Welding: tips and tricks to master this technique

laser welder

La welding is not easy. When starting out, it is normal to make many mistakes, such as imperfect joints, sticking the electrode to the metal, not adjusting the amperage correctly, piercing the metal, etc. However, with these tips and tricks on this technique, you will be able to learn to use your welding machine properly, since in the previous article I taught you everything you need to know to choose the right one.

I invite you to become a good welder for your DIY projects with metal and thermoplastics with this guide…

weld definition

welding

La welding represents a joining procedure that connects two or more parts of a material by fusion. Generally, these materials are metals or thermoplastics, which are what allow this type of joint. In this process, the parts are joined by being melted, and sometimes an additional material (metal or plastic) is introduced which, when melted, creates something known as a "solder pool" which is the deposited material that joins the parts together. Once the material cools and solidifies, it forms a strong bond called a 'bead'.

Various Energy sources, such as a gas flame, an electric arc, a laser, an electron beam, friction methods or ultrasonics, can be used to carry out welding. In general, the energy needed to join metal parts comes from an electric arc, while thermoplastics are joined through direct contact with a tool or through the use of a hot gas. Also, while welding is often done in industrial settings, it is also possible to do it in a variety of somewhat more inhospitable places, such as underwater and even in space.

types of welding

La soldering and brazing are two joining techniques used in the industry to connect pieces of metal or other materials. Although both involve the melting of a material to form a bond, there are key differences between them in terms of temperature, materials, and resulting properties.

  • Soft Solder: It is a process in which a low melting point solder is used to join workpieces. The melting temperature of solder is relatively low, typically below 450°C, which allows the material to melt without significantly affecting work pieces. Soldering is commonly used to join electronic components, plumbing pipes, and other applications where a delicate, non-high temperature resistant joint is required. For example, a type of soft solder can be the one used in electronics and plumbing with tin, or also the one used for thermoplastics.
  • Brazing: It is a joining process in which a filler material with a higher melting point is used than in soft soldering, generally between 450°C and 900°C. In this process, the work pieces are not cast, but the filler material is melted and introduced into the joint between the pieces. Once the filler material solidifies, it creates a strong and lasting connection. Brazing is used to join parts that need to withstand mechanical loads and high temperatures, such as in the manufacture of tools, vehicles, structures, etc. Examples of this type of welding is the one used for metals such as steel, iron, aluminum, etc.

Materials that can be welded (weldability)

metals

La weldability Refers to the ability of materials, whether similar or dissimilar in nature, to be permanently connected by welding procedures. Although, generally speaking, most metals can be welded, each metal has its own uniqueness, characterized by specific qualities that carry particular advantages and disadvantages. Factors that determine the weldability of a metal include the type of electrode used, the rate at which it cools, the use of shielding gases, and the speed with which the welding process is executed.

The same happens with plastics, not all of them can be welded, only thermoplastics, which are the ones that allow this type of process. Others, such as thermosets or elastomers, do not admit welding. Although there may be techniques to repair or join parts using adhesives, etc.

Weldable metals

Between the metals that can be welded we find the following:

  • Steels (stainless steel, carbon steel, galvanized steel,…)
  • Molten iron.
  • Aluminum and its alloys.
  • Nickel and its alloys.
  • Copper and its alloys.
  • Titanium and its alloys.

In addition, we have to classify these weldable metals according to different criteria, such as electrical resistance or conductivity they have, since this is important when soldering:

  • High electrical resistance/low electrical conductivity metals: they can be welded with low intensities (low currents), like steel.
  • Low electrical resistance/high electrical conductivity metals: they weld at high intensities, that is, they need more amperage. Examples of these metals are aluminum, copper, and other alloys.

On the other hand we can classify according to the type of metal:

  • Metals with Ferrous composition: ferrous metals, those in which iron is the preeminent element, exhibit remarkable attributes of tensile strength and hardness.
    • Steel: It has iron as its base, it is distinguished by its malleability, resistance and versatility. This metal is an excellent conductor of heat and electricity, making it ideal for various welding techniques. Despite these qualities, steel has limitations, such as its considerable weight and its susceptibility to rust. It is common to find variations with carbon, with higher concentrations of the latter strengthening the steel and making it more hardenable. However, weldability decreases in inverse proportion to hardenability. It is vital to maintain the cleanliness of the weld and to avoid scaling due to the tendency of steel to rust. High strength steels are the most suitable for welding processes.
    • Cast iron or cast iron: Obtained from the first smelting of iron in blast furnaces, it contains notable amounts of carbon and silicon, and is brittle. Although welding cast iron presents difficulties, it is not impossible. Any trace of oil or grease must be avoided during the welding process, as this could complicate the work. Welding cast iron is a complicated and expensive procedure that requires high temperatures and preheating with an oxyacetylene torch. Otherwise, the resulting weld will be unstable and difficult to handle. For these reasons, this task is not appropriate for hobbyists.
  • Nonferrous metals: are those whose composition does not include iron, are grouped into three main categories:
    • Heavy Metals (density equal to or greater than 5 Kg/dm³):
      • Tin: used in the manufacture of tinplate and in the electronics industry.
      • Copper: with outstanding electrical and thermal conductivity, resistant to corrosion. It requires maintaining impeccable welding to prevent the formation of oxides. Used in the manufacture of electrical cables, pipes, etc.
      • Zinc: has the maximum thermal expansion among metals. Used in the manufacture of sheets, deposits, etc. It is also used as a surface treatment to galvanize steel.
      • Lead: used in soft welds and coatings, as well as in pipes, although it has fallen into disuse due to its toxicity.
      • Chrome: used in the manufacture of stainless steels and tools.
      • Nickel: applied as a coating on metals and in the production of stainless steels.
      • wolfram: used to manufacture cutting tools in machines.
      • Cobalt: used in the manufacture of strong metals.
    • light metals (density between 2 and 5 Kg/dm³):
      • Titanium: It stands out in this category and is used in the aeronautical and turbine industries.
    • Ultralight metals (density less than 2 Kg/dm³):
      • Magnesium: Used as a deoxidizer in steel foundry, it excels in this extremely low density category.

Weldable Plastics

The thermoplastic are polymers characterized by their ability to undergo melting and solidification cycles practically uninterrupted. When subjected to heat, they become liquid and, when cooled, they recover their rigidity. However, upon reaching the freezing point, thermoplastics acquire a glassy structure and fracture. These particularities, which give the material its identity, present a reversible behavior, allowing the material to be subjected to heating, remodeling and cooling cycles on a recurring basis.

Some examples of thermoplastics are:

  • PET (Polyethylene Terephthalate): It belongs to the polyesters, is widely used in everyday items and is easily recyclable. Its semicrystalline form is stable. It is common in rigid and flexible packaging due to its lightness.
  • HDPE (High Density Polyethylene): It is very versatile, derived from petroleum. It is used in bottles, jugs, cutting boards and pipes, noting for its resistance and melting point.
  • LDPE (Low Density Polyethylene): polyethylene is soft, resistant and flexible, especially in low temperatures. It has good chemical and impact resistance, with a melting point of 110°C.
  • PVC (Polyvinyl Chloride): used in construction, piping, cable insulation, medical devices and more. It is versatile, economical and is replacing traditional materials.
  • PP (Polypropylene): It is a rigid, resistant and low-density polymer. It is used in bags, engineering applications, and bottle blow molding. It is the second most produced plastic.
  • PS (Polystyrene): Styrofoam is transparent and is used in consumer products and commercial packaging. It can be solid or foamy, used in medical devices, casings, and food packaging.
  • Nylon: It is a resistant, elastic and transparent polyamide. It is used in fishing, textiles, ropes, instruments, gears, stockings, etc., and melts at high temperatures (263ºC).

Some of these will also sound familiar to you from our articles about 3D printers, since they are used for these additive manufacturing applications.

What is scum?

solder slag

La human waste Solder is a non-metallic residue generated from certain welding methods. It originates when the flux material used in welding hardens once the process is finished. This dross is the result of the combination of the flux and undesirable substances or atmospheric gases that interact with it while soldering. The absence of flux and the slag that forms could cause oxidation of the solder.

In the welding of plastics, this slag that is typical of metals is not generated.

The slag usually remains on the weld seam, like a kind of brittle shell once it solidifies, and can be easily removed. If the weld is well done, with a few soft blows it usually comes off. However, it is also true that when welding begins, this slag is likely to become trapped within the bead, creating a brittle joint.

What is splash?

welder spatter

Hen/Stag splash Welding materials comprise minute droplets of molten metal or even non-metallic materials that are dispersed or ejected during the welding operation. These small hot particles can be ejected and land on the work surface or floor, while some can stick to the base material or any other nearby metal components. These splashes are easily recognizable, taking the form of small rounded spheres once they solidify.

They are not a major problem, but aesthetic level yes they can be. They may force additional treatments to remove those grains and leave a smooth surface.

How to weld properly

Soldering is a somewhat complex method, however, generic form, can be done in these steps (I recommend you watch the video for more graphic information):

  1. The first is prepare everything you need nearby, and have a safe work surface. This implies having a table or support where you can weld in a stable way, and in a place with ventilation. Also, avoid having flammable products nearby. Remember to prepare the welder with the appropriate electrode or wire, depending on the type of welding.
  2. Then you have to prepare the parts to be welded.. Many people make the big mistake of just soldering. But it is important to remove all dirt, rust, coatings such as paint, grease, etc., that the two surfaces to be joined may have. It is not necessary to clean the entire piece, but it is necessary to clean the area where the cord and the profiles will go.
  3. Connect the negative pole (ground or earth) to the piece to be welded. Thus, the necessary arc can be generated, since the terminal with the electrode or wire will be the positive pole. It is very important that the ground clamp is electrically connected to the part, otherwise it will not work. This can be connected directly to the piece or on other occasions, some use tables or metal supports that are the ones that connect to the ground. Therefore, all the metals in contact with this support will also be connected to ground.
  4. connect equipment to the mains and turn it on.
  5. Regulates the amperage necessary (we will explain this later in more detail).
  6. Put on protective equipment, such as gloves and mask.
  7. Now, with the electrode or thread, go touching the profiles to be welded, you must do it slowly and with a rocking movement. The electrode should form an angle of approximately 45º with the work surface. Also, remember to check the force with which you push the electrode, the speed, and if necessary adjust the amperage.
  8. At the end of the cord, hit it with a pick or hammer so that the cord detaches. scale (slag) and expose the bond metal.
  9. To finish, you may need treat the surface to leave it with better aesthetics, such as sanding the cord with a grinder, painting the surface so that it does not rust, etc.
  10. Once finished, remember to disconnect the equipment to avoid accidents. And don't forget that you can't touch the part, as it may have gotten quite hot.

Obviously, this process can change depending on the type of welding, and it will be even more different when it comes to welding thermoplastics…

regulate the intensity

Regulate current intensity, or amperage, is another of the fundamental issues to make a good weld. Many are very lost when they start welding when it comes to choosing amperage, but many times it is a matter of trial and error. However, to make things easier for you, here are two tables in which you can see the amps that you must select according to the thickness or thickness of the pieces to be welded and according to the electrode you have chosen. This can guide you, although then there may be slight differences depending on the welding machine chosen.

As a general rule, there is a easy trick to choose the amperage depending on the electrode, in case you do not have this table at hand. And it is simply multiplying the diameter of the electrode by x35, to obtain the maximum amps. For example, if we have a 2.5mm diameter electrode, it would be 2.5×35=87A, which rounded would be about 90A. Obviously, this rule does not work with wire welding machines...

Choosing the right electrodes / wire

Wire or continuous electrode

Choosing the right thread (also called continuous electrode) is a matter of taking into account the following aspects:

  • That the roll be compatible with the support of the welder, since you can find rolls of 0.5 kg, 1 kg, etc.
  • That the thread material is suitable for the union that you are going to do, according to the metal that you want to join.
  • That the thread thickness is adequate (0.8mm, 1mm,…), and this will depend on the width of the chord or the separation between the joints. A thicker thread will always be better for joints where there is more gap or more filler is needed.
  • Type welding wire or continuous electrode, where we have to differentiate between two different types:
    • Massive or solidThey are made up of a single metal. Generally, this metal has a similar composition to the base material, with the addition of some elements to improve the cleanliness of the substrate. These solid wires are frequently used to join low carbon steels and thin materials. Since they do not leave slag residue on the weld and cool down quickly, they are suitable for these applications.
    • tubular or core: they have a granular fluxing powder inside that fulfills a function similar to that of coated electrodes. These wires allow you to work without the need for a shielding gas during welding. They offer greater arc stability and deeper penetration, resulting in a superior joint finish due to a lower probability of defects and porosity. Cored wires are commonly used in thicker materials, since they generate slag on the bead and its cooling is slower. This characteristic makes them ideal for welding work on this type of material. However, it is important to mention that, as in MMA stick welding, slag removal is required when using cored wires.

consumable electrode

On the other hand we have consumable electrodes, in which we see a large number of types and diameters, so it becomes somewhat more complicated to choose the correct one. However, here we teach you:

Remember to keep the electrodes in a dry place. Moisture easily spoils them, producing a bad weld or not working.
  • Coating:
    • Coated: They are made up of a metallic core that fulfills the function of providing material during the welding process, together with a coating that contains various chemical substances. This lining performs two key functions: protecting the molten metal from the surrounding atmosphere and stabilizing the electrical arc. Within this type we have:
      • Rutile (R): they are covered by rutile or, what is the same, titanium oxide. They are easy to handle and ideal for welding thin as well as thick sheets of materials such as iron or mild steel. They are used in undemanding jobs, they are cheap, and quite common.
      • Basic (B): these are coated with calcium carbonate. As they are very resistant to cracks, they are perfect for welds of a certain complexity. Ideal for welding alloys. They are not that cheap or that easy to find.
      • Cellulosic (C): They are lined with cellulose or organic compounds. They are used, especially, in descending vertical and special type welding (such as gas pipelines), among other very demanding jobs.
      • From acid (A): silica, manganese and iron oxide are basic in the compound that covers these electrodes. They are used for work with a great thickness thanks to its great penetration. They can give cracks in cases where the base material is not suitable or does not have good characteristics to be welded.
    • not coated: they lack the protective layer, which limits their use to gas welding processes. In this case, external protection by means of an inert gas is required to prevent the infiltration of oxygen and nitrogen. These electrodes are used in the TIG welding technique, where tungsten electrodes are used. This technique allows obtaining high-quality finishes on various types of materials.
  • Material: once again, you have to choose the appropriate electrode according to the material that you are going to weld, since it can vary depending on whether it is iron/steel, or aluminum, etc.
  • Diameter: we can choose the appropriate size according to the amount of material we want to leave on the cord. There are more or less thicknesses, as we have seen, although a general choice for when in doubt is 2.5mm, which is the most used. However, if the junction must be thinner, choose a smaller diameter, and if the junction is further apart, you want to fill larger gaps, or cover holes, the ideal is to choose a thicker electrode.
  • Length: You can also find electrodes of more or less length. Obviously the longer ones will last longer, but they are also somewhat more tedious to control. One of the most used are those of 350mm in length, that is, 35 cm. However, some people cut them, because they prefer to work with a shorter electrode…
  • AWS nomenclature: This is determined by the electrode numbering, as each number indicates something. As you will have seen in commercial electrodes, a nomenclature type E-XXX-YZ appears. Now I will explain what this alphanumeric code means:
    • AWS A5.1 (E-XXYZ-1 HZR): electrodes for carbon steel.
      • E: indicates that it is an electrode for arc welding.
      • XX: indicates the minimum tensile strength, without post-welding treatments. For example, a 6011 is less robust than a 7011.
      • Y: indicates the position for which the electrode is ready to weld.
        • 1=All positions (flat, vertical, ceiling, horizontal).
        • 2=For flat and horizontal positions.
        • 3=Only for flat position.
        • 4=Overhead, vertical down, flat and horizontal weld.
      • Z: type of electrical current and polarity with which it can work. Also, identify the type of coating used.
      • HZR: This optional code can indicate:
        • HZ: complies with the diffusible hydrogen test.
        • R: meets the requirements of the moisture absorption test.
    • AWS A5.5 (E-XXYZ-**): for low alloy steels.
      • Same as above, but change the final suffix **.
      • Instead of letters they use a letter and a number. They indicate the approximate percentage of alloy in the weld deposit.
    • AWS A5.4 (E-XXX-YZ): for stainless steels.
      • E: indicates that it is an electrode for arc welding.
      • XXX: determines the AISI class of stainless steel for which the electrode is intended.
      • Y: refers to the position, and again we have:
        • 1=All positions (flat, vertical, ceiling, horizontal).
        • 2=For flat and horizontal positions.
        • 3=Only for flat position.
        • 4=Overhead, vertical down, flat and horizontal weld.
      • Z: type of coating and the class of current and polarity with which it can be used.
I have to add that, to fill in some spaces where the separation is greater than the thickness of the electrode, some use other additional connected electrodes, that is, they weld the part of the electrode that makes contact with the electrode holder to join, for example, 3 of them and then They use all three as if they were one. In this way it is possible to introduce more filler material, although this is a trick...

non-consumable electrodes

Finally, we must not forget the non-consumable electrodes, that is, the tungsten or tungsten ones, whatever you want to call them. In this case we can classify them as follows:

  • Tungsten 2% Thorium (WT20): it is red, used for DC TIG welding. You have to wear a mask, as it can be harmful to health. On the other hand, they work very well for oxidation, acids and heat resistant steels such as copper, tantalum and titanium.
  • 2% Cerium Tungsten (WC20): They are gray in color and have a long useful life, as well as being respectful of the environment and health. Therefore, they can be a great alternative to thorium ones.
  • Tungsten 2% Lanthanum (WL20): they have a blue color, used for automated welding, with a long useful life and high flash. It does not emit radiation.
  • Tungsten at 1% Lanthanum (WL5): the color is yellow in this case, and it is used for plasma cutting and welding.
  • Tungsten to Zirconium (WZ8): with a white color, they are used primarily for AC welding.
  • Pure Tungsten (W): the color is green, it can weld aluminum, magnesium, nickel and alloys by AC welding. It has no additives, so it is not harmful like thorium.

Common errors and solution

welding errors

Although there are a large number of possible defects, the most frequent that you can find and avoid are the following:

  • Poor cord appearance: this problem is possibly caused by overheating, inappropriate choice of electrodes, faulty connections or incorrect amperage. To resolve this issue, adjust the current used to find a proper balance, and select an appropriate electrode that runs at a specific speed to avoid overheating.
  • Excess spatter: When the splashing exceeds normal levels, it is probably caused by excessively high current or excessive magnetic influence. Again, the recommendation is to lower the amperage to identify the precise limit in your process.
  • excessive penetration: In this circumstance, the main problem is usually an inadequate position of the electrode. It is suggested to analyze the correct angle to achieve optimal filling.
  • cracked weld- Cracking in the weld results from an incorrect relationship between the size of the weld and the joined parts, resulting in a rigid joint. Given this, use your analytical skills to design an improved junction structure including size adjustments, uniform gaps, and possibly choosing a more suitable electrode.
  • brittle or brittle weld: This is one of the most serious problems in welding, since it can have a negative impact on the final quality of the parts. Causes can range from the wrong electrode choice to insufficient heat treatment or inadequate cooling. Therefore, make sure to use a suitable electrode (preferably with low hydrogen content), limit penetration and ensure adequate cooling.
  • Distortion: This defect can be caused by poor initial design or by not considering the shrinkage of the metals, resulting in a poor bond and, in some cases, overheating. At this stage, he reviews and, if necessary, redesigns the model, also considering options such as the use of higher velocity electrodes.
  • Poor melting and deformation: These problems are caused by uneven heating or improper operation sequence, resulting in improper shrinkage of parts. You can address these by forming and stress relieving parts before welding, as well as carefully inspecting the process sequence.
  • undermined: This problem is usually the result of poor electrode selection or handling, or using too high an amperage. Therefore, it is necessary to analyze if you are using the correct electrode and possibly reduce the welding speed.
  • Porosity: it can appear due to a mixture of the slag with the molten metal when it is passed several times without removing the slag first, due to contamination of the metal during the process, etc. In this case, making a good uniform bead at once, without going over several times (without having removed the slag), is essential.

Security and frequent doubts

welding, how to weld

Ensure Welding safety is essential to prevent accidents and personal injury. Here are some safety measures you should follow when doing welding work:

  • Do not weld in places with combustible or flammable materials nearby: the spark produced during the process could cause fires or explosions.
  • Use PPE or protective equipment: consisting of the mask to protect the eyes, gloves for the hands, footwear with insulating soles and long clothing to avoid skin burns. Also, if you are going to weld galvanized or tungsten electrodes with toxic elements, always use a filtering mask.
  • Well-ventilated area: work in an area with good ventilation to avoid the accumulation of fumes and toxic gases. If you work indoors, make sure there is adequate air circulation or use fume extraction systems.
  • Fire extinguisher and first aid: keep a suitable fire extinguisher and first aid kit on hand in case of any emergency. Familiarize yourself with its use and location.
  • Do not smoke or eat food: avoid smoking, eating or drinking near the welding area, as fumes and particles can contaminate food and be harmful to your health.
  • Equipment in good condition: Good maintenance of the welding machine is essential for it to be in good condition and to avoid discharge problems due to poor insulation, overheating, etc.
  • Power disconnect: Before adjusting or touching any part of the welding equipment, make sure it is disconnected from the electrical power source.

Furthermore, one of the The most frequent questions among novices is whether touching the part being welded or the electrode can give an electric shock. And the truth is:

  • You can touch the piece of metal you are welding with your bare hand without fear of shock when the electrode and ground clamp are in contact. However, it is not recommended, since you could burn yourself when the temperature of the parts rises.
  • The electrode is best left untouched, however many professional welders support it in their glove for greater precision. It must be said that those that are coated with rutile do not discharge, since the metal inside is covered by an insulator. But if you doubt whether or not the coating is insulating or if you have a bare electrode, never touch it.

Don't forget to read our article about The best welding machines you can buy...


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