Metallurgy - Heat Treatment

Many metals are only rendered useful throughheat treatment. The spectrum of product cha-racteristics obtained in this way includes hard,ductile, soft and differently colored surfaces. Asglowing metals react readily with air, protectinggases in the furnace atmosphere are indispens-able. In many cases, nitrogen is used as the inertmedium.

Competence through gas technologyIf a particular metallurgical effect is to be achie-ved with the gas, however, reactive gases mustbe added. The addition of small quantities ofpropane to the nitrogen, for example, has provedparticularly effective. This is regulated with thehelp of an integrated sensor system so that onlythe amount of propane needed is used. Thisoptimized technology of using propane in nitro-gen or hydrogen and hydrogen mixtures isprotected by a number of patents, again emph-asizing the competence of Messer in this field.

Hydrogen - reactive and effectiveHydrogen is mainly used for the annealing of highalloy steels. Here, not only is its reductivecapacity utilized, but also its cleansing effect onsurfaces. Its high thermal conductivity andthermal capacity also appreciably improve theeconomic efficiency of high convection annealingin bell furnaces.

Advantages through innovationIn the Endolin® process, a special shielding gasatmosphere of endogas/nitrogen mixtures isused for the heat treatment of steel and NFalloys in industrial furnaces. Endolin® gas mix-tures are an economical alternative wherever asupply of pure hydrogen is too costly and self-generated exogas or monogas no longer meetsthe stricter quality requirements for the finishedproducts. As opposed to exogas, the carbon levelin the furnace gas can only be set and regulatedwith diluted endogas. A major advantage,however, is that endogas and nitrogen can beintroduced separately in different regions of thefurnace. In addition to the recrystallizationannealing of steel, Endolin® can be used insintering, soldering and tempering processes,offering the user the advantages of costreduction, quality enhancement and increasedsafety.

The cold that came out of the nitrogenThrough the regulated cooling of hardened steelwith liquid nitrogen, the structure of steel isselectively modified. The transformation ofretarded austenite into martensite caused in thisway improves the wear resistance of cuttingtools and the dimensional stability of precisionparts. A variant of this technique is cryo-stretching. Here, stainless steel containers aresubmerged in liquid nitrogen and "inflated" with apressure of 700 bar. The result is a steel withconsiderably higher strength.

Oxidation? - yes, but defined!In the patented Blackrapid® process, however,the furnace gas atmosphere is specificallycomposed to define the oxidation of thecomponents to be hardened in order to form afast adhering and decorative oxide layer whichrenders subsequent burnishing unnecessary.

Hardness – the right recipeIn order to produce extremely hard and wear-resistant surfaces, components are treated withammonia and carbon dioxide, for example, atmedium temperatures. Very hard nitrides areformed in this process which can be modified intheir structure and composition through thecomposition of the furnace gas, while nitrogenatoms are also dissolved in the surface zone ofthe alloy, further contributing to the markedincrease in hardness.

Partnership through know-howThe use of technical gases in industrial furnacesand the effects achieved are dependent on manyparameters, so that cooperation between theMesser specialists and their users is not onlydesirable, but absolutely essential to ensure thefurther development and optimization of ourcustomers heat treatment processes.

Heat treatment, a linking process step in theproduction chain

Various parts, treated bythe patented Blackrapid®

process

Case hardened components for theproduction of gear boxes

Application: Know-how from Messer: Advantages:

Heat treatmentTempering, casehardening, low surfaceoxidation carburizing,carbonitriding, sintering

nitrocarburizing, nitriding

Annealing under reaction gases ofmethanol, propane, H2, NH3/nitrogenmixtures, hydrogen, nitrogen, argon,helium, Variocarb-therm®,Hydrocarb®,direct injecting, Vario-Nitrocarb®

No start-up or idling losses, constant quality,high flexibility, alternative to environmentallyharmful applications

Production of decorativesurfaces

Defined short-time oxidation duringhardening (Blackrapid® process) andcontrolled oxidation processes(Variospectrox® process)

Environmentally friendly process, decorative,uniform surfaces, increased corrosion resistance

Vacuum hardeningprocesses and plasmacarburization

High pressure gas quenching with N2,He, Ar, H2 or mixtures, pure reactivegases H2, N2, CH4, C2H2

Environmentally friendly process and clean, low-warp workpieces

Increase in the wearresistance and dimensionalstability of steel parts

Bright, stress-free,recrystallization andnormalization annealing

Retarded austenite conversionthrough cooling of parts in cryogenicrefrigeration chambers

Annealing under shielding andreactive gases (nitrogen,nitrogen/reactive gas mixturesEndolin®-process

Optimum dimensional stability and wearresistance, improved hardness and homogenityof structure

Quality improvement through simple, safe,flexible shielding gas supply, reduction ofoperating costs

Residue-free and cleansingannealing

Glueless annealing of coldrolled steel in the bellfurnace

Defined purging with Hydroclean®

and Turboclean®

Annealing under regulated reactiongases, Defox® process

Clean, bright metal surfaces, low investmentcosts, easy handling

sticker free surfaces, less scrap, increasedoutput, automatic process sequence

Increased output oncontinuously working heattreatment plants

Cryogenic Rapid Cooling with liquidnitrogen

Increased output, double utilization of nitrogenas shielding atmosphere in the furnace and ascoolant medium

Tempering of special wire in atubular wire drawing furnace