Jane Tian

Seamless Steel Pipe HS Code List (HS 7304)   Heading 7304: Tubes, pipes and hollow profiles, seamless, of iron (other than cast iron) or steel. The subheadings below follow the HS 2022 six-digit structure. National tariffs add further digits; see “Does the HS Code Differ by Country?” below.     Category HS code (6-digit) Description Carbon and non-alloy steel (general-purpose tubes) 7304.31 Circular cross-section, of iron or non-alloy steel, cold-drawn or cold-rolled   7304.39 Circular cross-section, of iron or non-alloy steel, other (not cold-drawn or cold-rolled) Stainless steel (general-purpose tubes) 7304.41 Circular cross-section, of stainless steel, cold-drawn or cold-rolled   7304.49 Circular cross-section, of stainless steel, other Other alloy steel (general-purpose tubes) 7304.51 Circular cross-section, of other alloy steel, cold-drawn or cold-rolled   7304.59 Circular cross-section, of other alloy steel, other Line pipe for oil or ... Continue reading →

Can Galvanized Steel Pipes Be Painted?   Yes, galvanized steel pipes can be painted to improve their appearance or add another protective layer. However, the zinc-coated surface requires proper preparation to ensure good paint adhesion. Cleaning the surface and choosing a compatible primer and topcoat are key steps in achieving a durable finish.   Paint for GI Pipe: Topcoat Options   Choose GI pipe paint that is compatible with your primer and suited to where the pipe will be used. Confirm on the data sheet that the whole system is rated for galvanized surfaces.   Epoxy paint: It offers good adhesion and corrosion resistance. Epoxy paint for steel pipe can be used as a primer or protective coat on galvanized pipe when the product is rated for galvanized surfaces. Standard epoxy coatings may chalk and fade in sunlight, so exposed outdoor pipes are often finished with a weather-resistant topcoat. Polyurethane paint: It has good weather resistance and high gloss, so ... Continue reading →

Quick Answer: The difference between GI and MS mainly comes down to zinc coating and corrosion protection. GI (Galvanized Iron) refers to iron or steel that has been coated with zinc, and modern GI pipe is usually galvanized steel pipe. The zinc layer helps protect the base metal from corrosion. MS (Mild Steel) is low-carbon steel with no zinc coating, so it usually needs paint, oil, or other protection depending on the service environment.   GI pipe is often made from mild steel, so the main difference is usually whether the steel is galvanized, not that the two are completely different base metals. Coating: GI has a zinc layer; MS has none Corrosion resistance: GI has built-in zinc protection; MS needs added protection Cost & weldability: MS is usually cheaper and easier to weld; GI usually costs more and needs extra care when welding In short, when comparing GI vs MS, GI is chosen when long-term corrosion resistance matters more than cost, while MS is chosen when strength, ... Continue reading →

After welding, post-weld treatments such as pickling and grinding are necessary to remove the oxide layer (colored) and restore corrosion resistance. A color chart is often used to determine whether the weld needs pickling based on the color grade. However, this decision is subjective, and in principle each color indicates the presence of oxidation and an affected oxide layer, so the corrosion resistance of the 304 stainless steel pipe is reduced.   Contaminated surfaces are usually cleaned using mechanical or chemical methods. Organic contamination may be caused by lubricating oil, while inorganic contamination such as foreign iron particles may be caused by contact with the tool. Generally, all kinds of surface contamination on stainless steel welded pipes can cause pitting. In addition, foreign iron particles may cause galvanic corrosion. Both pitting and galvanic corrosion are localized forms of corrosion that initially require water treatment. Therefore, surface ... Continue reading →

1. Manual deburring Use files, sandpaper and tools to polish 304 stainless steel pipes and remove burrs. This method does not require high technical skills of workers. This method is suitable for products with small burrs and simple structures. Therefore, it is also widely used in general enterprises to remove burrs. However, the cost of manual deburring is high, and the efficiency of deburring is not very high.   2. Punching and deburring Punching and deburring are carried out by processing the die on the punching machine. The punching die requires a certain amount of rough and fine punching die, and it may be necessary to make a finishing die. It is suitable for simple products, and the efficiency and effect of deburring are better than manual methods.   3. Grinding Deburring The method of removing burrs from steel pipes by vibration, sandblasting and rollers is widely used by enterprises. However, the problem with grinding deburring is that it is sometimes not removed ... Continue reading →

Elbow fittings are essential components in piping systems, used to change the direction of fluid flow. Elbow fittings are available in a variety of materials, such as carbon steel, stainless steel, and alloy steel. Elbow fittings can be classified by angle, radius, connection design, and function. Common types include 45-degree, 90-degree, 180-degree, long radius, short radius, reducing, and mitered elbows.   Types of Elbow Fittings   1. 90-Degree Elbow Description: This is the most common type of elbow, used to change the direction of the pipe by 90 degrees. Applications: Widely used in plumbing, heating, and cooling systems. Variants: Available as long radius (1.5D) and short radius (1D).   2. 45-Degree Elbow Description: Used to change the direction of the pipe by 45 degrees. Applications: Often used in situations where a slight change in direction is required, reducing the pressure drop compared to a 90-degree elbow.   3. 180-Degree Elbow (Return Bend) ... Continue reading →

Types of Elbow Fittings 45 Degree Elbow: A 45-degree elbow refers to an elbow with a bending angle of 45 degrees. It is usually used for turning and connecting pipes. It can effectively change the flow direction of the pipe, and because its angle is relatively small, the resistance of the fluid is relatively small, so it is often used in some situations with faster flow rates. 90 Degree Elbow: A 90-degree elbow refers to an elbow with a bending angle of 90 degrees. It is one of the commonly used types of elbows. However, due to its large angle, it will increase the fluid resistance around the pipe and also produce greater hydraulic losses. Therefore, when designing pipelines, it is necessary to select the appropriate elbow type according to the specific situation. 180 Degree Elbow: A 180-degree elbow refers to an elbow with a bending angle of 180 degrees. It is usually used for backflow and control of pipelines. Due to its large bending angle, it will cause large hydraulic losses and ... Continue reading →

The spiral steel pipe forming angle is the acute angle between the center line of the strip steel (or coil) and the axis of the formed pipe. In SSAW pipe production, it is calculated with the forming angle formula cos α = B / (π × D), where B is the strip width and D is the mean diameter of the pipe. The angle determines which strip width is needed for a given pipe diameter, so it directly affects raw material use, forming quality, and production efficiency. The formula is given below, followed by a calculation example. Spiral Steel Pipe Forming Angle Formula   The forming angle formula for spiral steel pipe (SSAW) is: cos α = B / (π × D)   Where: α = forming angle, the acute angle between the center line of the strip steel or coil and the axis of the formed spiral steel pipe B = width of the strip or coil D = mean diameter of the steel pipe (outer diameter − wall thickness) Once B and D are known, calculate the ratio B / (π ... Continue reading →

A steel pipe supplier quotation states the price and terms a supplier offers for your inquiry. When several suppliers quote the same inquiry, unit prices can differ widely, but a lower price does not always mean a cheaper offer. The quotations may cover different grades, wall thicknesses, testing scopes, or delivery terms.   To compare steel pipe supplier quotations, first confirm that every quotation matches your required specification and purchasing conditions. Then compare specifications, total cost, delivery, testing, and documentation side by side, using the same price basis and delivery point.   What is a Steel Pipe Supplier Quotation?   A steel pipe supplier quotation is a supplier's written response to a buyer's inquiry or RFQ. It sets out the pipe offered, the quantity, the price, and the commercial conditions. A complete steel pipe quotation usually contains:     Item What It Covers Pipe Specification Pipe type, grade, standard, size, length ... Continue reading →

304 stainless steel pipes can lose their brightness due to dust, dirt, oil, stains, and improper cleaning. Regular cleaning and proper surface care can help maintain their smooth and bright appearance.   This article introduces simple methods for cleaning, polishing, and maintaining the brightness of 304 stainless steel pipes.     (1) If there is dust and dirt on the surface of the stainless steel welded pipe, wash it with soap, weak detergent and warm water.   (2) Use warm water and weak detergent to wash the trademarks and films of 304 stainless steel pipes, and use alcohol or organic solvents to scrub the hard-to-tangle binder components.   (3) If acid adheres to the surface of the 304 stainless steel pipe, immediately rinse it with water, then soak it with ammonia solution or neutral carbonated soda water solution, and then wash it with neutral washing or warm water.   (4) The rust caused by dirt on the surface of the 304 stainless steel pipe can be ... Continue reading →

Hot rolled 304 stainless steel tube production follows a continuous sequence from solid billet to finished seamless steel pipe. Each stage affects the tube's final dimensions, surface condition, and mechanical properties, which is why manufacturers control the process closely rather than treating it as a single operation.   1. Raw Material Preparation The process starts with a solid 304 stainless steel round billet. Before it enters the line, the billet surface is inspected for cracks, scale, or other visible defects, and it is cut to the length required for the piercing operation. The center of the end face is marked to guide the piercing point.   2. Heating The prepared billet is charged into a heating furnace and brought to a uniform rolling temperature. Even heating throughout the billet is important — uneven temperature distribution can cause off-center piercing or wall thickness variation later in the process.   3. Piercing The heated billet is fed into ... Continue reading →

As we all know, 304 stainless steel pipes are added with chromium, nickel and other metal elements, and the composition is relatively high, which is easy to oxidize into a high-density passivation film. However, in some environments, such as coastal areas or humid warehouses, chloride ions can easily penetrate and corrode the passive film of stainless steel, and stainless steel will gradually corrode and rust over time. Passivation treatment can improve the corrosion resistance of stainless steel pipes.   Does 304 stainless steel pipe need passivation treatment? What are the benefits of passivating stainless steel pipes?   Passivation is a passivation film produced on the surface using chemical reagents under the action of metal. It is very thin, dense, has good coverage and is firmly adsorbed. It is usually a compound that oxidizes metals. It completely separates the metal from the corrosive medium, prevents the metal from contacting the corrosive medium, basically stops ... Continue reading →

What is a Steel Pipe MTC?   Quick Answer: A steel pipe MTC is a document that records material identification, chemical composition, mechanical properties, and applicable test results to demonstrate compliance with specified requirements.   MTC is used interchangeably with steel pipe mill test certificate, steel pipe material test certificate, and steel pipe material certificate in most B2B transactions — they refer to the same type of document, typically issued by the manufacturer or mill that produced the pipe.     What a specific MTC must contain depends on the standard called out in the purchase order (such as an ASTM, API, or EN specification), the product type, and any additional requirements agreed between buyer and supplier. Not every steel pipe MTC will contain identical fields, and buyers shouldn't assume one standard's requirements apply to a pipe ordered under a different standard. Steel Pipe MTC Buyer Checklist   Check Item What ... Continue reading →

304 stainless steel pipe cannot be hardened by heat treatment — its strength only increases through cold working. Annealing (solution treatment) is the process manufacturers use instead: it restores corrosion resistance, relieves internal stress from cold working, and rebuilds the material's original ductility. Getting the annealing process right matters just as much as the raw material grade, since incorrect temperature, atmosphere, or sealing can undo the benefits of the stainless steel itself. The annealing requirements for 304 stainless steel pipe are as follows:   1. Whether the annealing temperature reaches the specified temperature. 304 stainless steel pipe heat treatment is generally taken to solve the heat treatment, which is commonly known as the "annealing", the temperature range of 1040 ~ 1120 ℃ (Japanese standard). You can also observe the hole through the annealing furnace observation, the annealing area of the stainless steel pipe should be ... Continue reading →

The heat treatment of 304 stainless steel pipes mainly includes heating, heat preservation and cooling. It can improve the mechanical properties and processing properties of the steel pipe. Common heat treatment methods include annealing (reducing hardness and improving processing properties) and quenching (increasing hardness, but the quenching effect of 304 stainless steel is limited). However, due to the characteristics of 304 stainless steel itself, the heat treatment process requires delicate operation to avoid affecting its corrosion resistance and mechanical properties. But occasionally, some defects are found in the heat treated materials.   What Causes Material Defects in Heat Treatment?   1. Overheating When the material is kept at high temperature for too long or the temperature is too high during the heating process, the austenite grains will coarsen. This phenomenon is also called overheating, which will directly lead to a decrease in the toughness of the ... Continue reading →

Oil pipe systems are made up of several key components that work together during drilling and production. The main parts — casing, drill pipe, and derrick — each serve a distinct structural and functional role in the wellbore. This article breaks down what oil pipes are made of, how casing, drill pipe, and derrick are constructed, and how these components function together in oil rig operations. The Basic Components of Oil Pipes   Oil tubing is a casing made of cast steel and usually consists of three main parts: casing pipe, drill pipe and derrick. Among them, the casing is the main component installed in the wellbore, and its function is to support the oil layer and protect the borehole wall; the drill pipe is used to drill through the rock and soil, and can also be used to lift and install the casing; the derrick is the component that supports the drill pipe so that it can rotate in the wellbore.   Composition of casing   The casing is composed of a ... Continue reading →

Square Tube Thickness Specifications   1. Classification by thickness range   Thin-walled square tubes typically range in thickness from 0.8 to 3 mm and are often cold-rolled to achieve high precision. Suitable for decorative and lightweight supports (such as billboard frames and furniture frames), they offer advantages such as light weight, low cost, and ease of cutting and welding. Medium-walled square tubes: 4–10 mm thick, produced through hot-rolled or cold-drawn processes, offer balanced strength and toughness. Widely used in general industrial equipment (such as machinery housings and workshop guardrails) and building secondary structures (such as purlins and support beams). Thick-walled square tubes: ≥12 mm thick, mostly hot-rolled, offering strong pressure and impact resistance. Suitable for heavy-duty structures such as bridge load-bearing components, large equipment bases, and high-pressure pipeline frames.   2. Common standard specifications   ... Continue reading →

Electric resistance welded pipes (ERW steel pipe) are longitudinally welded from metal after moving it afterward. CDW pipes are produced by expelling the metal to the required length; Hence ERW pipes have a welded joint in its cross-section, while CDW pipes do not have any joint in its cross-section all through its length.   They are called CDW (Cold Drawn Welded) pipes; in some regions, the same pipes are also referred to as CEW (Cold Electric Welded) pipes, and the two names are generally used interchangeably. These pipes are broadly used in the automotive industry and furthermore to manufacture gears, special-purpose machines, hydraulic hardware, apparatus, and so forth. Much the same as seamless precision tubes, they too have low carbon content, are very flexible, reasonable for bowing. If required, these tubes will be toughened after being drawn, fixed, and experience a pickling procedure that gives it a fantastic flawless package process. ERW Pipe VS. CDW Pipe: What's ... Continue reading →

Food grade 304 stainless steel pipe and industrial 304 stainless steel pipe use the same basic 304 stainless steel grade, but they may differ in surface finish, cleanliness, manufacturing requirements, applicable standards and end use. Food grade pipes are designed for applications where hygiene and contamination control are important, while industrial pipes are selected mainly according to pressure, corrosion resistance, strength and service conditions. Understanding these differences can help you choose the right 304 stainless steel pipe for food processing or industrial applications. Difference between Food Grade 304 Stainless Steel Pipe and Industrial Stainless Steel Pipe   1. Heavy metal content The main difference between food grade 304 stainless steel pipe and industrial pipe is that the heavy metal content of food grade 304 stainless steel pipe is much lower than that of industrial pipe. According to the standard GB 31604.34-2016 "National Food Safety Standard Food ... Continue reading →

304 and 201 stainless steel pipes are both austenitic stainless steels, but they differ in composition, corrosion resistance, mechanical properties, cost, and applications. 304 stainless steel offers better corrosion resistance and is widely used in demanding environments, while 201 stainless steel is a more economical option for less corrosive applications. This article compares 304 and 201 stainless steel pipes to help you choose the right material for your project. 1. Material composition analysis   201 stainless steel pipe 201 stainless steel belongs to austenitic stainless steel, and its main components include: Nickel: low, generally between 3% and 5%. Chromium: usually between 16% and 18%, Manganese: high content, generally between 5% and 7.5%. Silicon and carbon: relatively low. Compared with 304 stainless steel, 201 stainless steel relies more on manganese to improve corrosion resistance, which is one of the important reasons for its lower cost.   304 stainless ... Continue reading →