Table of Contents

Stainless Steel Basic Knowledge

Stainless Steel Introduction

Stainless steel: In the field of metallurgy and materials science, according to the main performance characteristics of steel, a series of ferroalloys with a chromium content of more than 10.5% and with corrosion and rust resistance as the primary performance characteristics are called stainless steel.

The corrosion resistance of stainless steel is based on the action of Cr, and a dense Cr-rich passive film forms on the surface of the steel, which is insoluble in the media.

Some properties of stainless steel: beautiful surface and a variety of applications;
It has good corrosion resistance and is more durable than ordinary steel;
High strength. Therefore, the possibility of using thin plates is high;
High-temperature oxidation resistance and high strength so it can resist fire;
Standard temperature processing, i.e., simple plastic processing; no surface treatment, so simple and easy to maintain; clean, high-quality finish; good welding performance; good corrosion resistance.

Stainless Steel Production Process

Stainless steel production mainly includes crude steel melting, hot rolling, cold rolling, and other steps.

stainless steel crude steel melting process

Currently, the melting process for producing stainless steel worldwide is mainly divided into single-stage, two-stage, and three-stage processes, as well as new integrated production methods.

Single stage melting: molten iron + AOD (argon-oxygen refining furnace);

The two-stage process is: EAF (electric arc furnace) + AOD (argon-oxygen refining furnace).

The three-stage process is: EAF (electric arc furnace) + AOD (argon-oxygen refining furnace) + VOD (vacuum refining furnace).

In addition to several traditional production processes, the current integrated production process, many companies have also adopted the production process from molten iron to stainless steel. The production process is RKEF (Rotary Kiln Electric Furnace) + AOD (Argon Oxygen Refining Furnace).

stainless steel hot rolling process

In the stainless steel hot rolling process, slabs (mainly continuous cast slabs) are used as raw material, and after heating, strips are produced by roughing and finishing mills.

The hot steel strip is cooled to the set temperature and rolled into a steel coil by the machine. The surface of the cooled steel coil has an oxide scale and appears black. After annealing and pickling, the oxidized surface is removed, and it becomes a white stainless steel coil.

Most of the rolls currently on the market are stainless steel white rolls. The specific hot rolling process for stainless steel is as follows:

stainless steel hot rolling process

stainless steel cold rolling process

After hot rolling stainless steel, some hot rolled stainless steel products are used directly, and some hot-rolled products need to be further processed for cold rolling before use.

Cold-rolled stainless steel products are mainly made from hot-rolled stainless steel with a thickness of 3.0-5.5 mm. After rolling by cold rolling mills, they are processed into cold-rolled stainless steel products.

The main production processes of stainless steel cold rolling are single-column stainless steel cold rolling and multi-column stainless steel cold rolling. The specific production process is as follows:

stainless steel cold rolling process

After the stainless steel is cold rolled, it must undergo an annealing and pickling unit. The purpose of annealing stainless steel after cold rolling is to remove work hardening due to the recrystallization process to achieve the purpose of softening. The purpose of pickling is to remove the oxide layer formed on the surface of the steel strip during the annealing process, and the second is to passivate the surface of the stainless steel. To improve the corrosion resistance of steel plates.

Stainless Steel Classification

  • 200 series: austenitic chromium-manganese series stainless steel; 2%-5% nickel content; cheap substitute for 300 series (half the price of 300 series), but indistinguishable appearance; no magnetism; 30% of total stainless steel production.
  • 300 series: chromium-nickel austenitic stainless steel; Nickel content is 8% to 10%, which is most influenced by the price of nickel. The stainless steel boss, 304 stainless steel, is the protagonist and the supply product. The price change of 304 can be quoted from the stainless steel market.
  • 400 series: ferritic stainless steel; no nickel, so it is also called stainless iron, which contains 15% -30% chromium; magnetic; accounts for 20% of the total power of stainless steel crude; 304 for high-end tableware, 430 for low-end tableware.

Adding other elements to stainless steel can give stainless steel more properties, such as better hardness, plasticity, and toughness.

Stainless steel can be divided into austenitic stainless steel, ferritic stainless steel, duplex stainless steel, martensitic stainless steel, and precipitation hardening stainless steel.

The austenitic type has good corrosion resistance, comprehensive mechanical properties, and process performance, but the strength and hardness are low.

Ferritic stainless steel has high strength, low strain hardening tendency, excellent resistance to chloride stress corrosion, pitting corrosion, crevice corrosion, and other localized corrosion, but is sensitive to intergranular corrosion and has poor toughness at low temperatures.

Duplex stainless steel combines the advantages of both austenitic and ferritic steel. Martensitic stainless steel has high strength and hardness and is used for tableware, surgical instruments, etc. Precipitation hardening stainless steel has high strength and strong corrosion resistance.

Five Stainless Steel Facts

1. Growth in stainless steel production capacity in China slows down

From 2010 to 2015, stainless steel production capacity was released rapidly with an average growth rate of 14.22%; From 2015 to 2018, the growth rate of stainless steel production capacity began to slow down with an average growth rate of 4.81%.

From 2010 to 2012, new stainless steel production capacity stagnated due to internal and external factors such as macroeconomic adjustment, slower demand growth, and bottlenecks in industrial technology development.

From 2013 to 2015, the technological revolution ushered in the era of rapid expansion of stainless steel secondary production capacity. Private giants took advantage of the cost benefits of RKEF ferronickel smelting technology and integrated steelmaking technology to rapidly expand production capacity.

From 2016 to 2018, the reform forced many unlicensed steel mills in China to stop production and withdraw from the market. At the same time, the continuous strengthening of environmental protection caused the steel mills that did not take environmental protection measures and lose their competitive advantages due to the increased cost of environmental protection to stop production and withdraw from the market successively. In 2010, the speed of many hidden non-mainstream production capacities in eastern and southern China was significantly increased.

From the construction progress point of view, the new and upcoming stainless steel production capacity that can be counted in China in the future is currently about 11.92 million tons.

2. Changes in the structure of Chinese stainless steel grades.

From 2009 to 2018, china’s overall stainless steel production has grown from fast to slower growth; In terms of subdivision, the 200 series stainless steel has a faster growth rate compared to 300 series stainless steel, accounting for 19% of the total stainless steel since 2009, the growth rate was 33% in 2018, and the growth rate of The 400 series was slower, from 29% in 2009 to 18% in 2018. Compared with Europe and the United States, China’s 200 series accounts for a large proportion, and there is more room for future product optimization.

3. The global share of China’s stainless steel production shows a downward trend, and Indonesia’s global share is expected to increase

China’s stainless steel production has grown rapidly, and its global share has continued to grow. Since 2016, the growth rate of stainless steel production has slowed down, and its global share shows a downward trend. In 2010, China’s stainless steel production accounted for 35.35% of the global total. In 2018, it was 53.6%, up 18.25%. Currently, China is a major producer and consumer of stainless steel worldwide.

Chinese stainless steel enterprises are going abroad to establish raw material origins and stainless steel production and processing bases overseas.

The 300 series mainly dominate Indonesia; Indonesia’s stainless steel production in 2018 was 3.74 million tons. It is expected that Indonesia’s production will reach 5.31 million tons, an increase of 1.57 million tons of stainless steel, and the production growth rate will be 42%; Indonesia’s global stainless steel share can reach 9.43%, an annual increase of 2.06%.

4. Consumption, import, and export of stainless steel in China

In 2018, the per capita consumption of stainless steel in China was 15.3 kg, the per capita consumption in Italy, Taiwan, and South Korea was more than 30 kg, and the per capita consumption of stainless steel in Japan and Germany was more than 20 kg. There is still plenty of room for growth.

5. Stainless steel production areas

China’s stainless steel production capacity is mainly distributed in developed areas. Stainless steel production is mainly concentrated in East China, South China, and North China. Its production accounts for 39%, 25%, and 14% of the total domestic production, and the total output has reached 78%.

Stainless steel downstream applications

Stainless steel is widely used, of which 28% is used in metal products, 25% is used in construction, 18% is used in mechanical engineering, 11% is used in electrical machinery, 7% is used in motor vehicles and components, and 11% is used in other transportation.

The daily use products are cabinet products, daily use utensils, etc., mainly 201, 304, 430, and other stainless steel grades and cold-rolled stainless steel sheets with thickness ≤ 3 mm.

The construction category includes exterior decoration, building materials, and corrosion-resistant roofs, mainly 2012B, followed by 3042B and 304HL, 201HL, 439HL, and other stainless steel grades.

Chemical equipment, transportation equipment, marine equipment, environmental protection equipment, energy equipment, pharmaceutical machinery, etc., mainly use 1Cr18Ni9Ti stainless steel seamless pipes with a diameter of 16~325mm and matching stainless steel fasteners; Rolled stainless steel sheet and hot-rolled stainless steel plate with a thickness of 4~6mm

Household appliances and electronics include the inner cylinder of washing machines and dryers, the inner tank of water heaters, the inner and outer shell of microwave ovens, the refrigerator lining, etc., mainly 304, 316, 409L, 430 stainless steel, and other grades.

Automotive are automotive exhaust system parts, engine mounts, automotive fuel tanks, and automotive decorative panels, mainly 409, 430, 441, 429, 434, 436, and so on. Cold rolled stainless steel strip for the exhaust system is processed Special shaped welded pipe.