渗碳淬火工艺认可文件

通用工艺 Technical standards for carburizing and quenching 1. Technical standard of gas carburization 1.1 Technical specification of carburization Parts cleaning: All the carburizing parts must be cleaned carefully, and be free of dust and grease. Apply 8112 cleaning agent. The gasoline is allowed to use when the parts need to put into the furnace immediately. The solution must be treated appropriately and timely after cleaning. Coating of the leakage-proof agent After cleaning with the cleaning agent, paint the parts with leakage-proof agent according to the requirement wrote on the process card carefully (in order to identify the label number, do not paint on the stamp number). Mechanical property sample of each heat The tensile coupon (3 pieces) and impact coupon (9 pieces) taken from the crop piece of the forging must be treated with the parts together. The sampling of the mechanical property test piece should conform to the requirement of ABS society, drawing and Q/NGC－Z 037－2005 technical specification for forging of marine gearbox (see addendum I for more details). If there is any different requirement on these three sampling positions, it must be discussed in advance. Pit cooling protection All pit cooling parts (taken out of furnace after carburization or tempering) must be shield with carbinol, and the pit cover must be tight. Detailed process curves are as following : Process curve 1: Apply to the carburization of the gear less than 3m or the upper case depth not more than 1.0mm. Equipment: RJJ-75 and RJJ-105 (see addendum II for the main heat treatment equipment) 坑冷 pit cooling 炉冷 furnace cooling 等温 constant temperature 扩散 diffusion 强渗 carburization 均热排气 uniform exhaustion 升温排气 heating up exhaustion Explanation: 1)​ The temperature of getting into the furnace is above 800℃. 2)​ Discharge the air while the temperature is rising, and the speed is not limited and controlled by the instrument. 3)​ During the uniform discharging period, preset the carbon potential at 0.40, and time 30 minute. 4)​ Refer to table 1 for the setting of the carbon potential and time during the strong carburization period. 5)​ Refer to table 1 for the setting of the carbon potential and time during the diffusion period. 6)​ Keep the diffused carbon potential during the cooling period. 7)​ Keep for 10 minutes at the temperature 870℃, and keep the diffused carbon potential. Process curve II: Apply to the carburization of the parts whose upper case depth is no more then 3.0mm. Equipment：RJJ-75 and RJJ-105 1)​ The temperature when getting into the furnace is above 800℃. 2)​ Discharge the air while the temperature is raised, and the speed is not limit and controlled by the instrument. 3)​ Carbon potential is set on 0.80, and the time 30 minutes during the constant air-discharging period. 4)​ Refer to table 1 for the setting of carbon potential and time during the strong carburization period. 5)​ Refer to table 1 for the setting of carbon potential and time during the diffusion period. 6)​ Keep the diffused carbon potential during the cooling period. 7)​ Keep at the temperature 870℃for 30 minutes, and maintain the diffused carbon potential. Process curve III: Used for GSRU150/400 and 1M5 carburizing furnace. 1)​ The temperature when getting into the furnace is above 800℃. 2)​ The rate of temperature rising is not limited, keep the constant temperature for 1～2 hours at 650℃. 3)​ The setting of the carbon potential of steel foil is depended on the material during the strong carburization period. 4)​ The setting of the carbon potential of steel foil is depended on the material during the diffusion period. 5)​ Keep the diffused carbon potential during the cooling period. 6)​ Keep the constant temperature for 0～30 minutes at 870℃, and preserve the diffused carbon potential. Process curve IV: MRE10-280/200 carburizing furnace 1)​ The temperature when getting into the furnace is not limited. 2)​ The speed of temperature rising is not limited, whether need to preserve the temperature at 650℃ depends on the parts, for the parts which are easily to deform, such as gear ring, it is necessary to maintain at the temperature 650℃ for 1～2 hours. 3)​ At 880℃, the carbon potential of pre-carburizing period is 0.40～0.80. 4)​ The setting of the carbon potential of steel foil is depended on the material during the strong carburization period. 5)​ The setting of the carbon potential of steel foil is depended on the material during diffused period.。 6)​ Maintain the diffused carbon potential during the cooling period. 7)​ Keep the constant temperature for 0～30 minutes at 870℃, and preserve the diffused carbon potential. Process curve V: Use fro the deep carburization of MRE10-280/200、VBEK4000/2000、RJ160/55 carburizing furnace Material：20CrNi2MoA 强渗碳势carbon potential of strong carburization 扩散碳势diffused carbon potential 1)​ The temperature when getting into the furnace is not limited. 2)​ The speed of temperature rising is not limited, whether need to preserve the temperature at 650℃ depends on the parts, for the parts which are easily to deform, such as gear ring, it is necessary to maintain at the temperature 650℃ for 1～2 hours. 3)​ Maintain the diffused carbon potential during the cooling period. 4)​ Keep the constant temperature at 870℃ for 0～30 minutes, and maintain the diffused carbon potential. 5)​ Pit cooling protection. Process curve VI：Used for the deep carburization of MRE10-280/200、VBEK4000/2000、RJ160/550carburizing furnace Material：20CrMnMoA 1）The temperature when getting into the furnace is not limited. 2）The speed of temperature rising is not limited, whether need to preserve the temperature at 650℃ depends on the parts, for the parts which are easily to deform, such as gear ring, it is necessary to maintain at the temperature 650℃ for 1～2 hours. 3）When the temperature reaches 880℃, the carbon potential of pre-carburizing can be chosen within0.4～1.0, and time within 1～4h. 4）Maintain the diffused carbon potential during the cooling period. 5）Keep the constant temperature at 870℃ for 0～30 minutes, and maintain the diffused carbon potential. 6）When the parts are taken from the furnace at 870℃, they are need to be cooled in the sealing pit , and the cooling pit must be protected. Process curve VII: Used for the deep carburization of MRE10-280/200、VBEK4000/2000、RJ160/550 carburizing furnace. Material：18CrNiMo7－6 扩散： diffusion 等温 constant temperature 升温heating up 预渗 pre-carburization 炉冷 furnace cooling 强渗 carburization 1）The temperature when getting into the furnace is not limited. 2）The speed of temperature rising is not limited, whether need to preserve the temperature at 650℃ depends on the parts, for the parts which are easily to deform, such as gear ring, it is necessary to maintain at the temperature 650℃ for 1～2 hours. 3）When the temperature reaches 880℃, the carbon potential of pre-carburizing can be chosen within0.4～1.0, and time within 1～4h. 4）Maintain the diffused carbon potential during the cooling period. 5）Keep the constant temperature at 870℃ for 0～30 minutes, and maintain the diffused carbon potential. 6）Take the parts out of furnace at 870℃, and cool them in the sealing pit. 7）Temper the parts once they are cooled to 400℃ in the sealing pit. Please read the high tempering process. Process curve VIII: Used for the normalization + high tempering to remove net carbide after carburization. Applicable equipment: All equipment Applicable parts: Parts with low requirement on deformation and oxidizing-decarbonization. Process IX: Apply to the compensating treatment after carburization when the case depth is not enough. 1）Prior to the compensating treatment, the teeth flank and other to be compensated parts need to be cleaned. 2）Protect non-carburizing suface from carburization by painting a shield cover Process curve X: Apply to the diffusion process to avoid the exceeding carbide grade. Process curve XI: Apply to the spheroidal annealing to avoid the exceeding carbide grade. 工Process curve 12: Used for the high tempering process after the carburization. 1.2 Reference for the carburizing time and time allocation Table 1: reference table of carburizing time Reference case depth （mm） Time of strong carburization（h） Diffusion time （h） Total time （h） 0.7 2.00 0.67 2.67 1.0 3.50 1.17 4.67 1.2 4.70 1.30 6.00 1.5 6.00 1.67 7.67 1.8 8.00 2.00 10.00 2.4 12.00 2.67 14.67 2.8 16.67 3.33 20.00 3.2 21.00 6.00 27.00 DC3.2 25.00 8.50 33.50 DC3.5 29.50 10.00 39.50 DC3.8 36.00 12.50 48.50 DC4.2 46.00 16.50 62.50 DC4.5 55.00 19.00 74.00 DC4.8 62.00 22.00 84.00 DC5.2 70.00 25.00 95.00 DC5.6 79.00 28.00 107.00 DC5.8 85.00 30.00 115.00 DC6.0 90.00 33.00 123.00 DC6.5 105.00 40.00 145.00 DC4.8 48.00 18.00 66.00 DC5.5 65.00 23.00 88.00 DC6.5 88.00 32.00 120.00 DC7.5 105.00 40.00 145.00 Remark: pre-carburizing time and cooling time is not included. 1.3 Carburization quality control 1.3.1 After carburization, the case carbon of the parts should be within 0.75～0.95%, according to JB/T6141, the class of the carbide is not exceed Grade 3,. The carbide of the tooth top can be Grade 4. For the parts with core hardness sample, the axial diameter and end hardness, which are determined by the process allowance and material property, will not be checked during the inspection between carburization and quenching. 1.3.2 Inspection of the case depth The inspection of the case depth of the parts to be classified should be conducted according to the technical requirement on the drawing. 2. Technical standard of quenching (quenching after the carburization) 2.1 Technical specification of quenching Process curve 1: Apply to the parts, which need to be quenched one time after carburization. 1）​ When load the furnace, how to minimize the part deformation should be taken into consideration. 2）​ Get into the furnace at the quenching temperature. 3）​ The speed of temperature rising is not limited, keep the constant temperature at 650℃ for 0.5～2h, depending on the effective thickness and load coefficient. 4）​ Temperature holding time is determined by 0.5～0.6min/mm and loading coefficient. 2.2 Selection of the quenching temperature Table 2. Selection of quenching temperature for the common carburizing steel after carburization Material Quenching temperature℃ Cooling medium Remark 20CrMnTi after carburizing 830～870 Oil 20CrMnMoA after carburizing 850～820 Oil 20CrNi2MoA after carburizing 800～830 Oil 12CrNi3A after carburizing 790～820 Oil 20Cr2Ni4A after carburizing 790～820 Oil 18CrNiMo7—6 after carburizing 800～830 Oil 2.3 Tempering 2.3.1 Technical specification of tempering The parts need to be tempered after the quenching, normally they cannot stay under the room temperature over 3h. 温度 temperature 回火温度 tempering temperature 冷却 cooling 保温时间 temperature holding time 升温速度不限 no limit on the speed of temperature rising 2.3.2 Tempering temperature Table 3. Selection of low tempering temperature for the common carburizing steel after quenching Material Hardness after quenching HRC Tempering temperature and hardness Cooling method Requested hardness HRC Tempering temperature ℃ 20CrMnTi after carburizing >60 58～64 170～210 Air 20CrMnMoA after carburizing >60 58～64 170～220 Air 20CrNi2MoA after carburizing >60 58～64 170～220 Air 12CrNi3A after carburizing >60 58～64 170～220 Air 20Cr2Ni4A after carburizing >60 58～64 170～220 Air 18CrNiMo7－6 after carburizing >60 58～64 170～220 Air 2.3.3 Holding time of tempering： The holding time of tempering must accord with the following table, and the holding time should not lower than the time stated in the table. Table 4. The relation between the holding time of low tempering and effective thickness Effective thickness mm <25 25～50 50～75 75～100 100～150 150～200 200～300 Holding time h 2 2～3 3～4 4～5 5～7 7～9 9～13 Effective thickness mm 300～400 400～500 500～600 600～700 700～800 800～900 >900 Holding time h 13～17 17～21 21～25 25～29 29～33 33～37 37～48 Addendum I. Q/NGC－Z 037－2005 requirement of sampling location regulated in the technical specification for marine gearbox forging 1、​ For the forgings of the small gear (pinion), whose final diameter is over 200mm, the test piece should be tangentially cut from the place near to the teeth, showed as test position B in figure 1; if it is not able to take the sample from this position because of the dimension, the sample can be cut from the horizontal position of the head of the shaft journal (test position C in figure 1); however, if the diameter of the shaft journal is not more than 200mm, the sample can be taken from the longitudinal direction (test position A in figure 1); when the length of the teeth part of the finished gear is over 1250mm, the sample should be taken from the both sides of the forgings.; 横向transverse 纵向longitudinal L=length of gear teeth D=diameter of gear teeth d=diameter of shaft journal 2、The sample of the gear forgings must be taken from any test position B in figure 2 through tangential direction. 3、The sample of gear ring should be cut from one test position A in a tangential direction as showed in figure 3. When the diameter of the finished gear ring exceeds 2.5m or its weight exceeds 3t, you should take 2 sets of samples from the relative position of the gear ring through the diametral direction; the mechanical property of the test should meet the longitudinal requirement. 4、The sample of the small gear bush (shaft bush) should be taken from any test position C through tangential direction, see figure 4. It is necessary to take the samples from both sides when the length of finished product is over 1250mm 圆周方向 ：circumferencial direction 试验位置：test position Addendum II. Main equipment in Heat treatment branch factory General situation of the heat treatment equipment The numbering of the equipment here are for the common equipment in the branch factory, they are only indicated for the uniform designation of the internal information and technical documentation, not for the external standard. The heat treat factory is responsible to release the updated equipment number. I. Equipment classification Principle of classification: Divide the equipment into 2 classes based on the importance. Class I equipments are the large and important equipment in the factory, every equipment in this group is the quality control point, they will be maintained according to the daily maintenance and weekly maintenance plan, and all malfunction and maintenance need to be recorded. Class 2 equipment includes all the heating equipments, and they will be maintained based on the relative regulations of the branch factory. II. Equipment No. Class Name of Equipment Effective dimension Power Load Introduction time Manufacturer 1 Class 1 VBEK4000/2000 Φ4000×2000 760KW 40T 2001 AICHELIN 2 RJ160/550 Φ1600×5500 400KW 20T 2001 Beijing Electromechanical research institute 3 MRE280/200 Φ2800×2000 600KW 15T 1995 HERDIECKERHOFF 4 GURU140/400 Φ1400×4000 270KW 6.5T 1985 DEGUSSA 5 RJQ-150/400 Φ1500×4000 235KW 10T 2003 TLON 6 RJJ-120/220-9Q Φ1200×2200 160KW 10T 2003 Beijing Electromechanical research institute 7 VBEs2800/2500 Φ2800×2500 610KW 28T 2004 AICHELIN 8 Class 2 75Kwcarburizing furnace Φ560×900 75KW 1T 1980 Sheshan Electric Furnace Factory 9 105Kw carburizing furnace Φ720×1200 105KW 1T 1980 Sheshan Electric Furnace Factory 10 75Kw box furnace 1800×900×600 75KW 2T 1980 Wuxi Electric Furnace Factory 11 105KW trolley furnace 2000×900×600 105KW 2T 1990 南航 12 180KW trolley furnace 1 2500×1250×1100 180KW 8T 2004 Xuzhou Jiacheng 13 180KW trolley furnace 2 2500×1250×1100 180KW 8T 2004 Xuzhou Jiacheng 14 4KW experimental resistance furnace 1 300×200×120 4KW 60Kg 2002 Shanghai Experimental Electric Furnace Factory 15 4KW experimental resistance furnace 2 300×200×120 4KW 60Kg 2004 Shanghai Experimental Electric Furnace Factory 16 3000/3000 trolley type oven 3000×3000×2000 100KW 20T 2004 Changjiang Electric Furnace Factory 17 3000/3000 trolley type oven 3000×3000×2000 100KW 20T 2004 Xuzhou Jiacheng 18 5000/3500 trolley type oven 5000×5000×3000 200KW 50T 2001 Changjiang Electric Furnace Factory