine, makes the car lighter and hence fuel consumption goes down substantially.

The main parts that are made of high steel alloy are the main casting of the engine, the cylinder head, water and oil pumps, oil filter housing, end covers of the generator and starter, and the intake pipes. It has been observed that by using high steel alloys, the weight of the car is reduced by 35%.

The power per liter, per unit of piston area, and the brake effective pressure are 6% to 8% lower in air-cooled engines, compared to engines having liquid cooling mechanism. This is due to the fact that in engines with liquid cooling there are great losses in cylinder charging caused by the high temperature in pipes, ducts in the head, cylinder walls and head, etc.

The size of air cooled engines are much bigger than the engines with liquid cooling having the same capacity, and this is because the cylinder axes difference is larger in air-cooled engines. Taking account of the radiator dimensions, if both engines are compared, the air-cooled engine will vary slightly with its height a little longer than or approximately the same length as the water-cooled engine. As far as the width and the height is concerned both engines are about the same.

The auxiliary units of the feed and ignition, and generator and starter systems are a bit difficult to fit on the body of the air-cooled engines, because of the presence of hoods and having a danger of over-heating.

Welding and Farming – The Two Go Hand-In-Hand

September 8, 2011


 

Welding and FarmingWelding and farming? They have more in common than you might think. In fact, one astute farmer recently noted, “you can’t run a farm without welding.” This farmer was absolutely correct — to keep equipment in working order for the critical seasons of planting and harvesting, welding and hardfacing during the off-season are musts. A good working knowledge of these processes also comes in handy when your equipment breaks down during off-hours and you need to quickly fix so you can continue your work.

In this article, we will introduce you to some of the key concepts in welding and hardfacing. When we refer to welding, we are talking about joining metal pieces together to build something. The weld is primarily for strength purposes. Hardfacing, on the other hand, is depositing (by welding with special hardfacing electrodes) wear- resistant surfaces on existing metal components which are under stress to extend their service life. Hardfacing is very commonly done to metal edges that scrape or crush other tough materials -like the blade on a road grader.

Welding and FarmingWe will discuss different applications, ways to identify metallurgy, basic welding procedures and safety. So often, the beginning or novice welder will not get the desired results and assume his welding machine or electrodes are not working properly. In many of these instances, though, the farmer did not take the necessary preparations before welding or has chosen the wrong process, parameters or consumables. In this article, we hope to educate you so that you will know what to use in a few applications and can get the best results. Realize that although a little welding knowledge could help you a lot, there is a lot to becoming a true welding expert, which would cover many books!

Welding Applications

Welding and FarmingFarmers constantly need to repair and modify machinery and equipment to suit their specific needs. This instant ability to alter steel gates, chutes, animal pens, and machinery is such a tremendous benefit to the farmer. Repairing a broken plow or combine in the field by welding it where it broke in minutes can literally save an entire crop. The needs of beef cattle can usually be taken care of with mild steel. Dairy cattle, and virtually their entire milk-handling system require stainless steel. Two similar appearing animals with very different welding needs. But both needing welding to succeed.

Hardfacing Applications

There are many different items that could potentially benefit from hardfacing on the farm. They can basically be put into three “wear” categories – abrasion, impact, and metal-to-metal. Abrasion is one of the most common wears you will see on a farm, in this category falls all earth engaging implements such as tractor buckets, blades, teeth, grain handling products and feed mixers. Under the impact heading you will find equipment used to pound and smash such as crusher hammers. Metal-to-metal refers to wear from steel parts rolling or sliding against each other. Metal-to-metal wear occurs on such items as crane wheels, pulleys, idlers on track-drives, gear teeth and shafts.

Although farmers use welding and hardfacing techniques to rebuild old, worn-out components, Lincoln recommends hardfacing many new components as well. By hardfacing something that is new, it may increase the overall life expectancy of that product.

Basic Metallurgy

Before you can weld or hardface, you first need to identify the parent metal. A good rule of thumb on the farm is that nothing is mild steel. Almost all implements are high strength steels (either high or low alloy) and many are higher carbon steels. But how do you tell the difference? There are a couple of tests that can help.

Welding and FarmingThe first is a magnetic test. If a magnet will stick to the implement then it is likely iron-based. A magnet that will not stick indicates probably a manganese or stainless product. Secondly, try the spark test. If you take a grinder to the item, do you get 30″ long, moderately large volume of yellow sparks with just a few sprigs and/or forks indicating mild steel, or do you achieve 25″ long, slight to moderate volume of yellow orange sparks, a few forks with intermittent breaks but few if any sprigs to indicate alloy steels or do you get 15″ long short, red sparks in large volume with numerous and repeating sprigs, which are telltale signs of a high carbon metal? Another test, the chisel test, will help indicate the type of metal as well. If the metal fractures in large chunks when you take a chisel to it, this means you have cast iron, which can be very difficult to weld unless using special high-nickel electrodes and heat-treating. On the other hand, if the chisel yields corkscrew-like shavings, you are looking at a weldable steel.

What Is the Goal?

Now that you have identified the base material, you need to assess your final goal. In a farm type setting, you need to ascertain whether you need to strengthen the item or prevent wear? If the item in question is a hitch bar on a tractor, the ultimate goal is strength and ductility so that it will not break. WELD IT! If you are talking about an earth-engaging tool, you don’t want it to wear out. HARDFACE IT!

Identify What Method to Use

There are three types of welding methods to consider. They differ by speed and cost. The methods are all available to all welding and hardfacing products. However, specific products often have properties that are somewhat unique and not exactly duplicated when utilized by a different process.

Stick Welding

Manual or stick welding requires the least amount of equipment and provides maximum flexibility for welding in remote locations and in all positions. Typically, each rod permits welding for about one minute. In seconds, one can change from mild steel to stainless to hardfacing. In seconds, the electrode can change from small to large diameter for small or large welds. Although simplest, this type of welding takes the greatest operator skill.

Semiautomatic

This type of welding uses wire feeders and continuously fed electrodes. The welding gun is hand-held by the operator. The gun keeps feeding wire as long as the trigger is depressed. This is also much easier to learn than stick welding. This type of setup is becoming more popular on farms, which do more than minimal repair work. Semiautomatic welding increases deposition rates over manual welding because there is no need to stop after burning each rod.

Automatic

Requiring the greatest amount of initial setup, automatic welding has the highest deposition rates for maximum productivity. The welding gun is carried by a mechanized carriage and the welding operator just pushes a start button. This would rarely be found on a farm, but is common at repair centers for heavy equipment that would rebuild your parts for you if the schedule was mutually acceptable.

Welding Procedures

There are five basic steps when welding that must be followed.Welding and Farming

  • Proper Preparation – You first need to ensure that the metal you are welding is clean and dry. Remove rust, dirt, grease, oil and other contaminants by wire brushing. If not removed, these contaminants can cause porosity, cracking and poor weld deposit quality. You must also remove badly cracked, deformed or work-hardened surfaces by grinding, machining or carbon-arc gouging.
  • Proper Preheat – The combination of alloy content, carbon content, massive size and part rigidity creates a necessity to preheat in many welding or hardfacing operations. Most applications require preheating, as a minimum to bring the part to a room temperature of 70ƒ-100ƒ F. Medium to high carbon and low alloy steels may require higher preheat to prevent underbead cracking, welding cracking or stress failure of the part. Preheating can be done with either a torch, oven or electrical heating device. Special temperature-melting crayons can help you verify proper preheat. Too much heat and you can often ruin alloy materials!
  • Adequate Penetration – Correct Welding Procedure – Identify the correct amperage, travel speed, size of weld, polarity, etc. Make sure the completed weld meets your expectations in regards to size and appearance. Welds should be smooth and uniform, free from undercut or porosity. If possible, watch a video showing the type of welding you will be doing so you know what things are suppose to look like.
  • Proper Cool Down – Preheating is the most effective way of slowing the cooling rate of massive or restrained parts, which are inherently crack sensitive. Insulating the part immediately after welding with dry sand, lime, or a glass fiber blanket also helps minimize residual cooling stresses, weld cracking and distortion. Never quench a weld with ice or water as this will lead to greater internal stresses and potentially weld cracking.
  • Post Weld Heat Treatment – Some items may require tempering or heat-treating. What this means is that you warm the item up with your torch after welding and allow it to slowly cool.

Safety

There are a few rules you should follow as you are welding/hardfacing:
Welding and Farming

  • Protect yourself from fumes and gases – Always weld in an open, well-ventilated room and keep your head out of the fumes – especially with hardfacing
  • Wear protective clothing – Protect your eyes and face with a welding helmet designed for arc welding, not just gas welding goggles. In the same manner, protect your body from weld spatter and arc flash with woolen or cotton clothing, a flameproof apron and gloves, and boots. Also make sure to protect others around you from the arc rays as well.
  • Beware of electric shock – Do not touch live electrical parts and make sure that your welding machine is properly grounded. Never weld if you are wet or if your gloves have holes in them.
  • Fire/explosion hazard – Never weld in an enclosed space or near hay, feed bags, gasoline, diesel, hydraulic fluids or anything else that can be within the reach of your welding sparks that would cause a fire or explosion. Never weld alone. Always have a buddy nearby in case of an emergency.

Conclusion

After reading this article, you should be able to reap the benefits of welding in much the same way as you already reap the benefits of the earth on your farm.

Selecting Your Welding Process

Sure, you know you have a weld to make. . .that’s the easy part. . . but you need to start by examining your application.. Everybody’s job is individual and has specific requirements. Therefore, if you’re really confused the best idea is to consult a welding expert in person. If you still have questions after reading this article, just ask us online.

However, this article can help you with welding process selection in four easy steps:

1.) The joint to be welded is analyzed in terms of its requirements.

2.) The joint requirements are matched with the capabilities of available processes. One or more of the processes are selected for further examination.

3.) A checklist of variables is used to determine the ability of the selected processes(s) to meet the particular application.

4.) Finally, the proposed process or processes deemed most efficient are reviewed with an informed representative of the equipment manufacturer for verification of suitability and for more information

Step 1 – Analysis of Joint Requirements.

The first thing to look at is whether your weld joint is large or small, whether the joint is out-of-position or not, and whether the base metal is thick or thin.

In welding, the needs of any joint are expressed in four terms: Fast-Fill (high deposition rate), Fast-Freeze (the joint is out-of-position – overhead or vertical), Fast-Follow (high arc speed and very small welds), and Penetration (the depth the weld penetrates the base metal)

Fast-Fill is required when a large amount of weld metal is needed to fill the joint. A heavy weld bead can only be laid down in minimum arc time with a high deposition rate. However, Fast-Fill becomes a minor consideration when the weld is small.

Fast-Freeze implies that a joint is out-of-position, and therefore requires quick solidification of the molten crater. Not all semiautomatic processes can be used on fast-freeze joints.

Fast-Follow suggests that the molten metal follows the arc at rapid travel speed, giving continuous, well-shaped beads, without “skips” or islands. This trait is especially desirable on relatively small single-pass welds, such as those used in joining sheet metal.

Penetration varies with the joint. With some joints, penetration must be deep to provide adequate mixing of the weld and base metal and with others it must be limited to prevent burnthrough or cracking.

Any joint can be categorized in terms of the previously mentioned four factors. To determine the appropriate welding process, keep your efforts focused on the requirements of the weld joint. A joint that requires, or can be welded by, just one arc welding process is rare. In fact, the majority of joints usually are characterized
by a combination of these requirements to varying degrees. Once you’ve determined your appropriate joint requirements and ranked them, have your assessment reviewed by an experienced engineer or welder. With time and experience, you’ll be able to make these assessments more accurately and with less difficulty.

Step 2 – Matching Joint Requirements With Processes

Your equipment manufacturers’ literature usually will give information on the ability of various processes to fulfill the needs of the joint. (Or, a telephone call or email will bring the needed information.) A wrong answer is virtually impossible at this point, since the deposition rate and arc-speed characteristics of each process can be clearly defined. Since you have characterized your weld joint it is simply a matter of selecting the process that suits your characterization. To view some machines and consumables with various characteristics click here to view Lincoln Electric’s product line.

So what do you do when you find that two or more processes are suitable, which is sometimes the case? You create a checklist!

Step 3 – The Checklist

Considerations other than the joint itself have a bearing on selection decisions. Many of these are specific to your job or welding shop. However, they can be of great importance – and a key factor in eliminating alternate processes. Organize these factors into a checklist and consider them one-by-one:

Volume of Production. You must justify the cost of welding equipment by the amount of work, or productivity, required. Or, if the work volume for one application is not great enough, another application may be found to help offset the costs.

Weld Specifications. Rule out a process if it does not provide the weld properties specified by the code governing the work.

Operator Skill. Operators may develop skill with one process more rapidly than another. Will you have to train your operators in a new process? That adds cost!

Auxiliary Equipment. Every process has a recommended power source and other items of auxiliary equipment. If a process makes use of existing auxiliary equipment, the initial cost in changing to that process can be substantially reduced.

Accessory Equipment. Availability and cost of necessary accessory equipment – chipping hammers, deslagging tools, flux lay-down and pickup equipment, exhaust systems, et cetera – should be taken into account.

Base-Metal Conditions. Rust, oil, fit-up of the joint, weldability of the steel, and other conditions must be considered. These factors could limit the usefulness of a particular process.

Arc Visibility. Is there a problem following irregular seams? Then open-arc processes are advantageous. On the other hand, if there’s no difficulty in correct placement of the weld bead, there are “operator-comfort” benefits with the submerged-arc process; no head-shield required and heat from the arc is reduced.

Fixturing Requirements. A change to a semiautomatic process requires some fixturing if productivity is to be realized. Appraise the equipment to find out if it can adapt to processes.

Production Bottlenecks. If the process reduces unit fabrication cost, but creates a production bottleneck, its value is lost. Highly complicated equipment that requires frequent servicing by skilled technicians may slow up your actual production thereby diminishing its value.

The completed checklist should contain every factor known to affect the economics of the operation. Some may be specific to the weld job or weld shop. Other items might include:

  • Protection Requirements
  • Range of Weld Sizes
  • Application Flexibility
  • Seam Length
  • Setup Time Requirements
  • Initial Equipment Cost
  • Cleanliness Requirements

Evaluate these items realistically recognizing the peculiarities of the application as well as those of the process, and the equipment.

Human prejudice should not enter the selection process; otherwise objectivity is lost – when all other things are equal, the guiding criterion should be overall cost.

Step 4 – Review of the Application by Manufacturer’s Representative.

This may seem redundant, but the talents of experts should be utilized. Thus, the checklist to be used is tailored by the user to his individual situation. You know your application best and your welding expert knows his equipment best. Together, you should be able to confirm or modify the checklist. To contact a Lincoln Electric welding Expert click here.

Systemizing the Systematic Approach.

A system is of no value unless it is used. Create a chart and follow the steps to determining process. By taking the time to analyze each new weld joint, your operation will become more productive and your welding experience will be more fulfilling.

Source: Adapted from The Procedure Handbook of Arc Welding. The Lincoln Electric Company, 1994.

To order a copy of Lincoln Electric’s Procedure Handbook of Arc Welding or other welding textbooks and educational aids, click here to print out and fax an order form.

Arc-Welding Fundamentals
The Lincoln Electric Company, 1994.

Arc welding is one of several fusion processes for joining metals. By applying intense heat, metal at the joint between two parts is melted and caused to intermix – directly, or more commonly, with an intermediate molten filler metal. Upon cooling and solidification, a metallurgical bond is created. Since the joining is an intermixture of metals, the final weldment potentially has the same strength properties as the metal of the parts. This is in sharp contrast to non-fusion processes of joining (i.e. soldering, brazing etc.) in which the mechanical and physical properties of the base materials cannot be duplicated at the joint.

Fig. 1 The basic arc-welding circuit

In arc welding, the intense heat needed to melt metal is produced by an electric arc. The arc is formed between the actual work and an electrode (stick or wire) that is manually or mechanically guided along the joint. The electrode can either be a rod with the purpose of simply carrying the current between the tip and the work. Or, it may be a specially prepared rod or wire that not only conducts the current but also melts and supplies filler metal to the joint. Most welding in the manufacture of steel products uses the second type of electrode.

Basic Welding Circuit

The basic arc-welding circuit is illustrated in Fig. 1. An AC or DC power source, fitted with whatever controls may be needed, is connected by a work cable to the workpiece and by a “hot” cable to an electrode holder of some type, which makes an electrical contact with the welding electrode.

An arc is created across the gap when the energized circuit and the electrode tip touches the workpiece and is withdrawn, yet still with in close contact.

The arc produces a temperature of about 6500ºF at the tip. This heat melts both the base metal and the electrode, producing a pool of molten metal sometimes called a “crater.” The crater solidifies behind the electrode as it is moved along the joint. The result is a fusion bond.

Arc Shielding

However, joining metals requires more than moving an electrode along a joint. Metals at high temperatures tend to react chemically with elements in the air – oxygen and nitrogen. When metal in the molten pool comes into contact with air, oxides and nitrides form which destroy the strength and toughness of the weld joint. Therefore, many arc-welding processes provide some means of covering the arc and the molten pool with a protective shield of gas, vapor, or slag. This is called arc shielding. This shielding prevents or minimizes contact of the molten metal with air. Shielding also may improve the weld. An example is a granular flux, which actually adds deoxidizers to the weld.

Fig. 2 This shows how the coating on a coated (stick) electrode provides a gaseous shield around the arc and a slag covering on the hot weld deposit.

Figure 2 illustrates the shielding of the welding arc and molten pool with a Stick electrode. The extruded covering on the filler metal rod, provides a shielding gas at the point of contact while the slag protects the fresh weld from the air.

The arc itself is a very complex phenomenon. In-depth understanding of the physics of the arc is of little value to the welder, but some knowledge of its general characteristics can be useful.

Nature of the Arc

An arc is an electric current flowing between two electrodes through an ionized column of gas. A negatively charged cathode and a positively charged anode create the intense heat of the welding arc. Negative and positive ions are bounced off of each other in the plasma column at an accelerated rate.

In welding, the arc not only provides the heat needed to melt the electrode and the base metal, but under certain conditions must also supply the means to transport the molten metal from the tip of the electrode to the work. Several mechanisms for metal transfer exist. Two (of many) examples include:

  1. Surface Tension Transfer – a drop of molten metal touches the molten metal pool and is drawn into it by surface tension.
  2. Spray Arc – the drop is ejected from the molten metal at the electrode tip by an electric pinch propelling it to the molten pool. (great for overhead welding!)

If an electrode is consumable, the tip melts under the heat of the arc and molten droplets are detached and transported to the work through the arc column. Any arc welding system in which the electrode is melted off to become part of the weld is described as metal-arc. In carbon or tungsten (TIG) welding there are no molten droplets to be forced across the gap and onto the work. Filler metal is melted into the joint from a separate rod or wire.

More of the heat developed by the arc is transferred to the weld pool with consumable electrodes. This produces higher thermal efficiencies and narrower heat-affected zones.

Since there must be an ionized path to conduct electricity across a gap, the mere switching on of the welding current with an electrically cold electrode posed over it will not start the arc. The arc must be ignited. This is caused by either supplying an initial voltage high enough to cause a discharge or by touching the electrode to the work and then withdrawing it as the contact area becomes heated.

Arc welding may be done with direct current (DC) with the electrode either positive or negative or alternating current (AC). The choice of current and polarity depends on the process, the type of electrode, the arc atmosphere, and the metal being welded.

X RAY DIFFRACTION

August 23, 2011

It’s useful for studying Crystal structure

This method have the details about

    • Grain size (or) Crystal size
    • Orientation of the crystal
    • Cold worked, Distorted and Internally stressed crystals
    • Re-Crystallization
    • Preferred orientation etc

Methods of Examining and Measuring the condition of Crystal Structure

    1. The Laue back reflection method
    2. The Rotating Crystal method
    3. The DeBye- Scherrer (or) Powder method:

The Laue back Reflection method:

It’s applicable to single crystals (or) poly-Crystalline masses.

When a beam of Mono chromatic (i.e. of Single Wavelength) X-Ray is directed as a narrow pencil at a specimen of a metal diffraction takes place at certain of the crystallographic planes.


03-laue method- x-rays sheild

01-laue back reflection- method-X-ray-diffraction

01-electron-waves-travel-x-rays03-LaueBack reflection

02-lauemethod

The Rotating Crystal method:

It’s a useful method for determining angles and positions of planes.

Crystallographic planes are brought in to reflecting positions by rotating a crystal (Specimen) about one of it’s axis while simultaneously radially it with a beam of mono chromatic x-Rays.

If crystal orientation planes are known, the angles and directions can be calculated.

04-rotating-crytal-method-x-ray-diffration-crystal-structure

05-diffractometer-x ray detector-rotation crystal

The DeBye- Scherrer (or) Powder method:

The narrow pencil of monochromatic X-Rays is diffracted from the powder and recorded by the photographic film as a series of lines of varying armature.

By the Bragg Equation:

nλ=2d Sinθ

Where,

λ– Wave length of X-ray

d- Spacing of the atomic planes

θ – Angle of reflection

06-debye-scherrer-powder-method

 

 

 

 

 

07-debye-scherrer-powder-method

X RAY DIFFRACTION

August 23, 2011

It’s useful for studying Crystal structure

This method have the details about

    • Grain size (or) Crystal size
    • Orientation of the crystal
    • Cold worked, Distorted and Internally stressed crystals
    • Re-Crystallization
    • Preferred orientation etc

Methods of Examining and Measuring the condition of Crystal Structure

    1. The Laue back reflection method
    2. The Rotating Crystal method
    3. The DeBye- Scherrer (or) Powder method:

The Laue back Reflection method:

It’s applicable to single crystals (or) poly-Crystalline masses.

When a beam of Mono chromatic (i.e. of Single Wavelength) X-Ray is directed as a narrow pencil at a specimen of a metal diffraction takes place at certain of the crystallographic planes.


03-laue method- x-rays sheild

01-laue back reflection- method-X-ray-diffraction

01-electron-waves-travel-x-rays03-LaueBack reflection

02-lauemethod

The Rotating Crystal method:

It’s a useful method for determining angles and positions of planes.

Crystallographic planes are brought in to reflecting positions by rotating a crystal (Specimen) about one of it’s axis while simultaneously radially it with a beam of mono chromatic x-Rays.

If crystal orientation planes are known, the angles and directions can be calculated.

04-rotating-crytal-method-x-ray-diffration-crystal-structure

05-diffractometer-x ray detector-rotation crystal

The DeBye- Scherrer (or) Powder method:

The narrow pencil of monochromatic X-Rays is diffracted from the powder and recorded by the photographic film as a series of lines of varying armature.

By the Bragg Equation:

nλ=2d Sinθ

Where,

λ– Wave length of X-ray

d- Spacing of the atomic planes

θ – Angle of reflection

06-debye-scherrer-powder-method

 

 

 

 

 

07-debye-scherrer-powder-method

METALLURGY

August 23, 2011

Definition:

The Process of producing components from metallic powder parts made by powder metallurgy may contain non-metallic constituents to improve the bonding qualities and properties.

Number and variety of products made by powder metallurgy are continuously increasing:

    1. Tungsten Filaments for Lamps
    2. Contact Point relays
    3. Self lubricating bearings
    4. Cemented carbides for cutting tools etc.

02-PowderManufacturing-metallurgy-particles

 

Characters of Metal Powders:

  • Shape:

It is influenced by the way it’s made. The shape may be spherical (atomization) (Electrolysis) flat or angular (Mechanical crushing). The particle shape influences the flow characteristics of powders.

  • Particle Size (Fineness) and size distribution:

Particle Size and Distribution are important factors which controls the porosity, Compressibility and amount of shrinkage. Proper particle size and size distribution are determined by passing the powder through a standard sieves ranging from 45 to 150 micrometer mesh.

  • Flowability:

The ability of the powders to flow readily and conform to the mould cavity. The flow rate helps to determine to possible production rate.

  • Compressibility:

It’s defines as the volume of initial powder (Powder loosely filled in cavity) to the volume of compact part. Depends on particle shape & size distribution.

  • Apparent Density:

The Apparent density depends on particle size is defined as the ratio of volume to weight of loosely filled mixture.

  • Green strength:

It refer to strength of a compact part prior to sintering. It depends on compressibility and helps to handle the parts during the mass production.

  • Purity:

Impurities affects sintering & Compacting Oxides & Gaseous impurities can be removed from the part during sintering by the use of a reducing atmosphere.

  • Sintering ability:

It is the ability which promotes bonding of particles by the application of heat.

 

Powder Metallurgy Process steps:

 

01-powder-metallurgy-process-step by step


 

01-powder metallurgy processes-mixing-finished product

 

02-finished product 

Manufacture of Metal Powders:

Methods:

  • Mechanical pulverization:

Machining, Drilling or Grinding of metals is used to convert them to powders.

  • Machining:

It Produces coarse particles (Flack form) especially Magnesium powders.

  • Milling or Grinding:

It suitable for brittle materials.

  • Shorting:

The process of dropping molten metal through a Sieve or small orifice in to water. This produces Spherical particles or larger size. Commonly used for metals of low melting point.

03-mechanical pulverization-milling-powder

04-crushing-shredding-conveyors-powder

 

  • Atomizing:

In this molten metal is forced through a nozzle, and a stream of compressed air, stream or Inert gas is directed on it break up into five particles. Powders obtained in irregular in shapes. Atomization commonly used for aluminium, Zinc, Tin, Cadmium and other metals of low melting point.

03-atomization-powder metallurgy

 

  • Electrolytic deposition:

It’s used mainly for producing iron and copper powders. These are dense structure with low apparent density. It consists of depositing metal on cathode plate by conventional electrolysis processes. The Cathode paltes are removed and the deposited powder is scraped off. The powder is wasted, dried, screened & oversized particles are milled or ground for fineness. The powder is further subjected to heat treatment to remove the work hardening effect.

  • Chemical reduction:

It’s used for producing iron, Copper, Tungsten, Molybdenum, Nickel & Cobalt powder process consists of reducing the metal oxides by means of carbon monoxide or Hydrogen. After reduction, the powder is usually ground & Sized.

 

Forming to shape:

    1. The process of mixing the powders is called Blending.
    2. The Loose powders are formed in to shape by compacting.

METALLURGY

August 23, 2011

Definition:

The Process of producing components from metallic powder parts made by powder metallurgy may contain non-metallic constituents to improve the bonding qualities and properties.

Number and variety of products made by powder metallurgy are continuously increasing:

    1. Tungsten Filaments for Lamps
    2. Contact Point relays
    3. Self lubricating bearings
    4. Cemented carbides for cutting tools etc.

02-PowderManufacturing-metallurgy-particles

 

Characters of Metal Powders:

  • Shape:

It is influenced by the way it’s made. The shape may be spherical (atomization) (Electrolysis) flat or angular (Mechanical crushing). The particle shape influences the flow characteristics of powders.

  • Particle Size (Fineness) and size distribution:

Particle Size and Distribution are important factors which controls the porosity, Compressibility and amount of shrinkage. Proper particle size and size distribution are determined by passing the powder through a standard sieves ranging from 45 to 150 micrometer mesh.

  • Flowability:

The ability of the powders to flow readily and conform to the mould cavity. The flow rate helps to determine to possible production rate.

  • Compressibility:

It’s defines as the volume of initial powder (Powder loosely filled in cavity) to the volume of compact part. Depends on particle shape & size distribution.

  • Apparent Density:

The Apparent density depends on particle size is defined as the ratio of volume to weight of loosely filled mixture.

  • Green strength:

It refer to strength of a compact part prior to sintering. It depends on compressibility and helps to handle the parts during the mass production.

  • Purity:

Impurities affects sintering & Compacting Oxides & Gaseous impurities can be removed from the part during sintering by the use of a reducing atmosphere.

  • Sintering ability:

It is the ability which promotes bonding of particles by the application of heat.

 

Powder Metallurgy Process steps:

 

01-powder-metallurgy-process-step by step


 

01-powder metallurgy processes-mixing-finished product

 

02-finished product 

Manufacture of Metal Powders:

Methods:

  • Mechanical pulverization:

Machining, Drilling or Grinding of metals is used to convert them to powders.

  • Machining:

It Produces coarse particles (Flack form) especially Magnesium powders.

  • Milling or Grinding:

It suitable for brittle materials.

  • Shorting:

The process of dropping molten metal through a Sieve or small orifice in to water. This produces Spherical particles or larger size. Commonly used for metals of low melting point.

03-mechanical pulverization-milling-powder

04-crushing-shredding-conveyors-powder

 

  • Atomizing:

In this molten metal is forced through a nozzle, and a stream of compressed air, stream or Inert gas is directed on it break up into five particles. Powders obtained in irregular in shapes. Atomization commonly used for aluminium, Zinc, Tin, Cadmium and other metals of low melting point.

03-atomization-powder metallurgy

 

  • Electrolytic deposition:

It’s used mainly for producing iron and copper powders. These are dense structure with low apparent density. It consists of depositing metal on cathode plate by conventional electrolysis processes. The Cathode paltes are removed and the deposited powder is scraped off. The powder is wasted, dried, screened & oversized particles are milled or ground for fineness. The powder is further subjected to heat treatment to remove the work hardening effect.

  • Chemical reduction:

It’s used for producing iron, Copper, Tungsten, Molybdenum, Nickel & Cobalt powder process consists of reducing the metal oxides by means of carbon monoxide or Hydrogen. After reduction, the powder is usually ground & Sized.

 

Forming to shape:

    1. The process of mixing the powders is called Blending.
    2. The Loose powders are formed in to shape by compacting.

MECHANICAL TESTING

August 23, 2011

Various tests:

  • Tensile Test

A tensile test, also known as a tension test, tests a material’s strength. It’s a mechanical test where a pulling force is applied to a material from both sides until the sample changes its shape or breaks. It’s is a common and important test that provides a variety of information about the material being tested, including the elongation, yield point, tensile strength, and ultimate strength of the material. Tensile tests are commonly performed on substances such as metals, plastics, wood, and ceramics.

01-Electronic_Tensile_Testing_Machine-calculate tensile strength-yield strength-ultimate strength-break value-elongation-testing steels, iron, plastics and composite materials

Tensile testing systems use a number of different units of measurement. The International System of Units, or SI, recommends the use of either Pascals (Pa) or Newtons per square meter (N/m²) for describing tensile strength. In the United States, many engineers measure tensile strength in kilo-pound per square inch (KSI).

01-TensileStrength-tensile test-Calculate Ultimate tensile strength-tensile property testing of plastics, steel, iron-material strength calculate - pascals - newton per square meter

  • Tensile test with electronic extensometer

01-electronic_extensometer-calculate proof stress - youngs modulus values-material stress-acccepts load-extension value

This instrument is to be used on Tensile or Universal testing machines to find out Proof stress & Young’s modulus values. In case of many brittle materials such as high carbon steels, alloy steels, light aluminium & magnesium alloys, it is difficult to get yield values. For such materials stress corresponding to a certain allowable amount of plastic deformation is termed as proof stress say 0.1% or 0.2% proof stress. The measuring range is up to 5mm & resolution is 0.001mm.

01-mechanical_extensometer-tensile test calculation-universal testing machine-utm

  • Tensile testing at elevated temperature.

01-tensile test at elevated temperature-high temperature tensile test-specialist tensile test

High temperature tensile testing is a procedure to test the properties of a material at above room temperature. It will determine the following parameters:

  • Tensile strength (breaking strength)
  • Yield strength
  • Elongation
  • Reduction of area

Specialist testing, measurement and control equipment is required to perform this test.
The results of such a test will provide a good indication of the static load bearing capacity of the material and therefore establishes the suitability of a material for its intended purpose.

  • Tensile test on Tor steel Bars

01-tor-steel-bar-rods-TMT steel Bars-concrete technology-durable-corrosion resistant-engineering and construction

TOR steel is one of the best grade of steel used in concrete reinforced. It’s a kind of high adherence steel. Other types of steel are used for less resistance concrete. Thermo mechanically Treated (TMT) bars are a type of corrosion resistant steel reinforcing bar used in concrete construction.

  • Bend test on plates

01-bend test on steels- cold bars -cold bend testing for steels

A bend test is used to determine whether a specific piece of metal in question will break or fracture under pressure. This is important in the construction of any project using metal, otherwise the building or the item being made could collapse from the immense pressure exerted on it. Every piece of metal made cannot be tested, therefore certain pieces are tested and if they pass, the other pieces are made using the same process. The results of a bend test are reported differently depending on the type of material tested. There is no standard method for reporting the durability that applies to all materials, rather each group has its own set by which it is judged and compared to other metals in that group.

The bend test is essentially measuring a metal’s ductility. Ductility defines how easily a metal can bend without breaking. The higher the ductility of a metal, the more it can bend without breaking or becoming deformed from its original shape. This is important because certain metals must handle pressure without snapping yet still be ductile enough to bend slightly and not lose their support or shape. Copper and steel are two metals that have a high ductility and do well under pressure.

  • Bend test on pipes

01-bend test on pipes

Bending tests are carried out to ensure that a metal has sufficient ductility to stand bending without fracturing. A standard specimen is bent through a specified arc and in the case of strip, the direction of grain flow is noted and whether the bend is with or across the grain.

  • Bend Test on Tor steel

01-wire-rods-rebend test on steels

The purpose is to make certain the weld and the base metal are properly fused, and that the weld metal and the heat affected zone (HAZ) have appropriate mechanical properties

  • Re-Bend test on Tor steel

01-wire-rods-rebend test on steels

The purpose of re-bend test is to measure the effect of strain ageing on steel. Strain ageing has embrittlement effect which takes place after cold deformation by diffusion of nitrogen in steel. Hence, there is limitation stated in some design codes to restrict the nitrogen content of steel to 0.012%.

  • Nick Break Test

01-nick break test-welding-fabrication-on sheets

The NICK-BREAK TEST is useful for determining the internal quality of the weld metal. This test reveals various internal defects (if present), such as slag inclusions,  gas  pockets,  lack of  fusion,  and  oxidized  or burned metal. To accomplish the nick-break test for checking a butt weld, you must first flame-cut the test specimens from a sample weld.