Metal Welding Services
Metal Welding Services
Metal welding service is a manufacturing or sculpting process that joins metals. The welding process involves the melting or non-melting of the workpiece and the solder to form a direct joining weld of the material. This process usually also involves the application of pressure to join the weldments.
The workflow of welding and the different welding methods
The process of producing welded metal parts is a manufacturing or sculpting process that joins metals. The welding process involves the melting or non-melting of the workpiece and the solder to form a direct joining weld of the material. This process usually also involves the application of pressure to join the weldments.
There are various sources of energy for welding, including gas flames, electric arcs, lasers, electron beams, friction and ultrasound. As well as being used in factories, welding can also be carried out in a variety of environments such as in the field, underwater and in space. Wherever welding takes place, it can pose a risk to the operator, so it is important that appropriate protective measures are taken when welding is carried out. Possible injuries to the human body from welding include burns, electric shock, visual impairment, inhalation of toxic gases and excessive exposure to ultraviolet light.
4 types of metal welding methods
Metal welding is divided into four main categories: fusion welding, pressure welding and brazing as well as laser welding
- Fusion welding is a method of welding in which the interface of the workpiece is heated to a molten state without pressure. During fusion welding, the heat source heats the interface between the two workpieces to be welded and melts rapidly, forming a molten pool. The molten pool moves forward with the heat source and after cooling forms a continuous weld that joins the two workpieces into one.
- During the welding process, if the atmosphere is in direct contact with the high temperature pool, the oxygen in the atmosphere will oxidise the metal and various alloying elements. Atmospheric nitrogen and water vapour entering the molten pool will also form defects such as porosity, slag and cracks in the weld during subsequent cooling, deteriorating the quality and performance of the weld.
- In order to improve the quality of welding, various protection methods have been developed. For example, gas shielded arc welding is to use argon, carbon dioxide and other gases to isolate the atmosphere, in order to protect the arc from oxidation during welding, to avoid the formation of deficiencies; another example is the welding of steel, in the welding electrode flux to add a large affinity for oxygen titanium iron powder for deoxidation, you can protect the electrode in the beneficial elements of manganese, silicon, etc. from oxidation and enter the melt pool, after cooling to obtain a high-quality weld.
Pressure welding is the inter-atomic bonding of two workpieces in a solid state under pressurised conditions, also known as solid state welding. The commonly used pressure welding process is resistance butt welding, where the temperature rises due to the high resistance of the two workpieces as the current passes through their jointed ends, and when heated to a plastic state, the joint becomes one under axial pressure.
A common feature of the various pressure welding methods is that pressure is applied during the welding process without the addition of filler material. Most pressure welding methods such as diffusion welding, high-frequency welding, cold pressing welding, etc. are not melting process, so there is no beneficial alloying elements like fusion welding burn, and harmful elements into the weld problem, thus simplifying the welding process, but also improve the welding safety and health conditions. At the same time, the heating temperature is lower than that of fusion welding and the heating time is shorter, so the heat affected zone is smaller. Many materials that are difficult to weld with fusion welding can often be welded with pressure welding into a high quality joint with the same strength as the base material.
Brazing is a method of welding by using a metal with a lower melting point than the workpiece as the brazing material, heating the workpiece and the brazing material to a temperature higher than the melting point of the brazing material and lower than the melting point of the workpiece, using the liquid brazing material to wet the workpiece, fill the interface gap and achieve inter-atomic diffusion with the workpiece.
The laser welding process consists of an optical oscillator and a medium placed between the two end mirrors of the oscillator cavity. When the medium is excited to a high energy state, light waves are generated in phase and reflected back and forth between the two end mirrors, creating a photoelectric cascade effect that amplifies the light waves and gives them enough energy to start emitting laser light.
A laser can also be interpreted as a device that converts raw energy such as electrical, chemical, thermal, optical or nuclear energy into a beam of electromagnetic radiation at certain optical frequencies (ultraviolet, visible or infrared light). The conversion takes place easily in certain solid, liquid or gaseous media. When these media are excited in atomic or molecular form, a beam of light is produced which is almost identical in phase and has a nearly single wavelength - a laser. Due to the homogeneous phase and single wavelength, the angle of difference is very small and the distance travelled can be quite long before it is highly focused to provide functions such as welding, cutting and heat treatment.
In practice, the correct welding process can be divided into five steps.
(1) Step 1: Prepare for soldering Hold the solder wire in your left hand and the soldering iron in your right hand and enter the ready soldering state. The tip of the soldering iron is required to be kept clean and free of solder slag and other oxides, and a layer of tin is applied to the surface.
(2) Step 2: Heat the soldering iron tip against the connection of the two soldering parts and heat the whole soldering part for about 1~2 seconds. For soldering components on printed boards, pay attention to make the tip of the soldering iron while contacting the pads and components of the leads, this is to ensure that the wires and pads, wires and terminals between the same time evenly heated.
( (3) Step 3: When the soldering surface of the wire-fed solder is heated to a certain level, the solder wire contacts the solder from the opposite side of the soldering iron. Be careful not to feed the solder wire to the tip of the soldering iron!
(4) Step 4: Remove the solder wire As soon as the wire has melted to a certain amount, remove the wire in a 45° direction to the upper left. (5) Step 5: Move away from the soldering iron after the solder has wetted the pad and the soldering part of the solder, move the soldering iron in the direction of 45° up to the right to end the soldering. From step three to the end of step five, the time is about 1~2 seconds. Take care that the soldering time is not too long, especially for integrated circuit blocks/chips, triodes etc. which are not resistant to high temperatures during the period to avoid damaging the components.
Commonly used welding joint styles
(a) Butt joints
The two surfaces form a joint greater than or equal to 135°, less than or equal to 180° angle, called a butt joint. In various welding structures it is the most used a joint type.
Steel plate thickness below 6mm, except for important structures, generally not open bevel.
Thickness of different steel plates butt two plate thickness difference (δ-δ1) does not exceed the provisions of Table 1-2, then the basic form and size of the weld bevel according to the size of the thicker plate data to choose; otherwise, should be made in the thick plate as shown in Figure 1-8 single-sided or double-sided thinning; its thinning length L ≥ 3 (δ-δ1).
|Thinner plate thicknessδ1||≤2～5||>5～9||>9～12||>12|
|Permissible thickness difference(δ—δ1)||1||2||3||4|
(b) Angle joints
A joint with an angle of more than 30° and less than 135° between the ends of two weldments is called a fillet joint, see diagram. This type of joint is not very well stressed and is often used in unimportant structures.
(C) T-shaped joints
A joint in which the end face of one piece forms a right angle or near right angle to the surface of another piece is called a T-shaped joint, see figure
(d) lap joints
The joint formed by overlapping two parts is called a lap joint, see figure
The lap joint is divided into three forms according to its structural form and requirements for strength: no bevel, plug welding in a round hole and fillet welding in a long hole, see figure.
I-shaped beveled lap joints are generally used for steel plates up to 12 mm thick with an overlap of ≥ 2 (δ1 + δ2), welded on both sides. Such joints are used in unimportant structures.
When the area of the overlapping part is encountered to be larger, the joint type of plug welding in round holes or fillet welding in long holes of different sizes and numbers can be used according to the plate thickness and strength requirements, respectively.
Common materials used for welding
|Selection Of Welding Electrodes For Hand Arc Welding Of Low Carbon Steel|
|Steel No||General structure selected||Dynamic loads, complex, thick plate structures, boiler pressurised vessels, low temperature welding||Welding conditions|
|Welding rod type||Type of electrode to be used|
|Q235||E4313，E4303，E4301，E4320，E4311||E4316，E4315||No preheating in general|
|Q255||E5016，E5015||No preheating in general|
|Q275||E4316，E4315||E5016，E5015||Preheating of thick plate structures above 150°C|
|08、10、15、20||E4303，E4301，E4320，E4311||E4316，E4315||No preheating in general|
|25||E4316，E4315||E5016，E5015||Preheating of thick plate structures above 150°C|
|20g，22g||E4303，E4301||E4316，E4315||Preheating of thick plate structures 100 to 150°C|
|20R||E4303，E4301||E4316，E4315||No preheating in general|
Note: The type of welding rod in the table in brackets indicates that it can be substituted.
|Mild Steel Submerged Arc Welding Wire And Flux Matching Selection|
|Steel No||Solder Wire||Solder flux|
CO2 welding wire selection: solid core welding wire selected grades H08Mn2Si and H08Mn2SiA two, after welding the strength of the deposited metal is high. Flux cored wire is selected from YJ502-1, YJ506-2, YJ506-3 and YJ506-4.
Electroslag welding wire and flux matching selection: electroslag welding pool temperature is lower than submerged arc welding, so the flux in the silicon, manganese reduction effect is weak, should be selected with manganese, containing a higher amount of silicon wire. H10Mn2, H10MnSi wire with flux HJ360 or H10MnSi wire with flux HJ431 are often used.
|Selection Of Welding Materials For Low-alloy High-strength Steels|
|Steel No||Strength level||Hand arc welding||Submerged arc welding||Electroslag welding||CO2 welding wire|
|（MPa）||Welding rods||Solder flux||Welding wire||Solder flux||Welding wire|
|HJ431||Open bevel butt joint for centreboard|
|HJ430||Open I-bevel butt joint|
|HJ350||Deep beveling of thick plates|
|15MnV||392||E50||HJ430||Open I-bevel butt joint||HJ431||H10MnMo||H08Mn2Si|
|Open bevel butt joint for centreboard|
|HJ250||Deep beveling of thick plates|
|Selection Of Welding Materials When Welding Austenitic Stainless Steel|
|Steel No||Hand Arc Welding||Submerged arc welding||Argon arc welding|
|Welding electrodes||Solder wire||Solder||Solder wire|
|1Cr18Ni9Ti||E0-19-10-16 R0-19-10-15 E0-19-10Nb-16 R0-19-10Nb-15||A102||H0Cr20Ni10Ti||HJ260||H0Cr20Ni10Ti|