ERW steel pipe is in accordance with API-5L standard or GB / T 9711.1-1997 standard. These standards do not specify the temperature range of ERW welded pipe, and the discussion is as follows:
1. Regarding the range of welded steel pipes suitable for high temperature areas: foreign countries also use seamed pipes under high temperature and high pressure. Straight seam steel pipes and seamless pipes are all metal products. For example, the Japanese standard ISO only recognizes the standard, regardless of the seam and seamless.
Effect of temperature on metal deformation: At high temperatures, the ability of metals to resist plastic deformation is generally smaller than at low temperatures. Therefore, the higher the temperature, the lower the strength and hardness of the metal, and the higher the plasticity and toughness.
From the metallographic point of view, the temperature limit of hot or cold metal processing is distinguished by the recrystallization temperature. All pressure processing performed above the recrystallization temperature is called hot processing, and pressure processing performed below the recrystallization temperature is called cold processing. Steel must be processed at 600-700 ° C before it is considered hot, 400 ° C or cold.
b. From the general knowledge of metal heat treatment:
When the temperature is 200 ℃, the yield limit of carbon steel is not reduced but increased slightly. Therefore, when the carbon steel body is operated at a high temperature below 250 ℃, the effect of temperature on static strength may not be considered.
c. The effect of temperature on fatigue strength:
At a high temperature of 350 ℃ -400 ℃, the fatigue strength of carbon steel has not decreased, but increased.
The above analysis shows that there is a scientific basis for using cracked pipes under high temperature and high pressure conditions abroad.
