Stainless Steel Wire Mesh Quality Inspection Standards

2024-06-14 11:12:01 wiremeshxr

Stainless steel mesh is the most common, widely used, and largest-selling metal wire mesh on the market. What people usually refer to as stainless steel mesh is mainly stainless steel woven mesh.

1. Stainless steel knowledge: Stainless steel mesh

Before talking about stainless steel woven mesh, let us first briefly introduce the relevant knowledge of stainless steel:

Any steel that has high chemical stability in the air, water, seawater or various acid, alkali, salt and other aqueous solutions, and does not oxidize, rust or corrode even if placed in them for a long time, is generally called stainless steel.

Stainless steel is a large series of special steels. It plays a role that other steel types cannot replace in the chemical, petroleum, electronics, defense and other industries. At present, the most used metal woven mesh is stainless steel wire. Therefore, we need to understand the influence of several main elements in stainless steel on the performance of stainless steel:

1. Chromium (Cr) is the main factor that determines the corrosion resistance of stainless steel. Metal corrosion is divided into chemical corrosion and non-chemical corrosion. At high temperatures, metal directly reacts with oxygen in the air to form oxides (rust), which is chemical corrosion; at room temperature, this corrosion is non-chemical corrosion. Chromium can easily form a dense passivation film in an oxidizing medium. This passivation film is stable and complete, firmly combined with the base metal, completely separating the base from the medium, thereby improving the corrosion resistance of the alloy. 11% is the lowest limit of chromium content in stainless steel. Steel with a chromium content of less than 11% is generally not called stainless steel.

2. Nickel (Ni) is an excellent corrosion-resistant material and is the main element that forms austenite in steel. After adding nickel to stainless steel, the structure changes significantly. As the nickel content in stainless steel increases, austenite increases, and the corrosion resistance, high temperature resistance, and processing resistance of stainless steel are enhanced, thereby improving the cold processing performance of steel. Therefore, the higher the nickel content of stainless steel, the more suitable it is for drawing fine wires and micro wires.

3. Molybdenum (Mo) can improve the corrosion resistance of stainless steel. Adding molybdenum to stainless steel can further passivate the surface of stainless steel, thereby further improving the corrosion resistance of stainless steel. Molybdenum cannot form precipitation in stainless steel, thereby improving the tensile strength of stainless steel.

4. Carbon (C) is represented by "0" in stainless steel. One "0" means the carbon content is less than or equal to 0.09%; "00" means the carbon content is less than or equal to 0.03%. Higher carbon content will reduce the corrosion resistance of stainless steel, but it can increase the hardness of stainless steel.

There are many types of stainless steel grades, including austenite, ferrite, martensite and duplex stainless steel. Since austenite has the best comprehensive performance, is non-magnetic and has high toughness and plasticity, austenitic stainless steel is the best stainless steel wire for wire mesh processing. Austenitic stainless steel has grades such as 302 (1Cr8Ni9), 304 (0Cr18Ni9), 304L (00Cr19Ni10), 316 (0Cr17Ni12Mo2), 316L (00Cr17Ni14Mo2), and 321 (0Cr18Ni9Ti). From the content of chromium (Cr), nickel (Ni), and molybdenum (Mo), 304 and 304L wires have good comprehensive performance and corrosion resistance, and are currently the most used wires for stainless steel mesh; 316 and 316L contain high nickel and molybdenum, which are most suitable for drawing fine wires, and have good corrosion resistance and high temperature resistance. They are the best choice for high-mesh dense mesh.

In addition, friends who do wire mesh processing need to be reminded that stainless steel wire has a time effect. After it has been placed at room temperature for a period of time, the processing deformation stress is reduced. Therefore, stainless steel wire that has been placed for a period of time is better for making woven mesh.

Since stainless steel mesh is acid-resistant, alkali-resistant, high-temperature-resistant, tensile-resistant and wear-resistant, it is particularly suitable for screening and filtering under acidic and alkaline environmental conditions, such as mud mesh in the petroleum industry, filter mesh in the chemical and chemical fiber industry, pickling mesh in the electroplating industry, and for gas and liquid filtration and other media separation in metallurgy, rubber, aerospace, military, medicine, food and other industries.

2. Classification of stainless steel woven mesh:

1. Stainless steel square hole mesh Stainless steel mesh

(1) Specifications and definitions of square hole mesh:

The specifications of the square mesh are expressed by the basic size of the mesh and the wire diameter. For example, the square mesh with the specification of "0.15/0.1" has a mesh of 0.15mm and a wire diameter of 0.1mm. The mesh is interwoven by radial wires and weft wires, so it is also divided into radial mesh and weft mesh. When the radial mesh = weft mesh, it is a square mesh. When the radial mesh is larger than the weft mesh, it is called a radial long hole mesh; when the radial mesh is smaller than the weft mesh, it is called a weft long hole mesh. The diameters of the warp and weft wires of the square mesh are equal, and the warp shrinkage is generally greater than the weft shrinkage (that is, the warp wire is more curved in the mesh); the square mesh has both plain weave and twill weave.

(2) Porosity and filtration rate of square hole mesh:

The opening rate of the square mesh refers to the percentage of the total mesh area of the metal mesh to the area of the metal mesh. The size of the opening rate directly affects the screening efficiency of the screen. The screen with a large opening rate has a higher screening rate. When the square mesh is used as a filter, it can block the minimum diameter size of most solid particles, which is called the filtration degree of the square mesh. The filtration degree of the square mesh is its mesh size.

(3) Due to the length of the article, we will not introduce the 23 main mesh defects, their causes and prevention methods of square mesh in detail today. If you are interested, you can call our hotline 7722111 and we will give you a detailed introduction.

(4) The influence of the square mesh (hole/wire) ratio on the weaving process:

From the perspective of weaving theory, the (hole/wire) ratio of the square mesh should not be less than 1. It is generally difficult to weave when the (hole/wire) ratio is less than 1, and its minimum limit is 0.7. Usually, high-mesh square mesh with a weaving ratio of 1-1.5 is mostly woven with twill. However, when the ratio is greater than 1.35, especially greater than 1.5, it is advisable to use plain weave. If twill weaving is used, the warp and weft wires are not easily interwoven and the mesh is skewed; when the ratio is less than 1.35, it is advisable to use twill weaving. If plain weaving is used, a large number of warp breaks are easily generated, which greatly increases the difficulty of weaving the mesh.

(5) Characteristics and applications of square hole mesh:

Features: smooth mesh surface, mesh bending, tight interweaving, precise mesh openings; uniform structure, uniform thickness, acid and alkali resistance, corrosion resistance, etc. Suitable for petroleum, chemical, rubber, metallurgy, medicine, food and other industries.

2. Stainless steel dense mesh (commonly known as mat-type mesh)

(1) Specifications and definitions of dense mesh:

The specifications of dense mesh are expressed by "warp mesh number x weft mesh number / warp diameter x weft diameter". Its wire diameter can be as thin as 0.02mm, and its mesh number can be as high as 2800 meshes. From the specifications of dense mesh, it can be seen that its warp and weft wire diameters and warp and weft mesh numbers are different. Generally, dense mesh is interwoven with coarse warp wires and fine weft wires, and the mesh surface presents longitudinal convex stripes; reverse dense mesh (also called contrast dense mesh) is interwoven with fine warp wires and coarse weft wires, and the mesh surface presents transverse convex stripes. Its radial wires are more than the weft wires per unit area, and the absolute ratio of warp mesh to weft mesh is greater, so it is more difficult to weave; the key to the change of these two is that the mesh opening in a single direction can be equal to zero; this kind of mesh interweaving is dense mesh, commonly known as mat-type mesh. Dense mesh can be woven in plain weave or twill weave.

(2) Filtration degree of dense mesh:

There are three types of filtration degrees of dense mesh: nominal filtration degree, absolute filtration degree, and actual filtration degree. Nominal filtration degree and absolute filtration degree are structural parameters of dense mesh. For a certain specification, it is a fixed value. For all dense meshes, its nominal filtration degree is its nominal pore size, and its absolute filtration degree is its absolute pore size.

The actual filtration degree refers to the filtration degree under actual use conditions. It is directly affected by temperature, pressure, use time, medium viscosity, number of bending times of the filter hole, etc. Therefore, the actual filtration degree is a variable value.

The dense mesh has three layers of filter holes for filtering. The first and third layers are the filter holes on the front and back sides of the mesh. The filtered substances must first pass through the first or third layer of filter holes. We call these two layers of filter holes the first gate. The second layer of filter holes in the mesh is a cross-sectional triangular hole, which is the hole we calculate the filtration value of the dense mesh. We call it the second gate of the filter. The actual filtration value of the dense mesh is determined by the actual size of the two gates, which are generally not equal in size.

(3) Warp and weft shrinkage of dense mesh:

In general, the warp is thick and the weft is thin, so the warp does not bend in the net, so there is no warp shrinkage; while the weft is greatly deformed in the net, so the weft shrinkage is also large. In the reverse dutch mesh, the warp is thin and the weft is thick, so the weft does not bend in the net, so the warp is greatly deformed, so the warp shrinkage is also large. The size of the weft shrinkage of the dutch mesh directly affects the weaving quality of the mesh. The dutch mesh with a large weft shrinkage has a large weft clamping force, and it is easy to have bright spots of weft breakage.

(4) Characteristics and applications of dense mesh:

Features: high precision, precision, stable filtering performance, high load strength, high temperature resistance, high pressure resistance, corrosion resistance, etc.

Applicable to aviation, aerospace, military industry, scientific research, petroleum, chemical fiber, metallurgy, medicine, food and other industries.

3. Stainless steel mesh is classified by weaving type:

The weaving form of stainless steel woven mesh has developed from the simplest plain weave (two-harness) to multi-weave (5-harness, 8-harness or above) weaving; the mesh surface has developed from single layer to multi-layer, and there are more and more weaving forms.

1) 1/1 plain weave 2) plain dimpled weave 3) incompletely covered twill dimpled weave 4) 2/2 twill 5) 1/2 half twill 6) fully covered twill dimpled weave 7) broken twill 8) reverse plain dimpled weave 9) reverse twill dimpled weave 10) herringbone twill 11) herringbone twill 12) V-shaped twill 13) 5-harness satin 14) weft knitting 15) warp knitting 16) spiral string weave…

Here is a brief introduction to the three commonly used weaving methods:

(1) Plain weave

Plain weave is a method in which every other warp and weft yarn are interwoven up and down. It is the simplest, most common and most common weaving method.

(2) Twill weave

The characteristic of twill weaving is that the warp interlacing points or weft interlacing points continuously form a sagittal twill cycle on the mesh surface, and there must be at least 3 warp threads and 3 weft threads. These two conditions are indispensable. The twill lines that tilt from the lower right to the upper left are called left twill; the twill lines that tilt from the lower left to the upper right are called right twill.

(3) Satin weave

Satin weaving is a more complex weaving process. Its main feature is that the interlacing points are not continuous, but are evenly and sparsely distributed in a cycle. Its interlacing parameter R is greater than or equal to 5, that is, the number of warps or wefts in a cycle of the interlacing points of the satin mesh should be at least 5, and the interlacing point flying number S (the number of interlacing points between each other is called the interlacing point flying number) and R are not integer multiples of each other and cannot have a common divisor, otherwise the distribution of the interlacing points will be uneven.

3. The inspection of stainless steel woven mesh must be carried out in accordance with the technical requirements of the national standard GB/T5330-2003, and the relevant measuring tools and testing instruments must be used correctly. The quality inspection of stainless steel square hole mesh is 100% inspection, and no random inspection method is used.

1. Inspection of stainless steel wire diameter, deviation and material quality. The surface of stainless steel wire should be smooth and bright, without longitudinal marks, burrs, rust and other defects; the wire diameter tolerance should meet the regulations and the material should meet the requirements.

2. Inspection of weaving precision. It is divided into 3 levels: first-level precision, the mesh limit deviation cannot exceed 6%; second-level precision does not exceed 9%; third-level precision does not exceed 12%; mainly the inspection of the arithmetic mean of the mesh and the inspection of the large mesh size.

3. Inspection of weaving quality. It is impossible for metal wire mesh to be free of manufacturing defects during the production process. Generally, metal wire mesh delivered in rolls is not allowed to have major defects, but a small number of important defects and a certain number of general defects are allowed.

Major defects mainly refer to:

(1) The warp and weft are not interwoven firmly. When rubbing the warp and weft threads up and down with the fingers of both hands, the warp and weft threads are obviously loose and displaced.

(2) Severe curling, mesh size greater than or equal to 0.18mm, 1m long mesh surface natural curling diameter less than 80mm; mesh size less than 0.18mm, 1m long mesh surface natural bending diameter less than 60mm, should be judged as unqualified;

(3) The mesh is seriously tilted, and the warp and weft threads on the mesh surface are not vertical by more than 4 degrees in the width of the weaving width;

(4) Multiple creases over a large area;

(5) The radially large mesh size exceeds the tolerance;

(6) Large area density is out of tolerance;

(7) There is a large area of weft running and the mesh surface is uneven;

(8) The diameters of the warp and weft yarns are seriously out of tolerance;

(9) Holes, half-cut wefts, and large forks;

(10) Severe color unevenness over a large area and severe mechanical damage.

The main defects are:

1) Forks and holes (more than 3 broken warps); 2) Half-cut wefts (length greater than 50mm); 3) Partial unevenness of the mesh surface; 4) Sparse and dense lines; 5) Local wrinkles, creases, and ripples; 6) Slight curling; 7) Slight mesh slant; 8) Large skipped lines (length greater than 10mm); 9) Large loose lines, double lines, parallel lines (length greater than 30mm), ruffles or wavy edges.

General defects refer to: single broken wire, weft nest, back nose, small loose wire, small jumper, wrong twist, slightly uneven mesh surface, slight curling, dotted oil stains, small debris, slightly wavy edges, etc. The number of general defects cannot exceed 5 per 10 square meters.

4. Inspection of mesh width and length. The standard mesh roll length of the wire mesh is 30.5 meters, and only a positive tolerance of +0.5m is allowed, and negative tolerance is not allowed. Each roll of mesh can be composed of 1 section or up to 3 sections, and the minimum length of the smallest mesh section should be no less than 2 meters; within the mesh width of 2 meters, only a positive tolerance of +20mm is allowed, and negative tolerance is not allowed.

5. Inspection of dense mesh. Unlike square hole mesh, the inspection of mesh size between warp threads and weft thread density is measured using a steel ruler with a graduation value of 1mm or a reading microscope with a graduation value of 0.05mm and a magnification of 25 times. There are at least 3 measuring points, and the connecting lines between each point must not be parallel to the warp and weft lines. The distance between the measuring points and the edge of the mesh must not be less than 20mm; the number of large mesh holes between warp threads is allowed to not exceed 3% of the total number of warp threads. The specifications of the dense mesh, the deviation of the mesh size between warp threads, and the density of the weft threads should comply with the national standards. The dense mesh should be flat and clean, and the weft threads should be closely arranged without gaps or bright paths; there should be no mechanical damage, creases, rust spots, etc.