Optimierung des Schmiedeverfahrens für den Flanschdeckel eines Mannlochs

Optimierung des Schmiedeverfahrens für den Flanschdeckel eines Mannlochs

Die manhole hole flange cover is one of the important components in the small forgings of hydrogenation reactors, which is limited by its unique shape and size. Suppose traditional forging methods are used for forging. In that case, the remaining forging blocks are large, the forging cost is high, the production cycle is long, and the mechanical properties of the parts are affected. Based on production practice, optimize its forging process and explain its significance.

Hydrogenation reactors are the most commonly used and important equipment in the actual production process of the petrochemical industry. As an important component of hydrogenation reactors, the manhole hole flange cover has always been regarded as a cake shaped forging with a uniform outer diameter during the forging process due to the unique shape of the parts and the limitations of the manufacturing equipment capacity and attachments. This increases the number of forging blocks and increases production costs, prolongs the product production cycle, and reduces economic benefits. With the use of our 45MN hydraulic press and the improvement of related accessories, optimizing the process of such forgings is imperative. This article only takes optimizing the forging process for forgings such as manhole flange covers as an example to explain the practical significance of reducing forging allowance in improving forging performance, shortening the product production cycle, and reducing product production costs.

1. Product requirements and original forging process analysis

Taking the manhole flange cover of a hydrogenation reactor in a certain project as an example, the rough machining sampling position and size shape are shown in Figure 1. The mechanical performance requirements of the forging are shown in Table 1. After rough machining, ultrasonic testing is required according to JB/T4730.3, and the forging ratio requirement is>3.5. It can be seen that its comprehensive index requirements are very high. In addition, due to its small step height, based on experience, this product can only be forged into circular forgings with the same outer diameter and equal wall thickness, as shown in Figure 2. The forging deformation process is: cutting → upsetting → punching → rolling the outer circle → flattening the finished product.
Product gravimetric analysis, rough machining weight（ ρ=7.85×103kg/m³ is the density of the material, and V is the volume)

The weight of the forging blank is（ ρ、 V ditto, κ Compensation coefficient for forgings)

The forging allowance weight is approximate.

The forging allowance accounts for 43.7% of the total weight, which is close to half of the gross weight of the forging. This will inevitably increase the cost of the product (including gas consumption, heat treatment time, machining time, etc.) and extend the product’s production cycle.

2. Process optimization ideas

How to reduce machining allowance and improve forging quality has always been a topic that the industry is constantly exploring and improving. After analyzing the forging process of the manhole flange cover, one of the small forgings in the hydrogenation reactor, the actual forging process was improved by using a special washer to upset and level the blank, thereby reducing forging allowance and improving the performance of the forging. The comparison before and after process optimization is detailed in Table 2, and the processing equipment is shown in Table 3.

3. Effect of process optimization

(1) The reduction in the forging allowance is significant, and the shape and size of the forging blank are shown in Figure 4. The weight of the forging blank is（ ρ、 V ditto, κ Compensation coefficient for forgings):

Figure.1

Figure.2
Table.1 Requirements for Mechanical Properties of Forgings

Projekt	Numerical Value
Tensile Strength Rm/Mpa	510-680
Yield Strength Rp0.2/Mpa	310-620
Elongation After Fracture A (%)	≥19
Reduction Of Area Z (%)	≥45
-30°C Shock Absorption Energy Kv2/J	Three Average Values ≥ 54, One Allowed ≥ 47

Table.2 Comparison before and after process optimization

The forging allowance weight is approximate:

After optimization, the forging allowance accounts for 25.8% of the total weight of the forging, and the single-piece allowance reduces the weight by 1810kg.
(2) The obvious improvement in the performance of forgings is achieved by using washers for upsetting, which reduces the margin to a large extent and significantly improves the performance of forgings. As shown in Figure 5, using washers for upsetting maximizes the continuity of the metal flow line structure while also avoiding a large amount of exposure caused by cutting during the machining process. Under the same sampling location, the optimized process obtained more ideal mechanical properties for the forgings, as shown in Table 3.

Figure.3

Abbildung.4

Figure.5
Table.3 Mechanical Property Values after Process Optimization

Projekt	Numerical Value
Tensile Strength Rm/Mpa	625
Yield Strength Rp0.2/Mpa	510
Elongation After Fracture A (%)	26.4
Reduction Of Area Z (%)	81.4
-30°C Shock Absorption Energy Kv2/J	Mean 296

4. Conclusion

The above data shows that using the optimized process plan, the proportion of forging allowance to the total weight of forgings has decreased from 43.7% to 25.8%. Only a single product of manhole flange cover can save 1810kg of steel. The company produces a large number of similar forgings every year. We can comprehensively utilize existing equipment and accessories and adopt the optimization plan. In that case, it will save our company many production costs, improve economic efficiency, and enhance market competitive advantage. In addition, after adopting the optimization plan, the cold processing time of the blank can be reduced by about 24 hours, improving production efficiency, shortening the processing cycle, and winning time to ensure the delivery time. At the same time, using this method makes the shape of the forging closer to the size of the part, maximizing the retention of the metal fiber structure, avoiding excessive damage to the metal fiber structure during cold machining and cutting, and enabling the forging to have good mechanical properties. In summary, adopting optimized solutions significantly reduces internal cost consumption and improves the company’s market competitiveness.

Author: Wang Hexin

Quelle: China Flansche Hersteller - Yaang Pipe Industry Co, Limited (www.metallicsteel.com)