Cracks in knife blades

[Markiis]

Hello!  

I have an issue with cracks in my knife blades.
And yes, i do forge when the iron is hot.
I use ordinary construction steel and C75S as knife steel in the middle. (laminated knife)

I have been under training for an experienced blade smith and used the same technique.
But when i was under training, i did not know what kind of steel I was combining.

is it possible that the C75S steel is to porous, or it gets to hot when i forge weld it?
please help me out, i am a little frustrated.

I'm planning to try out 1095 carbon steel tomorrow instead of the C75S.
the 1095 carbon steel is also a little rusty, is it still okay to use it as a laminated knife blade?

sorry for bad English, still learning.  

 Best regards, from a young Norwegian who wants to get into bladesmithing.

[JHCC]

Welcome to IFI! If you haven't yet, please READ THIS FIRST!!!

[Steve Sells]

looks burned

[JHCC]

Do you think it got overheated in the welding, Steve?

[Markiis]

3 minutes ago, Steve Sells said:

looks burned

Hello! and thank you for answering.
Do you mean that i should not heat it so much when i draw/form the knife out or when i forge weld it? when i'm doing the forge weld i use borax and hit the work piece when the "stars" show. I'm i doing anything wrong in this process  ? 

[Daswulf]

The higher the carbon the worse it is for the "stars" to show. In other words you are overheating and burning the steel.  You have to learn and pay close attention to the working temperatures of higher carbon steels. When you start welding different alloys it just gets a little more difficult until you get some experience with it.

Have you made blades from a single steel alloy? You don't have to forge weld different steels for a good blade. And if just starting out, you might not get the best out of it until you know more. 

Just my thoughts. 

 

[SLAG]

Mr. Markiis,

Welcome to the forum.

Mr. Sells has written an excellent primer that can be purchased from this site.

It is called,  "Introduction to Knifemaking".

Try,

www.iforgeiron.com/topic/40865-introduction-to-knifemaking/

Regards,

SLAG.

[Markiis]

1 hour ago, Daswulf said:

The higher the carbon the worse it is for the "stars" to show.

Hey  

I will for sure pay more attention to temperatures of high carbon steels.
would you suggest that i should hit the work piece right away, when i see the first "stars"? And do i need to be more carefully with my hammer strikes under the welding of high carbon steel? 

I started out making knives from single steel alloy to get familiar with forming the blade with the hammer, and now i wanted to take this to the higher level  

Thank you for you're opinion!

[Irondragon Forge ClayWorks]

1 hour ago, Markiis said:

from a young Norwegian

Welcome to IFI... we won't remember your location once leaving this thread, hence the suggestion to edit your profile to show location. This thread will help you get the best out of the forum. https://www.iforgeiron.com/topic/48833-read-this-first/

 

[Daswulf]

If you do want to work on forge welding, you want to find that state before it sparkles "stars" and then all other info on forge welding on these forums applies. There are many posts that even helped me. In the "read this first" that is linked it mentions using your search engine plus iforgeiron after the topic. That will find you more results.

One thing is stick with one thing that is proven to work until you get it down, then you can move on and work on getting another one down. If two steels are known to weld well, stick with those till you have it figured out. And its better if those two are Well known to work if starting out  since many people have success with them. 

[ThomasPowers]

First of all: it is the lower carbon steel that is cracking as it's on the outside of the blade right?

Can you find our what alloy it is?  "ordinary construction steel" doesn't tell us much especially for folks working in the USA where what we use may not be what you are using!

I would try to get a known alloy like 1018 or 1020 (ANSI typology) to use on the outside.

And as everyone has mentioned---if it's producing sparks it's too hot for many steels!

As to the rust; why should that matter?----You are cleaning all the rust and scale off the pieces before you are trying to weld them right?

[Markiis]

11 hours ago, Daswulf said:

If you do want to work on forge welding, you want to find that state before it sparkles "stars" and then all other info on forge welding on these forums applies. There are many posts that even helped me. In the "read this first" that is linked it mentions using your search engine plus iforgeiron after the topic. That will find you more results.

One thing is stick with one thing that is proven to work until you get it down, then you can move on and work on getting another one down. If two steels are known to weld well, stick with those till you have it figured out. And its better if those two are Well known to work if starting out  since many people have success with them. 

I will start checking out these posts right away, and try figure out what kind of steels welds good together

Thank you!

8 hours ago, ThomasPowers said:

First of all: it is the lower carbon steel that is cracking as it's on the outside of the blade right?

Can you find our what alloy it is?  "ordinary construction steel" doesn't tell us much especially for folks working in the USA where what we use may not be what you are using!

I would try to get a known alloy like 1018 or 1020 (ANSI typology) to use on the outside.

And as everyone has mentioned---if it's producing sparks it's too hot for many steels!

As to the rust; why should that matter?----You are cleaning all the rust and scale off the pieces before you are trying to weld them right?

Hello  

Yes, i do think this is right. The lower carbon steel i use is called S235JR according to my supplier. I will for sure try out these 1018/1020 ANSI steels instead.

i will do my best to prevent these sparks, it seems logical. i guess at this point i failed.
would you know how many times i need to forge weld it, before it sticks properly? i usually does this around 2 - 3 times.

I usually clean the lower carbon steel while hot and brush it with a steel brush, then i add borax and just place the high carbon in as it is.  
But only this time, the surface of the high carbon is rusted. I  guess i can grind of the rust and clean it with a chemical methylated spirit?

[Latticino]

To improve your welding success I recommend that you grind all faces of your stock that you expect to weld together to a bright finish to remove any rust, scale or mill scale before heating it.  It is unclear whether you are making a sandwich with high carbon steel inside two layers of low carbon, or just bonding a layer of high carbon to low.  If the latter, I'm sure you are already aware that the high carbon steel welding temperature (and tolerance) is lower than the low carbon.  Depending on what type of forge you are using, you may want to be careful how you deferentially heat the stock.

Try to avoid selection of steel with chromium content, as they can be difficult to weld to others with the same.  I am certainly not familiar with S235JR or C75S, though I expect aht the latter has 75 points of carbon.  If s you may want to consider switching to something with at least 80 or 90 points of carbon to address any losses to carbon migration during the welding process (depending on how thick your center core stock is and how many times you bring it up to welding heats).

I've always found it easier to get a weld to work if the stock pieces are bonded together somehow prior to the forge weld.  If you don't have access to an electric welder to tack the pieces together after cleaning, you can use steel wire to keep things aligned.  Much easier than juggling several pieces of stock, and less chance of missing that critical moment when everything is up to the right temperature.

[Markiis]

4 hours ago, Latticino said:

To improve your welding success I recommend that you grind all faces of your stock that you expect to weld together to a bright finish to remove any rust, scale or mill scale before heating it.

Hello  

Thank you so much for these tips, i appreciate it!  I will give this a try.