Know-how NavigatorGases and Applications from Messer

Metallurgy - Heat Treatment

Many metals get only usage property throughheat treatment. The spectrum of productproperties obtained in this way includes hard,tough, soft and differently coloured surfaces. Asannealing metals react readily with air, protectivegases in the furnace atmosphere areindispensable during heat treatment. In manycases, nitrogen suffices as an inert medium.

Competence through gases technologyIf, however, a particular metallurgical effect is tobe achieved with the gas, it is necessary to addreactive gases. 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 method of adding propane to nitrogenor hydrogen, and mixtures thereof, is used bymany customers, emphasizing Messer’scompetence in this field.

Hydrogen - reactive and effectiveHydrogen is mainly used for annealing high-alloysteels. Both its reductive capacity and cleansingeffect on surfaces are required in this process. Itshigh thermal conductivity and thermal capacityalso considerably improve the economicefficiency of high convection annealing in belltype furnaces.

Advantages through innovationEndogas/nitrogen mixtures produce a specialprotective gas atmosphere for the heat treatmentof steel and NF alloys in industrial furnaces.Endogas mixtures are an economical alternativewherever a supply of pure hydrogen is too costlyand self-generated exogas or monogas no longermeets the stricter quality requirements for thefinished products. Unlike exogas, the carbon levelin the furnace gas can only be set and regulatedwith diluted endogas. However, it is a substantialadvantage to introduce endogas and nitrogenseparately in different areas of the furnace.Besides recrystallization annealing of steel,endogas mixtures can be used in sintering,brazing and tempering processes, offering theuser the advantages of lower costs, better qualityand enhanced safety.

Cold generated by nitrogenThrough controlled cooling of hardened steel withliquid nitrogen, the structure of the steel ismodified in a targeted way. The resultingtransformation of residual austenite intomartensite improves the wear resistance ofcutting tools and the dimensional stability ofprecision parts. Cryo stretching is a variant of thistechnique. It involves stainless steel vesselsbeing submerged in liquid nitrogen and "inflated"with a pressure of 700 bar. This gives the steelmuch greater strength.

Hardness - the right formulaIn order to produce particularly hard and wear-resistant surfaces, components are treated withammonia and, for example, carbon dioxide atmedium temperatures. This process involves theformation of very hard nitrides which can bemodified in their structure and compositionthrough the composition of the furnace gas,while nitrogen atoms are also dissolved in thesurface zone of the alloy, further contributing tothe marked increase in hardness.

Partnership through know-howThe use of industrial gases in industrial furnacesand the specific effects achieved are dependenton many parameters. Cooperation betweenMesser specialists and users of the gases is notonly desirable but absolutely essential to ensurefurther development and optimization of ourcustomers’ heat treatment processes.

Heat treatment, a step in the production chain

Case hardened components for themanufacture of gearboxes

Application Messer know-how Advantages

Tempering, casehardening, carbonitriding

Production of gas mixtures consistingof nitrogen, methanol, ammonia andpropane

High quality of furnace atmosphere, flexiblechoice of mixtures, no start-up losses,alternative to other carrier gases

Hardening of heat-treatedand special steels

Furnace atmospheres consisting ofnitrogen-hydrogen mixtures andcontrolled dosing of propane ormethane

Carburization-neutral atmospheres and adaptedheat transfer for hardening in continuouslyoperating furnaces

Plasma carburization, low-pressure carburization andvacuum hardening

Dosing of high-purity acetylene orpropane at low pressure andquenching with nitrogen or helium athigh pressure

Environmentally friendly processes due toreduced addition of carburizing gases and cleanhardening charge

Classic nitriding andnitrocarburizing

Use of ammonia and nitrogenmixtures with addition of carbondioxide or propane

Optimized use of pure gases for production ofdefined nitriding layers and increased efficiency

Bright annealing of chromesteels and sintering ofspecial metal powders

Targeted addition of hydrogen,nitrogen, argon or mixtures thereofto furnace installations

Optimization of hydrogen additions withimproved heat transfer through hydrogen

Normalization,recrystallization, solutionannealing, stress-reliefannealing, bright annealing

Requirements based production ofprotective gas atmospheresdepending on the alloys to be treated

Enhanced quality through flexible and safesupply of protective gas, lower operational costs

Residue free and purifyingannealing of cold-workedpre products

Dosing of process gases with definedpurge cycles and optimized gasquantities

Use of gases for production of clean, brightsurfaces, removing the need for subsequentcleaning processes

Increase in wear resistanceand dimensional stability ofhardened steel alloycomponents

Transformation of residual austenitecontent through targeted cooling withliquid nitrogen

Improved hardening structure and dimensionalstability of machine components, tools andmoulds

Use of liquid nitrogen’scooling energy in the heattreatment process

Determination of optimal injection ofliquid nitrogen into the furnace andinstallation of metering and controlequipment

Dual use of nitrogen as coolant and protectivegas with same gas requirement, increase inproduction

Calibration of sensors andgas analyzers withcalibration gases forprecise control of gasatmospheres

Choice of optimal gas concentrations,handling of calibration gas cylindersand installation of measuringequipment

Compliance with test specifications and qualitystandards regarding the documentation ofprocess parameters

Tempering of special wire in atubular wire drawing furnace

You work in the industry as an application expertand have specific questions regarding thisbrochure?

Your contact is:

Hans-Peter SchmidtTechnology Manager MetallurgyMesser Group GmbHGahlingspfad 31D-47803 KrefeldPhone: +49 2151 7811-233Fax: +49 2151 7811-503hans-peter.schmidt@messergroup.com

Günter WagendorferApplication TechnologyMesser Austria GmbHIndustriestraße 52352 GumpoldskirchenPhone: +43 664 819 50 23Fax: +43 50603 388guenter.wagendorfer@messergroup.com

Messer Group GmbHGahlingspfad 31

47803 KrefeldTel. +49 2151 7811-0

Fax +49 2151 7811-501info@messergroup.com

www.messergroup.com