Different industries have different requirements for stainless steel castings. The food industry focuses on hygiene and cleanliness. The marine environment needs to resist chloride ion corrosion. And chemical equipment must withstand various acid and alkali media.
Poor material selection can lead to equipment failure, higher maintenance costs, and even safety accidents.
QD is a foundry that specializes in investment casting technology. We will provide you with industry-specific material selection guides. This helps you accurately identify suitable grades. It ensures the best balance between performance and cost.
Food and Pharmaceutical Industries
In the food and pharmaceutical industries, stainless steel castings come into direct contact with food and pharmaceuticals. So they have extremely high requirements for hygiene, corrosion resistance and easy cleanability. Any material defect may lead to bacterial growth or product deterioration.
Core Requirements
- Hygiene: The material surface must be smooth and non-porous. This prevents the residue of bacteria and contaminants.
- Easy Cleanability: It can withstand frequent high-temperature and high-pressure cleaning and the corrosion of chemical disinfectants.
- Corrosion Resistance: It resists the erosion of organic acids in food and processing media such as salt and sugar.
Preferred Grade: 316L Stainless Steel
316L is a type of low-carbon austenitic stainless steel. It has become the first choice for the food and pharmaceutical industries because of its excellent corrosion resistance.
Its key features include:
- Low carbon content (carbon content ≤ 0.03%): It reduces carbide precipitation and prevents intergranular corrosion. It maintains stability especially during welding and heat treatment processes.
- Added molybdenum (about 2-3%): It enhances resistance to pitting corrosion and crevice corrosion. It is suitable for acidic foods and cleaning chemicals.
- Wide compatibility: It resists various food acids, alkaline cleaners and high-temperature steam.
- Good ductility: It meets the complex forming needs of investment casting. It can be used to produce parts such as pipes and valves with smooth inner walls.
According to international standards, food-grade stainless steel must meet specific surface treatment requirements. Usually, castings need to go through mechanical polishing or electropolishing. This is to achieve a surface roughness of Ra < 0.8µm. It ensures thorough cleaning without dead corners.
| Characteristics | Description |
| Recommended Grade | 316L |
| Key Elements | Low carbon, molybdenum |
| Corrosion Resistance Range | Organic acids, chloride ions, high-temperature disinfectants |
| Surface Treatment | Mechanical polishing or electropolishing, Ra < 0.8µm |
| Applicable Components | Pumps, valves, mixers, transfer pipes |
We provide customized surface treatment services. These services help customers pass industry certifications.
Marine and Offshore Engineering
High salinity, humidity and high chloride ion content can cause ordinary stainless steel to quickly develop pitting corrosion, stress corrosion cracking and rust. Therefore, marine and offshore engineering must use stainless steel with high corrosion resistance.
Core Requirements
- Resistance to chloride ion pitting: Chloride ions are the main corrosive medium in marine environments. Materials need to have high pitting resistance equivalent.
- Salt spray corrosion resistance: It maintains stable performance under long-term salt spray exposure.
- Mechanical strength: It maintains structural integrity under dynamic loads and high-pressure environments (such as deep-sea equipment).
Preferred Grades: 316/316L and Duplex Stainless Steel
- 316/316L: The molybdenum element provides moderate chloride ion resistance. It is suitable for general marine applications (such as marine accessories, coastal structures).
- Duplex Stainless Steel (e.g., 2205): It combines austenitic and ferritic structures. It has higher strength and corrosion resistance. Its PREN value usually exceeds 35. It is suitable for harsh environments.
Challenges and Solutions
Chloride ions and microorganisms in seawater may accelerate local corrosion. QD optimizes the investment casting process. It controls the grain structure and alloy composition of castings. This can significantly extend service life.
| Grade | Pitting Resistance Equivalent Number | Chloride Ion Resistance | Typical Applications |
| 316L | 24-28 | Medium | Marine pipes, fittings |
| 2205 Duplex Steel | 35-40 | High | Seawater pumps, subsea valves, platform structures |
| Super Duplex Steel | >40 | Extremely High | Deep-sea equipment, high-pressure environments |
Chemical Processing and Petrochemical Industries
The chemical industry involves strong acids, strong alkalis, oxides and high-temperature high-pressure media. Improper material selection may lead to risks of leakage, pollution or explosion.
Core Requirements
- Resistance to corrosion from a wide range of media: including sulfuric acid, hydrochloric acid, nitric acid, alkaline solutions, etc.
- High-temperature stability: maintains mechanical properties and corrosion resistance in high-temperature environments.
- Customized design: selects cost-effective grades based on specific medium concentration, temperature and pressure.
Grade Selection Guide
Selection of stainless steel for chemical industry must be based on medium characteristics:
- 304L: suitable for mild corrosion environments, such as low-concentration organic acids and alkaline media.
- 316L: resists medium-concentration acids and chlorides, widely used in general chemical equipment.
- Duplex Stainless Steel (e.g., 2205): resists stress corrosion and pitting corrosion, suitable for media containing chloride ions.
- High-grade alloys (e.g., Hastelloy): used in extreme environments, such as high-concentration acids or high-temperature oxidizing media.
| Medium Type | Recommended Grade | Corrosion Resistance Characteristics | Application Examples |
| Weak acid/alkali | 304L | Basic corrosion resistance. Economical and practical. | Storage tanks, reaction kettles |
| Acid containing chloride ions | 316L | Resists pitting. Withstands medium acid concentrations. | Pipes, heat exchangers |
| Strongly corrosive medium | 2205 Duplex Steel | High strength and resists stress corrosion. | Pump casings, compressor bodies |
| Extreme environment | Hastelloy | Withstands high-concentration acid Withstands high-temperature oxidation. | Catalytic reactors, special valves |
QD focus on controlling internal defects of castings and alloy uniformity. This ensures reliable performance in harsh chemical environments. We are familiar with industry standards such as ASME and NACE. We also provide material test reports.
Contact Us
Does your industry have special certification or standard requirements?
QD is familiar with various industry specifications. It has a complete quality control system and rich project experience.
Tell us about your industry and specific application. We will ensure that the castings fully meet your expectations from material to performance.
FAQ
1. How to choose the right stainless steel grade for your application?
First, analyze your operating environment (such as medium type, temperature, pressure). Then refer to industry standards. QD provides free material selection consultation. It helps you match the best grade.
2. What impact does the investment casting process have on stainless steel performance?
Investment casting can produce castings with complex shapes and high precision. It improves corrosion resistance and mechanical strength by controlling cooling rate and alloy composition. QD uses advanced technology. It ensures castings are dense and free of defects.
3. Can QD provide customized surface treatment?
Yes. We provide mechanical polishing, electropolishing and passivation treatment. It meets the requirements of different roughness and hygiene standards.
4. What successful cases does QD have in the chemical field?
We have produced pump casings, valves and reactor parts for many chemical enterprises. We helped customers extend equipment service life and reduce costs through material optimization. For specific cases, you can refer to our project library.
5. What is the most critical reference factor when choosing stainless steel grades in the chemical industry?
The most critical one is the medium characteristics: first clarify the medium type (acid/alkali/salt), concentration (such as 20% or 98% sulfuric acid), and temperature (normal temperature or high temperature). These three parameters directly determine the corrosion resistance requirements.
Second is the stress condition (such as whether it bears pressure or is impacted). You need to match a grade with corresponding strength.
Finally, there is the cost budget. Avoid over-selection like using Hastelloy for ordinary storage tanks.
6. What advantages does QD’s investment casting process have in stainless steel casting production?
Compared with traditional sand casting, QD’s investment casting has obvious advantages:
① High precision: The dimensional tolerance can reach CT6-CT7 level, and the surface roughness can reach Ra1.6μm. This reduces subsequent processing workload.
② Flexible structure: It can produce parts with complex inner cavities, thin walls (minimum wall thickness 2mm) and no splicing. This reduces the risk of leakage.
③ Uniform material quality: The molten metal is poured in a vacuum environment. This reduces defects such as air holes and inclusions, and improves corrosion resistance and strength.