How are these two types of pipes cut?

Cut with a cutter. In an emergency, the current of the welding machine can be increased to use the arc to cut through it.

A plasma machine will do; choose the appropriate specification for it based on the wall thickness

A cutting machine will do, but it’s important to use a good quality saw blade; this is determined mainly by the wall thickness of the pipe!

Cutting with a saw machine (the kind with a steel blade) yields better cuts than plasma cutting, and it provides better dimensional accuracy compared to toothed saws (those that use cutting blades). If a toothless saw is not cut properly, it will drift.

Plasma cutting is used for stainless steel, while a toothed saw is sufficient for chromium-molybdenum alloys. Gas cutting is practically useless for stainless steel, but it works okay for chromium-molybdenum alloys; however, the cut edge resulting from gas cutting is uneven and serrated in shape

Stainless steel contains a high amount of chromium, which leads to the formation of Cr2O3 slag with a high melting point and high viscosity at the cut site. This slag adheres to the cut surface, preventing the cutting oxygen from reacting with iron and thus interrupting the gas cutting process.

Grinding wheels... just have high consumption; suitable for small quantities

1. High-pressure water jet cutting: This new technology utilizes water jets with a diameter of 0.80–1.50 mm, and the jet velocity ranges from 600 to 800 meters per second (a speed greater than 2 Mach). The water pressure is 3,000 to 4,000 bars, with a water consumption of only 4 liters per minute. To cut stainless steel using abrasives such as alumina or silicon carbide, abrasive particles are **added to the water flow before it reaches the steel. Modern equipment can cut stainless steel that is 20.0 mm thick. The trimming is precise, and the cut surface is clean and smooth. The heat generated by the cutting process is carried away by water, keeping the metal temperature at only 50–60°C. This, combined with the force generated by the jetted water flow on the metal, can prevent deformation and improve cutting accuracy. 2. Stepped punching: This process uses circular and triangular dies to punch out a series of overlapping holes. Obviously, this process cannot produce extremely smooth cuts, but by using well-designed tools and overlapping the cuts, the edges can meet the requirements for most applications. Portable step-type punching machines are typically used for cutting thin carbon steel sheets; if used to cut austenitic stainless steel, 60% more force is required. Also, the maximum thickness that can be cut by the machine needs to be reduced. The machines in the processing plant can at least punch 8mm stainless steel. Modern machines can also use a combination of shearing and punching to produce the required blanks. 3. Guillotine shears: Most processing plants use this type of hand-operated shear. The blade length of such a shear can reach 3 meters, but if the end of the shear is open, continuous shearing can be used to create cuts that are longer than the blade itself. Be careful not to cut out the steps. Due to the high power required to shear stainless steel, the thickness that can be cut by a shear machine when working with soft steel must be reduced by two gauge sizes when cutting ferritic steel, and by 4 gauge sizes when cutting austenitic stainless steel. Therefore, a shear machine capable of cutting 2 mm of soft steel must have its cutting capacity reduced to below 1.6 mm when cutting ferritic steel, and to below 1.2 mm when cutting austenitic steel; the clearance between the cutting edges also needs to be decreased accordingly. The typical clearance value for cutting austenitic stainless steel is 5%. The vast majority of processing plants are aware of the importance of firmly holding the steel plate during shearing and maintaining the blades in good condition. However, those new to working with stainless steel may not know that, in order to prevent contamination of its surface, protective pads must be placed on the worktable of shear machines or in any areas where contact with carbon steel occurs. If this guillotine shear is also used to cut carbon steel, it is advisable to check the blades before cutting stainless steel in order to remove any carbon steel particles that may be attached and contaminate the stainless steel. 4. Disk shear: The basic working principle of a disk shear is the same as that of a scissor-type shear, but continuous cutting is possible by using disk blades. Steel mills use several blades mounted on two axes to longitudinally cut wide steel coils. However, a pair of blades can also be used to cut a single strip. Some shears can also move the blade to one side during cutting in order to cut wedge-shaped blanks, while others can rotate the cutting tool to cut circular blanks. 5. Saws: Although bow saws and band saws can be used to cut thin sheets, these two types of saws are generally used for cutting medium-thick sheets, structural steel, and pipes. Austenitic stainless steel can undergo cold working hardening; friction must be strictly avoided, and this is a very important point that needs to be kept in mind. Therefore, the saw must be lifted during its return movement. High-speed tool steel saw blades have 8 to 10 teeth per inch when cutting thick materials, and 24 to 32 teeth per inch when cutting thin sheets and tubes. When mechanically cutting austenitic stainless steel, they make 50/80 cuts per minute, while when cutting ferritic stainless steel, they make 100/200 cuts per minute. When cutting on a conventional band saw, use sharp teeth along with a low speed and consistent, small feed rate to maintain the cutting action of the saw blade. 6. Grinding wheel cutting: This method uses a high-speed rotating grinding wheel to cut steel. Grinding wheels are made by bonding abrasives with fibers, resins, or rubber. With skilled manual operation, the grinding wheel can perform fast and accurate cutting, producing neat and **sharp cuts. Using a grinding wheel only allows for straight-line cutting, but this is sufficient for the vast majority of applications. Grinding wheels are usually used to cut pipes. Factories also use grinding wheels to grind through long grooves. On-site repairs usually involve using a hand-held grinder. However, using a hand-operated grinder generates a large amount of dust and metal shavings, so dust removal or protective devices are required. Grinding machines used in manufacturing plants are generally equipped with cooling systems, which helps to reduce dust and prevent thermal damage to the materials. 7. Laser cutting: This technique uses the energy released when a laser beam hits the surface of a steel plate to melt and vaporize the stainless steel. Laser sources typically use carbon dioxide laser beams, with an operating power of 500 to 2500 watts. The power level is lower than that required by many household electric heaters, but the laser beam is focused into a very small area through lenses and mirrors. The high concentration of energy enables rapid local heating, causing the stainless steel to evaporate. Furthermore, due to the highly concentrated energy, only a small amount of heat is transferred to other parts of the steel, resulting in minimal or no deformation. Lasers can be used to cut blanks with complex shapes with great precision, and the resulting blanks do not require any further processing. Laser cutting equipment can be used to cut stainless steel up to 4 mm thick; by adding oxygen to the laser beam, it is possible to cut stainless steel that is 8–10 mm thick, but oxygen-assisted cutting results in a thin oxide layer forming on the cut surface. The maximum cutting thickness can be increased to 16 mm, but the dimensional accuracy of the cut parts is relatively high. Laser cutting equipment is quite expensive, costing over $150. However, since it reduces the costs of subsequent processing, it is still feasible to use such equipment in large-scale production. Since there are no tooling costs, laser cutting equipment is also suitable for producing small batches of components of various sizes that could not be manufactured before. Currently, laser cutting equipment typically uses computerized digital control technology (CNC) systems; with these systems in place, it is possible to receive cutting data from computer-aided design (CAD) workstations via telephone lines. 8. Plasma arc cutting: In this method, a mixed gas is passed through a high-frequency arc. The gas can be air, or a mixture of hydrogen, argon, and nitrogen. High-frequency arcs cause some gases to \"decompose\" or ionize into basic atomic particles, thereby creating \"plasma\". Then, the arc jumps to the stainless steel workpiece, and high-pressure gas blows the plasma out of the cutting torch nozzle at an exit velocity of 800–1000 meters per second (about 3 Mach). In this way, combined with the high energy released when various gases in the plasma return to their normal state, a temperature of 2700°C is generated. This temperature is almost twice the melting point of stainless steel. This causes the stainless steel to melt rapidly, with the molten metal being blown away by high-pressure air streams. Therefore, smoke exhaust and slag removal equipment are required. This method can be used to cut stainless steel with a thickness of 3.0–80.0 mm. The cut surface is oxidized, and due to the properties of plasma, the cut takes on a V-shaped appearance. 9. Manual cutting: Using a conventional manual shear, stainless steel with a thickness of 0.9 mm or less can be cut if the cutting blades are sharp. However, due to the short cutting length per cut, the steel plate tends to curl during the cutting process, and the quality of the cut edges is poor. Manual shear cutting is not recommended, unless the requirements for the edge finish are low or irregular edges do not pose any problems in the subsequent processing steps (such as making it difficult to align the welds). The vast majority of methods for cutting carbon steel can be used to cut stainless steel. However, due to the higher strength of stainless steel and its stronger cold work hardening effect, greater power is required for mechanical cutting, and it also reduces the maximum cutting thickness of the machine. Stainless steel does not burn when cut with oxy-acetylene, but powder can be sprayed into the flame as a heat source. However, burning the powder produces a large amount of smoke. A carbon arc welding torch can be used to drill holes in stainless steel, but the edges are irregular and require trimming in most cases.

Plasma cutting is a commonly used method.

There are numerous cutting methods. For chromium-molybdenum steel, the choice depends on the specific circumstances. Oxyacetylene cutting is quite troublesome when the alloy content is very high; it can be used in cases where the alloy content is lower. The remaining methods are similar to those used for stainless steel, such as plasma cutting, carbon arc gouging, grinding machine cutting, manual sawing, and lathe cutting. It depends on the construction conditions; generally, plasma cutting, carbon arc gas gouging, and grinder cutting are commonly used in on-site construction.