November 2020 Volume 2

aluminum and steel rings. The remaining ring specimens which were compressed using the other platen temperatures and lubricants were similar and are not shown for the sake of brevity but can be seen in reference [1]. Even though there was some variation in lubrication effectiveness with temperature, die temperature was not found to have a significant effect in any of the tests. As the difference was minor, die temperature will not be considered in the remainder of the discussion. alu inu and steel rings. he re aining ring speci ens hich ere co pressed using the other platen te peratures and lubricants ere si ilar and are not sho n for the sake of brevity but can be seen in reference [1]. ven though there as so e variation in lubrication effectiveness ith te perature, die te perature as not found to have a significant effect in any of the tests. s the difference as inor, die te perature ill not be considered in the re ainder of the discussion.

FORGING RESEARCH AND TECHNOLOGY

profile of the compressed workpieces, the maximum width and length was recorded and used to calculate the strain values as this was considered to be most sensitive to any changes in flow. Strains were calculated according to Equations 1 and 2 as follows: varied along these directions due to friction and corner effects. Due to the ofile of the compressed workpieces, the maximum width and length was nd used to calculate the strain values as this was considered to be most o any changes in flow. Strains were calculated according to Equations 1 and 2 : = = ln( ) [1] = = ln( ) [2] here and 0 are the final and initial widths, respectively; and and 0 are nd initial widths, resp c ively (Figure 4). Where l f and l 0 are the final and initial widths, respectively; and w f and w 0 are the final and initial widths, respectively (Figure 4).

(a) R a 0.25 µm (10 µin) (a) a 0.25 (10 in)

(b) R a 0.51 µm (20 µin) (b) a 0.51 (20 in)

(c) R a 1.02 µm (40 µin) (c) a 1.02 (40 in)

Figure 5. Aluminum ring test specimens after compression at a platen temperature of 149 °C (300 °F) using boron nitride lubricant. Specimens are arranged such that the horizontal axis is parallel to the platen lay. (f) R a 6.1 µm (240 µin) Figure 5. Aluminum ring test specimens after compression at a platen temperature of 149 °C (300 °F) using boron nitride lubricant. Specimens are arranged such that the horizontal axis is parallel to the platen lay. (d) a 1.52 (60 in) (e) a 3.3 (130 in) (f) a 6.1 (240 in) Figure 5. Alu inu ring test specimens after co pression at a platen te perature of 149 °C (300 °F) using boron nitride lubricant. Speci ens are arranged such that the horizontal axis is parallel to the platen lay. (d) R a 1.52 µm (60 µin) (e) R a 3.3 µm (130 µin)

(a) R a 0.25 µm (10 µin)

(b) R a 0.51 µm (20 µin)

(c) R a 1.02 µm (40 µin)

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Figure 4. Photograph showing the dimensions of a side pressed steel specimen. re 4. Photograph showing the dimensions of a side pressed steel specimen.

Results &Discussion Friction - Results obtained from ring testing showed that many of the specimens developed an oval shape. This was confirmed by CMM measurements and is consistent with the fact that there was less resistance to metal flow in the direction parallel to the platen surface lay. Conversely, in the direction perpendicular to the platen surface roughness, the resistance was much larger and the ID smaller as metal flow was more restricted. This trend was generally present in both aluminum and steel workpieces, but was most pronounced in the former. This is discussed later and was attributed to the different working regimes (warm and hot) that were used. Figures 5 and 6 provide a representation of how unidirectional surface lay resulted in elliptical geometries for both aluminum and steel rings. The remaining ring specimens which were compressed using the other platen temperatures and lubricants were similar and are not shown for the sake of brevity but can be seen in reference [1]. Even though there was some variation in lubrication effectiveness with temperature, die temperature was not found to have a significant effect in any of the tests. As the difference wasminor, die temperature will not be considered in the remainder of the discussion. 6 Discussion Results obtained from ring testing showed that many of the specimens an oval shape. This was confirmed by CMM measurements and is consistent act that there was less resistance to metal flow in the direction parallel to the face lay. Conversely, in the direction perpendicular to the platen surface , the resistance was much larger and the ID smaller as metal flow was more This trend was generally present in both aluminum and steel workpieces, but pronounced in the former. This is discussed later and was attributed to the working regimes (warm and hot) that were used. Figures 5 and 6 provide a

Figure 6. Steel ring test specimens after compression at a platen temperature of 149 °C (300 °F) using graphite lubricant. Specimens are arranged such that the horizontal axis is parallel to the platen lay. Friction Factor Trends and Analysis - As the deformed rings developed an elliptical shape, this suggested that friction factor also varied with respect to the lay direction. Calculation of friction factors using standard ring calibration curves are shown below for aluminum and steel in Figures 7-8 as a function of platen roughness. Friction factors measured parallel to the lay are designated as 0∗ while those perpendicular to the lay as 90 * . The data for aluminum shows that the difference between 0∗ and 90 * is significant for all platen roughnesses. Analyzing the ring test data obtained using steel showed that die roughness also has a substantial effect on the friction factor in both directions, but that the values for 0∗ and 90 * tended to be close together. (f) R a 6.1 µm (240 µin) Figure 6. Steel ring specimens after compression at platen temperature of 149 °C (300 °F) using graphite lubricant. Specimens are arranged such that the horizontal axis is parallel to the lay. Friction Factor Trends and Analysis - As the deformed rings developed an elliptical shape, this suggested that friction factor also varied with respect to the lay direction. Calculation of friction factors using standard ring calibration curves are shown below for aluminum and steel in Figures 7-8 as a function of platen roughness. Friction factors measured parallel to th lay are designated as 0∗ while those perpendicular t the lay as 90∗ . The dat for alu inum shows th t the difference between 0∗ and 90∗ is significant for al platen roughnesses. Analyzing the ring test data obtained using steel showed that die roughness also has a substantial ffect o the friction factor in both d re tions, but that the values f r 0∗ and 90∗ tended to be close together. (d) R a 1.52 µm (60 µin) (e) R a 3.3 µm (130 µin)

FIA MAGAZINE | NOVEMBER 2020 46

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