Used Tig Welding Equipment for sale (42,823)

Condition: refurbished (used), Year of construction: 2011, functionality: fully functional, Friction welding machine from MTI, equipped for welding turbochargers. The machine is equipped with: Iaedpfsv Uzf Esx Aquou - Siemens PLC, CPU 315 - Rexroth hydraulics - German user interface - CE Upon request, this machine can also be converted for many other welding tasks.

Year of construction: 2024, operating hours: 1 h, condition: new, functionality: fully functional, machine/vehicle number: 86-731-85552647/18153792542, We are a company based in 9000 St. Gallen (Switzerland) and imported this planetary ball mill from China in 2024. The unit is brand new and unused. We have switched the machine on and let it run empty for a few minutes to verify its functionality. It comes with 4 x 25-liter nylon containers. Additionally, 120 kg of zirconium beads with a 1 mm diameter are available. ~ Iaodpfjyilnzex Aquju Manufacturer's Description: The YXQM series of planetary ball mills for mass production is a machine designed for production applications, built to handle medium-scale capacities to meet industrial requirements. It facilitates the smooth transition of materials from laboratory scale to full production, ensuring consistency and repeatability of processes and thus reliable material quality. The equipment is widely used across new energy, metallurgy, electronics, ceramics, geology, mining, construction materials, chemical industry, light industry, cosmetics, environmental protection, and other enterprise-level material production sectors. Extremely high centrifugal forces inherent to planetary ball mills generate intensive grinding energy, resulting in short milling times. These machines are ideal wherever the quality control process demands the highest standards of purity, speed, fineness, and reproducibility. This series can be equipped with vacuum jars, allowing samples to be ground under vacuum conditions. It is well suited for research tasks at scientific institutes, universities, and industrial R&D laboratories to verify the feasibility of scale-up to mass production, as well as for routine operations such as mixing and homogenizing soft, hard, brittle, or fibrous materials—from laboratory tests through to production. - Key Features: - High-performance, nanometer-scale grinding - Digital display, intuitive operation, precise parameter setting - Variable speeds from approx. 10 to 440/360 rpm, speed ratio 1:2 - Batch processing with up to 4×6/9 L samples, simultaneous processing of 4 materials - Electric lid opening and integrated crane for easy and convenient operation - Storage for 3 modes and 15 programs - Power failure protection with memory function and automatic restart - Suitable for dry, wet, vacuum, and protective atmosphere grinding - Machine stops upon lid opening; automatic interlock prevents accidental release - Equipped with rollers and swiveling feet for easy movement and stable operation Applications: Grinding, mixing, homogenizing, colloidal milling, mechanical alloying, mechanochemistry Fields of Application: New energies, geology/metallurgy, glass/ceramics, engineering/electronics, building materials, environment/recycling, agriculture, chemistry, medical, biology Feed material: Soft, hard, brittle, fibrous – dry or wet Size reduction principle: Impact, friction Feed size: < 5 mm soil, < 10 mm Final fineness: For colloidal milling, samples below 0.1 micron Number of grinding stations: 4 Grinding methods: Dry grinding, wet grinding, vacuum grinding, grinding under protective atmosphere

Condition: good (used), Year of construction: 2020, functionality: fully functional, Mono Omega Cookie Depositor - used - year of manufacture: 2020 - computer-controlled - 2 heads - cutting wire - complete set of working nozzles - for 40x60 trays Iedpfxey Ald Hs Aqujau - good technical condition/machine checked and cleaned - collection from warehouse/shipping option available - price on request

Condition: new, An additional aircompressor are required to enable the nitrogen generator to produce nitrogen. Nitrogen purity: 99.999% Iajdpfxjxfrv Es Aquou Input pressure: 8Bar Output pressure: 7Bar Power: 75W(Power is the cost per hour to produce nitrogen ) 3 în 1 design, no need for extra air compressor and refrigerator or dryer Gas clean Price is EXW (Stock Europe), Include loaded on truck. Transport, installation, commissioning, training, and yearly service contracts are available upon request for an additional fee. Installation and training is always done by our high qualified Service team in 3 locations in Europe. Netherlands, Germany, Romania. Official Seller CNC Top Ten bv Coevorden, Netherlands

Condition: like new (used), Year of construction: 2018, Laser Welding Robotic system for welding steel, stainless steel. Scope of supply: Isdpsh Ad E Usfx Aqujau 1 x YASKAWA 6-axis robot YASKAWA HP20RD.(Payload: 20kg, H-Reach: 2017mm, Robot Mass: 293kg, 2010.04) 1 x YASKAWA DX100 controller.(2010.05). 1 x IPG YLS-4000.(2017). 1 x IPG CHILLER.(2017). 1 x HIGHYAG BIMO LASER WELDING HEAD(S.N.:BIMO2W17013). Machine can be inspected. Very good condition. Connected, can be tested. Shipping to EU countries is our responsibility and the shipping cost is free.

Condition: like new (used), Year of construction: 2020, operating hours: 200 h, functionality: fully functional, arm reach: 1,437 mm, For sale: Panasonic robotic TIG welding workstation purchased from ValkWelding. Workstation includes: Panasonic TM 1400 G3 robot (6 axes, reach 1437 mm, payload 6 kg), two-axis L positioner PD1000/500, TIG welding unit Tetrix 352 AC/DC Synergic CW, accessories, and safety equipment. Iajdpfxey Efmgs Aquju This workstation is distinguished by its ability to safely weld not only steels and stainless steels but also aluminum. The process is highly synchronized with wire feeding and is capable of seam tracking and adapting to changes in arc height. A very versatile device. I am selling this system because our original capacity expectations have not been met (we don’t have work in the hundreds or thousands of pieces). Over its entire lifetime (approximately 5 years), the workstation was powered on for around 200 hours and did actual test welding for less than an hour in total. It is practically in like-new condition. It would be a pity for it to just “collect dust.” All support has been directly provided by ValkWelding. In case of sale, they will arrange installation, commissioning, and personnel training as agreed.

Condition: new, Year of construction: 2026, functionality: fully functional, Ball Mill with Air Classifier: The Ultimate Powder Processing Equipment In the world of industrial powder production, precision, efficiency, and flexibility are paramount. Whether producing ultra-fine powders for high-tech applications or coarser materials for everyday products, the combination of a Ball Mill with Air Classifier offers unparalleled performance. This dynamic duo provides a comprehensive solution for industries ranging from chemicals and ceramics to paints, plastics, and pharmaceuticals. This article introduces the ball mill with an air classifier, explores its applications, and highlights the key advantages of this essential powder equipment. General Introduction to Ball Mill with Air Classifier ball mill with air classifier is an advanced grinding and classification system designed for efficient, high-quality powder production. The system consists of two main components: 1. Ball Mill: A cylindrical grinding device filled with grinding media (such as steel balls) that operates by rotating around its axis. The raw material is reduced to smaller particle sizes through impact and friction within the mill. 2. Air Classifier: A sophisticated device that separates particles based on size using airflow. Fine particles are carried away, while coarser particles are returned to the ball mill for further grinding. The combination of these two components creates a closed-loop system that ensures consistent particle size distribution, high efficiency, and minimal waste. Applications of Ball Mill with Air Classifier The ball mill with air classifier is a versatile solution used in a wide range of industries to process various materials. Key applications include: 1. Mineral Processing The system is widely used in the production of minerals such as calcium carbonate, quartz, feldspar, and talc. These finely ground minerals are essential for industries like ceramics, paints, plastics, and rubber. 2. Cement and Construction Materials Cement and other construction materials require precise particle size control for optimal performance. The ball mill with air classifier ensures uniformity and enhances the quality of construction materials. Iedpfxjvlwkxe Aqueau 3. Chemicals and Pharmaceuticals Fine powders play a critical role in the chemical and pharmaceutical industries. From active pharmaceutical ingredients (APIs) to industrial chemicals, this system delivers the consistent quality required for these applications. 4. Paints, Coatings, and Pigments The production of paints and coatings demands ultra-fine powders to achieve smooth finishes and vibrant colors. The ball mill with air classifier produces high-quality powders for superior results. #### 5. Food and Agriculture Food-grade powders such as additives, preservatives, and agricultural products like fertilizers can be efficiently processed using this system, meeting stringent regulatory requirements. Industries That Benefit from Ball Mill with Air Classifier Several industries rely on the capabilities of this system to produce fine powders with specific characteristics: - Ceramics: Produces high-purity powders for tiles, insulators, and advanced ceramics. - Rubber and Plastics: Creates fillers and additives for improved durability and performance. - Pharmaceuticals: Ensures consistent particle size for APIs and excipients. -Construction: Delivers materials for concrete, plaster, and other applications.

Condition: excellent (used), Machine ready for operation. 1000-litre tank. 500-litre tank. The station was used for cleaning a soup and mayonnaise production line. Please check my other listings as well. Iaodpfx Asytm Tioqusu

Condition: new, functionality: fully functional, power: 560 kW (761.39 HP), fuel type: electric, color: other, Year of construction: 2026, *All of our products are made with care and covered for 1 year warranty! *Installation and Operator Training FREE New Generation FULLSTAR Series Mobile Crushing, Screening and Washing Plants are the most preferred machines in recent years thanks to easy and cost free installation. The first crushing process is performed with Primery Jaw Crusher, we can design with secondary impact crusher or cone crusher for second crushing stage according to the requirements of our customers. FULLSTAR 110 plant has been projected for the first time in the world by Fabo and provides crushing, screening and as well as to wash 0-5 mm sand at the same time on a single chassis. Our FULLSTAR model operates in closed Crushing circuit system and allows user to obtain 4 different final fractions up to 300 T / S capacity. We are manufacturing FULLSTAR-90 and 110 models which has 3 functions at the same time by trailed-type 2 chassis with its own tires. FABO FULLSTAR-110 is a mobile type plant which perform crushing, washing and screening operations at the same time. This type of plant is very efficient as it is produced on a single chassis, which reduces both plant operation area and manufacture cost. TECHNICAL SPECIFICATIONS: - Model: FULLSTAR-110 - Production Capacity: 200-300 Tons Per Hour - 1st Crusher: Primary Jaw Crusher – 1100x850mm - 2nd Crusher: Secondary Impact Crusher – Rotor Ø1250x1500 mm - Maximum Feeding Size: 800 mm - Vibrating Screen Size and Deck: 1st Chassis: 2200x5500 mm : 2nd Chassis: 1700x4500 mm(Grizzly) ¬- Screw Washer Size: 800x8000 mm (Twins Helix) Iaedpfx Aqjy Dpg Ujusu - Total Motor Power: 560 Kw - Generator (optional): 700 kvA - Plant Dimensions: 1st Chassis: 22000 x 4700 x 4700mm : 2nd Chassis: 17500 x 4650 x 4600mm FULLSTAR-110 IS A COMBINATION OF: • Bunker(Hopper) • Vibrating Grizzly Feeder(Bypass) • Primary Jaw Crusher • Secondary Impact Crusher • High Stroke Type Vibrating Screen • Screw Sand Washer (Single Helix) • Folding type feeding, feedback, bypass and stock conveyor belts • Hydraulic feet • Mobile Chassis with axles and tires • Fully Automation System • Dust Suppression System • Easy walking platforms for maintenance • Diesel Generator (Optional) FOR FURTHER INFORMATION PLEASE FEEL FREE TO CALL US!!!

Condition: new, functionality: fully functional, power: 450 kW (611.83 HP), fuel type: electric, color: other, Year of construction: 2026, *All of our products are made with care and covered for 1 year warranty! *Installation and Operator Training FREE FABO MCK-115 is the biggest model of MCK series, those are a mobile type & closed circuit crushing and screening plants that is used for processing of hard materials such as basalt, granite, gabbro, dolomite and other types of hard stones. MCK-115 includes two stages of crushing process which is made by primary jaw crusher and secondary cone crusher. TECHNICAL SPECIFICATIONS: Iedpfsy Dca Uex Aqueau - Bunker: 35 m3 - Plant Dimensions (1st chassis): 13000x4700x4400 mm - Second chassis: 19620x4619x4364 mm - Production Capacity: 180-300 Tons Per Hour - 1st Crusher: Jaw Crusher – 1100x850 mm - 2nd Crusher: Cone Crusher – FABO CC 300 - Maximum Feeding Size: 800 mm - Vibrating Screen Size and Deck: 2200x5000mm 3-4 decks - Total Motor Power: 450 Kw - Generator (optional): 600 kvA MCK-115 IS A COMBINATION OF: • Bunker(Hopper) • Vibrating Grizzly Feeder (bypass) • Primary Jaw Crusher • Cone Crusher • High Stroke Type Vibrating Screen • Folding type feeding, feedback, bypass and stock conveyor belts • Hydraulic feet • Mobile Chassis with axles and tires • Fully Automation System • Dust Suppression System • Easy walking platforms for maintenance • Diesel Generator (Optional) FOR FURTHER INFORMATION PLEASE FEEL FREE TO CALL US!!!

Condition: new, functionality: fully functional, power: 340 kW (462.27 HP), fuel type: electric, color: other, Year of construction: 2026, *All of our products are made with care and covered for 1 year warranty! *Installation and Operator Training FREE FABO MCK-90 is a middle model of MCK series, those are a mobile type & closed circuit crushing and screening plants that is used for processing of hard materials such as basalt, granite, gabbro, dolomite and other types of hard stones. MCK-90 includes two stages of crushing process which is made by primary jaw crusher and Secondary impact crusher. TECHNICAL SPECIFICATIONS: - Bunker: 20 m3 - Plant Dimensions (1st chassis): 11500x4600x4200 mm - Second chassis: 15500x4650x4400 mm - Production Capacity: 100-180 Tons Per Hour - 1st Crusher: Jaw Crusher – 900x650 mm - 2nd Crusher: Secondary Impact Crusher – 1120x1250 mm - Maximum Feeding Size: 600 mm - Vibrating Screen Size and Deck: 1700x4500mm 3-4 decks - Total Motor Power: 340 Kw - Generator (optional): 450 kvA MCK-90 IS A COMBINATION OF: • Bunker(Hopper) • Vibrating Grizzly Feeder(bypass) • Primary Jaw Crusher • Secondary Impact Crusher • High Stroke Type Vibrating Screen • Folding type feeding, feedback, bypass and stock conveyor belts • Hydraulic feet • Mobile Chassis with axles and tires • Fully Automation System • Dust Suppression System • Easy walking platforms for maintenance Iasdpfx Ajy Db T Tsqueu • Diesel Generator (Optional) FOR FURTHER INFORMATION PLEASE FEEL FREE TO CALL US!!!

Condition: new, functionality: fully functional, power: 280 kW (380.69 HP), fuel type: electric, color: other, Year of construction: 2026, *All of our products are made with care and covered for 1 year warranty! *Installation and Operator Training FREE TECHNICAL SPECIFICATIONS: Iodpfx Aoy Db Svsquoau -Production Capacity: 200-450 Tons Per Hour -Crusher Type & Size: Turbo Impact Crusher – 1200x1200mm -Maximum Feeding Size: 700mm -Total Motor Power: 280 kW MIC-120 is a combination of: • Bunker • Vibrating Grizzly Feeder(Bypass) • Turbo Impact Crusher • Folding type bypass and stock conveyor belts • Hydraulic feet • Mobile Chassis with axles and tires • Fully Automation System • Easy walking platforms for maintenance • Diesel Generator (Optional) FOR FURTHER INFORMATION PLEASE FEEL FREE TO CALL US!!!

Condition: new, functionality: fully functional, fuel type: electric, color: other, Year of construction: 2026, Our 400 Ton/Hour Capacity Stationary Crushing and Screening Plant consists of 40 m³ vibrating feed bunker, wobbler feeder, CLK-110 jaw crusher, impact crusher, tunnel systems, stock and return belts, stock bunkers, control cabinet and automation system. The products transferred to the feed bunker are separated from dirt and mud in the first stage of the double-stage wobbler feeder and bypassed by the bypass belt conveyor In the second stage of the wobbler feeder, the products that are suitable for the jaw crusher are sent to the stock area with the transfer belt. The jaw crusher, with a maximum feed of 800 mm, crushes the products and sends them to the fist vibrating screen. In the first vibrating screen, the products are separated in 0-40 mm, 40-90 mm sizes and sent to the stock area. Products above 90 mm size are transferred to the secondary crushing and screening unıt. The products transferred to the tunnel system are sent to the 12-13 S impact crusher. The products crushed in the impact crusher are separated in different sizes by vibrating screen and sent to the stock area. Iedpfxey Db Rrj Aqueau The products stored in the stock area are transferred to the pan feeder by passing through the tunnel system according to the need. The vibrating pan feeder transfers the products to the stock bunkers with the transfer belt conveyor All equipment of the crushing &screening plant is controlled from 3 different automation panels.

Condition: new, Year of construction: 2022, functionality: fully functional, machine/vehicle number: 21_0346, NEW - NEVER USED heavy-duty positioner for manual or robotic welding - lifting and turning device. Special Device for Special Tasks designed and produced by FÖRSTER welding systems GmbH. Max diameter of the workpiece: 2500 mm Max weight of the workpiece: 20 tons Dimensions of the welding positioner: 7000x3000x3750 mm Iaodourlcrspfx Aqusu Weight [without counterweigh]: 20 000 kg Overall dimensions of the whole system: 8900x4800x3750 mm Total weight of the whole system: 40 000 kg Counterweight included with the machine. Full documentation available. Manufacturer's technical support on request. Machine located in central Poland.

Condition: new, power: 161.81 kW (220.00 HP), fuel type: diesel, Year of construction: 2024, For Sale: High-Performance NEW BUILD Dredger Perfect for Dredging in Marinas, Harbours, Sand & Gravel Mining Are you looking for a reliable floating dredger to meet your dredging needs? This high-efficiency with low cost suction dredger is ideal for a wide range of applications, including marinas, harbours, and mining operations. Key Features: Powerful Suction System: Ideal for dredging sand, gravel, slurry, and more. Versatile Applications: Perfect for clearing harbours, marinas, and inland waterways. Durable Construction: Built for long-term use in harsh marine environments. Efficient Operation: Maximize productivity in mining and excavation projects. Specifications: Dredging depth: 10 mtr (can be customized to 15 mtr dredging depth) Pump capacity: 450m3/h Isdpfx Aeu Afi Iequsau Engine power: 220hp Suction pipe diameter: DN200 Whether you're managing a marina, expanding a harbour, or working on a sand and gravel mining project, this suction dredger provides the performance and reliability you need. We design and build new dredging equipment, and we also have used dredgers on stock. Contact us today for pricing and more details!

Condition: new, Year of construction: 2025, Introduction Of Jaw Crusher Plant The capacity vary according customer request. And in order to meet the different demands of customers, the production line can equip with cone crusher, dust removal equipment and other equipment. It is suitable for the materials like hard limestone, granite,basalt, pebble, metallurgy slag and artificial sand making work. It is widely used in the industries of hydroelectric, building materials, highway, and urban construction. And according to different technological requirement, various types of equipment can be combined to meet the demands of different customers. Product Advantages of Stone Crusher Machine Plant 1.High reliability, good stability 2.Convenient maintenance, easy operation 3.Low operation costs, wide application range 4.Laminating crushing makes good discharging grain shape We also provide other stone crushing solutions like 1. Vibrating feeder + Jaw crusher + Fine jaw crusher + Vibrating screen 2. Vibrating feeder + Jaw crusher + Impact crusher + Vibrating screen 3. Vibrating feeder + Heavy hammer crusher + Vibrating screen 4. Sand Production Line 5. Gravel / Aggregate production line A stone crushing plant for sand and aggregate production involves several stages and equipment. Here's an overview of the process and the main components involved: Process Overview 1. Primary Crushing: Large stones from the quarry are fed into a primary crusher, typically a jaw crusher, which reduces them to smaller, manageable sizes. Ijdpfxjq Nyy Es Aqujau 2. Secondary Crushing: The output from the primary crusher is further reduced in size by a secondary crusher, usually a cone crusher or impact crusher. 3. Screening: The crushed material is separated into different size fractions using vibrating screens. Oversized material is returned to the crushers for further reduction. 4. Sand Making: For producing sand, the material might be passed through a sand making machine, like a vertical shaft impact crusher, to achieve the desired shape and size. 5. Washing: The final product is often washed to remove impurities and improve the quality of the aggregate. 6. Stockpiling: The finished product is stored in stockpiles before being transported to customers. Main Components of stone crushing plant 1. Jaw Crusher: Used for primary crushing of large stones. 2. Cone Crusher or Impact Crusher: Used for secondary crushing to produce finer aggregates. 3. Vibrating Screen: Separates the crushed material into different size fractions. 4. Sand Making Machine: Special equipment for producing sand. 5. Belt Conveyors: Transport materials between different stages of the process. 6. Vibrating Feeder: Feeds raw material into the crushers evenly and continuously. 7. Sand Washer: Cleans the sand by removing impurities. 8. Control System: Manages the entire process, ensuring efficient and safe operation. Implementing a well-designed stone crushing plant can significantly increase production efficiency and produce high-quality sand and aggregate.

Condition: like new (used), Year of construction: 2026, functionality: fully functional, machine/vehicle number: EQWDCOM, type of input current: AC, ZDI Quality Welding Consumables, Wires, Rods TIG Welding, Robotic Welding, Qualified Manufacturer, Quality Guaranteed. Iodpfx Aeyaw Hasquoau Wires, Rods, Stainless Steel, Nickel and Nickel Based Alloys, Strip Cladding. ERNiCrMo-3, ERNiCrMo-4, etc.

Condition: excellent (used), Year of construction: 2021, functionality: fully functional, machine/vehicle number: KB-20211022002, 3 x Hangzhou Kuangbo Machinery Equipment Co. Ltd 2000L beer tanks, previously used as a brite tank but can be used as an FV. Technical Specification: Model - KBBFT1300A. Serial number - KB-20211022002 Date of manufacture - 2021. Capacity - 2000 litres. Notes: All 1.5inch Tri Clamp connections other than DIN PRV port on top, manway door, and larger triclamp Iaedpfxjwl H Nij Aquou Features: Port on top for dry hopping etc. 2x thermowells, one for a thermometer at front and one for temp sensor in back & a CIP arm on the RHS, with sprayball.

Condition: used, machine/vehicle number: 92, Continous Form Collator Micro Pack S 50Serial-No. 92-164 / 1992/51/ mpkc 6 Stationen / Stations Iasdorbnnpspfx Aqueu Format / Size max. 330 x 12 Zoll umstellbar bis auf 7 Zoll / convertible until 7 inch Standard 240 x 12 Zoll / inch Einlauf breite bis / Infeed width until 55 cm Crimpung alle 2 Zoll mit Ersatzmesser / Crimp every 2 inches with spare blade Online-Video-Inspection by Skype-Video We would be very pleased with your visit - more machines on Stock Available Immediately - Can be inspect On Stock Emskirchen / Nürnberg - Can be test

Condition: new, Year of construction: 2026, Equipment: documentation/manual, Laser welding machine with 3 kW laser power, laser components from Siemens - welding machine with genuine CE and therefore also German manual, risk analysis and everything that is required to be able to operate a laser welding system in Germany. Wire feed case, also with genuine CE, is also included in the delivery. An introduction can take place here in the company. Ijdpfxjn Sl D Re Aqueau

Condition: excellent (used), Year of construction: 2017, Cell with TIG-OTC-NH52-NEFC welding robotCountry of origin of the cell: Italy Year of manufacture: 2017 Country of origin of the robot: Japan Iasdom Uyhhspfx Aqusu Brand: OTC NH5 Year of manufacture: 2016 Number of axes: 6 Reach: 866 mm Load capacity: 5 kg Control: OTC FD 11 Source: OTC DA 300-P Cell dimensions: Length 3500 mm 1900 width mm Height 2400 mm

Condition: used, This is an LSQ5X welding power source from SKS Welding Systems, together with a Weld Process Controller MULTIPROCESS - Q80 and an SKS Frontpull 8 (23°) Isdpfsuxbx Dex Aqujau

Condition: like new (used), Cove Equipment Shredder Model: SH-5 Iasdpfx Aqsf N Nd Sjuju Stainless shredder, continuous process, ideal for chicken and pulled pork, 750Kgs per hour, 1Ph

Year of construction: 2006, condition: good (used), Flame cutting system, torch, oxyfuel cutting system, machine cutting torch, flame cutting machine, cutting torch, cutting machine, oxyfuel cutting machine, gas cutting torch -Manufacturer: Messer Cutting & Welding, machine cutting torch, flame cutting machine -Type: Quicky Isdpjxy Hqtofx Aquoau -Cutting speed: adjustable -Voltage: 230 V 40 W -Dimensions: 520/280/H330 mm -Weight: 7.8 kg

Condition: used, Speed-Tech Equipment horizontal cardboard baler, bales are approx. 1200 lbs., 6' long x 36" wide x approx. 28" tall, 3 phase, in working condition, winning bidder responsible for proper removal. Iasdjxd D Nzepfx Aqueu