How should the bolts be maintained?

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Bolt fasteners have become a very important part of the mechanical field, which means that we usually need to pay attention to the maintenance and maintenance of bolts, so that they can play the greatest role in the mechanical field. If they are not standardized in use, they will reduce Its service life. For the maintenance of bolts, we should do the following

1. When heating the standard parts, it should be noted that they should be stacked reasonably. If there is a deviation, the standard parts will be slightly oxidized in the quenching oil, and there will be a phenomenon of discoloration when the tempering is delayed. , If you use ether to soak it again, oily impurities are very likely to appear.
2. Standard parts are generally cleaned with silicon-hydrochloric acid cleaning agents after quenching. They must be cleaned first and then rinsed. Be careful when rinsing them, and thoroughly check the rinsing tank to avoid leaving other substances. In the above, and the water used for rinsing must be changed frequently, otherwise the products produced may have quality problems.
3. When the standard parts are about to be heat-treated, they must be cleaned thoroughly, especially the alkaline substances remaining on the surface of the standard parts. If the impurities cannot be completely removed, the standard will be removed at high temperature. The part is burned, and when it is tempered again, it will make the standard part a waste.
4. If the quenching oil cannot be replaced in time when it is in use, it will cause pollution residues and black stripes on its appearance, which will cause its appearance to be very unsightly.

Decho is a professional supplier on bolts and nuts products . If you need any , pls contact us by email [email protected]

What is the correct installation method for stainless steel flanges?

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What is the correct installation method for stainless steel flanges?

1. the stainless steel flange should have sufficient strength and not deform when tightened. The flange sealing surface should be flat and clean, and the oil stains and rust spots should be carefully cleaned up when installing the stainless steel flange.

2.the gasket should have good oil resistance and anti-aging properties, as well as good elasticity and mechanical strength. When installing stainless steel flanges, seal gaskets of different cross-sections and sizes should be selected according to the shape of the connection, and placed correctly.

3. the fastening force of the stainless steel flange should be uniform, and the compression of the rubber gasket should be controlled at about 1/3. In addition, stainless steel flanges are used according to normal methods and principles in actual use. Stainless steel flanges ensure quality and value in use, and are used and installed in accordance with normal use standards. There are no certain quality and performance issues. The stainless steel flange is not a simple mechanical part in the usual sense. The stainless steel flange is a mechanical product carrier that contains abundant technical connotations, which is used in many equipment processing. Hydraulic oil stainless steel flange is a disc-shaped part, the most common in pipeline engineering, stainless steel flanges are used in pairs. Any connecting parts that are bolted on two planes and blocked at the same time are generally called ” “Flange”, such as the connection of ventilation pipes, this type of part can be called “flange type parts”. But this kind of connection is only a part of the equipment, such as the connection between the flange and the water pump, it is not good to call the water pump “method” “Blue parts”. Smaller ones, such as valves, can be called “flange parts”. In pipeline engineering, stainless steel flanges are mainly used for pipeline connection. In the pipelines that need to be connected, a variety of flanges are installed, low-pressure pipelines can use wire flanges, and welding flanges for pressures of more than 4 kg. Add sealing points between the flanges, and then fasten them with bolts. Flanges with different pressures have different thicknesses and use different bolts. Water pumps and valves, when connected to pipelines, are also made of parts of these equipment The corresponding flange shape is also called flange connection.

Decho is a professional supplier of flange products . If you need any , pls contact us by email [email protected]

Weldability and its test evaluation for carbon steel material

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Carbon steel weldability and its test evaluation

1. Welding:

A process in which two objects are combined between atoms to form an inseparable whole by heating or pressing, with or without filling materials.

2. Weldability:

refers to the ability of homogeneous or dissimilar materials to be welded to form a complete joint and meet the expected use requirements under the conditions of the manufacturing process.

3. The four major factors that affect weldability are:

material, design, process and service environment.

4. The principles for assessing weldability mainly include:

①Assess the tendency of welding joints to produce technological defects, and provide a basis for formulating reasonable welding procedures;

②Assess whether the welded joints can meet the requirements of structural serviceability; design new welding test methods to meet the following requirements The stated principles: comparability, pertinence, reproducibility and economy.

5. Carbon equivalent:

The content of alloying elements in steel is converted and superimposed according to the equivalent of several carbon content, which is used as a parameter index to roughly evaluate the cold crack tendency of steel.

6. Oblique Y-shaped groove butt joint crack test:

The purpose is mainly to identify the cold crack tendency of the first layer of low-alloy high-strength steel welds and HAZ, and it can also be used to develop welding procedures.
1) Preparation of the test piece, the thickness of the welded steel plate δ=9-38mm. The grooves of the butt joints are processed by mechanical methods, and the two ends of the test plate are welded within a range of 60mm, and the two-sided welding is adopted. Take care to prevent corner deformation and incomplete penetration. Ensure that there is a gap of 2mm at the weld of the sample to be welded in the middle.
2) Test conditions: The electrode selected for the test weld matches the base metal. The electrode used should be strictly dried. The diameter of the electrode is 4mm, the welding current (170±10) A, the welding voltage (24±2) V, and the welding speed ( 150±10) mm/min. The test welds can be welded at various temperatures, and the test welds are welded only one line without filling the groove. After welding, let it stand and cool down for 24 hours, and then take samples and conduct crack detection.
3) Detection and calculation of crack rate. Use the naked eye or hold a 5-10 times magnifying glass to detect whether there are cracks on the surface and section of the weld and heat-affected zone. It is generally believed that when the surface crack rate of low-alloy steel “Xiaotieyan” test is less than 20%, cracks generally do not occur.

7. Latch test:

purpose, mainly to evaluate the hydrogen-induced delayed cracking tendency of steel. With other equipment, it can also measure reheat crack sensitivity and laminar sensitivity.
1) For the preparation of the test piece, take the welded steel processing or cylindrical bolt test bar, take samples along the rolling direction and indicate the position of the bolt in the thickness direction. There is a ring or spiral gap near the upper end of the test bar. Insert the pin test rod into the corresponding hole of the bottom plate so that the notched end is flush with the surface of the bottom plate. For plug test rods with annular notches, the distance a between the notch and the end surface should be such that the penetration depth of the weld bead is tangent to or intersects with the cross-sectional plane of the notch root, but the penetration of the notch root circumference shall not exceed 20%. For low alloy steel, the a value is 2mm when the welding heat input is E=15KJ/cm.
2) In the test process, according to the selected welding method and strictly controlled process parameters, a layer of surfacing weld bead is melted on the bottom plate, the center line of the weld bead passes through the center of the sample, and the penetration depth should be such that the tip of the notch is located in the heat affected zone In the coarse-grained region, the weld bead length L is about 100-150mm. When welding, the cooling time value t8/5 value of 800-500℃ should be measured. When welding is not preheated, load it when it is cooled to 100-150℃ after welding; when preheating before welding, it should be 50- higher than the preheating temperature. Load at 70°C. The load should be applied within 1 min and before cooling to 100°C or 50-70°C higher than the preheating temperature. If there is post-heat, load it before post-heat. When the test bar is loaded, the bolt may break within the duration of the load, and record the load time.

Decho is a professional supplier on carbon steel pipes . If you need any , pls contact us by email [email protected]

What are the technical requirements for elbows in engineering projects?

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What are the technical requirements for elbows in engineering projects?

1. Since most of the pipe fittings are used for welding, in order to improve the welding quality, the ends are beveled, with a certain angle and a certain side. This requirement is also strict, how thick the side, how much angle and deviation The scope is stipulated. The surface quality and mechanical properties are basically the same as the pipe. For the convenience of welding, the steel grade of the pipe fitting and the pipe being connected is the same.

2. All pipe fittings must undergo surface treatment, and the oxide scale on the inner and outer surfaces shall be sprayed off by shot blasting, and then coated with anticorrosive paint.

3. For the packaging requirements of small pipe fittings, a wooden box is required, about 1 cubic meter, and the number of elbows in this box cannot exceed one ton. Sets are allowed, that is, large sets and small sets, but the total weight generally cannot exceed 1 ton. . For large-diameter elbows, single packaging is required, such as 24″ must be individually packaged. The other is the packaging mark, which must indicate the size, steel number, batch number, manufacturer’s trademark, etc.

Decho is a professional supplier on elbow fitting products . If you need any material for your project , pls contact us by email [email protected]

Features and structure shape of butt welding flange

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Butt welding flange is a kind of pipe fittings, which refers to the flange with neck and the transition of round pipe and butt welding with the pipe.

Butt welding flanges are not easy to deform, have good sealing, and are widely used. They have corresponding rigidity and elasticity requirements and reasonable butt welding thinning transition. The distance between the welding port and the joint surface is large, and the joint surface is protected from welding temperature deformation. The horn-shaped body structure is suitable for pipelines with large fluctuations in pressure or temperature or high temperature, high pressure and low temperature pipelines. It is generally used for the connection of pipelines and valves with a PN greater than 2.5MPa; it is also used for transporting expensive, flammable and explosive On the pipeline of the medium.

Production material

WCB (carbon steel), LCB (low temperature carbon steel), LC3 (3.5% nickel steel), WC5 (1.25% chromium 0.5% molybdenum steel), WC9 (2.25% chromium), C5 (5% chromium% molybdenum), C12 ( 9% chromium 1% molybdenum), CA6NM (4 (12% chromium steel), CA15(4) (12% chromium), CF8M (316 stainless steel), CF8C (347 stainless steel), CF8 (304 stainless steel), CF3 (304L stainless steel) ), CF3M (316L stainless steel), CN7M (alloy steel), M35-1 (Monel), N7M (Haast Nickel Alloy B), CW6M (Hasta Nickel Alloy C), CY40 (Inconel)

Connection form : One-sided welding, double-sided nut connection.
Product features : Beautiful appearance, smooth surface, acid and alkali resistance, anti-corrosion, and strong texture performance.
Production process : The material is cut in the sub-oxygen furnace, the whole is forged or the finished product is forged and cut.
Processing method: High-precision CNC lathe turning, CNC radial drilling and drilling.

Product parameter
(1) The diameter of the center circle of the bolt hole: 50mm—-2130mm
(2) Bolt hole diameter: 11mm-30mm
(3) Flange thickness: 12mm-58mm
(4) Tube outer diameter: A(17.2-2032MM) B(14-2020MM)
(5) Flange inner diameter: A (18-2036MM) B (15-2024MM)
(6) Theoretical weight of flange: 0.36kg–234.6kg (DN1800)

Decho is a professional supplier on flanges , if you need any for your project , pls contact us by email [email protected]

What are the connection methods of wear-resistant ceramic pipes?

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Wear-resistant ceramic pipes are widely used in the industrial field, especially in high-wear working environments, such as power plants, cement plants, mines and other enterprises. Wear-resistant ceramic pipes reflect the incomparable advantages of other products.

Wear-resistant ceramic pipe connection method

1. Fixed flange connection

Fixed flange connection means that the flange is directly welded to the pipeline and connected by bolts. However, once the flange is welded, the bolt hole cannot be adjusted, so some drawings will mark the angle of the bolt hole.

2. Live flange connection

The live flange welding head is turned up, so that the bolt hole can be adjusted, and there is no need to correct the position of the bolt hole when connecting with another flange.

3. Welding method

Glue is needed to fix wear-resistant ceramics, but the glue cannot withstand the high temperature during welding. Because the temperature of steel pipe welding is very high, it can be hundreds of degrees in an instant, and the heat transfer speed of steel is very fast, so the welding place needs to keep a certain distance from the ceramic. Leave a distance of at least 2 cm, which is generally called a 2 cm welding end.

Precautions for installation of wear-resistant ceramic pipes

1. In the process of handling and installation, wear-resistant ceramic pipes should be handled with care to avoid serious collisions. In particular, avoid direct contact with or impact on end ceramics by metal equipment.
2. When the wear-resistant ceramic pipe needs to be cut during the installation process, it can be cut with silicon carbide grinding wheel or plasma cutting machine, and gas cutting is not allowed.
3. When the wear-resistant ceramic pipeline is installed, the center line of the pipeline and the pipeline should be aligned to ensure that the two ends are connected accurately, and the amount of misalignment of the two ends should be controlled within 1.0mm.
4. When the flexible pipe socket is used to connect and install the pipeline, the double-end insertion length of the flexible pipe sleeve is adjusted symmetrically. Since the coefficient of thermal expansion of the wear-resistant ceramic pipe is 1/2 of that of the steel pipe, the expansion gap can be reduced by 3-5mm.
5. When using flange connection, the flange end surface must be flush with the wear-resistant ceramic pipe end surface to ensure the reliability of the connection method.

Decho is a professional supplier on wear resistant ceramic pipes , if you need any , pls contact us by email : [email protected]

What is a bimetal composite wear-resistant pipe?

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What is a bimetal composite wear-resistant pipe?

The outer wall of the bimetal composite wear-resistant pipe is made of ordinary seamless steel pipe, which is compounded by a high-chromium cast steel lining through a centrifugal forming process. The outer wall of the elbow is made of shrimp elbows, and the inner layer is made of high-chromium cast steel, which not only has the wear resistance of high-alloy cast steel, but also can withstand pressure, and has higher mechanical properties.

Bimetal wear-resistant pipeline characteristics:

1. Good wear resistance 　 the hardness of super-hard wear-resistant alloy HRC≥46, with good wear resistance and thermal stability.
2. Excellent impact resistance, metal bonding performance, thermal shock resistance 　KMTBCr28 bimetal composite wear-resistant elbow, the bonding surface of the two metals is completely metallurgical, and it is safe and reliable to use. The thermal expansion coefficients of the two are equivalent, and there will be no expansion and contraction. The outer wall of the elbow is made of steel pipe, and the inner lining is made of super-hard wear-resistant alloy. This product not only has the wear-resistant and corrosion-resistant characteristics of high-alloy products, but also has higher mechanical properties and higher impact resistance.
3. Good heat resistance and corrosion resistance. The matrix of super hard alloy material has strong heat resistance and corrosion resistance, and can show good corrosion resistance and wear resistance under high temperature or corrosive environment. Under the interaction of wet state, corrosive media and particle erosion, it is more appropriate to use super-hard wear-resistant alloys used in as-cast state; and under dry conditions where abrasive wear is the main failure mode, use a A super-hard and wear-resistant alloy material that can obtain a martensite matrix through heat treatment.
4. Low composite cost and good quality 　 The wear-resistant tube is manufactured using international advanced lost foam casting technology, with high yield, good product compactness, uniform thickness and stable quality.
5. Convenient transportation, installation and use 　 The bimetal composite wear-resistant pipe can be connected by flange, quick joint, direct welding and other methods. Moreover, due to the high impact resistance of the composite pipe, when a partial blockage occurs during the maintenance of the pipeline system, it can be knocked, hammered, or cut, removed, welded, installed and repaired at will.

 

Decho is a professional supplier of bimetal composite wear-resistant pipe. If you need any for your project, pls contact us by email [email protected]

Welding process of bimetal composite pipe

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The outer wall of the bimetal wear-resistant composite pipe is made of ordinary seamless steel pipe, which is compounded by a high chromium cast steel lining through a centrifugal forming process. The outer wall of the elbow is made of shrimp elbows, and the inner layer is made of high-chromium cast steel, which not only has the wear resistance of high-alloy cast steel, but also can withstand pressure, and has higher mechanical properties.

In the bimetal wear-resistant composite pipe lining alloy material, the hardness and wear resistance are high-chromium wear-resistant white cast iron and high-quality alloy wear-resistant cast steel (collectively referred to as super hard wear-resistant alloy). The hard phase of high chromium cast iron is M7C3 type carbide, its hardness reaches HV1500～1800, so it has good wear resistance, and because the structure of this Ka type carbide is rod-like, it has high toughness . On the basis of traditional ingredients, rare metals and boron carbide hardening agents are added, which greatly increases the hardness and fatigue resistance of traditional products and makes their wear resistance better than other products.

This process is suitable for welding requirements of bimetal composite pipe castings:
1. When installing the bimetal composite pipe, the pipe and the center line of the pipe should be aligned to ensure that the two ends of the pipe are connected accurately. Due to the high hardness of the high chromium alloy lining, only ordinary steel pipes on the outer wall can be welded, and penetration must be performed. When cutting on site, a plasma cutting machine must be selected for on-site cutting according to the thickness of the composite pipe.
2. Select J507 ordinary welding rod with a diameter of φ4.0mm.
3. Generally, DC electric welding machine is used for welding, and AC electric welding machine can also be used for welding.
4. After the bevel welding at both ends is completed, use the reinforcement hoop in the middle of the weld and continue welding with the outer wall of the composite pipe to ensure the firmness of the weld.
5. Avoid welding under 0℃ or low temperature and humidity.
6. Spot welding, symmetrical welding, and then integral welding should be adopted for welding parts to avoid stress concentration casting cracking.
7. In order to ensure the welding quality of the bimetal composite pipe, the welding surface should be cleaned to avoid defects such as oil stains and slag inclusions.

Decho is a professional supplier on bimetal composite pipe, if you need any , pls contact us by email [email protected]

What is the difference between PTFE lined pipe and rubber lined pipe?

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What is the difference between PTFE lined pipe and rubber lined pipe?

Tetrafluoro is a polymer of tetrafluoroethylen, short for PTFE. Polytetrafluoroethylene (Poly tetra fluoroethylene, abbreviated as PTFE), is generally called “non-stick coating” or “easy to clean material”. This material is resistant to acids, alkalis, and various organic solvents, and is almost insoluble in all solvents. At the same time, PTFE has the characteristics of high temperature resistance, and its friction coefficient is extremely low, so it can be used for lubrication and become an ideal coating for easy cleaning of the inner layer of water pipes.

The tetrafluoroethylene lining uses fluorine’s corrosion resistance, high temperature resistance, strong acid and alkali resistance, excellent adhesion, long service life, and strong penetration resistance. The entire spraying of PTFE is a high-tech work, and its process What are the processes?
1. Special spraying process. Before spraying, the surface needs to be roughened by sandblasting and sprayed with a special primer.
2. The fluoroplastic powder is then charged by a high-voltage electrostatic device, and is uniformly adsorbed on the surface of the workpiece under the action of an electric field.
3. After high temperature baking, the clinker particles will melt into a dense protective layer firmly attached to the surface of the workpiece. For example, a 1mm thick coating film also needs to be sprayed and baked repeatedly 5-6 times, usually the thickest Can be sprayed to 2mm.

Lining tetrafluoroethylene is currently a widely used technology. It makes full use of fluorine’s corrosion resistance, high purity cleanliness, non-stickiness, non-wetting, self-lubricating, abrasion resistance, high and low temperature resistance, and insulation During the construction process, the voltage and current are constantly adjusted to the ideal state to achieve the coating effect.

Rubber lining, also known as rubber lining, English translation is rubber lining. It is to stick the processed whole rubber sheet on the metal surface with adhesive to separate the corrosive medium from the metal matrix for the purpose of protection. The rubber used for lining includes natural rubber and synthetic rubber. The rubber used for chemical equipment lining is mostly natural rubber. The main component of natural rubber is a cis-polymer of isoprene, which is vulcanized by vulcanization, and the vulcanized rubber has certain heat resistance and mechanical strength. It can be divided into soft rubber, semi-hard rubber and hard rubber. Hard rubber has good corrosion resistance, aging resistance and strong adhesion to metal; soft rubber has good cold resistance, heat resistance and impact resistance, and has a certain degree of flexibility; while semi-hard rubber is between between the two. Except for strong oxidants and certain solvents, hard rubber can withstand most of the corrosion of inorganic acids, organic acids, alkalis, salts, and alcohols. Therefore, hard rubber lining is used as the main non-metallic anti-corrosion material. Vulcanized rubber can be divided into pre-vulcanized rubber, atmospheric hot water vulcanized rubber and natural vulcanized rubber. Pre-vulcanized rubber should be used in larger pickling equipment.

The above is the difference between the two. Decho can supply you pipeline either with PTFE linning or rubber lining . If you need any for your project , pls feel free to contact us by email [email protected]

PTFE pipeline is the first choice for industrial sewage lining

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Steel-lined PTFE pipe is a kind of green plastic pipe with the most anti-corrosion, wear-resisting, energy saving and environmental protection. Its wide application has accelerated the process of new environmental protection roads in mines to a certain extent. It not only realizes the low-carbon and environmental protection of mine operation, but also saves cost and manpower and material resources for mining investment enterprises, makes mine transportation safer and more reliable, and increases transportation speed.

Now, a new type of plastic pipe that meets the needs of society and has been applied-steel lined PTFE pipe. Most industrial sewage requires extremely corrosion-resistant pipelines, because industrial sewage contains corrosive media, and these corrosive media must be toxic and harmful chemicals. To transport and process these toxic and hazardous chemicals, green anticorrosive steel-lined PTFE pipelines are the best choice.

The tetrafluoroethylene pipe fittings are made of ordinary carbon steel pipe as the matrix, and are lined with thermoplastic polytetrafluoroethylene (Teflon or PTFE, F4) plastic with excellent chemical stability, processed by a specific process. It not only has the mechanical properties of steel pipes, but also has the characteristics of high corrosion resistance of tetrafluoroplastics, anti-scaling, and not easy to grow microorganisms. It is an ideal pipeline for transporting strong acids, strong alkalis, industrial salts and strong corrosive gases.

High chemical stability:
It can withstand all strong acids, including aqua regia, hydrofluoric acid, concentrated hydrochloric acid, nitric acid, fuming sulfuric acid, organic acids, etc., strong alkalis, strong oxidants, reducing agents and various organic solvents. Very suitable for feeding high-purity chemicals. The wide temperature range is -30℃~-250℃. The low friction coefficient is generally only 0.04, which is a very excellent self-lubricating material, and the friction coefficient does not change with temperature changes. Excellent anti-adhesion: the inner wall of the tube is not easy to adhere to colloids and chemicals. Excellent aging resistance, can be used outdoors for a long time. Excellent electrical insulation performance, PTFE is a highly non-polar material with good dielectric properties, extremely high electrical resistance, and a dielectric constant of about 2.0, which is the smallest among all electrical insulation materials. High flexibility and resistance to bending. Part of the tube has high transparency, and the internal fluid condition can be easily observed.

Product advantages:
1) High temperature resistance-working temperature up to 250℃
2) Low temperature resistance-has good mechanical toughness, even if the temperature drops to -196 ℃, it can maintain 5% elongation.
3) Corrosion resistance-It is inert to most chemicals and solvents, and can withstand strong acids and alkalis, water and various organic solvents.
4) Weather resistance-has the best aging life among plastics
5) High lubrication-is the smallest friction coefficient among solid materials.
6) No adhesion-it is the smallest surface tension among solid materials and does not adhere to any substance.
7) Non-toxicity|——non-toxicity to organisms

This product is widely used in electric power, chemical, petrochemical, environmental protection and other industries. Decho is a professional supplier on PTFE pipes, if you need any for your project, pls feel free to contact us by email [email protected]