A4-70 is not 316; it is an expression for fasteners.
Fastener manufacturers can use to meet the A4 all the materials to manufacture, this labeling focus on mechanical properties. Components can look at the fastener-related standards.
Generally speaking A4-70, can be manufactured with the following materials.
00Cr17Ni14Mo2
00Cr17Ni12Mo2
00Cr17Ni13Mo2N
The corrosion resistance of these materials is basically equivalent to that of 316.
A2-70 means.
A for austenitic stainless steel.
2 stands for 304 material.
A2-70 means: A stands for austenitic stainless steel; 2 stands for 304 material; 70 stands for the tensile strength of standardized parts shall not be less than 700.
A4-70 means.
A stands for austenitic stainless steel; 4 stands for 316 material; A4-70 means: A stands for austenitic stainless steel.
4 stands for 316 material; A4-70 means: A stands for austenitic stainless steel.
A4-70 means: A is for austenitic stainless steel; 4 is for 316 material; 70 is for standard parts with tensile strength not less than 700.
A2-70 and A4-70 stands for 700N per square millimeter of tensile strength.
A2-70, A4-80 and other performance marking indicates that the fasteners are manufactured from austenitic stainless steel materials, due to the austenitic stainless steel materials are more varied, so that each of the names indicated are not a steel number, but a class of steel number.
The performance mark consists of two parts: material group and performance grade.
The first part of the code (“_” before) indicates the material group;
The second part of the number (“_” after) indicates the performance level of the product, the number of nominal tensile strength (ob, N/mm * mm) of 1/10.
Material groups are divided into A, C, F three categories; Class A indicates austenitic steel A1 ~ A5; see GB3098.6-2000 for details.
Supplement: The above listed U.S. AISI/ASTM steel number corresponds to China's austenitic steel number are:: 304-0Cr19NiOi
304-0Cr19Ni9(0Cr18Ni9)316-0Cr17Ni12Mo2
316L-00Cr17Ni14M02 317-0Cr19Ni13Mo3
317L-00Cr19Ni13Mo3(00Cr17Ni14Mo3)
Identification of screws is made possible by the markings done on the head. Some specifications call for the use of marking on the heads, simply because it is easier to track the material. The markings are either in the form of a Code Or Reference. Usually, the code or the reference is to be either forged, stamped, or could even be engraved on the head of the screws. It is also possible to identify these stainless steel grades simply by the performance of a material test. A material test report or as known as a mill test report, detail the chemistry of an alloy. This test may also offer the buyer additional information such as the mechanical strength of the alloy as well as its physical properties.
Although the tensile and yield strength values for grade A2 or Alloy 304 tend to be at significantly higher levels in comparison to conventional low carbon steel alloys, they are weaker in comparison to alloy steel grades such as 8.8 or even 10.9. Whereas grade A4 is stronger than grade A2, and its tensile properties are almost similar to alloy steel grade 8.8.
