What is AR400 Steel?

[Ryan225]

This questions from the thread about welding it. I dont want to distract any attention from his thread. What is AR400 Steel and why is it used? What is it commonly used for?

[chip hayden]

it's abrasion resistant steel . it's used for plow blades and such. they add Boron, Manganese, Nickel, and Chromium to make it wear resistant. this also complicates things when you want to "work" it or, weld it.

[Ryan225]

Ok, why exactly would you want to use a 7018 to weld it? Is it the low hydrogen content in the rod that goes good with the makeup of the AR400 steel to prevent hydrogen cracking?

[chip hayden]

hydogen is a nasty little atom that likes to work it's way into the latticework of the steel. it [Hydrogen] tends to break the bond that holds the other elements together. low carbon steels don't have a real problem with this because they are pretty ductile. as hardness increases ductility decreases so the discontinuities [like hydrogen] become an issue when the metal is subjected to a load.
i can visualize this if i think of a piece of plate glass---hard with no flex to it. if i scratch it or, it has an imperfection, it will break at that point if it is pressed.

[Ryan225]

So do low carbon steels contain alot of hydrogen? Or can the levels of each type differ?

[chip hayden]

no. you don't want hydrogen in any steel at all [don't forget, hydrocarbons have hydrogen, i.e. paint, oil, etc.]. it's just that low carbon steels are more "tolerant" of it.

[Ryan225]

Oh ok. So basically then when people use 7018's to weld with, its a high strengh application and the welder is trying to minimize the hydrogen content in the weld. Weather there is little to no hydrogen in the work peices or not. Now I know that not everyone uses the 7018's in this area, but for the AR400 steel for instance, thats what they would do I imagine?

[chip hayden]

many people use 7018 for the wrong reason--appearance not application.
7018 is almost always handled with a glove on because it's gonna be around 225F when you put it in the electrode holder. the base metal is gonna be hot too because you just took the heat blankets off that have been keeping everything warm and dry the last few days.
that's what 7018 was really designed for.

[TOMWELDS]

I recently talked to an engineer at ESAB about 7018. He said it must be stored at 350deg. from the moment you open the box. I told him i keep it in a tube, so how about if i heat it up first? He said, its no longer good, must be kept in an oven. Now realistically, i dont know anyone who stores it in an oven, but thats why i only buy small quantities. I notice the change in performance as it ages. 90% of the time i heat all my rods in a 350deg oven before use, since i do alot of bakery repairs and theres always an oven around. One welder i know grounds the rods out on 10amps for a few minutes before use.

[chip hayden]

i think he had the right idea but, i believe 350F is a little on the hot side for storage. it might cause the flux to delaminate from the wire before you actually weld with it.

[enlpck]

Originally Posted by TOMWELDS

I recently talked to an engineer at ESAB about 7018. He said it must be stored at 350deg. from the moment you open the box. I told him i keep it in a tube, so how about if i heat it up first? He said, its no longer good, must be kept in an oven. Now realistically, i dont know anyone who stores it in an oven,

I do. As does anyone doing code welding. Not a big deal in a shop. On the road is a bit tougher.

Originally Posted by TOMWELDS

but thats why i only buy small quantities. I notice the change in performance as it ages. 90% of the time i heat all my rods in a 350deg oven before use, since i do alot of bakery repairs and theres always an oven around. One welder i know grounds the rods out on 10amps for a few minutes before use.

Lo-Hy rods ned to be stored in a low moisture environment, as the flux will draw moisture from the air. There are three parts to this: 1) the original container is sealed with the rods dry and a moisture free filler gas, 2) When the can is opened, you must stoe the rods at a high enough temp to prevent the flux from drawing moisture from the air, and 3) If the rods DO draw moisture due to improper storage, they can be baked dry at a much higher temp.

The best case is immediate use after opening the can. Most of us don't have that luxury (even a 10lb can is a lot of rod to run in four hours), so we use option 2, heated storage. Most manufacturers recommend about 225 to 275 degrees F-- read the can (or support documentation) for your brand. Generally 250F is sufficient. There may be varients that need a higher temp, but too high a temp will degrade the flux. 350 sounds a bit high, but there are a lot of variations in flux chemistry, so it is certainly reasonable.

Option 3 is a last resort. Most manufacturers don't recommend rebaking more than once, and the temp and time are fairly citical. Too cool or too short, they won't dry completely from worst case, too long or too hot degrades the flux. It is generally not good to rebake more than once. Some shouldn't be rebaked (at least one of the moisture resistant types has an explicit warning not to on the can)

[TOMWELDS]

I keep all my rods at one of the bakeries, were they're in rod cylinders and on a shelf high up. The temp is always 90-95 deg and dry. Ive never had any problems with the 7018 but notice a difference if there open all day while i work. I was thinking about making a cabinet i can mount on the oven so there always hot. There's no doubt that they work better hot.

[TRG-42]

Hi Ryan,

Quenched and Tempered Steel

Steel such as the common T-1 or AR plate all fall into the family of quenched and tempered steel

After the steel is rolled it is quenced ( water ) to increase the hardness and strength . In this state the material tends to be too brittle for practical use so it is then tempered ( in a furnace ) to regain the lost ductility and toughness

First off saying T-1 and AR is like saying Xerox Machine or Kleenex, these are trade names

T-1 Steels ( treade names such as Algoma 100, N-A-Xtra 100, HY-80 etc ) - these steels are generally 100ksi yield strength. Although you can strength match these materials when welding ( E11018 electrodes for example ) it is actually often less problematic to "undermatch " with say a 80ksi YS consumable . You find these materials in trailer frames , truck parts, structural members etc

AR Plate ( trade names such a Algoma 500 , AR500, Hardox etc ) are all quenched and tempered but through a higher alloy content the plate can achieve a much higher hardness and strength. These Q&T plates are generally used for abrasion resistance

Generally speaking steel mills name their AR plate as follows

AR400 = 400 brinell harness . A good rule to know is brinell hardness divided by 2 is the approximate tensile strength

For example, your AR400 is approximately 200ksi TS . Needless to say you don't have a hope in **** to strength match this plate, nor does it matter since thes AR type plates are used for the abrasion resistant properties not strength

Because of this the best filler material to weld AR plate ( since you can't strength match anyways ) is any low hydrogen filler such as E7018 / E8018 . Often in the heavy equipment industry they use a 80ksi filler that has 1% nickel ( such as E8018-C1 ) for the low temperature impact properties if the plate will see lots of pounding

Need for Low Hydrogen and Preheat

No need to get into specifics but it is because of the higher alloy content that increases the need for preheat and a low hydrogen process. Generally speaking these high strength plates are more crack sensitive. This problem is aggrevated by excessive hydrogen content ( from the welding consumable ) and excessive quench ( lack of preheat )

It has little to do with these plates having higher hydrogen content than their mild steel counterparts but rather they are just more succeptible to cracking if the hydrogen content is not controlled.

Just be careful with the preheat because it is real easy to get carried away

Need to Watch Excessive Preheat and Interpass Temp

The steel makers will all give a maximum interpass temp and / or heat input . The reason that you much watch these two is that you can put too much heat into the steel and thereby softening it . In essence you will destroy the hardness and abrasion properties of the material

Low Hydrogen Processes

Processes that are considered low hydrogen are all MIG , all submerged arc, most gas shielded flux cores, some self shielded flux cores and obviously low hydrogen stick electrodes. Where it gets tricky is self shielded flux cores. A good rule is most self shielded flux cores that are qualified for seismic welding will be low hydrogen

If you are ever in doubt, you can always look on the certificate of conformance ( legal document that all welding consumable manufacturers must have on all their filler material ) where it states the "diffusible hydrogen" . A number less than 8 is desirable . Units are ml ( of hydrogen ) per 100gms of weld metal . Typically the a low hydrogen stick electrode will be at least a H8 or H4

I hope this answers your question

[enlpck]

TIG (GTAW) is also lo hydrogen (though impractical for most uses of AR plate)

[Ryan225]

My questions are answered. I learned so much from this topic. Especially from TRG-42, all that was pretty interesting. That brings me to a good point, before you make a repair on heavy equipment its not good to assume its just another peice of steel and take a welder to it, always check with the manufacturer and see what has to be done. I know this does sound like common sense, but I would imagine that people overlook this every day.

Thanks for all the answers guys.

-Ryan