Tool steels - classification and basic properties

U ovom radu dan je pregled proučavanja metalurških procesa naprednih metalnih materijala. Termodinamičke karakteristike procesa obuhvadaju uvjete prema kojima je mogude pratiti odvijanje procesa u željenom pravcu te kinetiku odvijanja procesa. Alatni čelici pripadaju skupini naprednih metalnih materijala od kojih se zahtijevaju posebna svojstva poput visoke tvrdode i otpornosti na trošenje, postojanost čvrstode kod povišenih temperatura, dobro ponašanje pri toplinskoj obradi, korozijska otpornost i dr. Postizanje dobrih svojstava omogudeno je legiranjem kromom, volframom, vanadijem, molidbenom ili kobaltom. Veoma je bitno u kojoj mjeri se dodaju legirajudi elementi i kako teče proces proizvodnje, jer spojevi koji nastaju tijekom proizvodnje mogu se mijenjati i tako utjecati na transformacijske procese te se izlučiti u nepoželjnom obliku. Legirajudi elementi se najčešde spajaju s ugljikom u karbide, ali također mogu dijelom supstituirati u kristalnu rešetku željeza te stvarati nepoželjne intermetalne spojeve. U svrhu poboljšanja svojstava alatnih čelika, teži se pronalasku adekvatnog kemijskog sastava kako bi se omogudilo dobivanje stabilnih termodinamičkih parametara.This paper presents an overview of metallurgical processes of advanced metallic materials. The thermodynamic characteristics of the process include the conditions under which it is possible to follow the process in the desired direction and kinetics of the process. Tool steels belong to a group of advanced metallic materials, which are required by special properties such as high hardness and wear resistance, high strength stability at elevated temperatures, good behavior during heat treatment, high corrosion resistance etc. Achieving good properties is enabled by alloying with chromium, tungsten, vanadium, molybdenum or cobalt. It is very important to what extent the alloying elements are added and how the process of production proceeds, because the compounds formed during the production can be altered, and thus affect the transformation processes, and secreted in an undesirable form. Alloying elements are most often combined with carbon in carbides but can also be partially substituted in the iron crystal lattice and create undesirable intermetallic compounds. In order to improve the properties of tool steels, the aim is to find an adequate chemical composition to enable obtaining stable thermodynamic parameters

Influence of medium on corrosion and microstructural properties of HTCS-130 tool steel for hot work

In this paper the corrosion resistance of tool steel for hot work in the industrial emulsion medium (Lenox Band-Ade semi-synthetic oil + water, in ratio 1:10), water and 3.5% NaCl medium was tested. By Tafel’s extrapolation from polarization curves it was established that the tested tool steel showed extremely high corrosion rate in water and 3.5% NaCl medium in contrast to medium of Lenox BandAde emulsion. The double higher corrosion rate of tool steel is recorded in the chloride medium as opposed to that obtained in water, indicating that the tested steel is more corrosion resistant in water. The obtained results were confirmed by the method of electrochemical impedance spectroscopy. The sample of tool steel in the Lenox Band-Ade emulsion medium showed far greater value of charge transfer resistance Rct than that obtained in the water medium and 3.5% NaCl, which means that the Lenox Band-Ade emulsion formed a thicker oxide layer that has the role of barrier in further penetration of aggressive ions from the solution. The conducted SEM analysis after electrochemical measurements in 3.5% NaCl medium indicate the occurrence of pitting corrosion caused by breaking the passive surface of the material as a result of the action of aggressive ions from the solution. The EDS analysis of formed pits has been shown the increased oxygen content, but also the higher presence of sodium and chlorine, which accumulate in the pits, and come from the medium. Molybdenum and tungsten showed the highest presence in white deposits on the sample surface, which represent parts that did not completely cover with oxide layer, which is why the smallest oxygen content was recorded at these sites. The obtained corrosion rate values in the water medium and the chloride medium indicate that the studied tool steel is poorly stable in water and chloride media, and because of that it can only be used in exceptional cases under conditions in which it will come into contact with water or chloride medium

Influence of medium on corrosion and microstructural properties of HTCS-130 tool steel for hot work

In this paper the corrosion resistance of tool steel for hot work in the industrial emulsion medium (Lenox Band-Ade semi-synthetic oil + water, in ratio 1:10), water and 3.5% NaCl medium was tested. By Tafel’s extrapolation from polarization curves it was established that the tested tool steel showed extremely high corrosion rate in water and 3.5% NaCl medium in contrast to medium of Lenox BandAde emulsion. The double higher corrosion rate of tool steel is recorded in the chloride medium as opposed to that obtained in water, indicating that the tested steel is more corrosion resistant in water. The obtained results were confirmed by the method of electrochemical impedance spectroscopy. The sample of tool steel in the Lenox Band-Ade emulsion medium showed far greater value of charge transfer resistance Rct than that obtained in the water medium and 3.5% NaCl, which means that the Lenox Band-Ade emulsion formed a thicker oxide layer that has the role of barrier in further penetration of aggressive ions from the solution. The conducted SEM analysis after electrochemical measurements in 3.5% NaCl medium indicate the occurrence of pitting corrosion caused by breaking the passive surface of the material as a result of the action of aggressive ions from the solution. The EDS analysis of formed pits has been shown the increased oxygen content, but also the higher presence of sodium and chlorine, which accumulate in the pits, and come from the medium. Molybdenum and tungsten showed the highest presence in white deposits on the sample surface, which represent parts that did not completely cover with oxide layer, which is why the smallest oxygen content was recorded at these sites. The obtained corrosion rate values in the water medium and the chloride medium indicate that the studied tool steel is poorly stable in water and chloride media, and because of that it can only be used in exceptional cases under conditions in which it will come into contact with water or chloride medium

In situ prepared polyamide 6/DOPO-derivative nanocomposite for melt-spinning of flame retardant textile filaments

Abstract A novel flame retardant polyamide 6 (PA6)/bridged 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-derivative (PHED) nanocomposite textile filament yarns were developed. The scalable production approach includes in situ water-catalyzed ring-opening polymerization of e-caprolactam in the presence of the flame retardant PHED followed by melt-spinning of nanocomposite filament yarns and production of knitted fabrics. The specific chemical structure of the PHED additive enabled its excellent miscibility with molten e-caprolactam and the uninterrupted polymerization of e-caprolactam. The produced PA6/PHED nanocomposite was characterized by the preserved molecular structure of the polyamide 6 and uniformly distributed nano-dispersed FR at concentrations of 10 and 15 wt %. The PA6/PHED nanocomposite structure was successfully preserved after the melt-spinning processing. The PA6 nanocomposite filament yarns at the applied 15 wt %. loading of PHED showed (a) increased thermo-oxidative stability compared to neat PA6 up to 500 °C, with a 43% higher residue at 500 °C and (b) self-extinguishment of fiber strand and knitted samples within 1 s in standard vertical flame spread tests (ASTM D6413), followed by the significant reduction of the melt-dripping and the melt-drop flammability. Additionally, 1.2 mm-tick PA6/PHED bar samples achieved a V0 rating in UL94 vertical burning test at the applied 10 wt % concentration of PHED. This innovative and scalable approach could pave the way for the production of new-generation nanocomposite PA6 filament yarns with self-extinguishing properties at the macro-scale, which would be highly beneficial for increasing fire safety, whilst maintaining the use of a DOPO derivative at the minimum level

Inhibitory Effect of Commercial Inhibitor VCI 379/611 on the Corrosion Behaviour of HTCS-130 Tool Steel for Hot Work

This paper presents the results of a study of the influence of water and the commercial inhibitor VCI 379/611 on the corrosion behaviour of HTCS-130 hot work tool steel. Using the thermodynamic program Thermo-Calc, phase equilibria were determined according to the choice of calculation conditions and the known chemical composition of tool steels. From the obtained projections, it is possible to observe the secretion of individual phases at certain temperatures. To obtain insight into the corrosion resistance of steel, the following electrochemical methods were used: open circuit potential measurement; electrochemical impedance spectroscopy; and Tafel extrapolation. Metallographic tests were performed on a sample previously etched in nital to identify the microstructure of the steel. Using an optical microscope, the sample surface was analysed after each measurement. Images of the sample surface subjected to water without inhibitors indicate the occurrence of pitting corrosion. The presence of tungsten and molybdenum carbides was identified by scanning electron microscopy and energy dispersion spectroscopy. It was found that the corrosion process is more pronounced in the area of the metal base while in the areas of excreted carbides, weaker corrosion activity was observed

Investigation of recycled AlSi9Cu3(Fe) alloy

Due to European Union legislative and recently the difficulties faced by casting manufacturers, more and more attention is focused on raw materials. Raw materials are found at the beginning of all industrial value chains. These critical (CRMs) and strategic raw materials (SRMs) are often indispensable inputs for a wide set of strategic sectors including renewable energy, the digital industry, the space and defence sectors, health sector all connected to the metal industry. Aluminium and its alloys plays an important CRMs and SRMs. Standard aluminium alloy AlSi9Cu3(Fe) (EN AC 46000) is widely used in the automotive and transport industry. High mechanical properties such as strength and hardness, as well as elongation and corrosion resistance are the main advantages of AlSi9Cu3(Fe) alloy. The functional and useful properties of aluminium cast alloys are dependent from the chemical composition, melt treatment, solidification rate, casting process and potential heat treatment. Most of them are conditioned by the microstructural development. This paper investigates the recycling potential of AlSi9Cu3(Fe) alloy using completely return material without any additions or refining. The presence of wide range of alloying elements AlSi9Cu3(Fe) alloys indicates development α-Al15Si2M4 (M= Cr, Fe, Mn, Mo), β-Al5FeSi, Al2Cu and even more complex one such as Al3Cu2Mg9Si7 using theoretical modelling. Complex solidification path indicates primary aluminium αAl, eutectic phase αAl+βSi, intermetallic phase on the iron base in Al5FeSi and “Chinese script” morphology, intermetallic phase on the magnesium and copper base such as Mg2Si and Al2Cu, and complex intermetallic such as Al8Mg3FeSi2 and Al5Mg8Si2Cu2 phases. Thermodynamic effects of elements interaction during solidification sequence significantly influence on solidification path and manner. Although the investigated samples maintain high tensile strength and elongation, slight degradation in chemical composition and therefore in thermodynamic effect, significantly influence on microstructure development. In despite of chemical composition degeneration, obtained microstructure was correct and therefore justified achieved high mechanical properties. Therefore, on the base of thermodynamic and microstructural investigation of the secondary AlSi9Cu3(Fe) alloy indicated raw material as a quality charge material with good application and recycling potential

Transformation of the metastable Al6_6Fe intermetallic phase during homogenization of a binary Al-Fe alloy

Within the scope of this research the transformation of the Al$_6$Fe metastable phase was analyzed via Differential Scanning Calorimetry (DSC), optical and Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). A binary Al-Fe1.1 low-impurity alloy was produced with refined raw materials in a controlled environment. With a cooling rate of 35 K/s, solidification of the Al$_6$Fe metastable phase was achieved. The samples were homogenized at 600 °C for 2–24 h. Results of a qualitative analysis of metallographic samples show that the transformation began on grain boundaries, forming an Fe-phase free region, but after 2 h began to take place within the eutectic region. The transformation is mostly complete after 12 h, but after 24 h of homogenization it is fully complete as all samples, except the 24 h homogenized one, contain both the metastable Al$_6$Fe and the stable Al$_{13}$Fe$_4$ phase

A Preliminary Study of New Experimental Low-Cost Fe–P-Based and Mn–Fe–P-Based Brazing Filler Metals for Brazing of Non-Alloy and Low-Alloy Steels

Seventeen new experimental filler metals from eight different alloy systems based on Fe–P–X and Mn–Fe–P–X (X = B, C, Si in various combinations) were created and experimented with. DSC analyses were performed to determine the solidus and liquidus temperatures and the melting ranges. Hardness measurements of the alloys were performed in the as-cast state. The alloys contain primary and eutectic intermetallic compounds that make them very hard with average hardness values ranging from 590 HV10 to 876 HV10. The wettability was determined at 1000 °C, 1040 °C and 1080 °C on C22 non-alloy steel and 15CrNiS6 low-alloy steel in Ar 4.6 and 78 vol% H2-22 vol% N2 atmospheres. The results show good wettability at T = 1080 °C in both atmospheres, as the contact angles were mostly ≤30°. Thirteen alloys exhibit very good wettability with average contact angles of ≤15.5°. Nine alloys exhibit excellent wettability with their average contact angles being ≤10°. Wettability improves at higher temperatures. The liquid alloys are reactive to solid steels and form a diffusion joint. Diffusion of P, B, C, and Si from the filler metal into the base material dealloys the composition of the melt near the joint interface. For the same reason, a continuous layer of solid solution forms on the joint interface. When brazing with filler metals rich in carbon, strong carburisation of steels can be observed near the joint