10 Questions You Should to Know about Flux Drying Machine

How to weld > 20 questions about welding

20 questions about welding

1. What is welding?

Welding is a family of methods used for joining two workpieces; steel in the case of SSAB. Usually a single heat source, normally an electrical arc, locally melts the two workpieces to form a common liquid pool. When the steel solidifies, the pieces are joined. In many cases, a special steel rod or wire (consumable, filler) is melted into the weld pool to get a good weld joint.

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2. What are the most common welding methods?

The most common welding methods are Shielded Metal Arc Welding (SMAW) more commonly known as MMA or stick welding, Tungsten Inert Gas (TIG), Gas Metal Arc Welding (GMAW) more known as MIG/ MAG welding, submerged arc welding (SAW) and laser welding.

3. Can different welding methods be combined?

Yes. A typical example can be to weld the root pass with TIG and fill passes with MIG/MAG. 

4. Can all steels be welded?

Yes, but it is more challenging to weld some steels than others, depending on alloying and dimensions.

5. How can different steels be welded together?

Welding methods and parameters must be suitable for both steels. Usually, the least weldable steel determines the parameters to be used. 

6. What are the welding consumables?

There is a vast number of consumables. The steelmaker provides advice on these for their different grades. For SSAB steels, see the welding recommendations.

7. How is steel preheated before welding?

Workpieces can be preheated in a furnace with an oxy-fuel flame, with electrical heating mats or with electrical induction. It is crucial not to exceed the maximum temperatures given in the data sheet for the steel grade to be welded. Too high a temperature may negatively affect the properties of the steel.

8. How is welded steel postheated after welding?

Steel workpieces can be preheated in a furnace with an oxy-fuel flame, with electrical heating mats or with electrical induction. It is crucial not to exceed the maximum temperatures given in the data sheet for the steel grade involved. Too high a temperature may negatively affect the properties of the steel.

9. How much hydrogen is allowed in the welded joint?

A rule of thumb is a maximum of 5 ml hydrogen per 100 g weld metal. However, this is in practice not possible to measure. The hydrogen content in solid wires for MAG welding is typically around 1.5-2 ml hydrogen per 100 g weld metal, while cored wires can pick up moisture in the flux which might increase to higher values per 100 g weld metal. Keep all consumables dry and warm, in particular flux-covered and flux-core ones. Packages should be opened shortly before use. 

11. What steels can be welded using hardfacing?

Hardfacing is a procedure where a harder material is welded to the base metal surface to create a protective layer. The method can be applied to all SSAB steels, but for the hardest ones, a soft buffer layer must first be welded on the base plate to reduce the risk of cold cracking into the base plate. All types of conventional welding processes can be used for both the buffer layer and the hardfacing layer.

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12. Can welding be done on the primer?

Yes, it can. However, the primer will increase the porosity in the welded joint. A high-quality weld calls for complete removal of the primer in the welding area. 

13. How much hardness or strength is lost after heating the material?

Hardness deterioration is difficult to control. The maximum heating temperatures stated in the data sheets of the steel should always be respected.

14. What is the heat-affected zone (HAZ) of steel?

The heat-affected zone (HAZ) is close to the welded joint where the temperature has increased temporarily due to the liquid weld pool. HAZ size depends on the heat applied. The mechanical properties of the base steel in the HAZ may change, usually in a negative direction. 

15. How big should the throat thickness be for fillet welds?

The designer has chosen a suitable plate thickness for the expected structural stresses. A rule of thumb is that the throat thickness is equal to the plate thickness for a one-sided fillet weld. For two-sided fillet welds, the throat thickness should be approx. 0.7 times the plate thickness.

16. Why does the plate deform after welding?

Plate shrinkage in the vicinity of the welded joint will vary due to varying peak temperatures and residual stresses of varying sizes will appear. Thin plates will react with deformation and relaxation of the stresses, while the stresses will prevail in thick plates.  

18. What are hydrogen cracks?

Hydrogen cracks in welded joints can form due to the concentration of hydrogen in the material close to the weld, as hydrogen embrittles the material. Hydrogen atoms in a hot welded joint will diffuse and collect at “comfortable” spots, e.g. microdefects in the microstructure. Hydrogen gets trapped when the joint cools. Cracks can initiate from those hydrogen traps after hours or even days. The inevitable residual stresses will elongate the cracks. High hardness and alloying make steels more sensitive to hydrogen cracking. 

19. What can cause a welded joint to fail?

There are many factors that could cause a welded joint to fail. The most common ones are defects in the form of physical discontinuities, poor microstructure, and residual stresses. There are various reasons behind those factors, including choice of design, joint type, joint geometry, welding process, heat input, preheating, and welding consumables. 

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How to weld 20 questions about welding

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Hello everyone,
I’m a new member and a beginner with welding. I have had a few wire feed welders in the past as well as technical college courses on welding during my time in college to become a certified auto mechanic. That being said, I think I have a grasp on the basics but I still struggle with welding more than I’d like to admit. I currently own a Lincoln Electric Handy MIG, used without gas but with flux-cored wire.
I am currently working on a small weekend project with 1” square steel tubing. I am welding very basic butt joints at 45 degree angles and a few 22.5 degree pieces. The trouble I am having is basically every aspect of making a decent weld. (I have the machine set on the factory recommended settings for what I am welding, and I have very briefly experimented with tweaking them in small increments.)
I am unable to even lay a bead down, my welds are just uneven piles of slag and spatter and crud. One major problem I’ve been having is burning through my metal, and I’m not sure how to prevent that from happening while still penetrating the material. The welds that I do have are very bubbly with spatter around most of them, and the metal surrounding the welds is discolored and looks as if it’s been way too hot. I’ve tried changing my travel speed, but faster is just too fast to do anything and slower just blows holes right through my material.
I’m not quite sure how else to describe the problems I’m having, my welds just simply suck! I’m hoping a more experienced welder can help me tweak my process to get better welds.
Thank you guys for helping out the younger newer guys!

*Quick side note: I also struggle with keeping my pieces to maintain the angles they are supposed to sit at. I did my cutting and grinding carefully, but my angles are opening and closing as I weld and making it difficult to even have a simple rectangle with 90° corners! I'm very far from being competent with a welder.

But, I suggest you pause welding things together for a bit.

Get some thick steel, clean it perfectly, and practice on that, just getting the welder to weld.
Lay the steel on a bench, weight it with something, so it does not move, and get used to just welding it. Straight rows, follow a scribed line, that sort of thing.

Flux core isn't considered a good place to start, and also needs reverse polarity from gas mig, so check the set up of the machine.

Ignore factory settings for a bit, more power is better for now, as you've thick steel, you won't burn through.

Pictures will help the experienced welders critique your progress. Hi Wildefalcon thanks for your quick reply. I agree with you totally on practicing on scrap. I actually did do that before i attempted working on my good stuff. I used all sorts of scraps but I also used scrap that was exactly what I’m working on for my project, and i was able to get decent beads that appeared(to me) to have full penetration without burning holes in my stock. I think that’s what makes it so much more frustrating, is I figured I was good to go but as soon as I touched the good stuff I screwed it up.
I would imagine it has to do with the fact that I’m welding a butt joint rather than just laying a bead on a flat piece. As I said, I made sure to do my cutting and grinding carefully this time as I’ve had issues in the past where I was trying to weld up gaps in crooked cuts. I’m really stumped!
As far as the polarity goes, that could very well be a possible culprit. How could I tell the proper polarity/ how could I switch it? I see the +/- lugs under the side cover of my machine, but I’m not sure if it’s already how it needs to be or if I need to switch them.
Thanks! Here are you some pics to help describe my issues. The first ones are my worst ones and then my better ones(I know, still terrible) as well as a joint that i tacked but did not continue to weld on, which from what I’ve read online so far is not the way it’s supposed to look. Also attached is a pic of the machine I’m using. Not totally the bottom of the barrel but definitely one of the cheaper ones you can find out there.
Thanks

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As far as shop illumination, my garage (specifically my workspace) is very well lit with LED ceiling lights as I am always working on something or another here. I forget the exact brand of my mask but off the top of my head I believe it’s a Chicago Electric or Lincoln Electric, and it is a passive lens rather than a self darkening lens. Again, not the top of the line, but not horrible either. It has served me well so far, and when I do create an arc my vision of my workspace is clear. The passive lens does although make it difficult when just doing tacks or stitching short little welds(which does seem to produce much better results than attempting a steady solid bead.)
You both mentioned better prep/cleaning, is that because of the cleanliness of the metal you can see in the pictures or because you can tell by my welds that it is dirty?
I am currently using magnetic clamps designed to hold the two work pieces at different angles and such. Are these not strong enough and possibly causing my angle issues?
Thanks again guys, it’s a huge help to have input from more experienced welders!!

@Tangledfeet that is the EXACT wire I’m using actually! If I’m not mistaken, it came with the machine when I bought it a year or two ago.
Again, it seemed to work just fine when I did my practice runs on flat scrap metal of the same type that I’m using for this project. Could there be an issue with my butt joints somewhere??

Ah, that's good - I did wonder if it might come with the machine. I'm no expert, others here are; just clean the weld area beforehand, play around and practice!

(Also, for your own health - plenty of ventilation!) I had to dig for anything left of my practice runs as they were actually done quite some time ago, before I started on this current project. I have this one bit that I had been playing on. I’m sure the rust and grime that developed doesn’t help the image much and these are some of the worse ones. Again, I know they’re horrible to almost any standard, but where you see I did a simple line on top of the stock I feel as if I had decent penetration and I didn’t burn through at all. Where you see that I tried to weld the two scrap pieces together at a 45° butt joint, well....you guys can see how that went. Like I said, It seems as soon as I attempt a joint I just completely butcher it.
I definitely have seen and heard from countless experienced welders that the preparation makes all the difference, but I have also read that flux core is forgiving of dirty metal and wind etc. I haven’t experienced any forgiveness from this welder so far, haha.
Again I know my welds are not great to begin with, but is there maybe some trick or concept of butt joints that I’m unaware of/doing incorrectly that can cause some of these problems? It often seems almost as if I’m pushing weld right down in between the two pieces.

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