你不知道的活塞杆要求——漫话API618-2024

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API618-2024版中，将活塞杆的要求如下。

6.10.4.1 Unless otherwise specified, all piston rods, regardless of base material, shall be coated with a wear-resistant material.

除非另有规定，所有的活塞杆，无论是什么基材，都应带耐磨材料的涂层——活塞杆经常和填料接触，带了涂层是为了提高活塞杆和填料的寿命。

最常用的采用HVOF高速火焰喷涂碳化钨。

Uncoated piston rod may be proposed when the expected life equals or exceeds that of a coated rod for the specified operating conditions. Uncoated piston rods shall be surface-hardened in the packing area to a hardness of at least Rockwell C50 and shall be inspected for cracking by magnetic particle examination.

当无涂层的活塞杆的预期寿命得到或者超过带涂层的活塞杆时，可以提供无涂层的活塞杆方案。无涂层的活塞杆应该在填料处进行表面硬化，硬度至少达到Rc50，并且通过磁粉检测检查裂纹。

6.10.4.2 Techniques that require temperatures high enough to permanently affect the mechanical characteristics of the base material shall not be used. High-velocity and high-impact thermal coating processes are acceptable for the coating of piston rods. Metal spray techniques requiring roughening of the surface of the base metal shall not be used.

如果施工涂层时，需要高温，且高温会影响基材的机械特性时，这种施工工艺不能使用。可以使用高速高冲击热喷涂工艺。如果金属喷涂工艺需要刮毛基材，那这种喷涂工艺不得使用。

Piston rods that have been previously induction-hardened shall not be coated with a wear-resistant material over the induction-hardened case.

如果活塞杆在涂层前，已经感应淬火硬化了的话，就不能再涂耐磨材料涂层了。

6.10.4.4 Tolerances for finished rods shall be 12.5 μm (0.0005 in.) for roundness and 25 μm (0.001 in.) for diametral variation over the length of the rod.

最终活塞杆的成品的圆度公差为12.5微米，长度方向上的直径变化公差为25微米。

The surface finish in the packing areas for lubricated and nonlubricated services shall be 0.15 μm to 0.4 μm (6 μin. to 16 μin.) Ra.

最终成品活塞杆的填料处的粗糙度，如果是有油润滑时为0.15微米，如果时无油润滑时为0.4微米。——镜面精度了

Piston rods with threads shall be furnished with rolled threads

活塞杆如果带有螺纹，螺纹应该时旋压的。——相对于车削螺纹，滚压螺纹具有更高的强度，更好的表面质量，更高的精度等。