Method of plastic shaping on a hydraulic press of a AZ91 magnesium alloy wheel by forging, in particular from a forging preform cast into metal moulds, and a wheel shaped according to the method

Abstract

The object of the invention is a method for plastic forming on a hydraulic press of a wheel forgings made of AZ91 magnesium alloy for light vehicles, in particular from a forging preform into metal moulds, and a wheel forgings formed by this method characterised in that, the upper drop forging die tool (1) with a finishing impression (la) in the centre and a lower drop forging die tool (3) with a finishing impression (3a) in the form of a lump whose outline resembles a circle with circular recesses in the centre, is heated in a furnace to 260°C to 300 °C, then the heated upper drop forging die tool (1) and the heated lower drop forging die tool (3) are assembled in the workspace of the press, and then the forging impression (2a) cast into metal moulds of the AZ91 magnesium alloy (Mg- 9Al-lZn) is heated in an oven to 300 °C to 400°C for a period of 30 to 35 min, after which the heated forging blank (2a) cast into metal moulds is placed and centred in the finishing blank (3a) of the bottom drop forging die tool (3), after which the top drop forging die tool (1) is driven downwards on a hydraulic press at a speed (VI) of 20 mm / s towards the lower drop forging die tool (3) and the forging preform (2a) cast into metal moulds is compressed by the finishing impression (la) of the upper drop forging die tool (1) and the finishing impression (3a) of the lower drop forging die tool (3) with a forging force ranging from 1689, 9 kN to 2044.6 kN, a wheel forging (2b) is formed with a deformation in the range of 7.72 to 11. The object of the invention is also a wheel forging produced by the method as specified above.

Description

[0001] METHOD OF PLASTIC SHAPING ON A HYDRAULIC PRESS OF A AZ91 MAGNESIUM ALLOY WHEEL BY FORGING, IN PARTICULAR FROM A FORGING PREFORM CAST INTO METAL MOULDS, AND A WHEEL SHAPED ACCORDING TO THE METHOD

[0002] The obj ect of the invention is a method for plastic forming, on a hydraulic press , of a wheel forgings from AZ 91 magnesium alloy, in particular from a forging preform cast into metal moulds , and a wheel forging formed by this method . 0 So far , methods of shaping magnesium alloy wheels such as casting , machining, drop forging are known and used .

[0003] For the shaping of magnesium alloy wheels , the casting technology is used, which was described in the literature by K . E . Oczos , A. Kawalec "Shaping light metals" ( Polish :5 Ksztaltowanie metali lekkich ) , Wydawnictwo Naukowe PWN, Warsaw 2012 and A. A. Luo "Magnesium casting technology for structural applications" , Journal Magnesium Alloy, 2013 , vol . 1 , pp . 2-22 . The most commonly used types of magnesium alloy wheel casting are gravity casting , high pressure casting or low pressure casting . 0 Due to the strong reactivity and the need for a protective atmosphere , magnesium alloy wheels are most often cast in the process of hot or cold chamber casting . This process helps obtain products with high properties .

[0004] Pressure die-casting offers attractive flexibility in5 the design and manufacture of magnesium wheels . Pressure diecasting of magnesium alloy wheels are designed with thin walls in areas where the product should not have high strength and with thicker walls in areas with higher strength requirements .

[0005] Non-pressure die-casting of magnesium wheels takes place in0 sand and metal moulds , by the full mould method or by the smelted models method . Non-pressure die-casting of magnesium wheels is rarely used due to the inferior mechanical properties of the castings , surface roughness and lower dimensional accuracy compared to the wheels obtained by the pressure casting method . Cast magnesium wheels are characterized by high dimensional accuracy and low production costs . Cast wheels have casting defects such as: heterogeneity of structure, coarse grain, blisters, porosity, shrinkage cavities, rust, which affect their lower properties compared to those obtained by plastic processing methods .

[0006] When shaping magnesium alloy wheels, the machining technology is used, which is described in W. Olszak's literature "Machining", Wnt, Warsaw 2008. The machining of magnesium alloy wheels consists in giving the surfaces the desired shape, dimensions and surface quality by removing the material from the blank in the form of a roller using cutting tools . This method is labor-intensive, time-consuming and energy-intensive. During the machining process of magnesium wheels, large material losses are generated, and the quality of the obtained products is lower than that obtained by plastic processing methods.

[0007] The best mechanical and functional properties of magnesium alloy wheels for light vehicles are ensured by the plastic processing processes described in the literature by K. E. Oczos, A.Kawalec "Shaping light metals", Wydawnictwo Naukowe PWN, Warsaw 2012 and J. Sihczak "Processes of plastic processing", Wydawnictwo Naukowe AKAPIT, Krakow 2003. An example of the process is drop forging described in specialist literature by P. Skubisz "Technologies of drop forging", ARBOR FP, Krakow 2010 and L. Gebrehiwet, Y. Negussie, A. Tadesse " Business Opportunity of Wheel Rim Manufacturing in Ethiopia", International Journal of Advances in Engineering and Management, 2022, vol. 4, pp. 1148-1159. The drop forging process of a magnesium alloy wheel forgings is carried out in three stages - swelling, pre-forging, final forging of a semi-finished product in the form of a roller produced by extrusion. Expensive tool-mounted heating systems are used for the process. This method produces a large technological waste, which is 50% of the forging weight.

[0008] A method of forging a semi-finished product on a hydraulic press is known from the patent PL 237782 Bl, in particular for the production of an aviation fastening, wherein the upper and lower tools having working impressions in the central part are mounted on a hydraulic press with a pressure of 3000 kN and are heated using gas burners to a temperature of 300 ° C . After that , the input material in the form of a shaped forging preform cast in sand forms from less malleable magnesium alloys of the magnesium-aluminium-zinc group is heated in a furnace in the temperature range of 400 - 430 ° C, preferably 420 ° C, for up to 45 minutes . The heated input material is then placed in the working impression of the lower tool . After which, the hydraulic press is pressed on the upper tool having two identical blind guide holes with two identical guide pins located on the lower tool and the upper tool is set in progressive downward movement with a velocity of up to 15 mm / s towards the lower tool and the input material is compacted with the working impression of the upper tool and the working impression of the lower tool and a semi-finished product is formed with a lower degree of forging .

[0009] The purpose of the invention is to shape an AZ 91 magnesium alloy wheel forging in a single forging operation in a finishing blank on a hydraulic press from a forging preform cast in AZ 91 magnesium alloy metal moulds , reducing the material , labour and energy intensity of the process .

[0010] The essence of the invention is a method for plastic forming on a hydraulic press of a wheel forgings made of the magnesium alloy AZ 91 , particularly from a forging preform cast into metal moulds , and a wheel forging shaped according to the method, characterised in that the upper drop forging die tool and the lower drop forging die tool having a finishing impression in the form of a lump whose outline approximates that of a circle with circular recesses in the centre are heated in a furnace , and then the upper drop forging die tool and the lower drop forging die tool are assembled in the workspace of the hydraulic press in the working space of the hydraulic press , after which the metal forging impression is heated in the furnace , positioned and centred in the finishing impression of the lower drop forging die tool, and then the upper drop forging die tool is moved in a progressive motion on the hydraulic press towards the lower drop forging die tool, the metal forging impression is compressed by the finishing impression of the upper drop forging die tool and the finishing blank of the lower drop forging die tool, and the wheel forging is formed. The upper drop forging die tool and the lower drop forging die tool are heated in a furnace to a temperature between 260°C and 300°C, and the forging forged metal moulds in magnesium alloy AZ91 (Mg-9Al-lZn) is heated in an oven to a temperature between 350°C and 400°C for a period of between 30 minutes and 35 minutes, whereby the heated forging is compressed with an upper drop forging die tool in a progressive motion towards the lower drop forging die tool with a velocity of 20 mm / s with a forging force ranging from 1689.9 kN to 2044.6 kN and a wheel forging is formed with a deformation in the range of 7.72 to 11. The forging preform for metal moulds with a volume of 81961.7 mm3 and a weight of 0.1569 kg has the shape of a barrel with a height of 25.31 mm and a diameter of 65.9 mm at its widest point, which has a lower base with a diameter of 62.97 mm and an upper base with a diameter of 63.29 mm, where in the lower base there is a circular recess with a diameter of 18.22 mm and a height of 6.8 mm, and the walls of the barrel are inclined at an angle of 4°.

[0011] Preferably, the forging preform into metal moulds is heated in an oven at 400°C.

[0012] Preferably, the forging preform into metal moulds is heated in an oven for 30 minutes.

[0013] The essence of the invention is also the forging of the wheel shaped by the method as set out above.

[0014] It is an advantage of the present invention that the use of a cast forging preform for the forming process allows material savings in relation to the currently used machining technologies and multi-stage forging. The use of the cast forging preform for the shaping process makes it possible to obtain more accurate shapes of wheel forgings without excessive spout , which has a positive effect on the reduction of technological waste in relation to the production methods used so far .

[0015] Another advantage of the present invention is also that the shaping method according to the invention allows for the production of wheel forgings that are characterized by better quality associated with the fragmentation of the structure and obtaining a high surface smoothness , which translates into better mechanical properties in relation to products made by casting in sand moulds and machining .

[0016] The invention is described in the embodiments and in the drawing in which :

[0017] FIG . 1 shows a perspective view of drop forging die tools with a tear-off with a forging preform into metal moulds ;

[0018] FIG . 2 shows a perspective view of drop forging die tools in contact with a wheel forging;

[0019] FIG . 3 illustrates a perspective view of an upper drop forging die tool ;

[0020] FIG . 4 shows a perspective view of the lower drop forging die tool ;

[0021] FIG . 5 shows a perspective view from above of a forging preform cast into metal moulds ;

[0022] FIG . 6 shows a lower perspective view of a forging preform cast into metal moulds ;

[0023] FIG . 7 shows a longitudinal section of a forging preform cast into metal moulds ;

[0024] FIG . 8 shows a top perspective view of a wheel forging;

[0025] FIG . 9 shows a bottom perspective view of a wheel forging;

[0026] FIG . 10a shows the distribution of deformations in the wheel forging in a upper view for the temperature of drop forging die tools 260°C and the forging preform cast into metal moulds 350°C according to the invention obtained from FEM simulation;

[0027] FIG. 10b shows the distribution of deformations in the wheel forging in a lower view for the temperature of drop forging die tools 260°C and the forging preform cast into metal moulds 350°C according to the invention obtained from the FEM simulation;

[0028] FIG. 10c shows the distribution of deformations in the wheel forging in a upper view for the temperature of drop forging die tools 260°C and the forging preform cast into metal moulds 400°C according to the invention obtained from FEM simulation;

[0029] FIG. lOd shows the distribution of deformations in the wheel forging in the lower view for the temperature of drop forging die tools 260°C and the forging preform cast into metal moulds 400°C according to the invention obtained from the FEM simulation;

[0030] FIG. lOe shows the distribution of deformations in the wheel forging in a upper view for the temperature of drop forging die tools 300°C and the forging preform cast into metal moulds 350°C according to the invention obtained from FEM simulation;

[0031] FIG. lOf shows the distribution of deformations in the wheel forging in a lower view for the temperature of drop forging die tools 300°C and the forging preform cast into metal moulds 350°C according to the invention obtained from the FEM simulation;

[0032] FIG. 10g shows the deformation distribution in the wheel forging in upper view for the temperature of drop forging die tools 300 °C and the forging preform cast into metal moulds 400°C according to the invention obtained from FEM simulation;

[0033] FIG. lOh shows the distribution of deformations in the wheel forging in a lower view for the temperature of drop forging die tools 300°C and the forging preform cast into metal forms 400°C according to the invention obtained from the FEM simulation;

[0034] FIG. lOi shows the distribution of deformations in the semifinished product in a top view made on the basis of patent document PL237782B1 and obtained from a FEM simulation; FIG. 10 j shows the distribution of deformations in the semifinished product in a bottom view made on the basis of patent document PL237782B1 and obtained from FEM simulation;

[0035] FIG. Ila shows a graph of flow curves of AZ91 magnesium alloy cast in metal moulds at 350°C;

[0036] FIG. 11b shows a graph of flow curves of AZ91 magnesium alloy cast in metal moulds at 400 °C;

[0037] FIG. 11c shows a graph of flow curves of AZ91 magnesium alloy cast in metal moulds at 450°C;

[0038] FIG. lid shows a graph of flow curves of AZ61 magnesium alloy cast in sand moulds at 350°C;

[0039] FIG. lie shows a graph of flow curves of AZ61 magnesium alloy cast in sand moulds at 400°C;

[0040] FIG. Ilf shows a graph of flow curves of AZ61 magnesium alloy cast in sand moulds at 450°C;

[0041] FIG. 12a shows a graph of the forging force of the upper drop forging die tool as a function of time for the temperature of the drop forging die tools 260°C and the forging preform cast into metal moulds 350°C according to the invention, obtained from the FEM simulation;

[0042] FIG. 12b shows a graph of the forging force of the upper drop forging die tool as a function of time for the temperature of the drop forging die tools 260°C and the forging preform cast into metal moulds 400°C according to the invention, obtained from the FEM simulation;

[0043] FIG. 12c shows a graph of the forging force of the upper drop forging die tool as a function of time for the temperature of the drop forging die tools 300°C and the forging preform cast into metal moulds 350°C according to the invention, obtained from the FEM simulation;

[0044] FIG. 12d shows a graph of the forging force of the upper drop forging die tool as a function of time for a temperature of drop forging die tools 300°C and a forging preform cast into metal moulds 400°C according to the invention obtained from a FEM simulation;

[0045] FIG. 12e shows a graph of the dependence of the forging force of the upper drop forging die tool as a function of time, based on patent document PL237782B1 and obtained from FEM simulations.

[0046] For the plastic forming on a hydraulic press of an AZ91 magnesium alloy wheel forgings, in particular from a cast forging preform for metal moulds and a wheel forging shaped according to the method, a metal mould casting forging with a volume of 81961.7 mm3 and a mass of 0.1569 kg was used in examples 1 - 4, which has the shape of a barrel with a height of 25.31 mm and a diameter of 65.9 mm at its widest point, having a lower base with a diameter of 62.97 mm and an upper base with a diameter of 63.29 mm, with a circular recess in the lower base with a diameter of 18.22 mm and 6.8 mm high, and the walls of the barrel are inclined at an angle of 4°.

[0047] Example 1.

[0048] Method of forming a magnesium AZ91 magnesium alloy wheel forging on a hydraulic press, in particular from a forging preform cast into metal moulds, and a wheel forging formed by this method, intended for a wheelchair

[0049] An upper drop forging die tool 1 and a lower drop forging die tool 3 having working impressions la and 3a in the central part in the form of a lump whose outline approximates a circle with circular recesses in the centre, were heated in a furnace at 260°C and mounted in the working space of a hydraulic press . Forging preform 2a into metal moulds of AZ91 magnesium alloy (Mg-9Al-lZn) according to ASTM B107-13 was then heated in an oven at 350°C for 35 minutes. Then, the forging preform 2a into metal moulds was placed and centered in the finishing blank 3a of the lower drop forging die tool. Then, on the hydraulic press, the upper drop forging die tool 1 was driven in a progressive motion with a velocity of 20 mm / s towards the lower drop forging die tool 3 and the forging preform 2a was compressed into metal moulds by the finishing impression la of the upper drop forging die tool 1 and the finishing impression 3a of the lower drop forging die tool 3 with a maximum forging force of 2044 . 6 kN and the wheel forging 2b was shaped with a maximum deformation of 7 . 72 .

[0050] Example 2 .

[0051] Method of plastic forming on a hydraulic press of a forging of a wheel of magnesium alloy AZ 91 , in particular of a forging preform into metal moulds and a wheel forging formed by this method, intended for a wheelchair implemented according to example 1 , whereby the forging preform 2a cast into metal moulds was heated in an oven at 400 ° C for 30 minutes . Then, the forging preform 2a into metal moulds was placed and centered in the finishing impression 3a of the lower drop forging die tool . Then, on the hydraulic press , the upper drop forging die tool 1 was driven in a progressive motion with a velocity of 20 mm / s towards the lower drop forging die tool 3 and the forging preform 2a was compressed into metal moulds by the finishing impression la of the upper drop forging die tool 1 and the finishing impression 3a of the lower drop forging die tool 3 with a maximum forging force of 1970 kN and the wheel forging 2b was shaped with a maximum deformation of 10 . 2 .

[0052] Example 3 .

[0053] Method of plastic forming on a hydraulic press of an AZ 91 magnesium alloy wheel forging, in particular of a forging preform into metal moulds and a wheel forging formed by this method, intended for a wheelchair implemented according to example 1 , whereby the upper drop forging die tool 1 and the lower drop forging die tool 3 were heated in a furnace at 300 ° C, the forging preform 2a into metal moulds was heated in a furnace at 350 ° C for 35 minutes . Then, the forging preform 2a into metal moulds was placed and centered in the finishing impression 3a of the lower drop forging die tool . Then, on the hydraulic press , the upper drop forging die tool 1 was driven in a progressive motion with a velocity of 20 mm / s towards the lower drop forging die tool 3 and the forging preform 2a cast into metal moulds was compressed with the finishing impression la of the upper drop forging die tool 1 and the finishing impression 3a of the lower drop forging die tool 3 with a maximum forging force of 1995 . 9 kN and a wheel forging 2b was shaped with a maximum deformation of 11 .

[0054] Example 4 .

[0055] Method of plastic forming on a hydraulic press of a forging of a wheel of magnesium alloy AZ 91 , in particular of a forging preform into metal moulds , and a wheel forging formed by this method, intended for a wheelchair implemented according to example 1 , wherein the upper drop forging die tool 1 and the lower drop forging die tool 3 were heated in an oven at 300 ° C, the forging preform 2a cast into metal moulds was heated in a furnace at 400 ° C for 30 minutes . Then, the forging preform 2a cast into metal moulds was placed and centered in the finishing impression 3a of the lower drop forging die tool . Then, on the hydraulic press , the upper drop forging die tool 1 was driven in a progressive motion with a velocity of 20 mm / sec . in the direction of the upper drop forging die tool 3 and the forging preform 2a cast into metal moulds was compressed with the finishing impression la of the upper drop forging die tool 1 and the finishing impression 3a of the upper drop forging die tool 3 with a maximum forging force of 1689 . 9 kN and the wheel forging 2b was shaped with a maximum deformation of 10 . 1 .

[0056] A wheel forgings made of AZ 91 magnesium alloy with higher mechanical properties resulting from a more favorable structure of the shaped product in relation to the products made by casting and machining were obtained .

[0057] A comparative analysis was carried out using the Finished Element Method ( FEM) of the method of plastic forming on a hydraulic press of an AZ 91 magnesium alloy wheel forgings , in particular from a forging preform cast into metal moulds and a wheel forgings formed by this method according to the invention - model 1 (Ml . 1 - Ml . 4 ) , and of the method of forging a semi-finished product on a hydraulic press , in particular for the manufacture of an aviation fastening based on patent document PL237782B1 - model 2 (M2 ) . The numerical analysis was carried out in a system designed to simulate plastic working processes - 3D Deform in accordance with the parameters adopted in Table 1 . For the FEM analysis , the developed models of magnesium alloy materials AZ 91 were used and AZ 61 magnesium alloy based on plastometric tests .

[0058] Table 1 - Comparison of the method according to the invention with the state of the art

[0059] These tests were carried out for a metal-cast magnesium alloy of grade AZ 91 according to ASTM B107 -13 and a sand-cast magnesium alloy of grade AZ 61 according to ASTM B951-10 with the chemical composition presented in Table 2 . Table 2 - The chemical composition of the magnesium alloy AZ91 used in the process according to the present invention according to ASTM B107-13 and the magnesium alloy AZ61 according to ASTM B951-10 used in the process according to PL 237782 Bl

[0060] Plastometric tests were performed on a deformation dilatometer at temperatures of 350°C, 400°C, 450°C at deformation velocities of 0.1 s-1; 1 s-1; 10 s-1. Based on the obtained results from the measurements, the flow curves for the AZ91 alloy presented in the graphs of Fig. Ila - 11c and for magnesium alloy AZ61 shown in the graphs of FIGS, lid - Ilf. In numerical simulations, the following were analyzed: the maximum shaping force of the upper tool as a function of time, the maximum deformation in the shaped products, the contact area of the shaped forging with the upper tool, the contact area of the shaped forging with the lower tool for both analyzed methods.

[0061] The maximum forging force obtained from the numerical analysis and the maximum deformation in the shaped forging according to the invention Ml .1 - Ml .4 are shown in FIG.12a - 12d and FIG. 10a - lOh. The maximum forging force and maximum deformation in the shaped blank obtained from the numerical analysis performed on the basis of patent document PL 237782 Bl - M2 are presented in the graph of FIG. 12e and Fig. lOi and lOj . List of reference symbols

[0062] 1 - upper drop forging die tool la - finishing blank of the upper drop forging die tool 2a - forging preform cast into metal moulds

[0063] 2b - wheel forging

[0064] 3 - lower drop forging die tool

[0065] 3a - finishing blank of the lower drop forging die tool

[0066] Vi - upper drop forging die tool velocity

Claims

Claims1. Method for the plastic forming on a hydraulic press of an AZ91 magnesium alloy wheel forging, in particular of a forging preform cast into metal moulds, characterized in that the upper drop forging die tool (1) with a finishing impression (la) in the centre and a lower drop forging die tool (3) with a finishing impression (3a) in the form of a lump whose outline resembles a circle with circular recesses in the centre, is heated in a furnace to 260 °C to 300 °C, wherein the heated upper drop forging die tool (1) and the heated lower drop forging die tool (3) are mounted in the working space of the hydraulic press, and then the forging preform (2a) into magnesium alloy metal moulds AZ91 (Mg-9Al-lZn) is heated in a furnace to a temperature from 350 °C to 400 °C for a time from 30 to 35 minutes and minutes, wherein the heated forging preform (2a) into the metal moulds is placed and centered in the finishing impression (3a) of the lower drop forging die tool (3) on a hydraulic press the upper drop forging die tool (1) is set in a downward progressive motion with a velocity of (VI) 20 mm / s towards the lower drop forging die tool (3) and the forging preform (2a) cast into metal moulds is compressed with the finishing blank (la) of the upper drop forging die tool (1) and the finishing blank (3a) of the lower drop forging die tool (3) with a forging force in the range from 1689.9 kN to 2044.6 kN and the wheel forging (2b) with a deformation in the range from 7.72 to 11 is formed.

2. The method according to claim 1, characterized in that the forging preform (2a) for metal forms has the shape of a barrel with a volume of 81961.7 mm3, a weight of 0.1569 kg, a height of 25.31 mm and a diameter 65.9 mm at its widest point, the lower base has a diameter of 62.97 mm and the upper base has a diameter of 63.29 mm, wherein in the lower base there isalso a circular recess with a diameter of 18.22 mm and a height of 6.8 mm, and the walls of the barrel are inclined at an angle of 4°.

3. The method according to claim 1, characterized in that the forging preform (2a) into metal moulds is heated to 400 °C for30 minutes.

4. The wheel forging is shaped as defined in claims 1 to 3.

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