軸受鋼SUJ2の浸炭窒化処理時における雰囲気管理方法

1 NTN TECHNICAL REVIEW 2006 . [ ]. SUJ2 . The Atmosphere Control Method for JIS-SUJ2 on Carbonitriding Processes * Chikara OHKI. SUJ2 . EPMA . NH 3 . H2 .. SUJ2 . We have been investigating the nitrogen penetration mechanism into bearing steel JIS-SUJ2 on carbonitriding processes. In the course of carbonitriding experiments under various conditions and EPMA analysis, the influences of carbon activity and base gas components on nitrogen penetration behavior were examined. As a result, the nitrogen penetration content of steel increased with the increase of undecomposed NH3 partial pressure and with the decrease of carbon activity, and H2.

2 Partial pressure. Besides, assuming that the penetration mechanism of nitrogen is same as that of carbon, a calculation method was developed in order to estimate nitrogen concentration distribution profiles. It was confirmed that the nitrogen concentration distribution profiles predicted by our method agreed well with the experiment results under various conditions. Hence, a development of the new atmosphere control method for JIS-SUJ2 carbonitriding processes was achieved. 1 .. 1 . 2 .. 2. 1 . 2 120L . 1 . SUJ2 1 . 2 . 3 4 . SUJ2.

3 * . -42- SUJ2 . 1 . The analyzer for the atmosphere measurement .. CO/CO2 .. H2O . O2 . H2 . NH3 .. 2 . (A 5B . 1 C ). The furnace for heat treatment The feeder of base gas 2. 2 10mm . 5mm SUJ2 2 . 38. 30. 38 30 t10 . EPMA .. EPMA 2 m . 2 m 3 . 3 EPMA . Dimensions of test specimen and scanning position . 1. EPMA 4 10 -3 g /mm3 0. 0 2 (wt%) mm Chemical compositions of JIS-SUJ2 used (wt%). g/mm2 = 10-3 g/mm3 mm wt% 100 . C Si Mn P S Ni Cr Mo Cu 4 . The definition of nitrogen penetration content -43- NTN TECHNICAL REVIEW 2006 . 2. 3 2.

4 4. 2 .. Boudouard 850 9000s 1 . 2 . 3 .. C . CO2 2CO Boudouard NH3 3 H2 2. PCO L/min N2 0 L/min CO . ac 1 . K1 PCO2 . 0 . K1 exp G. 2 . RT. T.. 0 2 . GT 172500 T 3 . NH3 2 . ac K1 R . mol K T K . G 0T 5 PCO PCO2 3 .. CO CO2 atm Conditions for experiments to investigate the influence of ac 1 base gas components 1 NH3. H2 N2 CO .. ac 1 (L/min) 1) (L/min) 1) (L/min) 1) (L/min) 1). (atm). 6 1 1' . 0 2. PCO 0 ac* 1' K1 PCO2. a c * 1 a c * a c . ac* 1 ac* 1' . 2. 4 2. 4. 1 NH3 . 850 1atm 1 . 105Pa .. ac* . NH3 4 . ac* 6 . 1800 18000s 4.

5 6 20L/min 4 NH3. 10-3atm . 2.. -44- SUJ2 . NH3 =NH3 . 3 . 100 NH3 . 5 7 .. NH3 .. NH3 . 8 8 .. 3. 1 NH3 NH3 . NH3 . ac* . 9000s . NH3 . 10 10. 9 9. 10-6g/mm2. 10-6g/mm2. 8 8. 7 7. 6 6. 5 5. 4 4. 3 3.. 2 6L/min 2 6L/min 1 1. 20L/min 20L/min 0 0. 0 0 5 10 15 20. NH3 L/min NH3 . 5 NH3 6 NH3 . Relationship between the flow rate of Relationship between the addition ratio of NH3 and nitrogen penetration content NH3 and nitrogen penetration content 10. 9. 10-6g/mm2. 10-6g/mm2. 8. 7. 6. 5. 4 3 . 2 6L/min 1. 20L/min 0. 0 NH3 atm s NH3 atm 7 NH3 8 NH3.

6 Relationship between partial pressure Relationship among duration times and undecomposed of undecomposed NH3 and nitrogen penetration content NH3, and nitrogen penetration content -45- NTN TECHNICAL REVIEW 2006 . 3. 2 3. 3 . 3 . 9000s CO N 2 NH 3 H 2 . /min ac* 9 CO . NH3 ac* N 2 . NH3 H2 2 . NH3 1 . atm ac* 11 H2 NH3 . 10 . ac* 11 . 4 NH 3 H 2 .. ASN ac* 4 . ASN . wt% .. 10-6g/mm2. ac* ac* ac* ac* ac* ac* 12. 10-6g/mm2. 10. 8. 6. NH3 atm H2 atm 4. 11 H2 NH3 . 2 Relationship among partial pressures of undecomposed NH3 and H2, and nitrogen penetration content 0.

7 0 NH3 atm 9 NH3 . Relationship among undecomposed NH3 and nitrogen penetration content, and carbon activity ac* 4 . JIS- SUJ2 1 . NH3 2 ac* . wt%. 1. 3 H2 3 .. 1 4. 1 . ac* SUJ2 . 10 5 . Relationship between carbon activity ac* and the surface nitrogen concentration 5 KX 6 . -46- SUJ2 . 9 . 3/2H2 NH3 5 . N . NH 3 H 2 . PNH3. aN* 3 6 N s . KX PH2 2. N KX ASN D . aN* 9 N KX ASN 3. atm . 6 KX . 4. 2 .. 10 . 7 Neumann7 . 7 . X.. N Ns 1 erf 2 D tt . 10 . q CG Cs 7 . N X . q g/mm 2s N s X . g/mm2s C G m m . D . Cs mm 2/s tt s 10 . D .. C G 11.

8 Ac As . D Aexp B N . 11 . 7 7' . A B N . q ac As Cs 7 .. 10 . 7 8 tt . 9 s . 9 . 10 12 . qN N NG Ns 8 .. g/mm2s . qN N tt X. g/mm 2s N G q dt Q Ndx N . 0. N. 0 0. 2 D t dx 12 . 1 erf s t Ns .. 8 NG aN* ASN 8' Q t t s . g/mm2 10-3g/mm3 . mm . qN N aN* ASN Ns 8' . KX ASN A B . ASN .. 6 8' . 9 4. 3 . 4. 3. 1 . PNH3. qN N 3 ASN Ns KX PH2 2 . 9 . 5 . -47- NTN TECHNICAL REVIEW 2006 . CO 4 . Calculated unknown quantities N 2 .. N . N 10-7. NH3 H2 ac* ASN ac* /100. PNH3 KX 3 ASN. 9 . KX PH2 2 A 10-7. D. B 149.. qN g/mm2s Ns . N tt PNH3 ac*.

9 10 . 0. -7. P 100. 3. H2 2.. Ns dt . 4. 3. 2 ASN .. X. Ns 1 erf dx 13 . 8' 0. 2 10-7exp 149 N tt A SN .. 10 ac* . <ac*< .. ASN . 4. 4 . 4. 3. 3 KX A B . KX N . ac* . Ns 9 . 5 . EPMA . 11 . A B 12 . NH3 ac* H2 .. 4. 3. 4 . 4 . 9 12 . 13 13 . t tt=0s Ns 0 5 . Experimental conditions 13 . atm 1 .. ac*. NH3 H2 s . 1 9000. 13 2 9000. 3 9000.. 4 4500. 1 . -48- SUJ2 . 1 1. 1 2 . wt%. wt%.. 0 0. 0 0 mm mm 1 1. 3 4 . wt%. wt%.. 0 0. 0 0 mm mm 12 . Nitrogen concentration distribution profile of experimental numbers 1) 4). 3 . 5 . 62 . SUJ2.

10 2006 5. 4 .. 62 . 2006 17.. 5 1950 64. 6 and . 1 NH3 Influence of Reaction Rate on Gas Carburizing of Steel in a CO-H2-CO2-H2O- CH4-N2 Atmosphere Journal of The Iron 2 ac* H 2 . and Steel Institute 1972 777. 7 F. Neumann and . 3 NH3 ac* H2 Thermodynamische Grundlagen zum indirekten Messen des C-Pegels . 1994 255.. 4 . EPMA .. 1 SAE Technical paperseries . 1986 . 860725. 2 .. 61 .. 2005 5 . -49.