Heat Treatment – FAQs

What sizes can Holt’s handle?

We have crane capacity up to five tonnes but we also handle components weighing a fraction of a gram.

Obviously we do not process a component weighing a few tonnes in the same furnace as those weighing a fraction of a gram. It all depends on the treatment process, geometry and weight.

Please contact us for treatment specific capacities & facilities.


How do I define my heat treatment requirements?

Download our editable PDF file to take you through the details we need to quote quickly and efficiently

What is the difference between?

What does this term mean?

Use our dictionary to understand common heat treatment terms


Why stress relieve/anneal/normalise?

When metal cools from its manufacturing temperatures it locks in stresses from the differential cooling rates between surface and centre. It may also be rolled, forged or simply shrink from cooling after casting. Nor will the material be uniform because of the different thermal history across the section of the metal.


Machining will release stresses and unbalanced stress result in distortion

Heating above the last processing temperature will also release stresses.


The family of thermal cycles of stress relieving, annealing & normalising are used to counter these effects and provide as a stable & uniform product as possible for further manufacturing procedures or use in service.


What is the difference between Total Case Depth & Effective Case Depth

Effective case depth is defined by a cut off point at a given hardness along the hardness gradient between the surface & core of the steel. The effective case depth is the region in which enhanced material performance can be sustained.


Total case depth is the complete region that has been affected by the hardening process. It measured down to the point where the material’s inherent core hardness takes over. Total case depth extends past the cut off point of effective case depth but includes the areas where hardness has been increased by only one or two points which generates little if any enhancement in performance


Effective case depth takes longer process times to achieve and therefore costs more but delivers a significantly longer working life. Make sure you specify which one you need


Which steels are best for?

With mild steel the clue to its performance is in the name, so to get performance choose from an engineering grade alloy.


Popular Carburising Grades

EN32b / 080A15

EN34 / 655M17

EN36 / 655M13


Popular Through Hardening Grades (ruling section limitations apply)

EN24 / 817M40

EN26 / 826M40


Popular Nitriding Grades

EN19 / 709M40 EN24 / 817M40

EN40 B / 722M24 EN41 / 905M31


Popular Flame/Induction Hardening Grades

EN19 / 709M40

EN24 / 817M40

EN8D / 080M40


What can I do, I’ve only budgeted for mild steel?

Many precision engineers produce perfectly good, tightly toleranced components in mild steel which are ideal for their design application. But the clue to the limitations of mild steel is in its name – MILD STEEL.

Load bearing or high wear components demand more performance from the material than low cost steels like mild steel and EN8 can deliver.

Talk to us at the beginning of the quotation process and we can advise on the best balance of material cost, ease of manufacture, heat treatment and final performance requirements.

We will also give you the knowledge to explain to the customer why the apparently lowest cost material will deliver higher manufacturing and the highest in service costs.