CREMATION PROCESS: Technical overview.

References: Wikipedia:

At a crematorium, the deceased body, lying in a coffin, is placed in a cremator.

A cremator is an industrial furnace that generates enough heat to burn a body to ashes.
Typical heat: 760 - 1150 degrees Celsius (1400 - 2100 degrees Fahrenheit).

The intense heat can cause any implanted battery - in a pacemaker or defibrillator - to explode in the cremator.
A certification process must identify any such batteries (legally called “biomechanical aids”) and ensure removal before cremation.

Human bodies are made up of a high proportion of water - this vaporises in the furnace.
Most of the solid tissue is vaporised and/or combusted in the intense heat. The resulting gases are released into the atmosphere.

The process takes approximately 1.5 to 2 hours to complete.

At the end of the process there is some residual matter, including ash and fragments of bone, weighing approximately 1.5 - 3 kg.

Once these remains have cooled sufficiently, a special grinding process (in a cremulator) can reduce the fragments to a fine ash, similar in texture and colour to sand. These are the ashes that are returned to the family.

Surgical implants such as artificial joints, dental implants, fillings are safe to go into a cremator so long as there is no battery.
Titanium implants do not melt even at the high temperatures in a cremator: these are removed after the cremation process and can be disposed of separately.