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Forging process for automotive steering knuckle


Steering knuckle is the safety component of a car. It may cause heavy traffic accidents if there is any quality problem. The geometry of automobile steering knuckle is complex, belongs to compound type of forgings, consists of the fork, plate, bar of three parts. So the forging process need to aspire to forming characteristics of three kinds of forgings. Steering knuckle is regards as the most complex forging parts in forging industry.

Now there are some car steering knuckle also increased the steering arm and tie rod arm, whose structure is more complex, the current steering knuckle is widely used in the van and light vehicle, also have individual heavy vehicles use this structure of steering knuckle. As shown is a light vehicle steering knuckle, its structure is very special,and its forging is difficult. Steering knuckle forging in the part was made by use of 3t, 5t, 10t die forging hammer, 13 tm double-action hammer and some other forging equipments, but the production efficiency is low and product quality is poor. In recent years, auto production every year increases by double-digit growth, and the demand of steering knuckle is increasing rapidly, the old mode of production has not suitable for the needs of the modernization and mass production.

Steering knuckle can be divided into two categories from the geometry and forming technology: one is vertical metal forging. Another kind is horizontal forging forming.

2.Steering knuckle forging process:

Material testing-rod shearing-heating-blank forging-preforming-final forging-trimming-correction-cooling and heat treatment. Vertical forging blank process:upsetting-closed extrusion. Horizontal forging blank process: flatten-turn round flatten.

3.Forging equipments

Forging equipments selected will depond on the production batch. Currently, there are three kinds of equipments for choosing. One is die forging hammer, this kind of equipment is only suitable for small batch production and its technology is backward. So the quality is not so good and not suitable for modern production,but its investment is low. The second kind is the screw press or hydraulic press, this type of equipment can only be used for medium and small batch production. The third kind is hot die forging press, it is most appropriate for high-volume production of steering knuckle, at present, most of the forging manufacturers in the world is in the use of hot die forging press to forge steering knuckle. Hot forging press can be set up multiple slot, the equipment has a bottom dead center, can improve the die life, hot die forging press can complete a process on each trip, reliable operation, high efficiency, easy to realize automatic production, small affected by other factors, forging quality is stable, the disadvantage is that large investment in equipment.

4.Forging preparing procedure

4.1 Material fast testing

Because the steering knuckle is vital for the safety of the car, therefore, before material entering the blanking workshop, rapid detection should be tested for ingredients, qualitative check every ingredient of material. Each test time is short, just a few seconds.

4.2 Blanking way

The material of forging steering knuckle is thick and short, and there is higher requirements on the material end face, so sawing machine is required. More advanced method is to choose high speed sawing machine. High speed sawing machine can be expected on the steering knuckle under 3 pieces per minute, and you can put on a piece of material weight tolerance, reflected in the next block on the blanking process to meet automatic blanking length adjustment. Another way of blanking is rotation shearing and this shear method will not be a horseshoe, if the factory is a professional forging steering knuckle, using special heating mode, rotating shearing blanking method can be used.

4.3 Heating Process

There are furnace and gas heating ways, in the conditional place priority choose electric furnace heating way. There are a lot of advantages of electric furnace heating way, convenient operation, high energy utilization rate, good quality heating and less pollution to environment. Although one-time investment, but high comprehensive economic benefits.

5. Steering knuckle forging process

Considering the working conditions and the importance of car steering knuckle, we usually use low alloy steel as steering knuckle material, general common 42CrMo square or circular heat steel, or the equivalent of 42 CrMo material, there are also a few manufacturers use 40Cr. No matter which kind of steering knuckle, it is composed offork, plate and bar, there are also some steering knuckle increased the steering arm and tie rod arm, whose structure is more complex. The key of forging is that finish forging before blocking must be reasonable, so as to meet the requirements of finish forging forming.

5.1 Vertical forging process

Take steyr steering knuckle for example:forging material 42CrMo, forging weight 32 kg, length 220 mm, forging technology comply with DIN7526E grade standard. Two shifts production, the annual demand is 400000 pcs, is a medium large production forgings. According to the shape of the steering knuckle, can only use vertical forging. From analysis of factors like the advance of process, reliability, and automotic operation, closed extrusion technology is most advanced, stable quality, reliable production process, high class production, and easy to realize mechanization operation at the same time. Therefore, determine the process flow: upsetting, closed extrusion, preforging, finish forging.

Due to large weight of knuckle forging, wide working mesa of forging equipment, long working distance, so the steering knuckle forging process using two manipulator operation. When heated blank out of furnace reach the designated position, the first manipulator send hot billet to press first station for upsetting, the purpose of upsetting is to remove oxide skin, after upsetting, the first manipulator will pick up and turn 90 ° to the second location. The next station is extrusion process, extrude part of rod and fork. There are ejection devices on the upper and lower extrusion dies, and closed extrusion deforming force is about 45000 kn. After completing extrusion process, the second stage manipulator will pick up the forging, and deliver to the third location for preforging. Purpose of preforging is to allocate metal, then to make basic forming of each part for steering knuckle, the deforming force is about 40000 kn. Then again preforged steering knuckle will be delivered by the second stage forging manipulator to fourth Labour for finish forging. The deforming force of finish forging deformation force is slightly lower than preforging force. The whole forging production using manipulator operation will improve the production efficiency, which is much higher than the hammer, and improve the production efficiency. At present, there are hundreds of steering knuckle production lines in the world. And extrusion technology of Chinese automotive forging factories steering knuckle has reached the international level, there are also many drop forging manufacturers using this technology in domestic.

5.2 Horizontal forging process

Some of the automobile steering knuckles because of shape, can only adopt the method of horizontal forging. Past process of domestic horozontal forging automotive steering knuckle by hot die forging press production: crushed-second (run, turn 90 °) flattening, pre forging, finish forging forming. The production efficiency is low, also the worker labor intensity is larger.

Volvo forging factory forging steering knuckle uses 40000 kn hot die forging press produced by kling ning company. Billet after heating is delivered by slide to the specified location, and then workers pick up the blank on the closed pre forging dies, press pressed to finish forge sequence, and then the artificial flip into the finish forging type slot, final forging press. Finish forging type slot is horizontally parting the dies, then artificial send forming steering knuckle to the press, forging will be send through the conveyor belt to the trimming station for trimming. Production of three pieces per minute, high production speed, artificial operation in whole forging production process,which is simple.

6.Subsequent forging process includes trimming, collection, heat treatment, ect. Contact us for your forged 
steering kunckle needs or other automotive forgings.

can you pls explain post forging operation
- - - -> by: chethan

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