ALD / VAR / 2019.05 EN ALD Vacuum Technologies Vacuum Arc Remelting Processes andFurnaces Vacuum Arc Remelting (VAR) High Tech isourBusiness Vacuum Arc Remelting (VAR) ALD is one of the leading suppliers of vacuum melting furnace technologies for engineered

12 ton VAR furnace from ALD

VAR is widely used to improve the Fields of Application VAR Applications cleanliness and refine the structure of standard air-melted or vacuum in- OO Aerospace OO Superalloys for aerospace duction melted ingots (called OO Power generation OO High strength consumable electrodes). VAR steels OO Chemical industry OO Ball-bearing steels and superalloys as well as OO Medical and nuclear industries OO Tool steels (cold and hot work steels) for milling cutters, drill bits, etc. and and its alloys are used OO Die steels in a great number of high-integrity OO Melting of reactive metals (titanium, applications where cleanliness, zirconium and their alloys) for aero- homogeneity, improved fatigue space, chemical industry, off-shore and fracture toughness of the final technique and reactor technique product are essential.

02 VAR Advantages & ALD Features ALD has numerous references in the field offering the highest levels of system automatization

10 ton VAR furnace from ALD

Primary benefits of VAR Further advantages Features of VAR furnaces from ALD OO Removal of dissolved gases, such OO Removal of Oxides by chemical and as , and CO physical processes OO Ingot diameters up to 1,500 mm OO Reduction of undesired trace OO Removal of Nitrides by thermally OO Ingot weights up to 50 tons elements with high vapor pressure dissociation or reduction by OO Electrode is melted by means of a OO Achievement of directional present in the , and final removal DC arc under vacuum (electrode solidification of the ingot from via the gas phase negative, melt pool positive) bottom to top OO Removal of Stable Non-metallic OO Remelting currents up to 50 kA OO Elimination of macro-segregation Inclusions OO Vacuum range: 1 - 0.1 Pa (some and reduction of micro-segregation Some inclusions (e.g. alumina and applications up to 1,000 Pa) OO Improvement of oxide cleanliness titanium-carbonitrides) are removed OO Electrode weighing system by flotation during remelting. The OO Stable or free-standing gantry design remaining inclusions are broken OO Coaxial high current feeding system up and evenly distributed in the cross-section of the solidified ingot.

03 Process Technology and Process Characteristics ALD´s process expertise guarantees high process reproducibility and material quality

12 ton VAR furnace from ALD

VAR is the continuous remelting OO DC power is applied to strike an to remove impurities and prevent of a consumable electrode by arc between the electrode and the oxide formation means of an arc under vacuum. baseplate of a mold contained OO Ingot cooling is controlled for in a water jacket directional solidification The main process stages OO The intense heat generated by the ALD has improved the basic design of OO A consumable VAR electrode is melts the tip of the VAR furnace in computer control and generated by VIM, ESR, EB or plasma electrode and new ingot collects in regulation continuously over the years to methods, assembled from titanium the mold achieve: sponge, scrap or bulk, or by a prior OO The melt rate is precisely regulated OO Fully-Automatic remelting processes VAR melt by the VAR control system OO Improved Reproducibility of the OO A high vacuum is maintained metallurgical properties throughout the remelting process

04 Directional Solidification of the Vacuum Arc Remelting Process Precise control of the local solidification rate of the temperature gradient at the liquid/solid interface

Achieving the optimum VAR solidification, at the solidification front. Even in the case of directional solidification, ingot solidification structure The direction of the heat flow is always micro-segregation increases with dendrite requires precise control of the perpendicular to the solidification arm spacing. A solidification structure local solidification rate and the front or, in case of a curved interface, with dendrites parallel to the ingot axis temperature gradient at the perpendicular to the respective tangent. yields optimal results. liquid/solid interface. The growth direction of the dendrites is thus a function of the melt pool profile Optimal Melt Rates High Temperature Gradient during solidification. A good ingot surface requires a certain at the solidification front must be level of energy input. Optimal melt rates maintained during the entire Melt Pool Profile and energy inputs depend on ingot remelting process to achieve a As pool depth increases with the diameter and material grade, which directed dendritic primary structure. remelting rate, the growth angle of the means that the necessary low remelting dendrites, with respect to the ingot axis, rates for large diameter ingots cannot Dendrite Growth Direction also increases. Without proper VAR always be maintained to achieve axis- conforms to the direction of the melt controls, the ingot core can solidify parallel crystallization. temperature gradient, i.e., the direction non-directionally, e.g. in equiaxed grains, of the heat flow at the moment of leading to segregation and micro-shrinkage.

05 Understanding and Preventing Solidification Defects

Metallurgists agree that in spite of Tree ring patterns White Spots directional solidification, defects such as “tree ring patterns”, “freckles” and OO Can be identified in a macro-etched OO White spots are typical defects in VAR “white spots” can occur in remelted transverse section as light-etching ingots. They are recognizable as light ingots. These defects can lead to rings etching spots on a macro-etched rejection of the ingot, particularly in OO Usually represent a negative crystal surface the case of special alloys. segregation OO They are lower in alloying elements, e.g. OO Seem to have little effect on material titanium and in 718 properties ALD mitigates these problems Freckles in the VAR with precise and stable melt rate and arc gap Freckles and white spots have a much control, and robust power greater effect on material properties supplies designed specifically as compared to tree ring patterns and for this purpose. can represent a significant cause for premature failure of turbine disks in aircraft engines.

Tree Ring Patterns Freckles White Spots Intended

06 ALD VAR Furnaces Design

Features 1 8

3

5 Schematic of the VAR furnace 4 9

1 Electrode feed drive 2 Furnace chamber 3 Melting power supply 2 4 Busbars/cables 7 5 Electrode ram 6 Water jacket with 6 7 Vacuum suction port 8 X-Y adjustment 9 Load cell system

Design Features of all ALD VAR Furnaces

OO Gantry design of furnace head OO Power supply with space saving super-structure features design, thyristor or saturable simple platform installation reactor control designed with no flexure of the super- specifically for fast response structure under load. and tight current control. Consistent centering of the OO Sophisticated weight manage- electrode. ment system including highly OO Proven electro-mechanical accurate, fully temperature dual electrode drive system compensated load cell system for very precise control of and statistical based melt rate small melt speeds during algorithm. the remelting process and OO Completely automatic operation fast speeds for charging of the furnace by the use of procedures. password-protected preset melt OO Remotely controlled, pneu- recipes, stored locally or down- matically operated electrode/ loaded from any host system. stub clamp with maximum OO Statistical Process Analysis melting current transfer to (SPA) is possible with the data the electrode. acquisition system of the Operator OO The furnace is of fully coaxial Interface PC in combination design avoiding stirring action with the optional Supervisory of the melt bath due to unsym- Sytem PC. metrical magnetic stray fields.

07 Internet: www.ald-vt.com E-Mail: info Fax: +496181307-3290 Phone: +496181307-0 63457 Hanau,Germany Otto-von-Guericke Platz1 ALD Vacuum Technologies GmbH O O O O O ALD’s VAR control systems handle: specifications. stringent material quality furnaces fulfills today’s most automation usedbyVAR Computer controlled process structure andsuperiorcleanliness. and show controlled solidification which are free ofmacro-segregation production ofhomogeneousingots, remelting parameters for reproducible ALD provides precise control ofallVAR quality andeaseofoperation reproducible metallurgical in theworld for its accuracy, system (AMC)isunsurpassed ALD’s automatic meltcontrol Process Control VAR O O O O O Data management Data acquisition or drop shortpulserate) arc gapbasedonarc voltage parameters (e.g.remelting rate, Closed loop control ofprocess consumable electrode Continuous weighing ofthe Logic control functions @ ald-vt.de

Phone: +9122276067-76to 85 You can findyour corresponding representative office atwww.ald-vt.com/contact-sales-partners. ALD Vacuum Technologies GmbHisrepresented in various countries worldwide. sales www.ald-dynatech.com India Pvt.Ltd. (India) ALD Vacuum Technologies Phone: +18603867227 info www.ald-usa.com North America, Inc.(USA) ALD Vacuum Technologies @

@ ald-usa.com ald-dynatech.com Operator interface PC(OIP) specific interfaces Communication viafield busor

O O O O O O generation ofmeltrecords acquisition andstorage andfor handling ofremelting recipes, data operator commands, editingand graphic displays andsoftkeys for featuring parameter indications, Serves for process visualization, and VAR process Utilized asinterface between operator automatic meltcontrol system (AMC) Acts hierarchically asmaster ofthe Phone: +8135961 3017 peter.lang South Korea, Taiwan In charge of: Japan, Far East Co.,Ltd. (Japan) ALD ThermoTechnologies Phone: +8651263858833 info www.ald-cnk.com (Suzhou) Co.,Ltd. (PRChina) ALD-C&K Vacuum Technologies @ ald-cnk.com @

ald-vt.de

Melt Recipes O O

repeatable VAR production ofspecific

O O ALD furnaces work withestablished Can beoptionally equippedwithan combinations, to assure full ingot sizesandmaterial grade remelting parameters, stored as Ethernet network interface whichmay metallurgical ingotquality remelting recipes onhard disk,for be utilizedfor data transfer to other computers connected to thelocal area network (e.g.supervisoryPC, customer’s mainframe, etc.) Phone: info www.ald.vt.com/ru Technologies (Russia) OOO ALD Vacuum @ ald-russia.ru +7 495 78767-34/33/31

ALD / VAR / 2019.05 EN