Thin-walled carbon steel pipe (carbon steel pipe beveling machine)

1. Multiple-choice question 1. When the composition of the steel is constant, the metallographic structure mainly depends on the heat treatment of the steel, and the heat treatment method that has the greatest impact on the metallographic structure of the steel is (). A. Normalizing B. Annealing C. Tempering D. Quenching and tempering [Answer] D 2. According to the "General Installation Engineering Quantity Calculation Specification" (GB50856-2013), the following options do not belong to safe and civilized construction projects ( ). A. Temporary facilities B. Harmful gas protection C. Heatstroke prevention and cooling D. Construction site greening [Answer] B 3. Under the action of impact, vibration and alternating load, anti-loosening devices should be added to the bolt connection. The following options belong to the mechanical device nut yes(). A. Counter nut B. Self-locking nut C. Slotted nut D. Double nut [Answer] C 4. For the boiler system to induce air, the type of fan that should be selected is (). A. Roots fan B. Sliding vane fan C. Centrifugal fan D. Axial fan [Answer] C 5. According to "General Installer

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