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We manufacture steel poles and outdoor sports lighting fixtures. We experienced the same thing you are experiencing about 1 year ago.
( v+ F, n8 l! D5 L3 N8 u/ l& ROur problems were either related to- n' y- ^8 D( p3 S4 g. {
a) high phosphorus content
6 J2 ?6 W! |7 I" O' gor
/ |5 u, j3 I8 L# x* v- A7 Eb) high silicon content.
. m8 G9 E! {, k R4 s& L' z# NOur galvanizer first alerted us of the problem before the product had even made it out of their plant. They speculated what the problem was, but asked if they could keep a couple samples to have chemically analyzed to confirm for us. We agreed and sure enough they were right. To date, every time we've had problems with galvanizing this has been the problem.
7 F1 @1 }4 j& r% `! vThrough a lot of headaches, we were able to work with them to define the chemical content of the steel. This information is available through the American Hot Dip Galvanizers Assoc. They can also give you information that I won't really go into (particularly since I'm no expert) to explain the effects of high silicon and/or high phosphorus. If you continue to pursue, you will likely find, as we did, that good galvanizing can be assured if the chemical content of the steel meets one of the 3 following criteria.* S/ s& {7 ?$ O6 N$ V$ N* o7 O
1)" r7 T h# Q+ i7 U! e7 H/ Y( x4 m
Carbon < or = .25%
& m6 @. y b4 Y5 ]$ x4 i$ V; PSilicon < or = .04%
" y/ S1 `$ N5 k( L0 W8 n7 G7 aPhos. < or = .02%% h& M. }0 s# R4 |
2)
8 R) {& E7 A& @Carbon < or = .25%
* e/ M# o1 s! FSilicon between .15% and .20% {we've had success going as high as .25% on silicon with this criteria)
% y) |6 \& b) j, ~8 ^! mPhos. < or = .02%1 ~1 c) @2 Q( j8 d
3)
; H/ [$ C) Q! L gCarbon < or = .25%
: T* P6 t! |% S j* J6 ESilicon + 2.5 (PHOS) < or = .09%0 ^* [8 Z: j* s) |4 c3 W! x
The farther you can stay below the upper limits the better your success will be. Also, you'll find that equation 2 primarily pertains to ASTM A36 material. Equation 3 will allow silicon or Phos to exceed the limit in equation 1, as long as the other decreases.
: ^ B+ e% s- K8 G: |Lastly, when we added these specs to our prints our vendors' first reaction was that it would be more costly material. That has never really materialized. We do require mill certification now with all steel received that will be galvanized. |
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发表于 2008-10-15 21:08:15