Solutions to 5 Defects in Laser Welding

With the advantages of high efficiency, high precision, good effect, and easy automation integration, laser welding is widely used in various industries and plays a pivotal role in industrial manufacturing, including military, medical, aerospace, 3C auto parts, mechanical sheet metal Gold, new energy, bathroom hardware, and other industries.

However, if any processing method does not master its principle and process, it will produce certain defects or defective products, and laser welding is no exception. Only by having a good understanding of these defects and learning how to avoid them can we better utilize the value of laser welding and process products with a beautiful appearance and high quality. Through a long-term accumulation of experience, engineers have summarized some solutions to common welding defects for your reference!

1. Cracks

The cracks generated in laser continuous welding are mainly thermal cracks, such as crystallization cracks, liquefaction cracks, etc. The reason is mainly caused by the large shrinkage force of the weld before it is completely solidified, and measures such as wire filling and preheating can be reduced. or eliminate cracks.

2. Stomata

Porosity is a defect that is easily generated in laser welding. The molten pool of laser welding is deep and narrow, and the cooling rate is fast. The gas generated in the liquid molten pool does not have enough time to escape, which easily leads to the formation of pores. However, laser welding cools quickly, and the pores generated are generally smaller than those of traditional fusion welding. Cleaning the surface of the workpiece before welding can reduce the tendency of porosity, and the direction of blowing will also affect the generation of porosity.

3. Splash

The spatter produced by laser welding seriously affects the surface quality of the weld and can contaminate and damage the lens. Spatter is directly related to power density, and appropriate reduction of welding energy can reduce spatter. If the penetration is insufficient, the welding speed can be reduced.

Four, undercut
If the welding speed is too fast, the liquid metal at the back of the small hole pointing to the center of the weld will not have time to redistribute and will solidify on both sides of the weld to form an undercut. If the joint assembly gap is too large, the molten metal of the caulking is reduced, and it is easy to produce undercuts. At the end of laser welding, if the energy decline time is too fast, the small hole easily collapses, resulting in the local undercut. Controlling the matching of power and speed can well solve the generation of the undercut.

Five, collapse
If the welding speed is slow, the molten pool is large and wide, the number of molten metal increases and the surface tension is difficult to maintain the heavier liquid metal, the center of the weld will sink, forming collapses and pits. At this time, it is necessary to appropriately reduce the energy density to avoid The molten pool collapsing.

By correctly understanding the defects generated in the laser welding process and understanding the causes of different defects, we can more target solve the problem of abnormal welds in laser welding.

What are the common problems in the processing of titanium alloys?

Titanium alloy has the characteristics of high strength, small specific gravity, corrosion resistance, low-temperature resistance, and high-temperature resistance. According to its annealed structure, it can be divided into α-phase titanium alloy, β-phase titanium alloy, and α-β-phase titanium alloy. α-phase titanium alloy (TA type) cannot be strengthened by heat treatment, so the room temperature performance is not high, it has moderate plasticity, and its machinability is acceptable. β-phase titanium alloy can obtain higher room temperature performance through quenching and aging treatment. When the αβ phase titanium alloy (TC type) is processed, the contact length between the chip and the front is short, and the cutting force acts near the cutting edge. Due to the small thermal conductivity, the temperature of the cutting edge is high, which accelerates the wear of the drill bit, and due to work hardening The phenomenon is more serious and the elastic coefficient is small, so the shrinkage of the drill hole is large, which also affects the life of the drill bit.

What is the corrosion resistance of pure nickel NICKEL200?

Nickel-based alloys are excellent corrosion-resistant alloys. NICKEL200 has high corrosion resistance in many substances and even strong corrosive substances. Nickel-based alloys have excellent physical properties and process properties, but they are generally not used casually because of their high price. However, due to the development trend of high main parameters (temperature, working pressure, substance concentration) in the whole process of chemical plants, there are more and more places with highly corrosive substances, and the corrosion standards are becoming more and more stringent. Therefore, commonly used equipment is not only required to resist general corrosion but also more and more resistant to pitting corrosion, stress corrosion, crevice corrosion, etc. When selecting raw materials, not only the one-time project investment cost, but also the cost of maintenance, depreciation, downtime losses, and safety factors must be considered. Therefore, more attention should be paid to the stability of the long-term operation of machinery and equipment. This factor contributes to the increasingly common use of nickel-based alloys with high corrosion resistance.

At this stage, most of the nickel-based alloys commonly used in the manufacturing industry use international standard models. Therefore, the following is a brief and detailed introduction to pure nickel, dominated by the nickel-based deformed aluminum alloy of the American model.

Pure nickel has good corrosion resistance in a hot concentrated lye solution, does not cause alkali ductile stress corrosion cracking, and has excellent corrosion resistance to water, seawater, and high-temperature dry fluorine, but is not resistant to oxidizing acid and aqueous solution with reducing agent and its corrosion resistance. Corrosion of most molten metal materials. It can corrode and become brittle in the gas with high-temperature sulfur content. With the increase of nickel content in stainless steel and nickel-based alloys, the corrosion resistance in dilute hydrochloric acid, sulfuric acid, and ammonium sulfate is significantly enhanced, and the stress corrosion resistance in aqueous sodium hydroxide solution is also significantly enhanced. The corrosion resistance in caustic soda solution is basically positively related to the nickel content.

NICKEL200 price

NICKEL200 price

For a pure nickel, the market generally mainly includes NICKEL200 and NICKEL201.

NICKEL200 Ingredients:

Carbon C≤0.15

Silicon Si≤0.35

Manganese Mn≤0.35

Sulfur S≤0.01

Nickel Ni+Cobalt Co is higher than or equal to 99

Copper Cu≤0.25

Iron Fe≤0.4

The main use of NICKEL200: It is mainly used to solve the oxidizing halogen system vapor, alkali solution, non-reducing acid salt, organic acid, and other machinery and equipment and components, in the natural environment where the temperature should be less than 315 degrees. The corrosion resistance of NICKEL200: Corrosion is relatively slow in the air, and HCl in various sulfuric acids in the sea has excellent corrosion resistance, but it should be used with caution in HIC acid with high water flow, and it is not easy to use in H3PO4 and HNO3 In H2SO4, which is only used to block gas, it has very good corrosion resistance in HF without water at high temperature, and has excellent corrosion resistance in high-temperature chlorine and HCl, and has excellent corrosion resistance in chlorine and fluorine gas. Corrosion resistance.

Why is stainless steel welded pipe more and more popular?

Stainless steel welded pipe has good compression resistance, corrosion resistance, stress corrosion resistance, etc., so it is widely used in various fields. Today, Xiaobian, Xiyouwo, a stainless steel pipe manufacturer in Foshan, will briefly summarize why stainless steel welded pipes are becoming more and more popular.

1. High precision

Welded pipe is a deep-processed product of sheet metal, and its advantages of uniform wall thickness are unparalleled. At the same time, it can be arbitrarily fixed, with high precision; the welding method is simple, the product specification range is wide, the surface is smooth, and the yield is high. The commonly used “welding-cold rolling” production process of stainless steel pipes, after slitting and forming cold-rolled coils according to specifications, is welded into pipes by multi-gun argon arc welding machines, and then cold-rolled (drawn) to make the welds. The various performance indicators of the product can be basically consistent with the base metal, and the product quality and precision are improved

stainless steel welded pipe

stainless steel welded pipe

2. Economic and environmental protection

In the production process of stainless steel welded pipe, the pipe body is evenly extruded, and then after online bright solid-melting annealing, the surface becomes very smooth, and the smooth surface is not easy to scale and has the function of anti-scale. This is good for heat dissipation and does not require frequent cleaning, saving time, effort and money.

Stainless steel welded pipe is a very energy-saving and environmentally friendly product, and stainless steel welded pipe can guarantee 100% recycling. Waste stainless steel welded pipes can also be recycled 100% without causing pollution, which is in line with the requirements of the scientific development concept of energy conservation and environmental protection advocated by the state.

The stainless steel welded pipe has a long service life. After a period of use, it is no different from the initial use and is durable.

With the wide use of stainless steel welded pipes, the advantages of stainless steel welded pipes have been recognized by people, and their application scope is also expanding. Stainless steel pipes have become an indispensable part of people’s lives and will play an important role in future economic construction.

What is the structural performance of the titanium heat exchanger?

A Titanium heat exchanger is an excellent piece of equipment with high heat exchange efficiency, simple structure, and durability, and can prevent damage to the heat exchange tube formed by the impact of fluid. Its structural performance is described as follows:
1. A buffer plate and a diversion hole are arranged under the dual-purpose liquid inlet and outlet of the equipment, which can buffer the impact of the fluid with a higher flow rate at the liquid inlet on the heat exchange tube below, and prevent the heat exchange tube row from being impacted by the fluid for a long time. The deformation of the pipe body, the breakage of the interface, etc. are damaged.

2. The buffer plate and the diversion hole can also slow down the flow rate and improve the heat exchange efficiency; in addition, the heat exchange tube frame is formed by the long heat exchange tube and the short heat exchange tube, and the short heat exchange tube forms the heat exchange tube row so that the fluid is When passing through the titanium heat exchanger from top to bottom or from top to bottom, while continuously exchanging heat with the long heat exchange tube, it also needs to pass through the heat exchange tube row, which slows down the flow rate of the fluid and increases The heat exchange area and the short heat exchange tubes with oblate cross-sections can further increase the heat exchange area and improve the heat exchange efficiency.
3. The heat exchange tube row and the horizontal plane are at an angle of 0-45 degrees, so you can choose a suitable angle according to your needs to adjust the size of the slow flow effect. gaseous fluid.

4. The dual-purpose liquid inlet and outlet, and the outlet and air inlet realize the dual purpose of liquid phase and gas phase fluid. When the gas is exchanging heat, the air is fed from the lower liquid outlet and inlet dual-purpose port and is discharged from the liquid and gas phase. The upper liquid inlet and outlet are used for the air outlet, and when liquid heat exchange is performed, the liquid is supplied from the upper liquid inlet and outlet, and the liquid is discharged from the lower liquid inlet and outlet.
5. In a word, this high-efficiency and durable titanium heat exchanger has a simple structure, high heat-exchange efficiency, can prevent the damage of the heat-exchange tubes caused by fluid impact and is suitable for use in various heat-exchange links in industry and life.

Properties and application of Gr4 titanium plate

Industrial pure titanium is divided into four grades according to the number of impurity elements it contains, namely TA1, TA2, TA3, and TA4. They basically correspond to grades 1 to 4 of titanium in the United States, namely Gr.1, Gr.2, Gr.3, and Gr.4 titanium plate.

As the purity decreases, the strength and hardness of industrial pure titanium increase, while the plasticity, impact toughness, and fatigue resistance decrease. When high requirements on strength, hardness and wear resistance are required, TA3 and TA4 can be selected. When better formability is required, TA1 and TA2 can be used.

TA4 titanium alloy is an α-type titanium alloy. This type of alloy is in an α-type single-phase state at room temperature and service temperature, and cannot be strengthened by heat treatment (annealing is the only form of heat treatment). It mainly relies on solid solution strengthening.

Gr4 Titanium Plate

The room temperature strength of TA4 is generally lower than that of β’> type and α+β type titanium alloys (but higher than industrial pure titanium), while the strength and creep strength at high temperature (500-600℃) are the highest among the three types of titanium alloys. And the structure is stable, the oxidation resistance and welding performance are good, the corrosion resistance and machinability are also good, but the plasticity is low (the thermoplastic is still good), and the room temperature stamping performance is poor. Among them, the most widely used is TA7, which has moderate strength and sufficient plasticity in the annealed state, good weldability, and can be used below 500 ° C; when its interstitial impurity elements (oxygen, hydrogen, nitrogen, etc.) content are extremely low, It also has good toughness and comprehensive mechanical properties at ultra-low temperature and is one of the excellent ultra-low temperature alloys.

The tensile strength of TA4 is slightly higher than that of industrial pure titanium, and it can be used as a structural material in the medium strength range. It is mainly used as welding wire in China, and it is widely used in the high-end electroplating hanger industry abroad.

The difference between TC4 and TC4ELI of titanium alloy

TC4 titanium alloy is an α-β type titanium alloy successfully developed by the United States in 1954, containing 6% α stable element and 4% β stable element V. The nominal composition of it is 7.0 aluminum equivalent, molybdenum equivalent 2.9, and contains 10%-15% beta phase in the annealed state. Al improves the room temperature strength and thermal strength properties of alloys by solid solution strengthening α phase in the Ti-Al-V system, while V is one of the few alloying elements that can improve both strength and plasticity in titanium alloys. The beneficial effect of V on the plasticity of titanium alloys is that it does not increase the c/a-axis ratio of the α-state lattice-like most alloying elements, but reduces the ratio, thereby increasing the formation of α-phase and avoiding long-term use. Alloy embrittlement occurs during the process.

The main features of TC4 titanium alloy are excellent comprehensive performance and good process performance. It has moderate room temperature strength and high-temperature strength, good creep resistance and thermal stability, high fatigue resistance and crack propagation resistance in seawater, and satisfactory fracture toughness and thermal salt stress corrosion resistance, The sensitivity to hydrogen is also smaller than that of TC2 and TC1 alloys. It is suitable for the manufacture of various parts that work in a wide temperature range of -196~450 °C, especially the parts designed with the principle of damage tolerance limit. TC4 also has excellent process plasticity and superplasticity, suitable for forming with various pressure processing methods, and welding and machining in various ways.

The main semi-finished forms of TC4 titanium alloy are bars, forgings, sheets, thick plates, profiles, wires, etc., and are also used for castings (ZTC4).

TC4ELI Titanium Alloy

TC4ELI is an improved version of TC4, the main difference is the different Al content and lower content of interstitial elements Fe, N, H, and O.

TC4ELI titanium alloy has become a medical-surgical implant due to its good biocompatibility, low elastic modulus, low density, good corrosion resistance, non-toxicity, high yield strength, long fatigue life, and large plasticity at room temperature, and easy forming. ideal material. Medical TC4ELI titanium alloy sheet is mainly used for skull repair, bone setting, etc., which has higher requirements on its strength, fatigue life, and plasticity.

Titanium alloy is an alloy composed of titanium elements and other elements. Titanium has two kinds of isomorphic crystals: titanium is an allotrope with a melting point of 1668 °C, and it is a close-packed hexagonal lattice structure below 882 °C, called α-titanium; above 882 °C, it is body-centered cubic. A lattice structure is called beta-titanium. Using the different characteristics of the above two structures of titanium, appropriate alloying elements are added to gradually change the phase transition temperature and component content to obtain titanium alloys with different structures.

On the basis of TC4 alloy, TC4 ELI titanium alloy reduces the content of interstitial elements C, O, N and impurity element Fe, and the strength is reduced, but the capacity and toughness can be significantly improved. TC4 ELI has good plasticity, toughness, good welding performance, and low-temperature performance, and is widely used in important fields such as low-temperature engineering, medical treatment, ships, and aircraft.

TC4 alloy can be used in an ordinary environment or high-temperature environment, and TC4 ELI alloy can be used in an ultra-low temperature environment

Similar grades of TC4 titanium alloy and TC4ELI titanium alloy are T-6A-4V/Grade 5 (American grade), BT 6 (Russian grade), IMI 318 (British grade), TiAI6V4 (German grade).

Medical equipment manufacturing In the human body, the bone and joint damage caused by trauma and tumor, artificial joints, bone plates, and screws are made of titanium and titanium alloys, which are now widely used in clinical practice. Also used in hip joints (including femoral heads), knee joints, elbow joints, metacarpophalangeal joints, interphalangeal joints, mandibles, artificial vertebral bodies (spinal orthoses), pacemaker housings, artificial hearts (heart valves), artificial dental implants, titanium-nickel dental orthodontics and titanium mesh in cranioplasty, etc.

Titanium and titanium alloys are receiving increasing attention due to their high specific strength, good biocompatibility, and good resistance to body fluid corrosion.

Ti 6Al-4V ELI is a grade of Ti 6Al-4V with a smaller structure gap, which can achieve maximum toughness and is suitable for seawater and low-temperature environments. This grade of alloy is usually used in the annealed condition. Ti 6Al-4V is a good choice for medical implants.

The production process is: relaxation annealing and air cooling at 900-120 degrees Fahrenheit for 1-4 hours. Double annealed, round bars and forgings are solution annealed at a beta transition temperature of 50-100 degrees Fahrenheit, held for at least 1 hour and then air-cooled, then reheated at 1300-1400 degrees Fahrenheit for at least 1 hour, air-cooled. Relaxation annealing is suitable after welding

Briefly describe the characteristics of copper alloy free forging process

The macrostructure of copper alloy ingot can be divided into three regions: chilled region, columnar crystal region, and equiaxed crystal region. The chilled zone is a layer of the shell that is close to the mold wall of the ingot, and its thickness is relative to several grains. The equiaxed crystal region is located in the central area of ​​the ingot and is composed of relatively coarse equiaxed grains; the columnar crystal region is located between the two and consists of columnar grains perpendicular to the mold wall and parallel to each other. The width of the above three crystal regions varies with the chemical composition of the alloy, the casting method, and the process. By adjusting the casting process, a single equiaxed crystal or single columnar crystal ingot can be obtained. The columnar crystal structure has a great influence on the performance of the ingot. There are often low melting point eutectic structures and inclusions, pores, and porosity at the junction of the columnar crystal and the equiaxed crystal. There may also be intergranular cracks, which are a fragile place for the ingot. When the ingot is pressed worked, it tends to crack along this point. Therefore, in the ingot used for plastic deformation, the columnar crystal region should be as small as possible, and the equiaxed crystal region should be as wide as possible, especially to avoid the appearance of a coarse columnar crystal structure.

Controlling the structure of the ingot to form a uniform and fine equiaxed grain structure can effectively improve the deformation performance of the ingot. Adding refiners to the casting melt is an effective way to refine grains. For ingots used for plastic processing, especially free forging, the content of harmful impurities (such as lead, bismuth, etc.) should also be strictly controlled, otherwise, under the action of tensile stress, cracks will easily occur where low-melting-point impurities gather.

According to the characteristics of copper alloy ingots, the precautions for free forging are:

(1) The forging temperature range of copper alloys is narrow. In order to avoid the rapid drop of the billet temperature during the forging process and fall into the brittle zone, the hammerhead, anvil surface, and operating tools such as punches, mandrels, and tire molds should be removed before forging. , drain pan, etc. are preheated to above 200 ℃. The action should be brisk during operation, and the blank should be turned frequently on the anvil surface. When punching, the punch should be preheated to the highest possible temperature, so that the temperature of the metal in contact with the punch will not drop too much, so as to avoid cracks on the edge of the hole. During forging, if the temperature of the billet drops to the brittle zone, the forging should be stopped immediately, and the forging should be resumed after reheating.

(2) The copper alloy is soft in texture, and the extruded edges and corners are relatively sharp during drawing. In order to avoid folding defects, the edges of the anvils for forging copper alloys should be rounded by more than R10, and the amount of feeding and pressing during operation The ratio should be appropriately increased, which can be maintained at 0.7 to 1.0, and the hammering should be as fast as possible. When forging a flange with holes, if the hole is punched first, and then the head is upset in the tire mold, it is easy to produce folding defects on the inner wall of the hole. Therefore, when forging a copper alloy flange with holes, the upset head should generally be upset in the mold first. After punching, place a mandrel in the blank hole and upset the head in the tire mold.

(3) Brass is more sensitive to internal stress, and it is easy to crack by itself when the internal stress is large. When forging long-axis brass forgings, the forging should be turned around repeatedly, and the forgings should be turned evenly, so that the deformation temperature difference of each section of the forgings is not too large, so as to reduce the internal stress of the forgings and obtain a relatively uniform structure. Such forgings should be annealed in time after forging.

The above is all about the copper alloy, I hope it can be helpful for you to read.

Why is the thinner the wall thickness of the stainless steel pipe, the more expensive it is?

When we purchase stainless steel pipes, we will find out why the price difference between thin and thick stainless steel pipes of the same material can be one or two thousand? What is the reason?

This is because, in addition to material, precision, surface, and wall thickness is also a factor that affects the price. Under the same conditions, the price of thin walls is generally higher than that of thick walls. In the final analysis, it is because of cost. So, let’s take a closer look at why the thinner the wall thickness of the stainless steel pipe, the more expensive it is?

1. Calendering problem

The process level of the product also has a great influence on the price of the product, and the stainless steel tube rolling process is one of the more important processes.

The exact thickness of the pipe is inseparable from the rolling quality of its steel strip, but the cost of rolling is divided according to the thickness. The rolling thickness of the steel strip is different, and the rolling cost is also different. The thinner the thickness, the required the rolling processing fee will be more expensive.

In addition, the thickness or thicker that is not often made will also increase the cost of rolling, which will directly lead to an increase in the price of stainless steel pipes.

thick stainless steel pipes

thick stainless steel pipes

2. Yield problem

Each thickness of pipe has its own thickness range. Generally, the thickness that is more popular in precision stainless steel pipes is the thickness of 0.40mm and above, and the yield of such thick pipes is relatively high during pipe making and polishing.

However, the actual situation is that the needs of customers are constantly changing, and some of them will have thin-walled tubes. Like stainless steel precision tubes with a solid thickness of 0.25mm to 0.31mm, the thickness of the steel strip is relatively thin, the requirements for tube making or polishing are relatively high, and the yield is relatively low, so the higher the scrap rate.

Therefore, the cost of the finished product will go up accordingly, and the price will naturally be expensive.

3. Damage rate problem

For some thin pipes, not only the yield is low when making pipes, but also part of the damage during storage and transportation.

Because the inner wall of the pipe is relatively thin, the damage rate is higher than that of the thicker pipe, whether it is the manufacturer’s storage or logistics transportation, which also involves the problem of damage compensation, so the price of the thinner pipe will be relatively higher.

Finally, thick stainless steel pipe manufacturers are going to say goodbye to everyone here. If you want to know more relevant knowledge, follow us!

Which Solder Can Weld Titanium Alloys?

Eutectic solder can weld titanium alloys. The melting point of eutectic solder is 183 degrees. When the content of tin is higher than 63%, the melting temperature increases and the strength decreases. When the content of tin is less than 10%, the welding strength is poor, the joint becomes brittle, and the lubricating ability of the solder becomes poor.

titanium alloy weld picture
The most ideal is eutectic solder. At the eutectic temperature, the solder changes from solid to liquid directly without going through a semi-liquid state. The melting temperature of eutectic solder is lower than that of non-eutectic solder, which reduces the number of components to be soldered. At the same time, because the eutectic solder is directly changed from liquid to solid, it also reduces the phenomenon of virtual soldering, so the eutectic solder is widely used.