JNewman

1020 fully killed steel, a question for the metallurgists

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I have some eyebolts to make and my customer wants 1020 fine grained fully killed steel. My steel suppliers are shrugging their shoulders. From some quick looking on the net continuous cast bar is all fully killed? Is there anything appart from some aluminum in the chemistry on the certs I should be looking for?

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Hi J
thought that they controled oxygen content in most steels... so Al being present should combine with O and contribute to the flux
- i know with the higher carbon steels the grain is mostly to do with normalizing heat treatments and limiting exposure to high temps for long periods ..... there are alloys added to promote fine grain such as V

- i'm not sure how normalizing heats work with lower carbon steels... but i could see how large grain in the eye bolts would be dangerous (brittle )

easy to read into what they are saying... they just want a clean steel with .2 carb with controlled heat treatment ...

lets see what the met eng's have to say

G

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about half way down the page
http://www.engineersedge.com/steel_terms.htm

http://en.wikipedia.org/wiki/Deoxidized_steel


Hope this helps some. It looks like the chemistry of the steel can identify if it is killed or not, but someone with more knowledge will hopefully weigh in.

Phil

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Don't have an answer for you. I did try to do a little research earlier, and I learned that 1018 has more manganese than 1020 typically does. (0.6%-0.9% Mn for 1018, 0.3%-0.6% MN for 1020.) I was thinking that 1018 with carbon in the high end of the range (.15%-.2% for 1018) should be a satisfactory substitute for 1020, but I guess you'd also have to watch the Mn content.

I also found this, although I don't know if it is the applicable standard for what you are doing: http://www.scribd.com/doc/56014965/8/Metallurgical-Structure

When aluminum is used as the grain refining element and on heat analysis the aluminum content is found to be not less than 0.020% total aluminum, or alternately 0.015% acid soluble aluminum, the fine austenitic grain size requirement shall be deemed fulfilled and the testing requirement of 8.1 shall be waived. The aluminum content shall be reported if the testing requirement is waived.


Can't tell you where to buy the stuff, though. I hope this helps.

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Thanks for the replies. There is some good info there, I have gotten MTR's from a couple of suppliers and they say coarse grain. Which does not match what the customer is asking for.

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Hi Phil
that is interesting...i didn't know that Al would lessen alloy segregation.. .. thanks for posting that


timken does have 1020, but i saw that it had Mn in it... which can also refine the grain ...but it can make it abit deeper hardening
- there should be a spec sheet with it ...so you could note the Al level as Matt pointed out with that very cool article he linked
-it maybe worth it to give them a call for tech support..

same with armco
http://www.aksteel.com/markets_products/carbon.aspx

it maybe there are other high strength low alloy steels that can substitute ... if client supplies tech spec's

good luck
G




about half way down the page http://www.engineersedge.com/steel_terms.htm http://en.wikipedia.org/wiki/Deoxidized_steel Hope this helps some. It looks like the chemistry of the steel can identify if it is killed or not, but someone with more knowledge will hopefully weigh in. Phil

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I thought killed steel was used to stamp out valve covers and oil pans and such as it stretches like crazy I may be wrong


I think you are right. It was also the steel used by this mill's blacksmith shop for crane hooks. NOT a higher strength alloy but definitely without voids which cause cold shuts which could potentially cause cracks. Also overloading will cause bending rather than breaking. Bending gives you a warning because you can see movement and realize it it overloaded.

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Fully Killed steel was a term used for the post pouring treatment given to the ingot before it was rolled. It denoted that the top of the ingot was cut off and discarded, this was why fully killed steels were more expensive, to allow for the wastage. As very few places still use the ingot method for general steel manufacture, I cannot get a straight answer from any suppliers/mills here in Aus as to whether I can source true blue Fully Killed steels made recently.
PJH66 the 1020 that you refer to is actually designated CS1020 which is Commercially or Semi Killed plain carbon steel no alloying elements with .2percent carbon. It can't be called fully killed.

John maybe try suppliers who also supply valve steels such as the ASTM105 etc range.
I know that One Steel here in Aus does have a technical reference free call service. I rang it recently as one of their other departments wanted a quote on a 40ton hook and the steel that they requested was getting a little hard to source. You may find that they have such a service in Canada. Is'nt Atlas Steels a Candian company, I seem to recall that they have something similar

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I will ask around about the CS1020. I am also going to ask the customer about another alloy designation that he mentioned his customer asked about. The worst part of this is the job is only for two eye bolts 40mm shank 15mm round forming a seamless loop 140mm dia. So if I have to buy a whole bar, most of the bar is going to sit around for a long time or I will have to just use it as regular mild steel.

Atlas alloys used to be in Welland about an hour from here and was the go to place for a lot of alloy steels. It was shut down several years ago and my understanding that Atlas in now only in Australia.

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PRODUCTS

Bar Sections > Billets > Hot Rolled Merchant Bar > Light Billets Light Billets are available in a variety of steel grades and sizes as summarised below. For detailed information on grades select the appropriate link from the right hand menu.

Due to process limitations not all grades are available in all sizes. For new applications we recommend you confirm product availability with OneSteel Direct on 1800 1 78335 (within Australia only) or email to [email protected] at an early stage of design. Other specifications and sizes may also be available on enquiry.

Additional Info
AS Standard: AS 1442/1022, K1045
Size Range: 45mm, 50mm, 63mm, 75mm
Standard Length: 6.0m


General Enquiry


I have copied and pasted from the Onesteel website re 1022 billet. Also you may do better looking at getting a slab cut from MS plate.

Phil

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I had posted a bit more above on steels then when i pasted the Onesteel stuff I lost a fair bit of what I had typed. Basically that most plate is I think classed as merchant quality if you forge a billet of say 80mm plate down to your 40mm dia you should get enough grain refinement for your finegrained specs

Phil

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Thanks Phil I will check on square bar or plate in the new year. I have some tongs that I make that I have to use plate because the alloy is only available as plate. If I go with plate I can buy only the amount that I need.

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It seems that continuous process steel making would be the equivalent of cutting the top off the ingot to prevent contamination.

Phil

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This fits what I have always understood of "killing" steel



Background

During the steel making process, oxygen may become dissolved in the liquid metal. During solidification, the dissolved oxygen can combine with carbon to form carbon monoxide bubbles. The carbon is added to the steel as an alloying element.
The carbon monoxide bubbles are often trapped in the casting and can act as initiation points for failure.
How Killed Steels are Produced and Their Advantages

Formation of the carbon monoxide bubbles can be eliminated through the addition of deoxidising agents such as aluminium, ferrosilicon and manganese. In the case of aluminium, the dissolved oxygen reacts with it to form aluminium oxide (Alumina, Al2O3). The formation of alumina not only prevents the formation of bubbles or porosity, but the tiny particles or inclusions also pin grain boundaries during heat treatment processes, preventing grain growth. Completely deoxidised steel are known as “killed steels”.
They have a more uniform analysis and are relatively free from ageing. For a given carbon and manganese content, killed steels are usually harder then rimmed steels.
Disadvantages

The disadvantage of using killed steels is they often display deep pipe shrinkage.
Steels That are Typically Killed

Steel that are generally killed include:
• Steels with carbon contents greater then 0.25%
• All forging grades of steel
• Structural steels with carbon content between 0.15 to 0.25%
• Some special steel in the lower carbon ranges

Reference: http://www.azom.com/article.aspx?ArticleID=1697

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"Killing" Steel-

The term originated during the early years of high volume steel production and has to do specifically with the removal of oxygen which is dissolved in liquid steel. IF nothing is done to remove this dissolved oxygen, the liquid metal will appear to boil in the ingot mold as the oxygen is forced from the solidified shell towards the still liquid center and then attempts to float out of that liquid. Today, most steel is killed because that boiling can create problems with the solidified ingot and, more importantly, becasuse dissolved oxygen will reacte with iron, creating solid iron oxide which can remain as a solid particle or inclusion in the steel and these, in sufficient quantity, can have a significant negative impact on the performance properties of the finished component. Today, killing (or deoxidizing) is accomplished by the addition of either aluminum or silicon. These elements will more readily combine with dissolved oxygen than the iron. If the iron is allowed to remain liquid for a sufficient time after the deoxidizing elements are added, the oxide particles will float to the top of the liquid metal and, if good pouring practices are used, the majority of those inclusions will be excluded from the ingot.

Aluminum has the added advantage over silicon in that it can help keep grain size small during heat treatment since it will for aluminum nitride in addition to aluminum oxide. These nitrides will remain in the steelt some degree and, if there enough of them present, they will act like fence posts to prevent grains from growing during heat treatment. The nitrides are dissolved at temperatures above about 1850 F, so they have no affect on forging, but during normalizing and austenitizing, they are present.

Killing has nothing to do withe the steel making method (ingot cast vs. continuous cast) nor does it have anything to do with cropping of the the solidfied ingot. It is strictly related to what happens during the liquid stage of steel making. Cropping of ingots is very important from a forge product standpoint since that is the location in the ingot most likely to have inclusion material, but that is a seperate operation from Killing.

To gaurantee that you have fully killed steel, you may have to get ahold of the mill cert for the specific heat lot you intend to buy. That cert should state if the material has been killed and will what element. If not, look at the aluminum content. It should be at least 0.015% to be considered killed.

Patrick

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I worked in a steel mill for about 9 months and was on the pouring platform once when they made killed steel.. These were old timers which did not offer much in the way of explanations. They said it took out the oxygen. To see a guy walking around with an arm load of soap bar sized Aluminum ingots, and, tossing 2 or 3 into each just poured steel mold was amazing. The Aluminum would just go "poof" and be gone. Watching closely, it seemed that a thin flow of liquid was spread across the top of the steel. Not much in relevant facts, just amazing that Aluminum would disappear so quickly.

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