Low Alloy Steel Striations After Being Coated w/ Zinc Phosphate
Low Alloy Steel Striations After Being Coated w/ Zinc Phosphate
(OP)
Basically, we have some fully machined bolting inserts (7+'' O.D.)that are made from 4340 and were normalized, quenched and tempered, prior to machining. We sent these inserts out to get phosphated.
When the inserts were returned, there were light gray bands along the body, of varying diameter and varying shades of gray. I have attached a photo to this post.
The coater calls it heat treat marks and says he has seen it before in low alloy steels. However, he has no idea what causes it.
Has anyone else seen this phenomenon before and if they have do they know what causes it?
When the inserts were returned, there were light gray bands along the body, of varying diameter and varying shades of gray. I have attached a photo to this post.
The coater calls it heat treat marks and says he has seen it before in low alloy steels. However, he has no idea what causes it.
Has anyone else seen this phenomenon before and if they have do they know what causes it?





RE: Low Alloy Steel Striations After Being Coated w/ Zinc Phosphate
RE: Low Alloy Steel Striations After Being Coated w/ Zinc Phosphate
If there was not much machined from the OD after heat treatment (say, less than 1/32" on the diameter), you could be seeing effects from processing the original bar that remain after machining and heat treatment.
rp
RE: Low Alloy Steel Striations After Being Coated w/ Zinc Phosphate
These parts get sandblasted prior to coating. Is that not enough to remove any sort of etching defect that we would see on the surface?
RE: Low Alloy Steel Striations After Being Coated w/ Zinc Phosphate
RE: Low Alloy Steel Striations After Being Coated w/ Zinc Phosphate