Oxy Acetelyne heating ASTM A216

What may be happening in some cases is the presence of residual stresses due to temperature differentials.

You have a certain bore that is heated up locally. Your bore try to expand, but is held in place by the large part. So, it's deformed slightly under compressive tensions. Then, it's cooled, and the cooling size reduction tends to shrink the bore, and leave traction in material and, sometimes, appreciable differences in dimensions.

Of course this all depends on heating temperature, entire part temperature, etc. Should be a small effect if no phase transformation is taken. If so, remember that austenite has smaller volume than ferrite (and also martensite), so, upon heating with local phase transformation, the material reduces its volume, and in this case traction tensile results in bore surface, causing it to deform. Upon cooling, material with tensile deformation tends to expand during transformation back, and compressive tension is expected as a result, as well as a slightly bigger bore.

Carbon absortion does not cause volume change, it's content is really low is steels.

Induction heating could solve your problem, heating the bore up to trensformation temperature in a very thin superficial section of the material, solving your problem, and contributing to part long term resistance mainly against fatigue, due to the benefic compressive residual stresses.

If local heating is occurring in the large component, the only place the expanding metal will go, is inwards so as to reduce the diameter of the hole. The solution is to heat the entire component, not just the area into which the bearing is to be installed.

It would be wise to pass the procedure across the desk of an experienced Metallurgist for consideration prior to invoking it, lest stress-cracking and unwanted alloy formation might be the inadvertent result.

The component can not be totally heated. It is assembled between 2 components, and transition interference fit on OD and transition clce fit on ID. So we heat the ID of this component and the ID of the other component ,slide it in and tighten bolts. When it is heated, it will expand but again when cooled back, it should crawl back to its size isn't it? from where will it get the extra volume? It is plain C Steel (ASTM A216) and no appreciable alloys except Mn.

Chilling the bearing and letting it expand into the hole would seem a better solution, then.

Difficult, bearing already shrunk in a shaft.

ASTM A216 is a specification for cast steel. I'm going to go out on a limb here and bet that the casting is in the "as-cast" condition prior to being heated for bearing installation. Therefore it has a certain amount of residual stresses. these stresses are being locally relieved when the part is being heated leading to a reduction in the I.D. This is quite common when welding on the o.d. of pipe to find a reduced i.d. as well. short of reaming/honing the i.d afterwards, I'm really not sure there is much that can be done to prevent it.

Normalised+stress relieved

"Stress relieved" is a relative term. If you heat the entire mass of the part, and allow it to cool, some parts of the part (sections with thinner walls, or sections with more surface area) will cool faster than others, causing a certain amount of thermally induced stress to be created during "stress relieving". So just because something has been "stress relieved" it does not mean ALL stress, just most of it.

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