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Stainless steel tubing is one of the most versatile metal alloy materials used in manufacturing and fabrication. The two common types of tubing are seamless and welded. Deciding between welded vs. seamless tubing primarily depends on the application requirements of the product. In choosing between the two keep in mind that first the tubing must be compliant with your project specifications and that secondly, it must meet the conditions for which the tubing will ultimately be used.
Though both the words tube and pipe are often used interchangeably, largely because both are hollow shaped, there are important distinctions between the two when determining welded vs. seamless tubing needs. Tubes are measured by the outside diameter (OD) and wall thickness. A pipe, on the other hand, is measured by its inside diameter (ID). In terms of functionality, tubing is generally used in structural and aesthetic applications whereas piping is used for transporting fluids, liquids, and gases.
Knowing that distinction can also help in determining which tubing is best for a given application, welded or seamless. The method of manufacturing welded and seamless tubing is evident in their names alone. Seamless tubes are as defined – they do not have a welded seam. The tubing is manufactured through an extrusion process where the tube is drawn from a solid stainless steel billet and extruded into a hollow form. The billets are first heated and then formed into oblong circular molds that are hollowed in a piercing mill. While hot, the molds are drawn through a mandrel rod and elongated. The mandrel milling process increases the molds length by twenty times to form a seamless tube shape. Tubing is further shaped through pilgering, a cold rolling process, or cold drawing.
A welded stainless steel tube is produced through roll-forming strips or sheets of stainless steel into a tube shape and then welding the seam longitudinally. Welded tubing can be accomplished either by hot forming and cold forming processes. Of the two, cold forming results in smoother finishes and tighter tolerances. However, each method creates a durable, strong, steel tube that resists corrosion. The seam can be left beaded or it can be further worked by cold rolling and forging methods. The welded tube can also be drawn similar to seamless tubing to produce a finer weld seam with better surface finishes and tighter tolerances.
There are benefits and drawbacks in choosing welded vs. seamless tubing.
By definition seamless tubes are completely homogenous tubes, the properties of which give seamless tubing more strength, superior corrosion resistance, and the ability to withstand higher pressure than welded tubes. This makes them more suitable in critical applications in harsh environments, but it comes with a price.
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Welded tubing is generally less expensive than seamless tubing due to the simpler manufacturing process in creating welded tubing. It is also readily available, like seamless tubing, in long continuous lengths. Standard sizes can be produced with similar lead times for both welded and seamless tubing. Seamless tubing costs can be offset in smaller manufacturing runs if less quantity is required. Otherwise, though custom-sized seamless tubing can be produced and delivered more quickly, it is more costly.
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Costs of seamless and welded tubing are also related to such properties as strength and durability. Welded tubing’s easier manufacturing process can produce larger diameter tubing with thinner wall sizes for less. Such properties are more difficult to produce in seamless tubing. On the other hand, heavy walls can be achieved more easily with seamless tubing. Seamless tubing is often preferred for heavy wall tubing applications that require or can withstand high pressure or perform in extreme environments.
Stainless steel is the name of a family of iron-based alloys known for their corrosion and heat resistance. One of the main characteristics of stainless steel is its minimum chromium content of 10.5%, which gives it its superior resistance to corrosion in comparison to other types of steels. Like other steels, stainless steel is composed primarily from iron and carbon, but with the addition of several other alloying elements, the most prominent being chromium. Other common alloys found in stainless steel are nickel, magnesium, molybdenum, and nitrogen.
Stainless steel has many desirable properties that contribute greatly to its widespread application in the making of parts and components across many industrial sectors. Above all, because of its chromium content, it is extremely resistant to corrosion. The 10.5% minimum content makes steel approximately 200 times more resistant to corrosion than steels without chromium. Other favorable properties for consumers are its high strength and durability, its high and low temperature resistance, increased formability and easy fabrication, low maintenance, long-lasting, attractive appearance and it is environmentally friendly and recyclable. Once stainless steel is put into service, it does not need to be treated, coated or painted.
There are many numerical grading systems for stainless steel, designated according to their composition, physical properties, and applications. Each type of stainless steel is classified by its series number and then assigned a numerical grade. The most popular series numbers are 200, 300, 400, 600, and 2000. The most common grades are type 304 and 316 that consist of austenitic chromium-nickel alloys. Cutlery grade stainless steels are found in the 400 Series, which is derived from ferritic and martensitic chromium alloys. Type 420 is known as surgical steel, and type 440 is known as razor blade steel.
For more information, see our page on stainless steel types.
The family of stainless steels is primarily classified into four main categories based upon their crystal microstructure.
Ferritic steels are the 400 Grade stainless steels noted for their high chromium content, which can range from 10.5% to 27%. They have magnetic properties, too, offers good ductility, tensile-property stability, and resistance to corrosion, thermal fatigue, and stress-corrosion cracking.
Typical applications for ferritic stainless steels include automotive components and parts, petrochemical industry, heat exchangers, furnaces, and in durable goods like appliances and food equipment.
Perhaps the most common category of stainless steel, austenitic grade steels are high in chromium, with varying amounts of nickel, manganese, nitrogen, and some carbon. Austenitic steels are divided into the 300 series and 200 series subcategories, which are determined by which alloys are used. The austenitic structure of the 300 series is distinguished via the addition of nickel. The 200 series primarily uses the addition of manganese and nitrogen. Grade 304 is the most common stainless steel.
Sometimes referred to as 18/8 because of its 18% chromium and 8% nickel, it is used in kitchen equipment, cutlery, food processing equipment, and structural components in the automotive and aerospace industries. Grade 316 is another common stainless steel. It is used in the making of a wide range of products such as food preparation equipment, laboratory benches, medical and surgical equipment, boat fittings, pharmaceutical, textile, and chemical processing equipment.
Read more about 304 vs 316 stainless steel
Martensitic stainless steels are in the 400 Grade series of stainless steels. They have a low to high carbon content, and contain 12% to 15% chromium and up to 1% molybdenum. It’s used whenever corrosion resistance and-or oxidation resistance are required along with either high strength at low temperatures or creep resistance at elevated temperatures. Martensitic steels are also magnetic and possess relatively high ductility and toughness, which make them easier to form.
Applications for martensitic stainless steels include a wide range of parts and components, from compressor blades and turbine parts, kitchen utensils, bolts, nuts and screws, pump and valve parts, dental and surgical instruments, to electric motors, pumps, valves, machine parts sharp surgical instruments, cutlery, knife blades, and other cutting hand tools.
As the name implies, duplex stainless steels possess a mixed microstructure of ferrite and austenite. The chromium and molybdenum content is high, with 22% to 25%, and up to 5%, respectively, with very low nickel content. The duplex structure gives the stainless steel many desirable properties. For starters, it offers double the strength of ordinary austenitic or ferritic stainless steels, with excellent corrosion resistance and toughness.
Designated in the 2000 Grade series, duplex stainless steel is ideal for applications in demanding environments such as in chemical, oil, and gas processing and equipment, marine, high chloride environments, pulp and paper industry, cargo tanks for ships and truck, and bio-fuels plants, chloride containment or pressure vessels, transportation, heat exchanger tubes, construction, the food industry, desalination plants, and components for FGD systems.
Injection molding is a complex manufacturing process. Using a specialized hydraulic or electric machine, the process melts, injects and sets plastic into the shape of a metal mold that’s fitted into the machine.
Plastic injection molding is the most widely used components manufacturing process for a variety of reasons, including:
This cost-effectiveness, efficiency and component quality are just some of the reasons why many industries choose to use injection molded parts for their products.
Although on the face of it, the injection molding process may seem simple, there are many parameters which need to be tightly controlled to ensure the overall quality of the plastic components produced. Understanding the process and parameters in some depth will help manufacturers to identify plastic components producers who can provide the quality and consistency they need.
Before the actual process begins, it’s key that the right thermoplastics and molds are selected or created, as these are the essential elements that create and form the final components. Indeed, to make the right selection, manufacturers need to consider how the thermoplastic and mold interact together, as certain types of plastics might not be suitable for particular mold designs.
Each mold tool is made up of two parts: the cavity and the core. The cavity is a fixed part that the plastic is injected into, and the core is a moving part that fits into the cavity to help form the component’s final shape. Depending on requirements, mold tools can be designed to produce multiple or complex components. The repeated high pressures and temperatures that mold tools are put under mean they are typically made from steel or aluminum.
Due to the high level of design and quality of materials involved, developing mold tools is a long and expensive process. Hence, before creating a final bespoke mold, it’s recommended that tools are created, prototyped and tested using computer aided design (CAD) and 3D printing technology. These tools can be used to digitally develop or create a prototype mold that can then be tested in the machine with the chosen thermoplastic.
Testing the tool with the right thermoplastic is key to ensuring that the final component has the right properties. Each thermoplastic offers different characteristics, temperature and pressure resistances due to their molecular structure. Plastics with an ordered molecular structure are called semi-crystalline and those with a looser structure are known as amorphous plastics.
Each plastic’s properties will make them appropriate for use in certain molds and components. The most common thermoplastics used in injection molding and their characteristics include:
The final thermoplastic selection will depend on the characteristics that manufacturers need from their final component and the design of the mold tool. For example, if a manufacturer needs a lightweight part with electrical properties, then PC will be appropriate, but only if the mold doesn’t need to operate above 135C or at very high pressures, which the plastic won’t be able to resist.
Once the right thermoplastic and mold have been tested and selected, the injection molding process can begin.
Injection molding machines can be powered by either hydraulics or electricity. Increasingly, Essentra Components is replacing its hydraulic machines with electric-powered injection molding machines, showing significant cost and energy savings. At their most basic level, these machines consist of a feeder or ‘hopper’ at the top of the machine; a long, cylindrical heated barrel, which a large injection screw sits in; a gate, which sits at the end of the barrel; and the chosen mold tool, which the gate is connected to.
To start the process, raw pellets of the chosen thermoplastics are fed into the hopper at the top of the machine. As the screw turns, these pellets are fed gradually into the barrel of the machine. The turning of the screw and the heat from the barrel gradually warm and melt the thermoplastic until it is molten.
Maintaining the right temperatures within this part of the process is key to ensuring the plastic can be injected efficiently and the final part formed accurately.
Once the molten plastic reaches the end of the barrel, the gate (which controls the injection of plastic) closes and the screw moves back. This draws through a set amount of plastic and builds up the pressure in the screw ready for injection. At the same time, the two parts of the mold tool close together and are held under high pressure, known as clamp pressure.
Injection pressure and clamp pressure must be balanced to ensure the part forms correctly and that no plastic escapes the tool during injection. Once the right pressure in the tool and screw is reached, the gate opens, the screw moves forward, and the molten plastic is injected into the mold.
Once most of the plastic is injected into the mold, it is held under pressure for a set period. This is known as ‘holding time’ and can range from milliseconds to minutes depending on the type of thermoplastic and complexity of the part. This holding time is key to ensuring that the plastic packs out the tool and is formed correctly.
After the holding phase, the screw draws back, releasing pressure and allowing the part to cool in the mold. This is known as ‘cooling time’, it can also range from a few seconds to some minutes and ensures that the component sets correctly before being ejected and finished on the production line.
After the holding and cooling times have passed and the part is mostly formed, pins or plates eject the parts from the tool. These drop into a compartment or onto a conveyor belt at the bottom of the machine. In some cases, finishing processes such as polishing, dying or removing excess plastic (known as spurs) may be required, which can be completed by other machinery or operators. Once these processes are complete, the components will be ready to be packed up and distributed to manufacturers.
Stainless steel products have the characteristics of smooth and firm surface, not easy to accumulate dirt and easy to clean. They are widely used in building materials decoration, food processing, catering, brewing, chemical industry and other fields.
Item No.: 00103
Item No.: 00102
Item No.: 00101
Make an object take root on a wall or board. Twist the middle nut to make the middle screw open the outer pipe wall, squeeze the pre beaten hole wall, and make it not easy to fall off by using friction, so as to achieve the purpose of rooting.
The conventional type of throat hoop is also known as the great American type. The strength of its corrosion resistance is also different with different materials. Customers can choose the appropriate throat hoop according to their actual application.
