Stainless steel is indispensable across diverse sectors, from aerospace to medical technologies. Yet, the manufacturing processes for stainless steel parts vary significantly to meet the unique requirements of each industry and product.

This article guides you through two prominent manufacturing methods - machining and powder metallurgy (PM). By examining these two methodologies, we aim to offer valuable insights into the crucial decision-making process between machined and sintered stainless steel parts, considering their profound impact on costs, precision, and properties.

How are Sintered Stainless Steel Parts Made?

▲ Sintered Stainless Steel Parts

Did you know that powder metallurgy (PM) stainless steel has ancient origins dating back over 4000 years? In the Middle Ages, when melting iron appeared unfeasible, similar methods were employed to produce steel.

These age-old techniques experienced a revival in the 1930s and have since evolved into sophisticated processes crucial to modern manufacturing.

Manufacturing Process

PM involves three key steps: powder manufacturing, compaction, and sintering.

1. Powder Manufacturing: Stainless steel powders, often produced via water atomization for good compressibility.
   
   
2. Compaction: Stainless steel powders are consolidated using conventional rigid die compaction, known for its versatility.
   
   
3. Sintering: Sintering is conducted in a continuous furnace with ammonia gas continuously supplied. The furnace heats the ammonia gas to a high temperature, initiating the decomposition reaction. This reaction produces a gas mixture of nitrogen and hydrogen, which is then used to prevent oxidation and other unwanted reactions with the materials being processed.
   
   
   
   ▲Continuous Furnace

Key Benefits & Challenges

• Key Benefits
  • Low production costs in mass production
  • High material utilization
  • Streamlined manufacturing process
  • Ability to create complex-shaped parts with high accuracy and consistency
  • Exceptional strength, toughness, wear resistance, and corrosion resistance, even at elevated temperatures
    
    
• Challenges
  • Difficulty in reaching near full-density
  • Not cost-effective for small-volume production

Applications

• Widespread application across industries: aerospace, automotive, chemical processing, medical, recreational, and home appliances.

How are Machined Stainless Steel Parts Made?

Machined stainless steel parts are crafted by subtracting material from solid blocks of raw stainless steel using CNC (Computer Numerical Control) turning or milling machines.

Manufacturing Process

1. Steel Melting: In an arc furnace, steel is melted.
   
   
2. Carbon Removal: Argon and oxygen are added to the furnace to remove excess carbon.
   
   
3. Forming & Heating: The molten steel is then cast into various shapes and undergoes hot-rolling to enhance ductility.
   
   
4. Descaling: Chemical descaling removes mill scales accumulated during hot-rolling.
   
   
5. Finishing: A high-pressure water rinse achieves a bright finish.
   
   
6. Machining: CNC machining fabricates stainless steel parts with intricate designs.

Key Benefits & Challenges

• Key Benefits
  • Offer a high level of customization
  • Finished parts with high precision and accuracy
  • Long durability, high strength, and corrosion resistance

• Challenges
  • High tool wear and decreased tool life
  • Difficulty in machining stainless steel with high hardness
  • Result in considerable material waste, particularly problematic when working with expensive stainless steel alloys.

Applications

• Applicable in various industries, including aerospace, medical, and automotive.

Machined vs. Sintered Stainless Steel Parts: Properties, Processes, Applications & Costs

Properties

Both machined and sintered stainless steel parts demonstrate resilience against high temperatures and boast long-lasting durability.

Nevertheless, in comparison to machined stainless steel parts, sintered stainless parts manufactured via rigid die compaction exhibit moderate corrosion resistance due to their inherent porosity. This porous nature also contributes to a reduction in the strength of the components.

At Rainbow Ming, we are dedicated to enhancing density and exploring alternative compaction methods. If our clients' products require high density, we utilize raw materials produced by Metal Injection Molding in sintering. This method proves effective in producing pore-free and near-full-density sintered stainless steel parts.

▲Injection Molding Equipment

Processes

Powder Metallurgy (PM) technology revolutionizes stainless steel part production by enabling the creation of intricate shapes in a single manufacturing cycle, minimizing the need for secondary machining operations.

In contrast, machining technology requires stainless steel to undergo various steps to produce desired products, adding complexity and time to the manufacturing process.

Applications

PM technology stands out in industries demanding intricate shapes and large-scale production. Its additive process empowers component designers to commence from scratch, swiftly materializing precise part designs.

Nonetheless, its higher per-part and tooling costs may limit its feasibility for small production runs. In such scenarios, machining technology, leveraging existing cutting tools, is a more cost-effective option.

Costs

• Tooling
  

  
  Compaction, a crucial step in PM manufacturing, demands robust tooling or dies to shape stainless steel parts effectively. Crafting such tooling for stainless steel powder compaction can be costly due to the heavy pressure involved and the inherent hardness of stainless steel material.
  
  However, this initial investment can be considered a one-time expense. Well-designed and manufactured dies, paired with stainless steel powders with good compressibility, can endure hundreds of thousands of cycles without significant degradation.
                                                                                                                                                                                    
  Conversely, machining stainless steel parts often leads to rapid tool wear owing to the material’s hardness, necessitating frequent replacements and maintenance. This adds to the overall manufacturing costs associated with machining processes.
  
  
  
  ▲ Powder Compacting Press

• Energy

  
  Machining stainless steel parts involves multiple steps and necessitates significant force to cut through the hard material, consuming substantial energy.
  
  Conversely, PM manufacturing, with its streamlined process and reduced force requirements, demands less energy, making it not only more sustainable but also more cost-effective in the long run.
  
  

• Material

  
  During the production of sintered stainless steel parts through PM manufacturing, almost no steel material is wasted because it is an additive process, allowing manufacturers to use only the necessary amount of material for each part.
  
  In comparison, the subtractive nature of machining stainless steel parts can result in over 50% scrap generation. While some of this scrap can be recycled, the process is costly, adding to production expenses.

Are you ready to decide between machined vs. sintered stainless steel parts?

There is no right or wrong choice when it comes to deciding between machined and sintered stainless steel parts. As long as you select the method that aligns with your needs and preferences, it is the best decision.

If you believe that your stainless steel parts are suitable for production using powder metallurgy (PM) technology, please don’t hesitate to reach out to Rainbow Ming.

As a reputable and experienced PM stainless steel manufacturer, we are committed to conducting thorough feasibility assessments and providing effective recommendations based on our expertise. Our goal is to reduce manufacturing costs, enhance the possibility of batch production, and ultimately bring your ideas to life.