Utjecaj kvalitete pripreme površine osnovnog materijala na otpornost naštrcanog sloja radijalnom i aksijalnom smiku

For the purpose of this experiment, respective surfaces of 42CrMo4 base material specimens were prepared for spraying using different technologies: turning, cutting of radial notches and cutting of axial notches. Gas aided thermal spraying of wire material was performed, laying a first layer of a nickel aluminum compound and a final Chrome Molybdenum Steel coating. Metallographic structure analysis and hardness measurement suggested that surface preparation quality does not affect hardness of the sprayed layer, but its thickness. Using a suitable tool, specimens were examined on radial and axial shear and these results were compared to previous ones. It could be determined that the notch size significantly affects both the thickness of the intermediate layer and its even distribution around the edge of the notch. A smaller radial notch allows for a higher torque momentum at radial shear, whilst best overall properties are achieved with axial notches subjected to radial loads. Testing axial shear, the cutting power proved dependant of the depth of radial notches, where low depth was inherent with low shear resistance.Na ispitnim uzorcima osnovnog materijala 42CrMo4 izvršene su različite pripreme površine: tokarenjem, narezivanjem aksijalnih i narezivanjem radijalnih utora. Izvršeno je plinsko naštrcavanje žicom: međusloj nikl- aruminid i završnog sloja Cr-Mo čelik. Metalografskim pretragama strukture i kontrolom tvrdoća utvrđeno je da kvaliteta pripreme površine ne utječe značajno na tvrdoću ali utječe na postignutu debljinu sloja. Odgovarajućim alatom izvršena su ispitivanja uzoraka na radijalni i na aksijalni smik. Međusobnom usporedbom rezultata ovih mjerenja s rezultatima kontrole tvrdoće i metalografskim pretragama strukture dolazi se do zaključka da veličina utora značajno djeluje na debljinu podsloja a pogotovo na njegovu ravnomjerno naštrcavanje po obodu utora. Sitniji radijalni utor doprinosi povećanju momenta zakretanja pri radijalnom smiku, ali se najbolja svojstva postižu u uvjetima aksijalnih utora radijalno opterećenih. Pri ispitivanju na aksijalni smik sila odreza ovisi o dubini radijalnih utora pri čemu mala dubina utora daje i malu otpornost na smik

Application of Tribometer Measurements for Evaluation of Machinability

Investigation of machinability of materials is continuously faced with new demands, new principles and new achievements. The outcome of evaluation of machinability presented in this paper resulted out from observation of two tribological parameters: friction factor and width of the wear area on contact between two sliding bodies, blocks and discs. Measurements are performed on tribometer in condition of wet sliding while one body is sliding over the other. A block is made of material which is usually used for cutting tool, and a disc is made of material which is used as a material of workpiece. Achieved contact condition (normal loading and sliding speed) meets real machining-cutting condition. The aim of the tests performed on tribometer “Block on Disc” is to evaluate the opportunity of investigation of materials machinability by tribological parameters (friction factor and width of wear area on the block). Comparison of experimental results obtained during real cutting condition setup and tribological setup show a good correlation between wear values and cutting forces. For certain conditions, it is possible to acquire machinability indexes obtained on a tribometer with respect to friction factor and wear on the block as relevant and representative for real cutting condition

Study of Stainless Steel Resistance in Conditions of Tribocorrosion Wear

Analyzed was the influence of tribocorrosion wear due to effects of fatty acids present in the processed medium. The analysis was conducted on samples made of two austenitic and two martensitic stainless steels. Austenitic steels were tested in their nitrided state and martensitic in their induction hardened state. Conducted were laboratory tests of corrosion resistance of samples, analysis of the microstructure and hardness. To see how the applied processes for modifying the surface of stainless steels behave in realistic conditions, it was conducted the examination of samples/parts of a sunflower cake chain conveyer. Based on the comparison of results obtained in the laboratory and in real conditions, it was estimated that steels AISI 420 and AISI 431 with induction hardened surfaces have a satisfactory resistance to abrasive-adhesive wear in the presence of fatty acids

The Influence of Water on the Properties of Polyester Laminates Made by Manual Air Extrusion

The mechanical properties of polyester composites reinforced by various combinations of glass fibre types were investigated. The samples were tested before and after the operation of the wet media in the salt chamber. Cross sections were recorded to determine the presence of cavities. It was concluded that the properties of composites depended not only on the number and type of reinforcement but also much more on the portion of cavities. It is concluded that the intermediate surface with a smaller portion of the cavities contributes to the compositions to be firmer and stiffer, but also fragile. As a result, the negative influence of water increases with the increase of porosity

Investigation of the Impact of Hot Forming the Properties of Seamless Steel Bottles for Liquefied Gases

Mechanical tests were performed on samples prepared from the body and the neck of bottles made of seamless tube, steel 34CrMo4. Plastic material flow curves were taken from tensile tests on samples which were made from tubes and finished bottles. Deformation hardening intensity is calculated, and propensity towards brittle fracture is estimated on the basis of the ratio of total elongation and elongation at maximum load. Compared to the samples of quenched and tempered bottle body, quenched and tempered bottle neck samples indicate that characteristics of strength are almost unchanged with an increase in the minimum strain at the destruction from 12,8% to 15,1%. It was concluded that the results of the plastic material flow can serve as a preliminary indication of anomalies that could contribute to unsatisfactory results of the burst test

Utjecaj promjenjive sile držanja i nemonotonosti procesa dubokog vučenja na obradivost limova s prevlakama

The results of the research of influence of the blank holding force and nonmonotonous process of deep drawing on the formability of low-carbon steel sheet with one-side galvanic coating of zinc are presented in this paper. Identification and influence assessment was done by monitoring: forming force, the distribution of the principal strains in the sheet plane and their relationship to the forming limit diagram, changes of thinning strain and drawing depth as the most significant technological indicator. Based on the analysis of test results, it was concluded that the blank holding force has a significant influence in terms of intensified friction in the flange. Also, in terms of a single-phase monotonous process, the applied type of variable blank holding force had a beneficial effect on the results of forming. A nonmonotonous two-phase process with uniaxial tension in the first stage greatly affects the behaviour of materials. During the first phase, there is an increase of sheet anisotropy, which affects the formability decrease. The applied variable holding force shows favourable effects, especially when friction was increased, but they were not dominant.Istraživan je utjecaj promjenljive sile držanja i nemonotonosti procesa dubokog vučenja na obradivost niskougljičnog čeličnog lima s jednostranom galvanskom prevlakom od cinka. Identifikacija i procjena utjecaja izvršena je praćenjem: sile vučenja, distribucije glavnih deformacija u ravnini lima te njihovog odnosa prema dijagramu granične deformabilnosti, promjene deformacije stanjenja i dubine izvlačenja kao najznačajnijeg tehnološkog pokazatelja. Na temelju analize rezultata pokusa zaključeno je da sila držanja pokazuje značajniji utjecaj u uvjetima pojačanog trenja na obodu. Također, u uvjetima jednofaznog monotonog procesa primijenjeni tip promjenljive sile držanja povoljno djeluje na rezultate oblikovanja. Dvofazni nemonotoni proces s jednoosnim zatezanjem u prvoj fazi suštinski utječe na ponašanje materijala. Tijekom prve faze dolazi do povećanja anizotropije lima, što doprinosi padu deformabilnosti. Primjenjena promjenjiva sila držanja pokazuje povoljne efekte, naročito pri pojačanom trenju, ali oni nisu dominatni

Numerical Analysis of the Temperature Field in the Cutting Zone in Continuous and Discontinuous Metal Cutting by Turning

Temperature of cutting is a very important indicator of the cutting process. High specific pressures and high temperatures in the narrow cutting zone result in a drop of hardness of the tool material, the intensification of the abrasion and deformation of the cutting elements, losing the cutting abilities, and finally the failure of the cutting tool. The aim of this paper is to calculate the temperature fields using the existing numerical models for the simulation of thermodynamic processes on the wedge of the cutting tool (based on the finite element method). A special accent is given to the numerical calculation of temperatures in the conditions of continuous and discontinuous turning for specific cutting conditions (processing regime, tool geometry and thermo-mechanical characteristics of the tool materials and workpiece materials) using different simulation models. The Third Wave AdvantEdge software package was used for the simulation of orthogonal turning, and some of the results of the calculations of the temperature fields were compared with the results of experimental measurements

VERSCHLIESSFESTIGKEIT DER MARTENSITISCHEN NICHTROSTENDEN STÄHLE MIT OBERFLÄCHENMODIFIKATION FÜR BESSERE KORROSIONS- UND VERSCHLEISSEIGENSCHAFTEN

Na uzorcima korozijski postojanih čelika provedena su laboratorijska ispitivanja te ispitivanja u stvarnim uvjetima trošenja. Elektrokemijska ispitivanja provedena su radi provjere korozijske otpornosti modifi ciranih površina čelika. Na uzorcima korozijski postojanih čelika X20Cr13 i X17CrNi16-2 provedena je metalografska analiza i ispitivanje tvrdoće. Mogućnost primjene modifi ciranih površina na odabranim čelicima provjerena je ispitivanjem uzoraka svornjaka u stvarnim uvjetima trošenja. Uzorci svornjaka zavareni su REL postupkom, a korištena je elektroda Cr-Ni-Mn (18/8/6/). Dobiveni rezultati pokazuju da su indukcijski zakaljeni i naknadno nitrirani martenzitni čelici prosječno postigli otpornost trošenju do tri reda veličine veću u odnosu na dostavno stanje.On test samples of stainless steels, there were conducted laboratory tests and also sample tests in real wear conditions. Electrochemical testings were made towards control of corrosion resistance of modifi ed steel surfaces. On test samples of stainless steels X20Cr13 i X17CrNi16-2, there were conducted metallographic analysis and hardness testing. The possibility of applying modifi ed surfaces of selected steels was cntroled by sample testings in real wear conditions. Test bolts are welded with MMA procedure and it was used electrode Cr-Ni- Mn (18/8/6). Obtained results showed that induction hardened and post-nitrided martensitic stainless steels achieveed for three orders of magnitude bigger wear resistance in relation to asreceived condition.An den Proben der nichtrostenden Stähle wurden laboratorische Prüfungen durchgeführt in den realen Verschleiß Gegebenheiten. Elektrochemische Prüfungen wurden durchgeführt mit dem Ziel der Kontrolle der Korrosionsbeständigkeit bei Stählen mit modifi zierter Oberfl ächenstruktur. An Proben der nichtrostenden Stähle X20Cr13 und X17CrNi16-2, wurden metalographische Analysen und Härtemessungen durchgeführt. Eine Möglichkeit der Anwendung dieser Oberfl ächenmodifi zierten Stähle wurde an Bolzen in realen Verschleiß Gegebenheiten geprüft. Diese Bolzen wurden mit E-Hand und der Cr-Ni-Mn (18/8/6) Elektrode geschweißt. Die Resultate haben darauf eingewiesen dass die induktionsgehärteten und nachträglich nitrierende martensitischen Stähle im durchschnitt eine dreifach bessere Verschleißfestigkeit im Gegensatz zu den Stählen im gelieferten Zustand hatten

Utjecaj parametara kaljenja čeličnog lijeva GS30Mn5 na svojstva utora užnica broda jaružara

Dredgers are special sea floating vessels used for removing sea bottom material in order to: reshape harbor underwater areas and waterways, assembling pipelines, preparing sand beaches and coasts to handle with erosion impact, oil resources exploitation, forming man-made islands… This paper is based on selection of heat treatment parameters of sheaves, surface errors determination method and surface damages recovery. Om test samples made out of same material (GS30Mn5) built—up welding test was carried out of (SMAW procedure) by fluting prepared damage area. Next step was induction hardening using various parameters. Determination of cracks appearance was done by magnet method. By recording cross section structure as well as hardness measuring it has been determined that besides certain level of energy input (electrical current frequency) surface layer properties of sheave edge depend also about choosing proper cooling medium. Satisfying hardness values (320400 HB) were achieved combining air and water cooling simultaneously with avoiding cracks appearance. Parameters selected that way should ensure long working period of ropes (hardness 500550 HB) as well as safe dredgers performance.Jaružari su specijalna morska plovila kojima se materijal s morskog dna uklanja u cilju: oblikovanja - produbljivanja lučnih pristaništa i plovnih puteva, polaganja cjevovoda, održavanja pješčanih plaža i obale od erozije, exploatacije naftnih izvora, formiranja umjetnih otoka nasipavanjem pijeska… Na ispitnim uzorcima izrađenim od istog materijala kao i užnice (GS30Mn5) izvršene su probe navarivanja (REL postupkom). Nakon toga izvršeno je indukcijsko kaljenje, različitim parametrima. Kontrola pojave pukotina utvrđivana je magnetskom metodom. Snimanjem strukture poprečnog presjeka i mjerenjem tvrdoće utvrđeno je da osim o odgovarajućem unosu energije (frekvencija struje) svojstva površinskog sloja utora užnice ovise i o izboru sredstva za hlađenje. Zadovoljavajuće tvrdoće (320÷400 HB) postižu se kombinacijom hlađenja zrakom i vodom uz istovremeno izbjegavanje pojave pukotina. Takav izbor parametara treba da omogući zadovoljavajući vijek užadi (tvrdoće 500550 HB) te pouzdanu exploataciju jaružara