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

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

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

Wear resistance of layers hard faced by the high-alloyed filler metal

The objective of this work was to determine the wear resistance of layers hard faced by the high-alloyed filler metal, with or without the austenite inter-layer, on parts that operate at different sliding speeds in conditions without lubrication. The samples were hard faced with the filler metal E 10-UM-60-C with high content of C, Cr and W. Used filler metal belongs into group of alloys aimed for reparatory hard facing of parts damaged by abrasive and erosive wear and it is characterized by high hardness and wear resistance. In experiments, the sliding speed and the normal loading were varied and the wear scar was monitored, based on which the volume of the worn material was calculated analytically. The contact duration time was monitored over the sliding path of 300 mm. The most intensive wear was established for the loading force of 100 N and the sliding speed of 1 m.s-1, though the significant wear was also noticed in conditions of the small loading and speed of 0.25 m.s-1, which was even greater that at larger speeds.

Utjecaj promjenjivog kontaktnog tlaka i promjenljive visine zateznog rebra na duboko vučenje limova od Al legura

The process of deep drawing is influenced by many factors. During the forming process, only two of those factors can be controlled. They are blank holding force and drawbead height. Realisation of such control requires relatively complex computerized apparatus. For this experimental research, electro-hydraulic sheet-metal strip sliding device has been constructed. Basic capacity of realized device is obtaining contact pressure and drawbead height as functions of time or stripe displacement. Additional features consist of the ability to measure drawing force, contact pressure, drawbead displacement etc. Presented in the paper are the results of influencing of increasing and decreasing drawbead height functions in combination with increasing-decreasing function of contact pressure. Stripe material is aluminium alloy AlMg4,5Mn0,7 sheet metal. Contact condition are additionally influenced by application of mineral oil or completely dry tool and stripe surfaces. Drawbead geometry, with rounding radii of 2 and 5 mm, is also varied. The accomplished results indicate that simultaneous effects of variable drawbead height, variable contact pressure, tool geometry and appropriate friction conditions can influence the plastic flow process in line with desired change of forming force.Na proces dubokog vučenja utječe više faktora. Tijekom trajanja procesa oblikovanja moguće je upravljati samo s dva faktora. To su sila držanja i visina zateznog (vlačnog) rebra. Ostvarivanje takvog upravljanja zahtjeva relativno složenu kompjutoriziranu aparaturu. Za ovo pokusno istraživanje razvijen je elektro-hidraulički uređaj za klizanje traka od lima s kompjutorskim upravljanjem. Njegova osnovna karakteristika je ostvarivanje kontaktnog tlaka i visine zateznog rebra, kao funkcijskih ovisnosti o vremenu, odnosno hodu trake. Pored toga, moguće je mjeriti vučnu silu, silu pritiska, pomak rebra itd. U radu su izloženi rezultati ispitivanja utjecaja opadajuće i rastuće ovisnosti visine rebra u kombinaciji s rastuće-opadajućom funkcijom kontaktnog tlaka. Materijal trake je legura aluminija AlMg4,5Mn0,7 debljine 0,9 mm. Na kontaktne uvjete se dopunski utječe s dva tipa trenja. U prvom slučaju površine su suhe, a u drugom se primjenjuje podmazivanje odgovarajućim mineralnim uljem. Geometrija rebra se mijenja preko polumjera zaobljenja 2 i 5 mm. Ostvareni rezultati pokusa pokazuju istodobno djelovanje promjenljive visine rebra, promjenljivog kontaktnog tlaka, geometrije rebra i odgovarajućih uvjeta trenja, mogu utjecati na proces plastičnog tečenja u skladu sa željenom promjenom sile oblikovanja

Effect of elevated temperatures on mechanical properties of ultra high strength hot work tool steel h11

This paper presents an experimental and numerical study into the influence of elevated temperatures on mechanical properties of the heat treated high quality hot work tool steel H11. This steel belongs to a group of alloyed steels with extraordinary mechanical properties. The aim of this study was to determine the highest temperature at which these properties are still maintained. The experimental investigation focused on the tensile testing of specimens at seven different temperatures, including the room temperature. The highest testing temperature was 700 degrees C. The heat treatment of plates (specimens) consisted of quenching and tempering. Although the strain hardening of this type of materials is small, the strain hardening curves were calculated to show if there was a possibility for the material to increase its strength due to exploitation loads. Also, a numerical analysis of the tensile test by using the finite element method was done in order to define an appropriate model for numerical testing. The obtained results are then compared with the experimental results

Selection of the optimal hard facing (HF) technology of damaged forging dies based on cooling time t8/5

In exploitation, the forging dies are exposed to heating up to very high temperatures, variable loads: compressive, impact and shear. In this paper, the reparatory hard facing of the damaged forging dies is considered. The objective was to establish the optimal reparatory technology based on cooling time t8/5. The verification of the adopted technology was done by investigation of the hard faced layers microstructure and measurements of hardness within the welded layers’ characteristic zones. Cooling time was determined theoretically, numerically and experimentally

The influence of temperature on mechanical properties of the base material (BM) and welded joint (WJ) made of steel S690QL

This paper presents the analysis of the influence of temperature on mechanic properties of the base material and welded joints made of high strength steel. The joints were welded on S690QL high strength steel plates using the Metal Active Gas (MAG) Welding and two filler materials of different properties. Since the steel S690QL belongs to a group of steels with high strength, the aim of this paper is to determine the temperature at which strength starts to decrease. Experimental tensile testings of the welded joints were performed at five different temperatures in the range from 20 to 550 °C

Simulation of Flat Die Deep Drawing Process by Variable Contact Pressure Sliding Model

Influence of the contact pressure in the deep drawing processes is a very actual research topic in the metal forming technology. Within this research the tribological model of the strip sliding in the flat die was developed. The original experimental computerized apparatus for testing of the strip sliding in the variable contact pressure conditions was developed, as well. The complex, multi-factor experiment was performed by application of the Al thin sheet, with the contact elements of various roughnesses, with different lubricants application and with the variable contact pressure. Besides the description of the developed apparatus, the theoretical way for determination of the pressure dependences was also presented. Based on the theoretical changes of pressure, set in advance, the real influence of the contact pressure was obtained, for each of the given conditions. That makes possible to determine the influence of the tribological factors on the actual pressure. The obtained real contact pressure has verified the reliability of the experimental apparatus, namely the degree of the theoretical pressure dependences deviation from the real ones

Wear resistance of layers hard faced by the high-alloyed filler metal

The objective of this work was to determine the wear resistance of layers hard faced by the high-alloyed filler metal, with or without the austenite inter-layer, on parts that operate at different sliding speeds in conditions without lubrication. The samples were hard faced with the filler metal E 10-UM-60-C with high content of C, Cr and W. Used filler metal belongs into group of alloys aimed for reparatory hard facing of parts damaged by abrasive and erosive wear and it is characterized by high hardness and wear resistance. In experiments, the sliding speed and the normal loading were varied and the wear scar was monitored, based on which the volume of the worn material was calculated analytically. The contact duration time was monitored over the sliding path of 300 mm. The most intensive wear was established for the loading force of 100 N and the sliding speed of 1 m.s-1, though the significant wear was also noticed in conditions of the small loading and speed of 0.25 m.s-1, which was even greater that at larger speeds.