Tube Specifications
- A213 – Seamless Stainless Steel Boiler, Super heater, and Heat-Exchanger Tubes
- A249 – Welded Stainless Steel Boiler, Super heater, Heat Exchanger, and Condenser Tubes
- A268 – Seamless and Welded Stainless Steel Tubing for General Service
- A269 – Seamless and Welded Austenitic Stainless Steel Tubing for General Service
- A270 – Seamless and Welded Stainless Steel Sanitary Tubing
- A688 – Welded Austenitic Stainless Steel Feedwater Heater Tubes
- A789 – Seamless and Welded Stainless Steel Tubing for General Service
Custom Grades of Stainless Steel Tube
- Austenitic: 201, 304/304L, 316/316L, 317/317L, 347/347H, 321/321H, 904L
- Ferritic: 409, 430, 439, 441, 434, 436, 444, 446
- Martensitic: 403, 410, 410S, 414/L, 441, 418, 420, 440, 416
- Duplex: 2205/S31803, S32750, S32760
Cold finished stainless steel tube technology flow chart:
Our specialized process for seamless tubing manufacturing begins with either an extruded hollow tube or a solid bar drilled to our exacting specifications. The material is then reduced in size a number of times through various cold working techniques until it reaches the specific size, tolerances, and temper required by our customer. After each cold working cycle the tubes are cut, cleaned and heat treated in preparation for the next cold working step.
Stainless Steel Bar-Inspection – Peeling – Cut – Center – Heating – Piercing – Inspection/Grinding – Pickling – Cold Rolling/Drawing – Pickling – Solution Annealing – Straightening – Cutting – Bright Annealing/Annealing Pickeling – Composition Inspect – Marking – Packing – Storing – shipping
Pilfering
Pilfering reduces the size of the tube across three dimensions – outside diameter (OD), internal diameter (ID) and wall thickness. We roll a die set with a tapered groove across the outside of the tube while supporting the inside diameter using a taper-matched, hardened steel mandrel.
In a single cold working step, we can achieve a significant reduction in cross-sectional area while minimizing material loss and, most importantly, improving the material’s microstructure. Seamless tubes constitute the majority of volume processed by tube reducing or pilgering.
Cold Rolling
Like pilgering, tube rolling also uses compression to reduce the size of seamless tubes. However, while pilgering uses a pair of grooved, tapered dies to work the metal over a tapered mandrel, tube rolling utilizes one or two sets of rolls with constant cross-section grooves on the circumference of the tube.
Generally, the process employs a cylindrical mandrel with little or no taper. The rolls are driven by rack and pinion gears of different radii along profiled cams, completing multiple 360º rotations around the tube.
Cold rolling is a very precise method of reducing very thin walled and/or smaller diameter tubes, and is often used as the final cold working step. By rolling, we’re able to achieve exceptional control over dimensional tolerances and surface finish while also minimizing material loss and improving the metal’s microstructure.
Because it uses compression, tube rolling is well suited to processing unique metals like titanium and zirconium alloys.
Our cold rolling capabilities include both classic 2-roll (single roll set) tube rollers and an advanced 3-roll approach.
Cold Drawing
Typically used as the first form of size reduction for seamless tubes, cold drawing reduces the diameter by pulling the tube through a die that is smaller than the tube. In order to fit the tube into the die, one end is ‘swaged’ or ‘tagged’ thereby reducing the diameter of the leading end before drawing. Next, the narrowed end is passed through the die and clamped to a drawing trolley which pulls the tube through the die. After drawing the ‘tag’ is cropped from the tube end prior to cleaning.
Three types of cold drawing techniques:
Sink drawing
This is the simplest of the three drawing methods, as there is no tooling to support the ID surface. The tube is drawn through a die made of polished tool steel or industrial diamond, thereby reducing its inside and outside diameters. Our specialized lubrication and application techniques, combined with our proprietary die profiles, enable the OD surface to become smoother as the tube is drawn. Since the inside diameter is not constrained, the wall thickness of the tube will normally increase during drawing, and the ID surface finish will normally become rougher during a sink draw.
Rod drawing
Rod drawing is our most commonly used cold draw method, primarily for intermediate or in-process drawing stages, where both the outside diameter and wall thickness are reduced at the same time.
The tube is loaded over a hardened steel mandrel rod and both are then drawn through a die. This squeezes the tube onto the rod, reducing the outside diameter and thinning the wall simultaneously. The die and mandrel determine the size of the drawn tube, which is then slightly expanded by applying pressure to the outside of the tube so that the rod can be removed. Since larger reductions in cross-sectional area can be achieved by rod drawing, this method is used for mid-process stages to reduce tube sizes prior to the final drawing cycle.
Plug drawing
This type of drawing is used to achieve the best possible surface finish and the greatest control over both dimensions and final temper. The outside diameter and wall thickness of the tube are both reduced during plug drawing, as the tube travels through a die and over a stationary plug/mandrel made of high grade tool steel. The plug or mandrel has a polished surface and is attached to a fixed back rod, which is carefully positioned within the drawing die. The tube is loaded over the mandrel/back rod. As the tube passes through the die, the burnishing action of the metal flowing over the stationary plug imparts a high tolerance surface finish inside the tube.
When properly lubricated and prepared, the ID will show very few flaws and finishes of 16 RMS or better can be achieved. Plug drawing is normally chosen for the final draw stage because it achieves a high quality surface finish, exceptional dimensional control, and positive influence on tensile strength requirements.
Annealing
Annealing is used to soften the metal before further cold working or fabrication processes, and improves the overall metallurgical microstructure of the tube. During tube reduction or cold drawing, it can become hard and somewhat brittle. To be able to draw the tube again, stresses formed during cold working need to be removed to return the material to its normal state.
During annealing the tube is heated to a controlled temperature (up to 2100°F) and soak time. Through this process the tube remains in shape, but the grains in the structure of the tube reform into a regular unstressed pattern. The resulting annealed tube is softer and suitable for redrawing.
Our closely controlled annealing and heat treat processes are audited regularly by our nuclear, medical, and aerospace customers.
Straightening
Drawing and annealing generally results in some degree of bowing, producing a slight bend in the tubing. We use multiple roll mechanical straighteners in the first stage of finishing. The straightener applies pressure and flex to the product in order to remove bends or bows, resulting in a straightness level of 0.010” per foot, or better. Straightening can introduce slight changes to the size and mechanical properties of the tubing, so these aspects are very carefully controlled during the process.
- Marking: SunnySteel, material grade, standard, specification, heat no.
- Surface Treatment: Bright annealed, polished outside and inside surface.
- Package: knitting strip bundle, wooden box or steel box
- Mill test certificate: according to EN 10204 3.2
- Inspection: Third party inspection, or by clints
Range of application
Common Applications for Stainless Steel Tubing Stainless steel tubing has a number of uses in a wide variety of industries. It can be used during manufacturing in processing plants or can become part of a final product. Stainless steel tubing can also be used in pipelines to transport oil, gas, water, or chemicals.
Stainless steel tube is typically measured by its outer diameter and can be used in a variety of applications including a number of structural applications. Stainless steel tubing is extremely durable and able to withstand corrosion. This tubing will not rust, even if exposed to the elements, heat, and other extreme conditions. Because of these factors, stainless steel tubing can be used for a wide variety of applications.
The stainless steel tubing that is supplied by SunnySteel can used in a variety of industries, including:
Considering the importance of outside and inside surface of stainless steel tubes for fluid power industry, Our mills are providing tubes that are free from scale, rust, seams, laps.
- Machinery Parts
- Food and Beverage Processing
- Pharmaceutical
- Biotechnology
- Automotive
- Marine
- Construction
- Chemical
- Oil and Gas
The main requirement for stainless steels is that they should be corrosion resistant for a specified application or environment. The selection of a particular "type" and "grade" of stainless steel must initially meet the corrosion resistance requirements.
Additional mechanical or physical properties may also need to be considered to achieve the overall service performance requirements.
Ferritic stainless steel tubes
Ferritic Stainless Steel Tubes, in principle, ferrite at all temperatures. This is achieved by a low content of austenitic forming elements, mainly nickel, and a high content of ferrite forming elements, mainly chromium. Ferritic types, such as 4003 and 4016, are mainly used for household utensils, catering equipment and other purposes where corrosion conditions are not particularly demanding.
Steel with high chromium content, such as 4762 with 24% chromium, are used at high temperature where their resistance to sulphurous flue gages is an advantage. However, the risk of 475 °C embrittlement and precipitation of brittle sigma phase in high-chromium steel must always be taken into consideration. Ferritic stainless steel, such as 4521 with extremely low carbon and nitrogen contents, find greatest use where there is a risk of stress-corrosion cracking.
Ferritic stainless steel have slightly higher yield strength (Rp 0.2) than austenitic steels, but they have less elongation at fracture. Another characteristic that distinguishes ferritic steel from austenitic material is that ferritic steel have much lower strain hardening.
Ferritic grades have been developed to provide a group of stainless steel to resist corrosion and oxidation, while being highly resistant to stress corrosion cracking. These steels are magnetic but cannot be hardened or strengthened by heat treatment. They can be cold worked and softened by annealing. As a group, they are more corrosive resistant than the martensitic grades, but generally inferior to the austenitic grades. Like martensitic grades, these are straight chromium steels with no nickel. They are used for decorative trim, sinks, and automotive applications, particularly exhaust systems.
Mainly Standard include:
- ASTM A268 Standard Specification for Seamless and Welded Ferritic and Martensitic Stainless Steel Tubing for General Service
- JIS G3463 Stainless Steel for Boiler and Heat Exchanger Tubes
- GB/T 30065 Welded ferritic stainless steel tubes for feedwater heater
- GB/T 30066 Welded ferritic stainless steel tubes for heat-exchanger and condenser
The stainless steel tubing that is supplied by SunnySteel can used in a variety of industries, including:
- Type 430 The basic ferritic grade, with a little less corrosion resistance than Type 304. This type combines high resistance to such corrosives as nitric acid, sulfur gases, and many organic and food acids.
- Type 405 Has lower chromium and added aluminum to prevent hardening when cooled from high temperatures. Typical applications include heat exchangers.
- Type 409 Contains the lowest chromium content of all stainless steels and is also the least expensive. Originally designed for muffler stock and also used for exterior parts in non-critical corrosive environments.
- Type 434 Has molybdenum added for improved corrosion resistance. Typical applications include automotive trim and fasteners.
- Type 436 Type 436 has columbium added for corrosion and heat resistance. Typical applications include deep-drawn parts.
- Type 442 Has increased chromium to improve scaling resistance. Typical applications include furnace and heater parts.
- Type 446 Contains even more chromium added to further improve corrosion and scaling resistance at high temperatures. Especially good for oxidation resistance in sulfuric atmospheres.
Comparison Chart
| GB | ISO Unified Digital Code | ASTM / ASME | UNS Code | EN Code | Company Commercial Grade |
|---|---|---|---|---|---|
| 06Cr13Al | S11348 | 405 | S40500 | 1.4002 | – |
| – | 409 409L | S40900 | 1.4512 | ||
| 0Cr13SiAl | – | – | – | 1.4724 | SIC9(Sanyo)/ 1C256(Sandvik) |
| 10Cr17 | S11710 | 430 | S43000 | 1.4016 | – |
| 022Cr18Ti | S11863 | 439 | S43035 | 1.451 | – |
| 019Cr19Mo2NbTi | S11972 | 444 | S44400 | 1.4521 | – |
| 0Cr18SiAl | – | – | – | 1.4742 | SIC10(Sanyo)/ 1C356(Sandvik) |
| 0Cr24SiAl | – | – | – | 1.4762 | SIC12(Sanyo) |
| 16Cr25N | S12550 | TP446-1/TP446-2 | S44600 | 1.4762 | 2C52/2C48(Sandvik) |
| 1Cr25Ti | – | – | – | – | QS25T(Sanyo) |
| 00Cr27Mo3Ni2TiNb | – | S44660 | S44660 | – | Sea-Cure(Plymouth Tube) |
| 00Cr29Mo4TiNb | – | S44735 | S44735 | – | AL29-4C(ATI) |
| 00Cr29Mo4Ni2TiNb | – | S44736 | S44736 | – | AL29-4-2(ATI) |
| – | S44300 | S44300 | 1.4522 | 443 |
