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Sage advice on welding fancy steels for fun and profit without electricity

Hardware

Member
I am seeking a sage of the old ways of welding with Oxy acetylene torch. I have a very good handle on the equipment and the safety/responsibilities of handling the gasses, I have been using it as a cutting tool all my life and had a brief introduction to welding with it back in high school (though they skipped bronze brazing for some reason) I have taken on a decently complete setup through inheritance and acquisition as a way around my very under-amped shop space limitations. I am trying to help out my friends with swords who keep breaking them at the welded tangs. I understand the blades to be 5160 and the threaded rod welded to them to be bog standard zinc coated m6 and m8 bolts grade 8.8. I want to get some advice and guidance on how to best go about re-welding these *(fume protection already understood with the zinc) in a way that will not ruin the heat treat of the 5160 and ensure they remain durable with the limitation of an oxy acetylene torch welding set up.

Main things I want to learn is pre-heat and post-heat actions, proper filler rod choice, and considerations for tip size with relation to the material thickness (usually around 3/16ths thick at the point of connection) and of course very important how to protect the temper of the rest of this piece of spring steel while making sure the heat affected zone doesn't cause a brittle spot.


As well as any general advice around oxy acetylene welding beyond the safety stuff that has already been drilled into me all my life by everyone who has ever talked to me about oxy acetylene because yes, I am very aware of it's explosive properties and leak detection complacency concerns. I'm not a welder by trade but I enjoy my industrial work.
 
pictures may be of help to see what you're working with
in regards to maintaining temper, a possible thought would be to insulate the workpiece by means of wet sogged clothes wrapped around wherever you don't want heat to propagate
(An uncle used this method to do some plumbing repairs, the idea to keep the joint next to the repair intact I think??)
is there material available to you to mimic the sword steel? Or even a broken one to practice on?
better to learn what's needed in regards to order of operations that way
what are they hitting with the sword that is breaking them anyway?
 
pictures may be of help to see what you're working with
in regards to maintaining temper, a possible thought would be to insulate the workpiece by means of wet sogged clothes wrapped around wherever you don't want heat to propagate
(An uncle used this method to do some plumbing repairs, the idea to keep the joint next to the repair intact I think??)
is there material available to you to mimic the sword steel? Or even a broken one to practice on?
better to learn what's needed in regards to order of operations that way
what are they hitting with the sword that is breaking them anyway?
I can hopefully get some photos later, I have got some coupons made up of the 5160 my friend uses to make swords I was planning to get some practice reps on, I have to first attempt to heat treat them to mimic the sword hardness and temper though.

I've been advised as well that slow cooling in vermiculite is going to be very important as well as a pre heat. I'm acquiring some rg45 rods this afternoon to give this a go tomorrow.

They are hitting other swords, and eachother. I've seen some pretty impressive ways these lads destroy their equipment at this point.
 
ohh...like the Society for Creative Acronyms...
Yes...some of their sparring events are pretty brutal...a fella can get his bell rung pretty hard, even with a padded helm on his noggin...I've watched a couple YT videos on it.
money's on the welding process not being quite right...the joint's are getting brittle...might be worth trying annealing them after welding?
 
ohh...like the Society for Creative Acronyms...
Yes...some of their sparring events are pretty brutal...a fella can get his bell rung pretty hard, even with a padded helm on his noggin...I've watched a couple YT videos on it.
money's on the welding process not being quite right...the joint's are getting brittle...might be worth trying annealing them after welding?
This is actually more of a HEMA issue than the SCA, SCA folks are generally gentle with their swords but the heavy fighters break armor and fight with rattan sticks. Usually the broken tangs seem to happen from stress or a drop, blade breaks I can't do anything for as they require a new distal taper and fresh spatulated tips welded on without affecting the heat treat of the rest of the blade again but more significant because the blade is under so much more stress than the tang.
 
#2 or #3 tip is where i would start for that thickness, you can always drill it out larger if you find you dont have enough btu's

There will always be a transition zone from the softer weld deposit/bolt to the harder/tougher heat treated blade that will be prone to breakage. A slow cool should help you achieve more toughness than brittleness in that area, i doubt you need to preheat, o/a is so slow and has such a large heat affected zone its likely that will put enough heat into the material to aid in the slow cooling that is needed

How much area you effect the temper will depend on how slow you are and how big that heat affected zone gets, anything that gets above the transition temperature will loose or have the temper affected, how large of an area that is will depend on your technique
 
#2 or #3 tip is where i would start for that thickness, you can always drill it out larger if you find you dont have enough btu's

There will always be a transition zone from the softer weld deposit/bolt to the harder/tougher heat treated blade that will be prone to breakage. A slow cool should help you achieve more toughness than brittleness in that area, i doubt you need to preheat, o/a is so slow and has such a large heat affected zone its likely that will put enough heat into the material to aid in the slow cooling that is needed

How much area you effect the temper will depend on how slow you are and how big that heat affected zone gets, anything that gets above the transition temperature will loose or have the temper affected, how large of an area that is will depend on your technique
Is there a visual indicator I should watch for regarding the heat affected zone and where the and the transition temperature of 5160 /medium-high carbon steels that can be referred to?
 
im not an expert at heat treating, that is a big rabbit hole

the info i can give you, 1400-1500f is roughly the transition temperature for 5160, its a dullish red color if you are looking at a color chart, this only works if the steel is ground shiny/polished, if there is any scale the color will be masked, the curie temperature of steel is also just above 1400f (when steel becomes non-magnetic) so that is an easy one if you are quick with a magnet.

you can guarantee any part was molten will have its temper effected, as well as the areas directly adjacent. The slow cool will help with the crystalline structure.

Using o/a will help with keeping the crystalline structure small because of the large haz and large heat input, and relatively slow cool, so you are winning there

Tempering it after welding would also help with the toughness, if you have an oven large enough for the swords (375-400f for 1-2hrs)

Heat treatment is a science and a bit of a black art, you will probably have to just do the best you can do with the knowledge you can acquire, and then evolve your procedures over time as you learn what works the best for that particular application


EDIT : Absolutely DO NOT grantee that it will not break, tell these customers/friends/clients that there is no guarantees on this type of work, you will do the best you can, but that is all you can do. I am a professional welder, and I would not, nor do i know anyone that would grantee something like this, so take that for what its worth.
 
im not an expert at heat treating, that is a big rabbit hole

the info i can give you, 1400-1500f is roughly the transition temperature for 5160, its a dullish red color if you are looking at a color chart, this only works if the steel is ground shiny/polished, if there is any scale the color will be masked, the curie temperature of steel is also just above 1400f (when steel becomes non-magnetic) so that is an easy one if you are quick with a magnet.

you can guarantee any part was molten will have its temper effected, as well as the areas directly adjacent. The slow cool will help with the crystalline structure.

Using o/a will help with keeping the crystalline structure small because of the large haz and large heat input, and relatively slow cool, so you are winning there

Tempering it after welding would also help with the toughness, if you have an oven large enough for the swords (375-400f for 1-2hrs)

Heat treatment is a science and a bit of a black art, you will probably have to just do the best you can do with the knowledge you can acquire, and then evolve your procedures over time as you learn what works the best for that particular application


EDIT : Absolutely DO NOT grantee that it will not break, tell these customers/friends/clients that there is no guarantees on this type of work, you will do the best you can, but that is all you can do. I am a professional welder, and I would not, nor do i know anyone that would grantee something like this, so take that for what its worth.
Unfortunately I never guarantee any work, I can warranty things if I felt I did a mechanical rebuild to exact specifications but that's a pretty rare thing to be able to pull off with the lack of documentation and parts available.
Welds like this though are very experimental and are the reason I won't do them anywhere but the tang where a break isn't so much of a safety hazard as it would be up on the actual blade which could break sharp and cause injury. A broken tang is just a missing blade when someone goes to parry and is unfortunate but usually harmless.
 
It would seem this is common happening? Please note I am not an expert on heatment nor a bladesmith. I have done some heat treatment and made a few knife blades. So take what I offer as possible ideas.
First off I would not use a coated bolt, may not be getting all the coating off. Possible weld contamination. As there are no pictures, the connection area should be very large, no sharp corners, all finished surfaces very smooth, no gouges, no deep marks in or near the joint when finished. Also no holes near this area to hold anything on. The bolt maybe hardening from the welding also, not good.
The filler rod, (if used), maybe harder than the blade or the bolt when finished, a problem. The filler rod may not have needed strength, and ductile properties
A full tang is generally stronger than a partial tang, often when a sword was made the tang was the same material as the blade. I am not sure but would think the hardness would be lower in the handle area/hilt area then the blade.
The stresses in this area are likely very high, this is a bending/pivot point at the junction, a rigid handle, and a rigid blade joined by a small amount of material.
There seemed to be a statement that a bent sword could be straightened, a sword that broke at the hilt/handle was not more than a short club. Not sure where I read/got that from.
Hope something here maybe of use.
 
There seemed to be a statement that a bent sword could be straightened,

Pretty sure I've seen swords get a wild bend on that Forged in Fire show. The bladesmith was given the opportunity to try and straighten it out to continue competing...One had at least a 25 degree whoop de doo, and the fella more or less laid the tip on the floor and applied size 12 kinetic energy to make it usable...I believe it suffered "catastrophic failure" anyway...but I was impressed the steel had the elasticity to regain shape
 
Many of the swords in our sport take a set after a good hit, this tends to have minimal adverse effects on the long term but is aesthetically not great. Strategies to straighten the set is pretty much the stand on it and drag method, usually the temper is soft enough that they won't shatter but if a blade is going to break it's when trying to straighten the set.

Welded tangs are fairly common in the Hema world, the other option are peened tangs but those don't have the ability to replace the blades as easily when they eventually need to be retired or break.

Tangs seem to break during fights or when a sword is dropped on the pommel as seen here.1000011666.jpg

This blade break came from a very strong side parry with the flat near the center of percussion vs a very strong and well structured cut, the video shows the blade taking on an S curve and just going beyond its capabilities.
IMG_20250126_115939170_HDR_AE.jpg

This is a photo of a tang at the weld, sister to one of the tangs that had failed pre-maturely, the maker noted that he suspected he was rushing on that weld and may have not gotten complete penetration and welded too cold to get a good one, he warrantied the broken sister and this one when it gave up.

1000009953.jpg


This one was a pretty interesting one to see, a messer in service for quite awhile eventually just gave up this piece of the blade mid fight on a strange strike, edge on apparently, it has been retired now.
IMG_20250126_120059651_HDR_AE.jpg20250320_204141.jpg

I can get more photos eventually, I've just been too busy getting my work space squared away to be safe to work in the past few days, plus familial obligations.
 
oh, that connection a recipe for a fracture

i would suggest using a bolt that is long and cutting the head off so that you are welding to the shank rather than the threads. It looks like threaded rod is being used, welding to the threads leaves all sorts of notches that cant be avoided because of the threads

bevel it, weld the shank, and using o/a i doubt you will have to many problems, its unlikely that portion of the blade is even heat treated at all, just dont quench it.

i wouldnt worry about the zinc coating on the plated bolts, it is very thin, what ever you don't get off with the buffer will burn off long before the base material is molten using o/a
 
oh, that connection a recipe for a fracture

i would suggest using a bolt that is long and cutting the head off so that you are welding to the shank rather than the threads. It looks like threaded rod is being used, welding to the threads leaves all sorts of notches that cant be avoided because of the threads

bevel it, weld the shank, and using o/a i doubt you will have to many problems, its unlikely that portion of the blade is even heat treated at all, just dont quench it.

i wouldnt worry about the zinc coating on the plated bolts, it is very thin, what ever you don't get off with the buffer will burn off long before the base material is molten using o/a
Yeah my plan it to actually take the bolt shank above the threads and bevel it into a cone and file a notch into the tang to seat the two together. And figure out the welding.

The whole blade is in fact heat treated though all the way to the tangs as they're full depth quenched, got to see and help with some production. The broken pommel being just 6mm threaded rod from the original production company Zen warrior has been that way for a surprisingly long time and only broken when I dropped it.

This one is tang welded to the shank of an m8 bolt
IMG_20250126_120016774_HDR_AE.jpg
 
Yeah my plan it to actually take the bolt shank above the threads and bevel it into a cone and file a notch into the tang to seat the two together. And figure out the welding.

The whole blade is in fact heat treated though all the way to the tangs as they're full depth quenched, got to see and help with some production. The broken pommel being just 6mm threaded rod from the original production company Zen warrior has been that way for a surprisingly long time and only broken when I dropped it.

Yea, that is what i had in mind for the prep

it looks like tig originally, the o/a weld will be much softer, i think you will be fine. The welding might take some practice, that's a tricky little joint, i would do a few little practice pieces to get the hang of it if i were you
 
Yea, that is what i had in mind for the prep

it looks like tig originally, the o/a weld will be much softer, i think you will be fine. The welding might take some practice, that's a tricky little joint, i would do a few little practice pieces to get the hang of it if i were you
Yep, I've got some coupons of the 5160 made up that I'll be heat treating and tempering this week to make sure I get some competency before taking on the fixes.
 
I would like to suggest notching the bolt, so as to slip over the tang tip...you'd end up with more surface to make the joint, rather than a butted joint.
unless of course, that's not feasible due to the grip's inside dimensions...
 
I would like to suggest notching the bolt, so as to slip over the tang tip...you'd end up with more surface to make the joint, rather than a butted joint.
unless of course, that's not feasible due to the grip's inside dimensions...
Won't be feasible due to the hilt dimension actually, the assembly relies on the thickness of the blade being consistent until the distal taper where it will start thinning out. Ideally I'd just have one solid tang and thread the whole thing in a lathe not having to worry about welding at all, but in the repair situation welding is the only way.

Here is a hilt I was working on a few months ago.
1000011068.jpg
 
So, having seen some pictures, I now realize that the breaks look to be well up the tang. The first part of the tang being part of the sword blade, and a bolt/stud being welded on to extend the tang.
It appears the welded area is too hard/brittle, in hand with the one having been dropped on the pommel and breaking at/near the threaded section. I think I would weld up a few pieces with the bolts, mount in a vise/holder and see how easy it is to break the stud off the tang using various blows and or flexing the stud with a piece of pipe on the stud.
One set of tests with the stud welded and left to cool in vermiculite etc. The others with the weld and surrounding area heated to a medium? red, held for a period of time after welding, to hopefully normalize the materials and cool very slowly. NOTE, that having used 2 different types of steel, possibly 3 including welding rod, getting given hardness, temper maybe impossible. Am not sure hardness is even wanted in this area.
While it is difficult to see in the pictures whether the metal has failed due to repeated flexing of welded joint, can often be seen by area slightly necking down, and crystalaion forming before breaking, or being brittle and snapping due to a blow etc.
Think of bending a piece of wire etc. many times to break it, it often necks down slightly, becomes a bit harder to bend, then breaks in the area worked.
Even when applying a pulling force the metal will neck down a bit before parting.
Trying to remember some metal testing done more then 50 years ago in school, I could say, how time flies, though it staggers, drags, accelerates as a person get older.
Once again, I am only offering some ideas.
 
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