You can buy the new cast iron flanges, with the expandable O rings that push into the pipe or you'll have to do the old style or pouring lead onto a cast iron flange. The latter option should only be done by professionals.
If it were mine I would chip out the concrete down to the point where the pipe is solid then I would install a new closet flange.
Toilet flanges OUTSIDE of the pipe including cast iron and brass to lead
To install a blind flange, first ensure that the pipe ends are clean and free from debris. Align the blind flange with the pipe, ensuring the gasket is placed correctly between the flange and the pipe. Use appropriate bolts to secure the flange, tightening them in a crisscross pattern to ensure even pressure. Finally, check for any leaks by testing the system under pressure.
You have to take the lead and packing out that is holding the flange in the next piece of pipe. If your flange is broke where the toilet bolts go, this is very common. There is a repair available for this. It consists of two curved pieces of metal that are about 1/3 of the circumference of the flange. They go under the flange and give you a new place to put the bolt. They are a lot easier to use than replacing the whole flange.
Install a ty fitting on the stack in the basement then run it to the sink. Put it low enough to account for a fall in the pipe, to allow proper drainage. Be sure to install a waste and vent pipe to code for both fixtures.
If it were mine I would chip out the concrete down to the point where the pipe is solid then I would install a new closet flange.
The best method for installing a toilet flange on a cast iron pipe is to use a wax ring and secure the flange with screws. Make sure the flange is level and properly aligned with the pipe before tightening the screws.
If you can get to the 6 inch cast iron, you could use a rubber coupler between the cast and the flange. If it is in the concrete, put a piece of 4 inch PVC inside the 6 inch and lead it in like you would a regular cast joint. Leave the 4 inch above the floor and slide the flange over it, screw it down and cut the 4 inch flush with the flange. They make just the flange that will slide over the pipe.
A cast iron toilet flange adapter is used to connect a toilet to a cast iron pipe. It serves the purpose of providing a secure and watertight connection between the toilet and the pipe. The adapter helps to ensure proper alignment and stability of the toilet on the cast iron pipe, preventing leaks and ensuring efficient waste removal.
Toilet flanges OUTSIDE of the pipe including cast iron and brass to lead
Considering the waste inlet of the pipe of this pipe should be 4" possibly 3" you can buy an inside cast iron cutter .=You must measure the inside diameter and then buy /rent the one for the size you need THEN you can buy a new cast iron floor flange and use either a caulked joint (lead and oakum) or possibly a quick set type if the cast iron is no hub or standard weight=
To install a blind flange, first ensure that the pipe ends are clean and free from debris. Align the blind flange with the pipe, ensuring the gasket is placed correctly between the flange and the pipe. Use appropriate bolts to secure the flange, tightening them in a crisscross pattern to ensure even pressure. Finally, check for any leaks by testing the system under pressure.
What is actually broken the flnge ring rusted out and broke or the abs pipe? Abs pipe/flange broken: Use a ram bit to cut it out and install a new one. http://www.plumbingsupply.com/pvcsaver.html use a compression or expansion flange http://www.plumbingsupply.com/toiletflanges.html or just cut the pipe and put in a new one Flange ring rusted/broken: install a toilet flange repair ring or a spanner flange.
If you are a do it yourselfer, there are many adapters available to replace a broken cast-iron toilet flange. These adapters can be made of cast-iron itself or PVC. They are made to be inserted into the existing pipe where a rubber gasket is tightened to create a water tight seal. The adapter incorporates a new flange which is attached to the existing sub-floor. Other adapters even help in the case of damaged or rotten sub-floor around the waste pipe. If you do a search on "Repair Kit For Cast-Iron Closet Flange" you should come up with numerous options or you can visit your local pluming supply company who can provide you with both products and answers to any questions/concerns you might have. And if you don't feel comfortable doing this yourself after investigating what is involved, call a licensed plumber.
Clean the inside of the pipe and floor top with a wire brush. Apply silicon to inside of pipe and top of floor, you are making an airtight seal. Install lead dutchman into pipe and repair flange on top, which will secure the lead dutchman. You can now install your toilet as usual, since you have a flange for mounting your bowl ( this is assuming you are updating to a flange mount bowl).
To replace a shower drain flange, you will need to remove the old flange by unscrewing it from the drain pipe. Then, clean the area around the drain pipe and install the new flange by screwing it into place. Make sure to seal the flange properly to prevent leaks.
Very carefully because if there is any moisture present and precautions are not taken the lead will react very violently and can cause blindness or death