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.

Bright annealing tube

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
Bright annealed stainless steel welded pipe

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.

anaerobic bright annealing furnace

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.

The inside surface of bright annealed (left) and annealed and pickled (right) tubing
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
anaerobic bright annealing furnace

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
anaerobic bright annealing furnace

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.

We have precision equipment to test according to the standard required and PMI test to check the material before delivery.



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