Brief discussion on the annealing temperature

Annealing temperature is the parameter temperature for the combination of the primer and the template, and when the 50% primers and its complementary sequence are shown as the double-stranded DNA molecule, the temperature is a very important factor that affect the PCR specificity. Ideally, the annealing temperature is low enough to ensure effective annealing of the primers and the target sequences, and meantime keep high enough to minimize nonspecific binding. And the proper annealing temperature is ranging from 55  to 70 . Annealing temperature is generally set 5  lower than the Tm of the primers.Above is the definition of annealing temperature applied in the biological engineering. While it has a quite different meaning in the steel pipe welding industry.

In the field of metal processing, annealing temperature is refers to the temperature the metal should be heated to when annealing. And the annealing process is a necessary part no matter in the production of erw steel pipe, ssaw steel pipe or other different kind of welded pipes. According to literatures, different annealing temperature of the metal material is: platinum, 900-1000 ;Copper, 650 ;Brass, 600-650 ;Nickel silver, 650-680 ;Aluminum, 283-350 , etc.

In welded steel pipe production process, whether the annealing temperature reaches the required temperature plays an important role.Welded steel pipe heat treatment usually takes solid solution heat treatment, also known as the so-called "annealing" usually, temperature ranges from 1040 to 1120  (Japan standard). You can also observe through the observing hole of annealing furnace and the welded steel pipe in the annealing area should be in candescent state, but did not appear to soften prolapse.

Followed by the annealing atmosphere. Pure hydrogen gas is usually used as the annealing atmosphere, with its purity best more than 99.99%, and if the other part is an inert gas atmosphere, can also lower the purity, but absolutely can't have too much oxygen and water vapor. Bright annealing furnace should be closed, cut off from the air outside; For adopting hydrogen gas as shielding gas, only a vent is open (used to ignite the discharged hydrogen).Check method is wiping with soap water in each joint cracks in annealing furnace to see if there is gas escaping;One of the easiest place to escape gas is connecting part of the annealing furnace and the pipe, where the sealing ring particularly easy to wear and should be checked and changed regularly.

Finally is to protect the gas pressure.In order to prevent leakage, protection gas should maintain a positive pressure in the furnace, if the hydrogen gas is the protection gas, it general requires above 20 kbar. On the one hand, check whether the furnace material is dry, for the first time loading furnace, furnace material must be dry; On the other hand is to check whether the welded steel pipe residues too much stain, especially if there is a hole in the pipe, do not let the water leak in, or we'll get the furnace atmosphere all destroyed.