In the field of heavy industry manufacturing, there has always been a saying: Only by understanding crankshaft manufacturing can one truly understand heavy equipment.
As a core component of ship main engines, large generator sets, and heavy engineering machinery, large-diameter crankshafts directly determine the operational stability and service life of the entire equipment.
Different from ordinary parts, large-diameter multi-turn crankshafts have to withstand high-intensity torsional forces and alternating impact loads for a long time. They have harsh service conditions and extremely high manufacturing thresholds.
Many outsiders think that the crankshaft manufacturing processes are similar, but in fact there are many ways to do it.
At present, the mainstream industry includes three production modes: casting, die forging, and free forging. After years of survival of the fittest in the market, free forging has become the preferred process for heavy-duty large-diameter crankshafts.
Let us use easy-to-understand language to gain an in-depth understanding of this core process, and at the same time introduce to you a reliable source manufacturer of crankshaft forgings.
1. When comparing the three major manufacturing processes, why does free forging win?
In order to facilitate the understanding of industry colleagues and purchasing friends, we will directly dismantle the advantages and disadvantages of the three processes.
The first is the casting process.
Its biggest highlights are low cost, fast mass production, and almost no production barriers.
But the short board is also very fatal. Defects such as pores, shrinkage, and impurities are easy to remain inside the casting, and the metal structure is loose.
To put it simply, this type of crankshaft can only be used for small equipment with low load. Once it encounters a heavy load impact, it is very prone to cracking and fracture problems, and it is completely unsuitable for large ships and power generation equipment.
The second is closed die forging.
The finished product of this process has high precision and strong product consistency, and is suitable for mass production of small and medium-sized crankshafts.
However, the flaws cannot be solved. Customized molds are expensive and the initial investment cost is high.
At the same time, due to the limitation of mold size, it is impossible to produce ultra-large diameter and ultra-long multi-turn crankshafts. The customization flexibility is poor and cannot meet the individual needs of large-scale heavy industry projects.
The last is the free forging process, which is currently the optimal solution for heavy-duty crankshafts.
Relying on large hydraulic presses and intelligent forging hammer equipment, through basic processes such as upsetting, lengthening, bending, and staggered shaping, large-diameter crankshafts with full specifications of 1 to 12 turns can be easily produced without customizing exclusive molds.
Forging can break the original cast structure of the steel ingot and compact the internal micropores; when the forging ratio reaches above 4.0, the grain density of the crankshaft is greatly improved, and the fatigue resistance and impact resistance are directly rolled into the casting. The comprehensive cost performance is irreplaceable.
2. In-depth dismantling: the entire free-forged production process of large-diameter crankshaft
The seemingly simple forging process is actually interlocking. Every detail error will directly lead to the scrapping of the finished product. The entire process is mainly divided into three major stages.
The first stage: billet pretreatment and constant temperature heating.
Good products start with raw materials. At the beginning of production, high-purity alloy steel ingots are given priority, excess risers are cut off, corners of the billet are trimmed, and impurity-rich areas are eliminated.
Heating adopts a segmented gradient heating method to stably control the temperature within the golden forging range of 1000°C – 1200°C to avoid thermal stress cracking caused by excessive temperature differences and reduce the risk of scrapping from the source.
The second stage: multi-fire step-by-step forging (core link).
The industry uniformly follows the principle of “making the blank first, forming later”. It first repeatedly upsetting and elongating the blank to optimize the internal structure and increase the density of the material; then it accurately positions the crankshaft position and forms it one by one through processes such as staggered shifting and local bending.
For complex crankshafts with six or more crankshafts, it is necessary to appropriately extend the heat preservation time, balance the heat dissipation speed, and solve high-frequency quality problems such as crankshaft asymmetry and wall thickness deviation.
The third stage: finishing, correction and multiple quality inspections.
After forging is completed, the staff immediately corrects the straightness of the crankshaft and polishes the surface burrs.
Then, dual heat treatment of normalizing and quenching and tempering is used to completely eliminate forging residual stress and balance hardness and toughness.
Finally, through dual inspections of ultrasonic flaw detection and mechanical property testing, internal cracks and inclusion hazards are comprehensively checked, and only qualified products will flow into the deep processing link.
3. Existing pain points and upgrade directions in the industry
To be honest, even if the free forging process has matured, there are still two major pain points in the industry at this stage.
On the one hand, key processes such as turning and bending are extremely dependent on the practical experience of senior masters. Human factors have a great influence and product uniformity is uneven; on the other hand, the heat dissipation speed inside and outside of large-size blanks is inconsistent, and the forging temperature is difficult to accurately control. There is often insufficient local plasticity, which increases the production cost of the company.
Nowadays, head forging companies have completed technological upgrades: equipped with intelligent temperature control systems, which monitor the internal and external temperatures of the billet in real time 24 hours a day; solidifying forging parameters, unifying the holding time and pressing amplitude, weakening human errors; popularizing full-fiber forging technology, allowing metal streamlines to fit the stress trajectory of the crankshaft, which can increase the anti-fatigue life by up to 30%.
4. A must-see for purchasing!
Jiangyin Wanheng – a benchmark manufacturer of high-quality crankshaft forgings
For equipment manufacturers and purchasers, choosing the right supplier can avoid detours and save a lot of costs.
Here I would like to recommend to you Jiangyin Wanheng, a source forging company with an excellent reputation in the industry.
Having been deeply involved in the field of free forging of large-diameter crankshafts for many years, Jiangyin Wanheng has accumulated rich practical experience and is proficient in core technologies such as multi-fire step-by-step forming and full-fiber forging.
The team can customize forging solutions one-to-one according to different working conditions such as ship power, industrial power generation, heavy machinery, etc., to solve industry problems such as uneven molding of multi-turn crankshafts and excessive internal stress.
In terms of hardware configuration, the company is equipped with high-end equipment such as large-scale fully-automatic hydraulic presses and intelligent constant-temperature heating furnaces. It has sufficient production capacity reserves and can not only undertake ultra-large single-piece customization, but also meet large-volume regular supply, and its delivery efficiency far exceeds the industry average.
In terms of quality control, a full-process closed-loop quality inspection system has been established, from raw material screening, process sampling to finished product flaw detection, strict control at all levels, and a full set of test reports can be provided for all factory forgings.
Relying on Jiangyin’s complete industrial cluster advantages, Jiangyin Wanheng cuts out all middlemen and directly faces customers at ex-factory prices, which is highly cost-effective.
With its stable product quality and considerate after-sales service, it has become a long-term fixed partner of many heavy industry companies at home and abroad.
Summary: In the short term, free forging is still an irreplaceable manufacturing process for large-diameter, heavy-duty crankshafts.
As intelligent forging technology continues to spread, the quality of crankshaft forgings will continue to upgrade.
If you have any process-related questions or purchasing needs, please leave a message to communicate!
