The issue of using 10 steel in place of 20 steel
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The 20 steel used for design purposes, (8163 9948), was welded after the material arrived; testing revealed that its carbon content was low, falling within the range of 10 steel. The wall thickness was checked again using the allowable stress for 10 steel, and there were no issues. I wonder if there are any other issues with using 10 steel in place of 20 steel? Thank you for your guidance, Haiyou.
This post was last edited by Baoji Chaosheng Titanium Industry on 2018-9-12 at 19:57. Within a certain range, the lower the carbon content in steel, the worse its toughness; the higher the carbon content, the better its toughness.
Sorry, there was an error in my previous statement; it has been corrected now.
Carbon is the most important element that determines the properties of steel. When the carbon content in steel is below 0.8%, as the carbon content increases, the strength and hardness of the steel increase, while its plasticity and toughness decrease ； However, when the carbon content is above 1.0%, as the carbon content increases, the strength of the steel actually decreases. As the carbon content increases, the weldability of steel deteriorates (for steels with a carbon content above 0.3%, weldability declines significantly), cold brittleness and sensitivity to aging increase, and resistance to atmospheric corrosion decreases. Carbon steel used in general engineering is always low-carbon steel, that is, it contains less than 0.25% carbon ； The low-alloy steel used in the project has a carbon content of less than 0.52%.
It’s not just a matter of carbon content; standards are also a factor. It’s unclear whether the 10# steel purchased is of type 8163, 9948, or 8162, and 8162 is not allowed to be used for fluid transportation.
9948 can replace 8163, but 8163 cannot replace 9948; 9948 enables non-destructive testing of each wire individually.
If the material list specifies 20# steel but the test results show a low carbon content, then it is an unqualified product. It cannot be assumed to be 10# steel just because its carbon content meets the standards for that grade, as there are other testing parameters specific to 10# steel that cannot all be checked; therefore, the materials cannot be substituted for one another.
It cannot be simply replaced; if replacement is necessary, a process must be followed. Material selection and evaluation are required based on the medium, and parameters such as wall thickness must be recalculated. This process is equivalent to redesigning rather than simply using an alternative material
I asked two teachers from the Eighth Institute about this issue, and I received two different answers.
It can meet the requirements for pipeline corrosion and wall thickness calculation, in addition to pipeline stress analysis； Then it must be possible to use them; all of our heat exchangers’ coils are 10#