The density of steel generally used for 304 stainless steel honing pipe is 7.85kg/dm3. 304 stainless steel honing pipe has a hollow section and is used as a pipeline for transporting fluids, such as pipelines for transporting oil, natural gas, gas, water and certain solid materials. Compared with solid steel such as round steel, 304 stainless steel honing pipe has a lighter weight when the bending and torsion strength is the same. It is a kind of economical cross-section steel, which is widely used in the manufacture of structural parts and mechanical parts, such as oil drill pipes and automobile transmission. 304 stainless steel honing pipes are used to make ring parts for axles, bicycle frames and steel scaffolds used in building construction, which can improve material utilization, simplify manufacturing procedures, and save materials and processing man-hours. 304 stainless steel honing pipes have been widely used for manufacturing.

304 stainless steel is a common material in stainless steel, with a density of 7.93 g/cm³; it is also called 18/8 stainless steel in the industry, meaning it contains more than 18% chromium and more than 8% nickel; high temperature resistance of 800 ℃, with good processing performance , With the characteristics of high toughness , it is widely used in industry and furniture decoration industry and food and medical industry. However, it should be noted that food-grade 304 stainless steel has stricter content indicators than ordinary 304 stainless steel. For example: the international definition of 304 stainless steel is basically 18%-20% of chromium and 8%-10% of nickel, but food-grade 304 stainless steel is 18% of chromium and 8% of nickel, which is allowed to fluctuate within a certain range, and Limit the content of various heavy metals. In other words, 304 stainless steel is not necessarily food grade 304 stainless steel
Common labeling methods on the market include 06Cr19Ni10 and SUS304 , of which 06Cr19Ni10 generally means national standard production, 304 generally means ASTM standard production, and SUS 304 means Japanese standard production.
304 is a general purpose stainless steel that is widely used to make equipment and parts that require a good combination of properties (corrosion resistance and formability). In order to maintain the inherent corrosion resistance of stainless steel , the steel must contain more than 18% chromium and more than 8% nickel. 304 stainless steel is a grade of stainless steel produced according to the American ASTM standard.

Physical properties

304 Stainless Steel Atlas (19)

Tensile strengthσb (MPa)≥515-1035

Conditional yield strengthσ0.2 (MPa)≥205

Elongation δ5 (%)≥40

Area shrinkage ψ (%)≥?

Hardness : ≤201HBW;≤92HRB;≤210HV

Density (20℃, g/cm³): 7.93

Melting point (℃): 1398~1454

Specific heat capacity (0~100℃, KJ·kg ^-1 K ^-1 ): 0.50

Thermal conductivity (W·m ^-1 ·K ^-1 ): (100°C) 16.3, (500°C) 21.5

Linear expansion coefficient (10 ^-6 ·K ^-1 ): (0~100℃) 17.2, (0~500℃) 18.4

Resistivity (20°C, 10 ^-6 Ω·m ² /m): 0.73

Longitudinal elastic modulus (20℃, KN/mm ² ): 193

Product Standards

For 304 stainless steel, the Ni element in its composition is very important, which directly determines the corrosion resistance of 304 stainless steel and its value.

The most important elements in 304 are Ni and Cr, but they are not limited to these two elements. Specific requirements are specified by product standards. The common judgment in the industry is that as long as the Ni content is greater than 8% and the Cr content is greater than 18%, it can be considered as 304 stainless steel. This is why the industry calls this type of stainless steel 18/8 stainless steel. In fact, the relevant product standards have very clear regulations for 304, and these product standards have some differences for different shapes of stainless steel. Below are some common product standards and tests.

To determine whether a material is 304 stainless steel, it must meet the requirements of each element in the product standard. As long as one does not meet the requirements, it cannot be called 304 stainless steel.

1. ASTM A276 (Standard Specification for Stainless Steel Bars and Shapes)

2、ASTM A240（Chromium and Chromium-Nickel Stainless Steel Plate板材,Sheet片材, and Strip带材 for Pressure essels and for General Applications）

3. JIS G4305 (cold-rolled stainless steel plate, sheet and strip)

4. JIS G4303 (Stainless steel bars )

The above four standards are just a few common standards. In fact , there are more than these standards mentioned in ASTM and JIS 304. In fact, each standard has different requirements for 304, so to determine whether a material is 304, the accurate expression should be whether it meets the 304 requirements in a product standard. The material certificate generally requires the following types of reports:

Detailed standard specification comparison: as of 2015-12-08

Scope of application

System description: 304 stainless steel is the most widely used chromium-nickel stainless steel. As a widely used steel, it has good corrosion resistance, heat resistance, low temperature strength and mechanical properties; good hot workability such as stamping and bending , No heat treatment hardening phenomenon (use temperature -196 ℃ ~ 800 ℃). Corrosion resistance in the atmosphere, if it is an industrial atmosphere or heavily polluted area, it needs to be cleaned in time to avoid corrosion. Suitable for food processing, storage and transportation. Has good processability and weldability. Plate heat exchangers, bellows, household products (Class 1 and 2 tableware, cabinets, indoor pipelines, water heaters, boilers, bathtubs), auto parts (windshield wipers, mufflers, molded products), medical appliances, building materials, chemicals, food industry , agriculture, ship parts, etc. The 304 stainless steel with strictly controlled content can also be called food grade 304 stainless steel

Most of the usage requirements are to maintain the original appearance of the building for a long time. When determining the type of stainless steel to choose, the main considerations are the required aesthetic standards, the corrosiveness of the local atmosphere, and the cleaning system to be used. However, other applications increasingly seek only structural integrity or water impermeability. For example, roofs and side walls of industrial buildings. In these applications, the owner's construction cost may be more important than aesthetics, and the surface is not very clean. 304 stainless steel works reasonably well in dry indoor environments. However, to maintain its appearance outdoors in rural and urban areas, frequent cleaning is required. In heavily polluted industrial and coastal areas, the surface can be very dirty and even rust.

However, for an aesthetic effect in an outdoor environment, nickel-containing stainless steel is required. Therefore, 304 stainless steel is widely used in curtain walls, side walls, roofs and other construction purposes, but in severely corrosive industrial or marine atmospheres, 316 stainless steel is preferred. Stainless steel sliding doors, people have fully realized the advantages of using stainless steel in structural applications. 304 and 316 stainless steels are included in several design guidelines. Because the "duplex" stainless steel 2205 combines good atmospheric corrosion resistance with high tensile and elastic strengths, this steel is also included in European guidelines. Product Shapes In fact, stainless steel is manufactured in full standard metal shapes and sizes, and many special shapes are also available. The most commonly used products are made from sheet and strip, but also special products are produced from medium and heavy plates, for example, in the production of hot-rolled structural steel and extruded structural steel. There are also round, oval, square, rectangular and hexagonal welded or seamless pipes and other forms, including profiles, bars, wires and castings.

Product Standards

International stainless steel marking method

The American Iron and Steel Institute uses three digits to designate various standard grades of malleable stainless steel. in:

①Austenitic stainless steel is marked with numbers of 200 and 300 series. For example, some of the more common austenitic stainless steels are marked with 201, 304, 316 and 310.

② Ferritic and martensitic stainless steels are represented by numbers in the 400 series.

③ Ferritic stainless steel is marked with 430 and 446, and martensitic stainless steel is marked with 410, 420 and 440C.

④ Duplex (austenite-ferrite), stainless steel, precipitation hardening stainless steel and high alloys with less than 50% iron content are usually named by patent names or trademarks.

4). Standard Classification and Grading

4-1 Classification: ①National Standard GB ②Industry Standard YB ③Local Standard ④Enterprise Standard Q/CB

4-2 Classification: ① product standard ② packaging standard ③ method standard ④ basic standard

4-3 Standard level (three levels): Y level: international advanced level I level: international general level H level: domestic advanced level

4-4 GB

GB1220-2007 Stainless Steel Bar (Grade I) GB4241-84 Stainless Steel Welded Plate (Grade H)

GB4356-2002 Stainless Steel Welded Disk (Class I) GB1270-80 Stainless Steel Pipe (Class I)

GB12771-2000 Stainless Steel Welded Pipe (Y Grade) GB3280-2007 Stainless Steel Cold Plate (I Grade)

GB4237-2007 Stainless Steel Hot Plate (Class I) GB4239-91 Stainless Steel Cold Strip (Class I)

Processing methods

Etching

The etching processing method is to use screen printing acid-resistant protective film on the surface of stainless steel, and then etch with ferrous chloride solution to form an artistic pattern.

spray paint

The spray color method is to spray pigment particles after screen printing to form a pear skin-like surface and form an artistic pattern.

crafting process

The process of spray color art processing method of stainless steel products is: stainless steel products→screen printing→etching→alkali treatment→screen printing→oxidative coloring→alkali treatment→finished product.

The process of etching art processing method of stainless steel products is: stainless steel products → silk screen → etching → alkali treatment → oxidation coloring → finished product.

The chemical coloring method of stainless steel does not use pigments and dyes, but immerses stainless steel in a heated concentrated chromium sulfate solution for chemical coloring, which is characterized by good food resistance. The ink used in this processing method must have very strong acid resistance. Generally, UV vulcanized ink with special properties suitable for the processing technology is used.

Stamping

304 stainless steel tool cabinet

Stainless steel products, especially stainless steel belts , are often the most primitive processing method in factories to use punching machines to stamp products. Stamping includes two methods: straight punching and stretching. Generally, the hardness is lower than 1/2 by stretching and bending, and the hardness is higher than 1/2 and more rigid, and it is straight punching.

rust cause

The rust phenomenon of 304 stainless steel material may have the following reasons:

Chloride

Chloride ions exist widely, such as salt/sweat/seawater/sea breeze/soil and so on. In the presence of chloride ions, stainless steel corrodes rapidly, even more than ordinary low carbon steel. Therefore, there are requirements for the use environment of stainless steel, and it needs to be wiped frequently to remove dust and keep it clean and dry. There is an example in the United States: a company uses an oak container to hold a solution containing chloride ions. The container has been used for nearly a hundred years. It was planned to be replaced in the 1990s. Because the oak material is not modern enough, the stainless steel container was used for 16 days after replacement. Leak due to corrosion.

Solution treatment

Alloy elements are not dissolved into the matrix, resulting in low alloy content in the matrix structure and poor corrosion resistance.

intergranular corrosion

This titanium- and niobium-free material is prone to intergranular corrosion. The addition of titanium and niobium, together with stabilization treatment, can reduce intergranular corrosion. A high-alloy steel that can resist corrosion in the air or in chemically corrosive media. Stainless steel has a beautiful surface and good corrosion resistance. It does not need to undergo surface treatment such as color plating, but instead exerts the inherent surface properties of stainless steel. It is used in many A type of steel, commonly referred to as stainless steel. The representative performance is high alloy steel such as 13 chrome steel and 18-8 chrome nickel steel. From the metallographic point of view, because the stainless steel contains chromium, a very thin chromium film is formed on the surface, which isolates the oxygen from the steel and plays a role in corrosion resistance. In order to maintain the inherent corrosion resistance of stainless steel, the steel must contain more than 12% chromium. For occasions where welding is required. The lower carbon content minimizes carbide precipitation in the heat-affected zone near the weld, which can lead to intergranular corrosion (weld erosion) of stainless steel in some environments.

surface marks

The phenomenon of surface marks refers to the occurrence of wire-mounted or point-shaped pit marks on the surface of 304 stainless steel after deep processing or grinding of processed products.

Reason: There are foreign objects on the surface and mold surface, and there are scars on the surface of the blanking pad.

Countermeasures: Remove foreign bodies, scars, and orange peel by fully grinding before processing.

The orange peel phenomenon refers to the phenomenon that the surface of 304 stainless steel moldings has a shape like orange peel under grinding or other conditions.

Reason: Insufficient grinding, the larger the processing, the more serious the orange peel, the coarse grains of the raw materials, and the softening of heat treatment.

Countermeasures: Fully grind the deep-processed products, select suitable heat treatment conditions, and control the grain size of the raw materials.