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Wire Drawing of High Tensile Strength and Tough Material

05/30/2013 2:02 AM

Hi Forum,

I am stuck in a problem. We do spring steel wire drawing to make engine valeve springs. The wire rod material has Cr 1% and vanadium 0.05% and usual others. This is a high alooy material but when we do drawing we see lot of scratches, button defects and mechanical defects and oxide problem on final wire. Can you suggest if we need to focus on some particular point in wire drawing to overcome this ?? like drawing lubricants, pickling or phosphate coating etc....kindly help!

thanks in advance

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#1

Re: Wire drawing of high tensile strength and tough material

05/30/2013 4:44 AM

Looks as though you need to take more care in the manufacture of the rods to control the content and uniformity of the alloy AND/OR prepare the surface of the rods before stretching by shaving or grinding.

It's obviously more difficult than this, or, your competitors wouldn't be publishing the solutions:-

http://www.amspringwire.com/valvetechbulletin.pdf

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#2
In reply to #1

Re: Wire drawing of high tensile strength and tough material

05/30/2013 4:54 AM

Hej Randell.....Thanks for your reply!
okay, i understand its important with wire rod making. We get wire rod from Nippon steel which is very high standard manufacturer. Also, we do shaving before drawing . Something in pickling is fishy or wire drawing. your comments

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#3
In reply to #2

Re: Wire drawing of high tensile strength and tough material

05/30/2013 5:28 AM

Can you do a short sample run (or interrupt a run to take a sample) to see if there are any defects immediately after drawing, and, before pickling?

Disclaimer: I know absolutely nothing about this subject, but, sometimes I guess it takes an outsider to ask the obvious questions.

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#7
In reply to #2

Re: Wire drawing of high tensile strength and tough material

05/31/2013 11:02 AM

For a reputable supplier like Nippon, they will help you solve your problems.

They have a vested interest in keeping you happy.

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#4

Re: Wire Drawing of High Tensile Strength and Tough Material

05/31/2013 3:53 AM

Not an specialist in the issue, but some knowledge related, what rises my attention are button defects and oxide problem. I would suggest to inspect the original wire steel as it could be a problem of unsuficient deoxidation or degasing of the steel when steelmaking.

Do you apply cold wire drawing? or you heat to some temperature?

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#5

Re: Wire Drawing of High Tensile Strength and Tough Material

05/31/2013 4:07 AM

Can you get a sample rod from another steel supplier?

If it draws OK, but, you don't really want to change supplier: it will give you some ammunition to ask Nippon steel to look at their process.

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#6

Re: Wire Drawing of High Tensile Strength and Tough Material

05/31/2013 6:48 AM

Please do chemical and physical testing of the wire rod. Check if wire rods are annealed if required as per specifications. Also check the hardness of the rods. Check the wire drawing dies and see if proper lubricant is used while drawing.

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#8

Re: Wire Drawing of High Tensile Strength and Tough Material

05/31/2013 2:09 PM

Uniformity of alloy? What the heck is that supposed to mean? I don't know what button defect means.

I do have many years of steel bar drawing experience and I do know the causes for scratches.

Here is what you didn't tell us that we need to know to actually try to solve the problem rather than just prescribe solutions:

What is carbon content? Is material annealed? Difference between batches that scratch or not? Frequency of scratches?

What lube are you using for drawing? powder/ soap/ liquid oil? are you using a pressure die setup? If oil, how are you filtering it? Are you filtering it?

If I look at your prestraightener ahead of the die, will I find a pile of shavings on the floor?Are the bearings shot on the rollers? are the rollers worn into flat spots? Do some turn intermittently? Can you find scratches going into the die? who looked?

What about bundle tags? Are they held on with steel wire clips? is your operator unable to remove them with his fingers and so letting them get pulled into the initial die?

What carrier are you using ahead of drawing to assure lubricant pick up in drawing?

What is drawing speed?

What means do you have to assure that no swarf from your shaving operation is clinging to the rod and thus building up on die causing intermnittent scratches?

Why are you pickling if you are shaving? (One post suggests that you are shaving the rod ahead of drawing) What acid for that matter? Show me control charts.

What inhibitor are you using in your pickle bath? what is Iron Concentration? What are you adding in your final rinse?

When you say oxide problem on final wire, do you mean red or black? Spotty, streaky or patchy? Any evidence of scale being drawn in?

Now that I think of it, I am thinking about a single draw die operation. Are you talking about a multiple die,multi step process? i so have you calculated step drafts correctly?

Have you looked at the die(s):Wear rings? Die angles? Build up material? how old are dies? If multiple die process are they matched and is reduction schedule appropriate? is the die bearing length appropriate for grade and tensile strength? Angle?

After drawing, what products are applied? What is the exit temperature as drawn? What is the flash point of the products applied after drawing?

One final look at your original post indicates that you are asking about phos coating. Are you actually doing that? or are you considering that? Phos plus Bonderlube? Just plain Phos? How about a list of the steps and processes so that we can point out where you might most profitably look for corrective actions.

It is always easy to blame the supplier, and ask for a comparison to another mills products.I am sure that there are times where giving that kind of advice is appropriate, and maybe even helpful. But I am not one to first blame the supplier.

Problems are seldom solved by denial. A clear look at the process will almost always reveal plenty of opportunities for improvement. Normally I would ask you to take my questions and put them on a fishbone chart, but as I am just focussed on your process, no need to look at other categories. I have full confidence in the qability of Nippon Steel to provide alloy steel rods suitable for drawing.

Good luck.

Milo

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