Forklift gear lost mold process paper


1. Product Overview

Forklift teeth as the name suggests is a kind of forklift accessories, its special working environment requires that the teeth have good wear resistance and good strength and toughness at the same time, so the material selection and pouring process design and pouring process control on product performance played a key role and influence.

  

Fig. 1 Forklift teeth

2. material selection

1. Material selection

Because the shovel tooth requires good wear resistance and certain strength and toughness, we first choose low carbon alloy steel material. Low carbon steel has very low carbon content, so its toughness and plasticity are very good, but its strength is low and its castability is poor. We add appropriate alloying elements Mn and Cr on the basis of low carbon steel, which can not only improve its strength and wear resistance while maintaining good toughness, but also improve its castability and meet the production requirements of lost vanity mold process.

2, Design of Chemical Elements

Table1 low carbon alloy steel material design

 

3. gating system and parameter design

1. Design of gating system

The use part of the shovel tooth is the part below the installation hole, so the vertical pouring method is adopted to make the lower tissue the most dense, and the vertical pouring is divided

The vertical pouring top injection type: the pouring speed is fast but it is easy to cause reverse spraying, and the wall thickness of the installation hole is relatively thin, it is not suitable to set the in-gate;

The vertical pouring bottom injection type: the pouring filling is stable, but the pouring speed is slow and the inner gate setting is difficult;

Side injection type of vertical casting: smooth filling, fast speed and not easy to reverse spray, moderate wall thickness and convenient setting of inner gate.

Based on the above, we finally choose the vertical pouring side injection gating system. And the top of the mounting hole is provided with a micro riser for exhaust and slag aggregation.

  

Figure 2: Design drawing of gating system

2. Design of pouring parameters

Table 2 Parameters of the first pouring

 

Table 3 Parameters of the second pouring

 

Table 4 Parameters of the third pouring

 

 

Table 5 Parameters of the fourth pouring

Fourth, product quality and process control.

1. The first pouring

Using refractory brick pouring cup and ring, the slag beating operation of slag polymerizer in furnace and package was not carried out because the customer did not prepare enough.

 

  

Figure 3: Photo of the first pouring buried box

  

Figure 4: First poured product

Problems: 1. There is obvious large area slag inclusion in the upper part of the casting; 2. The upper half of the more serious casting is full of glaze, and molten steel cannot be filled at all. 3. Cold insulation and insufficient pouring occur in thin wall parts such as installation holes of some castings.

Implementation measures: 1. Slag polymerization agent is used, and slag must be beaten in the furnace and the bag; 2. Use clean raw materials to reduce impurities in the original molten steel; 3. The three groups of models are clustered into one group to improve the pouring speed and ensure rapid filling. 4. Use high-temperature slag-blocking cotton to cover the nozzle.

2. Second pouring

  

Figure 5: Second pouring of buried box

  

Figure 6: Second pouring product

Compared with last time: cold insulation, insufficient pouring and large area slag inclusion defects have been solved.

Problems: 1. There are pores in the appearance, the cross-section of the inner gate is thick and the cross-section has shrinkage; 2. The quality of one cluster in the middle of the three groups of model clusters is higher than that of the two clusters on the side.

Implementation measures: 1. Reduce the thickness of the coating and increase the negative pressure; 2. Reduce the pouring temperature; 3. Shorten the turning time. 4. A gate cup with a cluster of castings.

3. Third pouring

  

Figure 7: Third pouring buried box  

    

Figure 8: Third pouring product

Compared with the last time: the cross-sectional structure of the inner gate has become obviously compact, the pouring speed can reach 5-6 kg/s, and the product appearance and stomatal defects have been significantly reduced.

Problems: 1. The appearance of individual products still has pore defects; 2. Slag defects exist on the top of individual castings.

Implementation measures: 1. Continue to increase the negative pressure and evenly tie small eyes at the top of each model; 2. Use aluminum piston in the furnace for deoxidation before molten steel is discharged, and place aluminum wire in the ladle for deoxidation when discharging water.

4.Fourth pouring

  

  

Figure 9: Fourth pouring product

Summary: After many attempts, the qualified castings were successfully poured, and the materials and series of pouring parameters of the qualified castings were finally confirmed.

Table 6 Chemical elements of qualified castings

Table 7 Pouring Parameters of Qualified Castings

Summary of key points of 5. process

1. The pouring production must be carried out in the mode of high temperature deoxygenated water outlet-calming slag in the package-low temperature rapid pouring-turning over the box in advance and air cooling;

2, pouring speed of not less than 6 kg/s, pouring molten steel as far as possible to keep stable and each package of molten steel must be poured within 2min.

3. Negative pressure degree: -0.06-0.05Mpa during pouring and -0.03Mpa during pressure maintaining, and the negative pressure degree shall be adjusted at any time according to the air holes and pouring conditions;

4. Coating: the thickness is not less than 1.5mm and not more than 2mm, and the lower limit of use is met under the condition of pouring;

5. Try to use clean raw materials for smelting, and the water can be discharged after reaching the water temperature without long-term retention;

6. High-temperature slag retaining rock wool must be used in the bag for slag retaining, and the slag retaining cotton can be pressed by pressing iron;

7, paint mixing time 1.5-2h, stirring after the completion of the static 10 minutes after the use;

8. When using a square runner, use fine sandpaper to polish the edges and corners of the runner smoothly to facilitate coating and hanging and avoid sticking sand.

 

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