Modeling and manufacturing method for reversible plow point with characteristics of low resistance and being strong inside and hard outside

Abstract

The present invention provides a modeling and manufacturing method for a reversible plow point with the characteristics of a low resistance and being strong inside and hard outside. By means of performing parameter optimization, three-dimensional modeling and numerical simulation analysis on a curved surface of a plough point, parameters, i.e. a plowshare angle λ 0 , a plowshare surface angle ε, an included angle η between a soil trace and a plowshare edge, and a soil lifting angle θ, at which the lowest working resistance is achieved, are determined, and composition optimization design and die forging-machining-carburization-quenching-tempering treatment are performed on a base material of the plough point, such that a new reversible plow point with the characteristics of a low operation resistance, high strength toughness of a core portion, and high wear resistance of a surface layer is obtained. The present invention can effectively solve the problems of wear, failure and resistance increase which easily occur due to a plough point being subjected to high-speed impact and wear from soil, sand, stones and root blocks for a long period of time during a service process, and the present invention is expected to be widely applied to the field of manufacturing of soil contact components of agricultural machinery.

1 . A method for manufacturing a reversible plow point that combines low resistance and internal strength with external hardness, characterized by comprising:
 Step S5: preparing 34MnCrB5-M steel, including:
 on the basis of the existing composition of 34MnCrB5 steel, forming novel 34MnCrB5-M steel with new composition by adding 0.1-0.3% Nb and 0.1-0.3% V elements by mass fraction, and melting the 34MnCrB5-M steel in a medium frequency induction melting furnace and casting it into an ingot with a size of φ100 mm×500 mm; 
 heating the ingot to 920° C.-960° C., keeping the ingot at the temperature for 1.0 h-1.2 h, and, after taking the ingot out of the furnace, forming the ingot into 34MnCrB5-M rod with a size of φ60 mm×1380 mm with one initial rolling and two finishing rolling; 
 cutting the 34MnCrB5-M rod into plow point blank with a length of 340 mm-360 mm; 
   step S6: performing die forging-annealing treatment of the plow point blank, including:
 placing the plow point blank of step S5 in a heating furnace and heating it to 900° C.-950° C. for 1-2 hours before removing it from the furnace and transferring it to a die forging machine, and, after die forging it, cooling it to room temperature in air to form the forged plow point blank; 
 transferring the forged plow point blank into an annealing furnace and heating it to 600° C.-650° C. for 1-2 hours, then cooling it to room temperature with the furnace; 
 welding a hard alloy layer on the back of the plow point blank tip; 
   step S7: performing plowing tip machining, including: based on the three-dimensional model data of the plow point component, performing precision machining of the plow point using a computerized numerical control machine tool according to drawing requirements, wherein the three-dimensional model data is determined by the following operations:
 determining basic parameters, including establishing the relationship between the plowshare edge angle λ 0 , and the internal friction angle φ t  of the soil as: 
   
       
         
           
             
               
                 
                   
                     
                       
                         
                           π 
                           4 
                         
                         - 
                         
                           
                             ϕ 
                             t 
                           
                           2 
                         
                       
                       ≤ 
                       
                         λ 
                         0 
                       
                       ≤ 
                       
                         π 
                         4 
                       
                     
                     , 
                   
                 
                 
                   
                     ( 
                     1 
                     ) 
                   
                 
               
             
           
         
         establishing the relationship among the angle η between the soil trace and the plowshare edge, the plowshare surface angle ε and the soil lifting angle θ as: 
       
       
         
           
             
               
                 
                   
                     
                       tan 
                       ⁢ 
                       η 
                     
                     = 
                     
                       tan 
                       ⁢ 
                       
                         θcosε 
                         . 
                       
                     
                   
                 
                 
                   
                     ( 
                     2 
                     ) 
                   
                 
               
             
           
         
         establishing three-dimensional model, including generating the main curve using the curve construction command in the UG software according to the determined plowshare edge angle λ 0 , the plowshare surface angle ε, the angle η between the soil trace and the plowshare edge and soil lifting angle θ, and then completing the overall structure by trimming, connecting, smoothing, and editing of the curved surface, and exporting .stl model file, 
         step S8: performing plow point carburizing-quenching-tempering treatment, including:
 placing the plow point in step S7 into a gas carburizing furnace, setting the carburizing temperature to 910° C.-930° C., the time to 9-10 h, and carbon potential to 1.0%-1.2%; 
 after completing carburizing, quenching the plow point in quenching oil at a temperature of 45° C.-55° C.; 
 after quenching, transferring the plow point into a tempering furnace with a temperature of 180° C.-200° C. and keeping in the temperature for 1.8 h to 2.0 h, and then cooling it in air to room temperature; 
 performing shot peening and spraying plastics treatments. 
 
       
     
     
         2 . The method for manufacturing a reversible plow's plow point that combines low resistance and internal strength with external hardness according to  claim 1 , characterized by:
 the compositions of the existing 33MnCrB5 Steel and the novel 34MnCrB5-M Steel are:   
       
         
           
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
               
                     
                 
                   Name 
                   C 
                   Si 
                   Mn 
                   P 
                   S 
                   Cr 
                   Nb 
                   V 
                   Ni 
                   Ti 
                   B 
                 
                     
                 
                     
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
                 
               
                   34MnCrB5-M 
                   0.35 
                   0.21 
                   1.22 
                   0.01 
                   0.01 
                   0.26 
                   0.1-0.3 
                   0.1-0.3 
                   0.1-0.3 
                   0.037 
                   0.004 
                 
                   34MnCrB5 
                   0.35 
                   0.21 
                   1.22 
                   0.01 
                   0.01 
                   0.26 
                   — 
                   — 
                     
                   0.037 
                   0.004 
                 
                     
                 
             
                
                
                
               
               
                
               
            
             
                
                
                
               
            
           
         
       
       where the units are in mass fraction %. 
     
     
         3 . The method for manufacturing a reversible plow's plow point that combines low resistance and internal strength with external hardness according to  claim 1 , characterized by:
 the internal friction angle φ t  of the soil is less than 4; the value range of the plowshare angle λ 0  is 40°-45°.   
     
     
         4 . The method for manufacturing a reversible plow's plow point that combines low resistance and internal strength with external hardness according to  claim 1 , characterized by:
 the angle η between the soil trace and the plowshare edge is set to 16-24 degrees, the ploughshare surface angle εd is set to 30-40 degrees, and the range of soil lifting angle θ is 18°-30°.   
     
     
         5 . The method for manufacturing a reversible plow's plow point that combines low resistance and internal strength with external hardness according to  claim 1 , characterized by further comprising:
 performing early stage preparation of EDEM discrete element simulation, including setting the plow body material properties as:   setting the plow body material density as 7800 kg/m 3 , the shear modulus as 7.0×10 10  Pa, and the Poisson's ratio as 0.3;   setting the soil properties as: the soil density as 2600 kg/m 3 , the shear modulus as 2.5×10 7  Pa, the Poisson's ratio as 0.5, and the soil particle radius as 2 mm;   setting interaction parameters between the soil particles and the plow body entry part as: the static friction coefficient between the soil particles as 0.40, the kinetic friction coefficient between the soil particles as 0.32, the coefficient of restitution between the soil particles as 0.11, the static friction coefficient between the soil particles and the plow body as 0.30, the kinetic friction coefficient between the soil particles and the plow body as 0.22, and the coefficient of restitution between the soil particles and the plow body as 0.18;   and   performing analog simulation, including:
 introducing the .stl model file in step S7 into the EDEM software, setting the running speed of the plow body component to be 3.6-3.8 m/s, and setting the advancing direction as the X-axis direction; 
 performing simulation setting to set the time step length and the simulation time to be 10 s and to set the cell-size to be 2.5 Rmin; and 
 starting simulation to obtain the average resistance value of the plow body component through simulation. 
   
     
     
         6 . The method for manufacturing a reversible plow's plow point that combines low resistance and internal strength with external hardness according to  claim 5 , characterized by:
 setting the internal friction angle φ t  of the soil to be less than 4 degrees, setting the value range of the plowshare angle λ 0  to be 40-45 degrees.   
     
     
         7 . The method for manufacturing a reversible plow's plow point that combines low resistance and internal strength with external hardness according to  claim 1 , characterized by: 
       the angle η between the soil trace and the plowshare edge is set to 16-24 degrees, the plowshare surface angle η is set to 30-40 degrees, and the range of soil lifting angle θ is set to 18°-30°.