Lead-free solder wires refer to the consumables used in the welding process. There are numerous types of lead-free solder wires, which can easily lead to confusion in application. It is necessary to use and manage various lead-free solder wires correctly during production. The solder wires that are shipped out have been subjected to high-temperature drying and are packaged with moisture-proof materials (such as plastic bags, paper boxes, etc.) to some extent, which can help prevent the wires from getting damp.
Welding rods have a high hygroscopicity during storage, which is related to various factors such as the storage environment's temperature and humidity, time, the content and type of organic matter (as reported), adhesive content and quality, the manufacturing process of the welding rod, and packaging quality. When welding with damp welding rods, if the moisture content in the rod skin is high, it may even be observed that water vapor is evaporating from the rod skin surface; or when most of the rod has been welded, cracks and porosity may appear at the end of the weld. During lead-free soldering, damp welding rods often exhibit increased arc blowing force, deeper melting, and increased spatter. Titanium and titanium calcium welding rods may show poor slag coverage and poor shaping; for low-hydrogen welding rods, the slag surface usually has many small holes, and in severe cases, gas holes may appear in the weld.
Lead-free solder wire consists of an internal metal core and a coating applied to the outside. The core takes the form of a wire with specific diameters and lengths. Its primary function is to conduct electricity, heating itself to melt, and then fill the gap between workpieces to fuse them together, creating a weld. The variety and complexity of solder wire types, along with numerous specifications and stringent quality requirements, make manufacturing them a process with short production cycles, high continuity, and large output. To produce an excellent solder wire, it is not only necessary to have designs from multiple regions and correctly select raw materials but also to have corresponding manufacturing processes, equipment, and rigorous inspection and testing methods. The lead-free solder wire is coated with a layer of paint, which is referred to as the skin. This skin plays a crucial role in welding. Directly welding with the core would allow air and other substances to enter the molten metal, leading to chemical reactions within the metal, which could directly cause defects like air pockets and cracks in the weld, negatively impacting the strength of the weld. The skin, with its special elements, decomposes and melts into gas and slag at high temperatures, preventing air from entering and thus enhancing the quality of the weld.
Lead-Free Solder Wire Welding Technology Issues: General welding machines can weld up to 60 points per minute in spot welding; high-speed spot welding can exceed 500 points per minute; a 40mm diameter bar can be焊接 one joint per minute; for resistance welding on 14mm thick sheets, the production rate is good. The welding speed is about 0.51 meters per minute. Resistance welding does not require filling materials, usually requires no gas maintenance, and has relatively low welding costs. The metallurgical process of resistance welding is simple, the chemical composition of the weld metal is uniform, and is basically consistent with the base material; resistance heating is concentrated, with a small heated area and minimal heat-affected zone, resulting in less and easier-to-control deformation. Resistance welding is easy to mechanize, automate, and intelligentize, without intense light and excessive splatter, offering good working conditions. However, resistance welding has its drawbacks: since the welding process is fast, adjustments are often not possible if there are fluctuations due to certain factors that affect welding quality stability; in addition, as of now, there is no good non-destructive inspection method, so it is rarely used in important load-bearing structures. The thickness, shape, and joint type of the workpieces are subject to respective limitations during resistance welding.
Insufficient welding current not only makes arc striking difficult, but also causes an unstable arc, leading to defects such as incomplete fusion and slag inclusion. Due to the insufficient heat from the low welding current, the welding rod's molten droplets accumulate on the surface, resulting in an unattractive weld bead shape. Excessive current in lead-free soldering results in deeper melting. If the welding current is too high, it not only makes burn-through and edge defects more likely, but also causes excessive loss of alloy elements, overheating of the weld, and large grain size in the heat-affected zone of the joint, affecting the weld's mechanical properties. Moreover, an overly high welding current can cause the tip of the welding rod to become red prematurely, leading to skin peeling and failure, which in turn can cause porosity.
Common venting issues in lead-free solder bars: Based on several years of experience in manual tungsten argon arc welding, this article analyzes the causes of gas pores in argon arc welding and introduces some solutions and precautions. These methods are widely applied in actual production. However, due to the weak wind resistance of argon arc welding, it is particularly sensitive to rust, water, and oil stains, and has strict requirements for gas purity, groove cleaning, and welding techniques, making gas pores more likely to occur.
This article analyzes the gas porosity issue in argon arc welding from a production perspective and proposes some handling methods and precautions. Argon arc welding is an electric arc welding method using the inert gas "argon" as a protective gas. The argon is ejected from the nozzle, forming an inert gas protective layer in the welding zone, which isolates air intrusion, thereby protecting the arc and the molten pool. Jining Lead-Free Tin Wire offers excellent protective effects, does not cause spatter, and forms aesthetically pleasing weld seams; it minimizes welding deformation, allowing for single-sided welding with double-sided formation, ensuring root weld penetration, and enabling welding in various positions. It can weld various metals and alloys, with stable arc combustion, clear arc visibility, no slag, and is easy to automate.
Cold cracks are categorized differently depending on the type of steel and its structure, generally falling into the following three types:
Quenching Cracks
These cracks generally exhibit no delay, and are discovered immediately after welding. They can occur on the weld seam or within the heat-affected zone. Primarily, they are cracks resulting from quench-hardened structures under the action of welding stresses.
Not high plasticity brittle cracking.
Materials with lower plasticity, when cooled to temperatures not excessively high, can experience strains due to shrinkage that exceed the material's inherent plastic reserve or cause the material to become brittle, leading to cracks. As these cracks form at temperatures not excessively high, they also represent another form of cold cracks, but without any delayed phenomena.
III. Delayed Cracking
It is a common form of cold crack, characterized by not appearing immediately after welding but rather developing after a certain incubation period, resulting from the combined effects of quench-hardened tissue, hydrogen, and restraint stress, and exhibiting delayed crack characteristics.
