As long-time part­ners, the Arcelor­Mit­tal Glob­al R&D research cen­tre in Mon­tataire, which spe­cialis­es in auto­mo­tive appli­ca­tions, and UTC have cre­at­ed this joint lab­o­ra­to­ry in 2019, which is sup­port­ed by the Hauts-de-France Region and part­ly fund­ed by the ERDF (also calle Enedis- pow­er grid man­age­ment). The work car­ried out with­in the frame­work of FuseMet­al focus­es on the weld­ing of 3^rd gen­er­a­tion high strength steels and the mod­el­ling of addi­tive man­u­fac­tur­ing process­es. The 6 PhD stu­dents, Elise, Daom­ing, Hélé­na, Mar­cia, Ghas­sen and Ana Julia present their research work in the laboratory.

Ghassen Dali, a 3rd year PhD student, is conducting a thesis on the modelling and simulation of metal additive manufacturing for metallurgical and process optimisation.

“My the­sis project start­ed on Octo­ber 1, 2020, and is part of the lab­o­ra­to­ry’s strat­e­gy to devel­op and strength­en its skills in the field of addi­tive man­u­fac­tur­ing (3D print­ing), which is a focal point of the FuseMet­al joint lab­o­ra­to­ry. Indeed, this tech­nol­o­gy has a promis­ing poten­tial because it allows the pro­duc­tion of com­plex and non-tra­di­tion­al geome­tries, thus bypass­ing the design/manufacturing con­straints imposed by con­ven­tion­al process­es, short­en­ing devel­op­ment cycles and reduc­ing costs. On the oth­er hand, addi­tive man­u­fac­tur­ing process­es can lead to defects dur­ing and after man­u­fac­tur­ing (insta­bil­i­ty of the liq­uid bath, porosi­ties, delam­i­na­tion between lay­ers, het­ero­ge­neous prop­er­ties). To rem­e­dy these draw­backs, the use of sim­u­la­tion soft­ware is rec­om­mend­ed in order to reduce the num­ber of tests required to pro­duce a part that com­plies with the tech­ni­cal spec­i­fi­ca­tions in 3D print­ing.) I am there­fore work­ing on the sim­u­la­tion and mod­el­ling of 3D print­ing of steels. The aim is to devel­op so-called pre­dic­tive dig­i­tal mod­els. The mod­el will be able to bet­ter describe the rela­tion­ships between the oper­at­ing para­me­ters, the prop­er­ties of the mate­r­i­al and the man­u­fac­tur­ing state of the final part.

Marcia Meireles, a 3rd year PhD student, is conducting a thesis on the experimental identification of the links between process parameters, thermal cycles and metallurgical transformations during the additive manufacturing of steels.

“My the­sis work con­cerns the study of an addi­tive man­u­fac­tur­ing process for parts (3D print­ing). This con­sists of man­u­fac­tur­ing 3D parts by adding suc­ces­sive lay­ers of molten mate­r­i­al. This process is very promis­ing in the indus­tri­al sec­tor because it allows the man­u­fac­ture of parts with very com­plex geome­tries, while avoid­ing addi­tion­al assem­bly phas­es and pro­duces very lit­tle waste. Thus, 3D print­ing is a process that com­bines remark­able and unique capa­bil­i­ties. The mate­r­i­al I am study­ing is a type of steel devel­oped by Arcelor­Mit­tal specif­i­cal­ly for 3D print­ing. Indeed, to obtain parts that meet the require­ments of their appli­ca­tion, it is essen­tial to under­stand the effect of the cho­sen print­ing para­me­ters on the qual­i­ty of the parts. This is why, in my the­sis, I study the phys­i­cal phe­nom­e­na that take place dur­ing 3D print­ing and eval­u­ate their effects on the final char­ac­ter­is­tics of the parts. Thus, the goal of my stud­ies is to be able to man­u­fac­ture 3D parts in an opti­mal way.”

Daoming Yu, a 3rd year PhD student, is conducting his thesis on the optimisation of 3D printed hot stamping tools.

“My research project focus­es on the topo­log­i­cal opti­mi­sa­tion of hot stamp­ing tools obtained by met­al addi­tive man­u­fac­tur­ing. Hot stamp­ing is a form­ing process in which a met­al sheet is first heat­ed in an oven to a tem­per­a­ture of approx­i­mate­ly 900°C. The sheet is then shaped at high tem­per­a­ture in a press and, thanks to intense cool­ing (in con­tact with cold tools), met­al­lur­gi­cal trans­for­ma­tions allow the final part to have high mechan­i­cal char­ac­ter­is­tics (the final part is case-hard­ened). Thanks to the high mechan­i­cal prop­er­ties thus obtained, it is pos­si­ble to reduce the thick­ness of the parts, which makes it pos­si­ble to light­en the vehi­cles. Ulti­mate­ly, fuel con­sump­tion and CO₂ emis­sions will be reduced. In addi­tion, this process has sev­er­al oth­er advan­tages: it allows com­plex geome­tries to be formed, requires less press pres­sure, the parts do not show spring­back, etc. Because of these advan­tages, hot form­ing is a wide­ly used form­ing process for the man­u­fac­ture of auto­mo­tive parts. In the hot form­ing process, the tool is par­tic­u­lar­ly com­plex, as it incor­po­rates a cool­ing cir­cuit. It seemed impor­tant to us to eval­u­ate the poten­tial of addi­tive man­u­fac­tur­ing to pro­duce these stamp­ing tools. In par­tic­u­lar, this tech­nique can be used to opti­mise the cool­ing cir­cuit and thus improve the effi­cien­cy of the hot stamp­ing process. The objec­tive is to devel­op a uni­fied pro­ce­dure for design­ing form­ing lines, includ­ing the design of tools by com­bin­ing mod­el­ling of the form­ing process and topo­log­i­cal opti­mi­sa­tion, free­ing the con­straints imposed by machin­ing and tak­ing into account the con­straints imposed by addi­tive man­u­fac­tur­ing. This pro­ce­dure is test­ed on pro­to­type tools to val­i­date the via­bil­i­ty of the pro­posed solu­tions in terms of con­for­mi­ty and tool­ing performance.

Elise Champolivier, a 2nd year PhD student, is conducting a thesis with experimental and numerical studies on modelling and scale transition for the prediction of the shaping of laser assembled structures.

“For sev­er­al years now, car man­u­fac­tur­ers have been con­stant­ly chal­lenged to reduce the con­sump­tion of their vehi­cles while main­tain­ing their per­for­mance in terms of safe­ty. Arcelor­Mit­tal is devel­op­ing new solu­tions to meet these objec­tives by com­bin­ing two tech­nolo­gies: Laser-Flat­tened Blanks and 3^rd gen­er­a­tion ultra-high strength steels. The Laser Flap Blank tech­nol­o­gy con­sists of join­ing steel sheets of dif­fer­ent grades, thick­ness­es or coat­ings by laser weld­ing. The assem­bled sheets are then shaped to obtain the shape of the auto­mo­tive part: this is the stamp­ing stage. Cou­pled with the use of very high strength steels, this tech­nol­o­gy makes it pos­si­ble to light­en auto­mo­tive parts with the same per­for­mance while main­tain­ing their strength prop­er­ties. My PhD the­sis focus­es on the study of the forma­bil­i­ty of Laser-Flat­tened Blanks made of 3^rd gen­er­a­tion steels. My work con­sists of study­ing the mechan­i­cal behav­iour of the welds of these assem­blies dur­ing the form­ing stage in order to define rec­om­men­da­tions and fail­ure cri­te­ria that man­u­fac­tur­ers can apply to the design of their parts. The study is based on exper­i­ments that allow the feed­ing of mod­els The study is based on exper­i­ments that feed into numer­i­cal mod­els with the aim of devel­op­ing pre­dic­tive mod­els for the behav­iour of laser weld­ed assemblies.

Ana Julia Vasconcelos de Moreira, 3rd year PhD student, is carrying out a PhD thesis on the evolution of local microstructures of 3rd generation steels in the presence of strong thermal and chemical gradients.

“My the­sis focus­es on the study of the join­ing of two iden­ti­cal or dif­fer­ent 3rd gen­er­a­tion steel sheets by laser weld­ing for the man­u­fac­ture of auto­mo­tive parts. In order to meet the require­ments of the auto­mo­tive indus­try regard­ing weight reduc­tion and improved mechan­i­cal per­for­mance. In addi­tion to meet­ing these require­ments, laser weld­ing tech­nol­o­gy makes it pos­si­ble to design auto­mo­tive parts with spe­cif­ic prop­er­ties where they are need­ed. The chal­lenge lies in the change in the char­ac­ter­is­tics and behav­iour of the steels around the weld seam, due to the high tem­per­a­tures reached dur­ing laser weld­ing fol­lowed by rapid cool­ing. Con­se­quent­ly, I am study­ing the dif­fer­ent areas of the dif­fer­ent steel assem­blies designed by Arcelor­Mit­tal, in order to iden­ti­fy and under­stand the ori­gin of the mechan­i­cal and met­al­lur­gi­cal defects and thus be able to opti­mise the laser weld­ing process.