Bright annealing tube

Bright annealing tube under a reducing atmosphere or in a vacuum protection, after high temperature solid melting and rapid cooling to get the stainless steel tube, requiring the inner surface has a very good surface roughness and cleanliness, is a comprehensive consideration of organizational stability corrosion resistance and workability of the pipe.

Please send your inquiry by sales@sunnysteel.com

Category: Stainless pipe

Description

Bright annealed tube inner surface roughness Ra values and their own cleanliness is extremely demanding, so the particles can occur during transport and accumulation of fluid retention has been effectively curbed. In addition, the chemical composition of the pipe and the base material dimensional tolerances need to be strictly controlled to ensure the weldability of steel and the welding quality in the welding fumes, which can reduce the occurrence of particle generation and improving the corrosion resistance of welded parts, and smoothness.

Bright annealed stainless steel welded pipe is widely used in making military products, semiconductor, biological medicine, precision instruments and meters, hydraulic parts and many other industrial products.

Bright annealing is an annealing process performed in a vacuum or a controlled atmosphere containing inert gases (such as hydrogen). This controlled atmosphere reduces the surface oxidation to a minimum which results in a brighter surface and a much thinner oxide layer. Pickling is not needed after bright annealing since the oxidation is minimal. Since there is no pickling, the surface is much smoother which results in better resistance to pitting corrosion.

Bright annealing tube production control:

Smelting raw materials must have good control, the level required to meet the microstructure times better level.
Cold rolling volume control and reasonable within the organization in order to avoid defects.
Mold control, to ensure the inner and outer surface roughness R a ≤ 0.3μm.
Bright annealing control to ensure reasonable mechanical properties and surface brightness, and eliminate the pass mechanical polishing (MP), to ensure the smoothness of the inner surface under microscopic state, to avoid transmission fluid residues.
Cleaning the control surfaces should have the products delivered better cleanliness and cleanliness, with metallic colors, no oil adhesion, oxide adhesion.
Single hats loss prevention bagging, overall braid or wooden packaging.

The material of the stainless steel round bar is from Jiuli and Baosteel China, we control the quality from the very start. We polished three times to make sure the surface is perfect bright and smooth, and without any deficiency in quality.

bright annealed and annealed — The inside surface of bright annealed (left) and annealed and pickled (right) tubing

The Bright Annealing Tube System can either be placed standalone or in-line with surface reduction equipment to create a total in-line process. Innovative design allows for easy changeover from product to product, and each system is equipped with automatic power control and precision temperature control through recipe parameters.

Designed for ease of operation and maintenance
Automatic speed sensor controls power proportionate to line speed
Recipe storage and retrieval
Integrated temperature sensing
High wear ceramic tube guides
Integrated pumping system
Solid state inverters, operating in both medium and high frequencies

Bright annealing (BA) refers to stainless steel material is heated in closed furnace in reducing atmosphere of inert gases, common Hydrogen gas, after fast annealing, rapid cooling, stainless steel has a protective layer on the outer surface, no reflect in open air environment, this layer can resist corrosion attack. In general, material surface is more smooth and brighter.

Bright Annealing Tube

Tube is processed in bright annealing finish, in this process, some factors are important for quality tube, if bright annealing process is not proper, that will result in crack, then may corrosion.

Before Bright Annealing

The surface of the tube must be clean, no other foreign matter, any matter left on the tubing surface can cause damage during the process.

Inserted Gas

Annealing atmosphere should be free from Oxygen, isolating material, creating a vacuum condition. Inserted gas, common dry hydrogen or argon, can obtain bright result.

Annealing Temperature

Annealing temperature should be noticed depending on different stainless grades, commonly Austenitic steels annealing temperature is at least 1040 degree, soak time is not important. high temperature must be required to have brighter appearance. Heating is done as fast as possible, slow heat results in oxidation.

Some Ferritic stainless steels require lower annealing temperature, such as TP439, cannot be effectively bright annealed, Water quenching will cause scale formation.

Specifications

Welded : A249, A269, A789, EN10217-7
Seamless: A213, A269, A789
Grade: 304, 304L, 316, 316L, 321, 2205
Finishing: Bright annealing

Sized:

Out diameter: 3 mm – 50.8 mm;
Wall thickness: 0.3 mm – 3 mm
Forms: round, U bend, coiling

Stainless Steel Tube Bright Annealing Marking & Packing

Marking according to MPS and Standard
Stainless Steel Tubes Ends with Caps according to PO
In Seaworthy Wooden Cases With Plastic Paper protect
In Plywood Cases With Plastic Paper Protect(Recommend, All Plywood Cases made by ourselves with lower cost.)
Steel Racks Package
Hexagonal packing in Bundles

Bright Annealing Technology of 316 Thin Wall Stainless Steel Tube

1) Elimination of work hardening to obtain a satisfactory metallographic arrangement

When the performance requirements are not used together, the request for the metallographic arrangement after the light annealing is different, and the technology of the light heat treatment is also different.

300 series austenitic stainless steel like the 316 stainless steel tube typical heat treatment technology is solution treatment. During the heating process, the carbides are dissolved into the austenite and heated to 1050-1,150°C. for a short time so that all the carbides are dissolved in the austenite and then rapidly cooled to below 350°C. To obtain a supersaturated solid solution one-way austenitic arrangements. The key to this heat treatment technique is rapid cooling, which requires the cooling rate to reach 55 °C / s and rapidly pass through the carbide remelt temperature zone (550-850 ° C). Insulation time to try to be short, otherwise coarse grains, affecting the appearance of finish.

400 series ferritic stainless steel like the 410 stainless steel tube heating temperature is relatively low (about 900 ℃), and more use of slow cooling to obtain annealing softening arrangements. Martensitic stainless steel annealing method used, but also the choice of sub-quenching and tempering method of treatment.

From the above we can see that 300 series and 400 series stainless steel in the heat treatment system vary greatly, in order to obtain qualified metallographic arrangements, to request light annealing furnace cooling section equipment has great conditioning. Therefore, the modern leading light annealing furnace, the cooling section is usually used in the selection of strong convection cooling, set up three cooling sections, can regulate air flow alone. Along the width of the strip is divided into three sections, through the air flow diversion conditioning strip width of the cooling rate, the control panel stainless steel cold-rolled strip heat treatment. Another crucial question is that the whole strip is required to be arranged in width and length are uniform. Muffle light annealing furnace selection of large-scale muffle tube, muffle tube from outside the uniform arrangement of heated air spiral around, so that strip uniform heating. But to ensure that the strip along the length of the uniform arrangement, we must adhere to the strip in the furnace speed unchanged. Therefore, before and after the modern vertical light heat treatment furnace can be equipped with a fine adjustment of the roller tension adjustment equipment. Not only does it make the import and export speed of steel strip satisfied with the request of heat treatment speed, it is not influenced by the empty set or full set of looper, and the tension of strip should be established and finely adjusted according to the strip shape condition of strip steel, request.

2) Obtain the appearance of non-oxidative light

Bright annealing, is the H2 maintenance atmosphere on the strip heat treatment. To reach the request of the BA board, it is necessary to very strictly control the furnace maintenance atmosphere, try to avoid oxidation. How does H2 maintain the oxidation of the atmosphere?

The main alloy components of stainless steel are Fe, Cr, Ni, Mn, Ti, Si and so on. In the annealing temperature range, oxidation of Fe and Ni is not the primary question. However, the oxidation intervals of Cr, Mn, Si and Ti are just within the heating temperature range. It is the oxidation of these alloying elements that affect the strip’s apparent brightness. In particular, the oxidation of chromium strip appearance of chromium, will reduce the corrosion resistance of stainless steel. When Cr content is 17% ~ 18% and Ti content is 0.5%, it is necessary to lower the dew point of H2 below -60 ℃ to avoid the oxidation of Cr and Ti in the heating range of 800 ℃ ~ 1150 ℃.

In addition, how to maintain the purity of the gas in the furnace is also questionable. In this regard, the muffle seal is good, and will not attack such as electric heating furnace pollution of the maintenance atmosphere, providing a more purely environmental space. In addition, vertical furnace strip entrances and exits are located at the bottom of the furnace, the furnace pressure is stable, so compared with the horizontal furnace, the risk of air entering much smaller. But bright annealing furnace import and export of sealed boxes, strip delivery section, tension conditioning roller and roof guide roller box should be guaranteed to reach the parts per million (ppM grade) of the sealing request, so that oxygen, water vapor can not enter the maintenance of gas can not escape.

Standard & Grade

Normal standard

Item	ASTM A213/A213M		ASTM A312/A312M
Grade	TP304	TP304L	TP304	TP304L
	TP316	TP316L	TP316	TP316L
	TP317	TP317L	TP317	TP317L
	TP347	TP310S	TP347	TP310S
	TP309H*	TP310H*	TP317*	TP310H*
		TP321HΔ		TP321HΔ

Normal chemical composition of stainless steel

Grade	C (max)	Si (max)	Mn (max)	P (max)	S (max)	Ni	Cr
TP 304	0.08	0.75	2	0.04	0.03	8-11	18-20
TP 304H	0.04-0.10	0.75	2	0.04	0.03	8-11	18-20
TP 304L	0.035	0.75	2	0.04	0.03	8-13	18-20
TP 309S	0.08	0.75	2	0.04	0.03	8-13	18-20
TP 310S	0.08	0.75	2	0.045	0.03	12-15	22-24
TP 316	0.08	0.75	2	0.04	0.03	19-22	24-26
TP 316L	0.035	0.75	2	0.04	0.03	10-15	16-18
TP 316Ti	0.08	0.75	2	0.04	0.03	11-14	16-18
TP 317	0.08	0.75	2	0.04	0.03	11-14	16-18
TP 321	0.08	0.75	2	0.04	0.03	9-13	18-20
TP 321H	0.04-0.10	0.75	2	0.04	0.03	9-13	17-20
TP 347	0.08	0.75	2	0.04	0.03	9-13	17-20
TP 347H	0.04-0.10	0.75	2	0.04	0.03	9-13	17-20

Grade	Tensile Strength Min(Mpa)	Yeild Point Min(Mpa)	EL. Min(%)	Rockwell Max
TP 304	515	205	35	90
TP 304H	550	240	35	90
TP 304L	485	170	35	90
TP 309S	515	205	35	90
TP 310S	515	205	35	90
TP 316	515	205	35	90
TP 316L	485	170	35	90
TP 316Ti	515	205	35	90
TP 317	515	205	35	90
TP 321	515	205	35	90
TP 321H	515	205	35	90
TP 347	515	205	35	90
TP 347H	515	205	35	90

Heat treatment technology of stainless steel pipe surface

For the heat treatment technology of the surface of stainless steel pipes, non-oxidation continuous heat treatment furnaces with protective gas are generally used abroad for intermediate heat treatment and final heat treatment of finished products. As a bright surface without oxidation can be obtained, the traditional pickling process is eliminated. The adoption of this heat treatment process not only improves the surface of stainless steel pipes, but also overcomes the environmental pollution caused by pickling.

According to the manufacturer of stainless steel pipes, according to the current world development trend, bright annealing continuous heat treatment furnaces are basically divided into the following two types:

(1) Roller-type bright annealing heat treatment furnace.

This bright annealing furnace type is suitable for heat treatment of large-size and large-volume special-shaped stainless steel pipes, with an hourly output of above 1.0 Tons. The protective gases that can be used are high-purity hydrogen, decomposed ammonia and other protective gases. It can be equipped with a convection cooling system to cool the special-shaped stainless steel tube faster.

(2) Mesh belt type bright annealing heat treatment furnace.

This bright annealing furnace type is suitable for small-diameter thin-walled precision special-shaped stainless steel pipes. The hourly output is about 0.3 to 1.0 Tons. The length of the steel pipe can be up to 40m. It can also be used to process capillary tubes in coils. Equipped with convection cooling system for fast cooling. Using gas fuel or electric heating, various protective gases can be used. The stainless steel pipe after this furnace-type heat treatment has no scratches and good brightness surface.

Tensile test and hardness test of stainless steel pipe?

Tensile strength test is to make a sample of stainless steel pipe, pull the sample to break on a tensile testing machine, and then measure one or several mechanical properties, usually only the tensile strength, yield strength, elongation after fracture and section are measured Shrinkage. Tensile strength test is the most basic test method for mechanical properties of metal materials. Almost all metal materials require tensile test as long as they have requirements for mechanical properties. Especially for those materials whose shape is not convenient for hardness test, tensile strength test becomes the only means of testing mechanical properties.

The hardness test is to slowly press a hard indenter into the surface of the sample with a durometer under specified conditions, and then test the depth or size of the indentation to determine the hardness of the material. Hardness test is the simplest, fastest and easiest method in material mechanical property test. The hardness test is non-destructive, and there is an approximate conversion relationship between the material hardness value and the tensile strength value. The hardness value of the material can be converted into the tensile strength value, which has great practical significance.

Because the tensile strength test is not easy to test, and it is convenient to convert the hardness to the strength, more and more people only test the hardness of the material and less test its strength. In particular, due to the continuous advancement of hardness tester manufacturing technology and innovations, it is now possible to directly test the hardness of some materials that could not be directly tested before, such as stainless steel tube, stainless steel sheet and stainless steel strip. Therefore, there is a tendency for hardness tests to gradually replace tensile tests.

Process

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.

Cold finished stainless steel tube technology flow chart

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

Packing

There are probably hundreds of different methods for packing stainless pipe, and most of them have merit, but there are two principles that are vital for any method to work prevent rusting and Sea transportation security.

We inventory stainless steel grades that are readily used in manufacturing such as 304, 304L and 316/L to harder to find items such as 309H, 330 or 405 stainless.

the wooden boxes packing for stainless products

Application

Stainless steel pipe (tube) has excellent characteristics of corrosion resistance and smooth finishing. Stainless steel pipe (tube) is commonly used in demanding equipment like automobiles, food processing, water treatment facilities, oil and gas processing, refinery and petrochemicals, breweries and energy industries.

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.

Inquiry

Need to inquire about our products? Fill out the form below and our staff will be in touch!

FAQ

Q: How long is your delivery time?
A: The delivery time of customized products is generally 25 35 days, and non customized products are generally shipped within 24 hours after payment.

Q: Do you provide samples? Is it free?
A: If the value of the sample is low, we will provide it for free, but the freight needs to be paid by the customer. But for some high value samples, we need to charge a fee.

Q: What are your payment terms?
A: T/T 30% as the deposit,The balance payment is paid in full before shipment

Q: What is the packaging and transportation form?
A: Non steaming wooden box and iron frame packaging. Special packaging is available according to customer needs. The transportation is mainly by sea.

Q: What is your minimum order quantity?
A: There is no minimum order quantity requirement. Customized products are tailor made according to the drawings provided by the customer.