The screw is a tool to fasten the object's mechanical parts step by step by using the physical and mathematical principles of the oblique circular rotation and friction force. Screw is the general term for fasteners. Screws are indispensable industrial necessities in daily life: tiny screws used for cameras, glasses, clocks and electronics; general screws for television, electrical products, musical instruments, furniture, etc.; large screws and nuts are used for engineering, construction and bridges; large screws and nuts are used for traffic appliances, airplanes, trams and automobiles. Screws play an important role in industry. As long as there is industry on earth, the function of screws is always important. Screw is a common invention in people's production and life for thousands of years. According to the application field, it is the first invention of mankind.
Screw, also known as "screw", "screw" (screw rod). In fact, screw is a general term, and screw, screw rod are different from each other. Screw is generally called wood screw; it is the kind with pointed head at the front end, with large screw pitch, which is generally used to fasten wood products and plastic parts. The screw rod is a machine screw (mechanical screw), which has a flat head at the front end. The screw pitch is small and uniform. It is generally used to fasten metal and machine parts.
The first person to describe the spiral was the Greek scientist Archimedes (ca. 287-212 BC). The Archimedean spiral is a huge spiral in a wooden cylinder that lifts water from one level to another to irrigate fields. The real inventor may not be Archimedes himself. Maybe he just described something that already exists. Perhaps it was the craftsmen of ancient Egypt who designed it for irrigation on both sides of the Nile.
In the middle ages, carpenters used wooden nails or metal nails to connect furniture to wooden buildings. In the 16th century, nail makers began to produce nails with spirals that were able to connect things more firmly. That's a small step from this kind of nail to a screw.
Around 1550, the first metal nuts and bolts used as fasteners in Europe were made by hand on a simple wooden lathe.
Screwdrivers appeared in London around 1780. Carpenters found that screwing a screw with a screwdriver can hold things in place better than hammers, especially when it comes to fine-grained screws.
In 1797, mozley invented the all metal precision screw lathe in London. The following year, Wilkinson made a nut and bolt manufacturing machine in the United States. Both machines produce universal nuts and bolts. Screws were very popular as fixing parts because a cheap method of production had been found at that time.
In 1836, Henry M. Philips applied for a patent for the screw with cross groove head, which marked the great progress of screw base technology. Different from the traditional slotted head screw, the edge of the cross slot head screw head of the cross slotted head screw is different. This design makes the screw driver automatically centered and not easy to slip off, so it is very popular. Universal nuts and bolts can connect metal parts together. Therefore, by the 19th century, the wood used to build houses by machines could be replaced by metal bolts and nuts.
A: Metric screw B: American screw C: English screw
A: Metric mechanical screw: metric
Ex: m3 x 6 – P P B: m3 machine screw, 6mm long, cross, round flat head, black plated
Finish Code: appearance processing specification
Head code: head shape.
Screw head shape. Cylindrical head. Half sunk head. Sink your head. Spherical cylindrical head. Pan head. Half round head. Hexagon.
Screw model: head groove, feature model
Length code: screw length (mm)
A-1: thread code: screw model
Metric screw is directly marked with screw outer diameter,
For example, m3 means the outer diameter of the screw is 3.00mm; M4 is the outer diameter of the screw is 4.00mm
Metric Thread Size x Pitch:
Note: metric screw is located at the back of screw model, and screw pitch is sometimes indicated
For example, m3x0.5, m4x0.70, m5x0.8, M6X1
But because of the standard specification, usually does not mention
A-2: length code: screw length:
Metric screw, directly indicating the length of screw, unit: mm
The total length of screw is only calculated below the head, excluding the head height
Except for flat head screws, the total length of screws is indicated with head height
A-3: drive code / head incision, features
a. Slotted: a word (minus)
Various common screws
Various common screws (20 pieces)
b. Phillips: plus
c. Phil slot: word / cross
d. Hex socket: Hexagon
e. One way: one way
A-4: head code / head shape
a. Flat: flat head (after locking, the top is flush with the work piece)
b. Oval: salad head, o-head, half sunk head
c. Round: round head
Screw unit of measurement
Screw unit of measurement
d. Pan: round flat head
e. Truss: big round flat head
f. Hex: Hexagon
A-5: finish code / appearance treatment
Metric self tapping screw: marking tapping type directly after the product name
Ex: M3 x 6 –PPB,Tapping Type:
M3 self tapping screw, 6mm long, cross, round flat head, black plated
Generally, it is judged as sheet metal or plastic parts based on product category or label
***Teeth per inch***
American gauge screw length must be converted to metric mm size
Conversion formula: (length code / 32) x 25.40 = metric length mm
B-3, B-4, B-5: same as metric system
C-1: Thread Code:
The denominator is 8, and then the numerator number is directly called
Ex: 1 / 8 x 0.50 – ppb: 1 split screw x 0.50 "long, ppb
Ex: 5 / 16 x 0.50 - ppb = 2.5 / 8 x 0.50-ppb: 2-point half screw x 0.50 "long, ppb
Ex: 5 / 32 x 0.50 - ppb = 1.25 / 8 x 0.50-ppb: 1 minute 2.5 cm screw x 0.50 "long, ppb
Ex: 1 / 4 x 0.50-ppb = 2 / 8 x 0.50-ppb: 2 split screw x 0.50 "long, ppb
Note: coarse or fine teeth are sometimes indicated
UNF: fine teeth: more commonly used in electronics
UNCC: coarse tooth: heavy machinery structure is more commonly used
Ex: 3 / 8 x 0.50, UNF – ppb: 3-point fine pitch screw x 0.50 "long, ppb
C-2: Length Code:
For inch indication, it must be multiplied by 25.40 to convert to mm
Measuring with thread gauge, it is metric thread to match with metric thread, and British thread to match with British thread.
You can also use calipers to measure the outside diameter and pitch of the thread.
The outer diameter of metric thread is in mm, such as 6, 8, 10, 12, 18, 20 mm, etc., and pitch is also in mm, such as 0.5, 0.75, 1, 1.5, 2, 3, etc
The outside diameter of British screw thread is in inches (25.4 mm per inch), such as 3 / 16, 5 / 8, 1 / 4, 1 / 2, etc. Therefore, when measuring the outside diameter with metric caliper, there are often irregular decimals.
English pitch is expressed by the number of teeth per inch. Set the caliper at 25.4 mm, and align one ruler tip with the thread tip. If the other ruler tip is aligned with the thread tip, it is British thread. If the thread tip is not aligned, it should be metric thread.
When measuring the pitch, it is better to mark the tip of the thread on the white chalk, which is clear and easy to measure. Measuring metric pitch should measure a length, such as 10, 15, 20, mm, etc., count how many teeth it contains and calculate the pitch
Where the thread size is specified in inches, it is an inch thread, such as G1 ". Metric thread is used to specify thread specification in metric unit millimeter. For example, M30.
The English system is determined by the number of teeth in an inch (2.54 cm), which is generally 55 degrees. The metric system is the pitch determined by the distance between the two teeth tips, which is generally 60 degrees
Anchor screw: a screw used to fasten a machine to the ground. Also called anchor bolt.
The difference between British screw and American screw is very difficult to distinguish by visual inspection. The difference between British screw and American screw is that the angle of rubbing teeth of British screw is 55 degrees, while that of American screw is 60 degrees. These two standard screws can be used in most cases, but 1 / 2 specification screw is not allowed, because British 1 / 2 standard thread is 1 / 2-12 teeth, while American screw is 1 / 2-13 teeth.
The main purpose is to make the industrial products form a fixed body. In use, it often occurs that the teeth can't be sealed tightly, the screw head will be broken if it is locked too hard, or the tooth pattern is bad and the lock is not tight. All these are quality problems. Screws are "quantity products", not hand-made artworks. In mass production, the purpose is to achieve high-precision and stable quality and popular price supply to consumers. The accuracy of screws is usually grade 6G (grade 2, American specification "IFI" is 2A thread), and grade 8g (grade 3, "IFI" is 1A thread) for construction engineering. The value of screws is very important. In the world, there are examples of automobile factories going bankrupt due to poor screw quality; there are also cases of aircraft falling and vehicles overturning due to poor screw quality.
Common types of screws
A: Machine screw: machine screw
B: Tapping screw: tapping screw (used in metal and plastic respectively)
B-1: sheet metal taping screw
B-2: Plastic taping screw
C: Wood screw: wood screw
D: Drywall screw: cement wall screw
E: Self drilling screws (stainless steel drilling screws, composite drilling screws)
F: Expansion screw, four expansion screws, also known as: four gecko. The grade of expansion bolt is 45, 50, 60, 70 and 80. The material of expansion screw is mainly composed of austenite A1, A2 and A4,
1 stainless steel plate, metal plate, galvanized steel plate, engineering installation.
2. Metal curtain wall, metal light compartment and other indoor and outdoor installation
3. Generally, angle steel, channel steel and iron plate shall be installed in combination with other metal materials.
4. Automobile, container, shipbuilding, refrigeration, screw machine equipment assembly engineering.
1. Drilling and tapping, locking once completed, strong binding force.
2. It can save construction time and improve work efficiency.
E-1: stainless steel self drilling screws
E-2: Bi metal self drilling screws
Screws are indispensable industrial necessities in daily life: for example, micro screws are used for cameras, glasses, clocks and electronics; general screws are used for television, electrical products, musical instruments, furniture, etc.; large screws and nuts are used for engineering, construction and bridges; and large and small screws are used for traffic appliances, airplanes, trams and automobiles. Screw plays an important role in industry. As long as there is industry on earth, the function of screw is always important.
There are many types of screws, whether they are micro screws for glasses or large screws for large-scale heavy and electric engineering. The accuracy of screw is usually 6G (grade 2, American specification "IFI" is 2A thread), and the coarse screw used in construction engineering is 1g (grade 3, "IFI" is 1A thread).
a. Carbon steel is divided into low carbon steel, medium carbon steel, high carbon steel and alloy steel.
b. SS-304: stainless steel 304 and 316 are all stainless steel
c. Ss-302: stainless steel 302: good structural toughness
d. Aluminum 5052: aluminum alloy 5052
d. Brass: brass
e. Bronze: Bronze
f. UNS C11000 copper: Antimony copper
The standard parts in the former market are mainly made of carbon steel, stainless steel and copper.
A carbon steel. We distinguish low carbon steel, medium carbon steel, high carbon steel and alloy steel by carbon content in carbon steel.
Low carbon steel C% ≤ 0.25% is usually called A3 steel in China. It is called 1008101510181022 in foreign countries. It is mainly used for grade 4.8 bolts, grade 4 nuts, small screws and other products without hardness requirements. (Note: the drill tail nail is mainly made of 1022 material.)
2 carbon steel 0.25%
3 high carbon steel C% > 0.45%. It's basically not used in the market
4 alloy steel: adding alloy elements to ordinary carbon steel, increasing some special properties of steel, such as 35, 40 Cr Mo, SCM435, 10b38. Fangsheng screw mainly uses SCM435 chromium molybdenum alloy steel, the main components are C, Si, Mn, P, s, Cr, mo.
2. Stainless steel. Performance level: 45, 50, 60, 70, 80
1. Austenite (18% Cr, 8% Ni) has good heat resistance, corrosion resistance and weldability. A1，A2，A4
2 martensite and 13% Cr have poor corrosion resistance, high strength and good wear resistance. C1, C2, C4 ferritic stainless steel. The forging property of 18% Cr is better than that of martensite. The main imported materials on the market are Japan. It is mainly divided into SUS302, SUS304 and SUS316 by level.
Three copper. The common material is brass Zinc copper alloy. H62, H65 and H68 copper are used as standard parts in the market.
The marking format of thread mark is as follows:
Thread code -- thread tolerance zone code (pitch diameter and top diameter) -- screw in length
l) Tolerance zone code is represented by numbers and letters (internal thread is in capital letters, external thread is in lowercase letters), such as 7h, 6G, etc., it should be specially pointed out that 7h, 6G, etc. represent thread tolerance, while H7 and G6 represent cylinder tolerance code.
2) The spinning length is defined as short (s), medium (n) and long (L). In general, the screw thread length is not marked, and the thread tolerance zone is determined by the medium screw in length (n). If necessary, spin length code s or l can be added, such as "m20-5g6g-l". In case of special needs, the value of spinning length can be indicated, such as "m20-5g6g-30".
General coarse thread: feature code m + nominal diameter + thread direction + thread tolerance zone code (pitch diameter and top diameter) - thread thread closing length
General fine thread: feature code m + nominal diameter * pitch + thread direction + thread tolerance zone code (pitch diameter and top diameter) - thread thread length
The right-hand thread is omitted and left-hand thread is indicated by "LH".
M 16-5g6g means coarse thread, nominal diameter is 16, right-handed, pitch diameter of thread tolerance zone is 5g, major diameter is 6G, screwing length is considered as medium length.
M16 × 1 lh-6g means fine thread, nominal diameter is 16, pitch is 1, left-handed, pitch of thread tolerance zone is 6G, and screw in length is considered as medium length.
The marking format is: feature code (cylindrical pipe thread is represented by G, tapered pipe thread is represented by NPT) + dimension code + tolerance class code + rotation direction
G1a -- LH means British non thread sealing pipe thread, size code is 1in, left-handed, tolerance grade is a.
RCL / 2 stands for British thread sealing taper pipe thread, size code 1 / 2in, right-handed.
The main classification includes ordinary screw, machine screw, self tapping screw and expansion screw.
Cap screw cap screw used to be a fastener limited to the whole tooth.
As the name implies, Hex Cap Screw and hex bolt are hexagon type external thread fasteners, which are designed to be turned by wrench. According to ASME b18.2.1, the tolerance of head height and rod length of Hex Cap screw is smaller than that of general hex bolt. Therefore, ASME b18.2.1 hex head screw is suitable for installation where all hexagon bolts can be used, and where large hexagon bolts are too large to be used.
Socket cap screw, also known as socket screw or socket head screw, is a screw with a hexagonal hole in the head. It can be tightened or loosened only after it is inserted into the hole with hex key, Allen wrench or Allen key. The cylindrical head screw is the most commonly used hexagon socket head screw. The head diameter is about 1.5 times of the main thread diameter (1960 series). Other head types include the bottom head cap screw which makes the surface beautiful and the countersunk head cap screw suitable for the conical screw hole. The countersunk design allows the screw head to rotate without being exposed on the surface of the fixed object, so it is often used in places where the surface is small and the traditional spanner is inconvenient to use.
Generally speaking, machine screw is a screw with a diameter less than & frac14; inch (4 ා ~ 12 ා), which is usually full teeth and rotated by a driver, such as slotting, cross or hexagon.
Wood screw, machine screw; but according to different uses, it can be divided into many categories; within the machine screw category, it can be divided into longitudinal fastening screw and transverse expansion screw; according to the screw thread, it can also be divided into:
A: Triangular thread (60 degrees): engagement / locking / expansion
B: Triangular thread for pipe (55 degrees): Union / locking 3)
C: Trapezoidal thread (30 or 29 degrees): power transmission
D: Square thread (90 degrees): power transmission
Stainless steel screw
Screw and shafts for motorcycle
Stainless steel screw
Screw and shafts for motorcycle or bicycle
Stainless steel nano screw
Stainless steel nano screw
Screw and shafts for sewing machining
Socket set screws
Stainless steel thread screws
Stainless steel high low thread screws
Stainless steel machine screws
Stainless steel self drilling screws
Stainless steel self tapping screws
Stainless steel thread cutting screws
Stainless steel tri angular thread screws
P refers to the finger type pan head; a refers to the fingertip tail teeth, and B refers to the flat tail teeth, i.e. PA round head pointed teeth and Pb round head flat mouth steel teeth.
Round head self tapping screw pa
Round head flat tail self tapping screw PB
Round head tapping screw Pt
Round head self tapping screw PWA
Round head and flat tail self tapping PWB
Self tapping PWT with round head and cutting tail
Countersunk head tapping screw Ka
Self tapping screw KB with countersunk head and flat tail
Self tapping screw KT with countersunk head and tail cutting
Self tapping screw with half countersunk head OA
Large head self tapping screw Ba
Large head flat tail self tapping screw BB
Large flat head tapping screw ta
Large flat head flat tail self tapping screw TB
Large flat head tapping screw TT
Thin head self tapping screw CA
Self tapping screw CB with thin head and flat tail
Self tapping ha of cup head hexagon
Dry wall nails / wallboard nails / fiber nails
Round head screw PM
Round head screw with intermediate tooth PWM
Large flat head screw TM
Countersunk screw km
Semicountersunk head screw OM
Large head screw BM
Thin head screw cm
Cup head machine tooth bolt HM
Application common sense
1. Firstly, remove the sludge on the surface of the broken screw, and use the center gun to make the center of the section dead. Then, use the electric drill to install a drill bit with a diameter of 6-8 mm to drill the hole at the center of the section. Pay attention that the hole must be drilled through. After the hole is drilled through, take down the small drill bit and replace it with a drill bit with a diameter of 16mm, and continue to enlarge and drill through the hole of broken bolt.
2. Take the welding rod with diameter less than 3.2 mm, and use small and medium current to carry out surfacing welding in the hole of broken bolt from inside to outside. Half of the whole length of the bolt can be taken at the beginning of surfacing welding. The arc striking should not be too long to avoid burning through the outer wall of the broken bolt. After surfacing to the upper end face of the broken bolt, continue to build up a cylinder with a diameter of 14-16 mm and a height of 8-10 mm.
3. After surfacing, hammer the end face with a hammer to make the broken bolt vibrate along its axial direction. Due to the heat generated by the previous arc and the subsequent cooling, plus the vibration at this time, the broken bolt and the thread of the body will be loose.
4. Observe carefully. When it is found that a small amount of rust leaks from the fracture surface after knocking, M18 nut can be used to cover the bead welding column head and weld the two.
5. Cool slightly after welding, while hot, use a ring spanner on the nut and twist it left and right, or knock the nut end face with a small hammer while twisting back and forth, so as to take out the broken bolt.
6. After taking out the broken bolt, process the screw thread in the frame with a suitable tap to remove the rust and other impurities in the hole.
Screw surface inspection can be divided into two types: one is the inspection before electroplating after screw production; the other is the inspection after the screw is plated, that is, after the screw is hardened, the inspection after the screw surface treatment is completed. After the screw is produced and before plating, we inspect the size, tolerance and other aspects of the screw. See if it meets the national standards or customer requirements. After the surface treatment of screws, we will inspect the plated screws, mainly to check the color of plating and whether there are broken screws. In this way, when we send the screw goods to the customers, the customers can pass the customs smoothly when receiving the goods. Inspection after screw treatment:
1、 Appearance quality requirements
Screw appearance inspection is from the appearance, electroplating and other aspects of inspection.
2、 Inspection of screw plating thickness
1. Measuring method
The use of micrometer, vernier caliper, plug gauge, etc.
2. Magnetic method
Magnetic method is a non-destructive measurement of non-magnetic coating on magnetic substrate by magnetic thickness gauge.
3. Microscope method
Microscope method is called metallographic method. It is to enlarge the etched fasteners on the metallographic microscope with micrometer eyepiece to measure the thickness of coating on the section.
The time flow method is to use the solution that can dissolve the coating to flow on the local surface of the coating, and calculate the thickness of the coating according to the time required for the completion of the local coating dissolution. There are coating drop method, anodic dissolution coulometry method and so on.
3、 Inspection of adhesion strength of screw coating
There are many methods to evaluate the adhesion between the coating and the base metal.
1. There are 3, 6; hot grinding test; 3, 6; hot grinding test.
4、 Inspection of screw coating corrosion resistance
The inspection methods of coating corrosion resistance include: atmospheric explosion test; neutral salt spray test (NSS test); acetate spray test (ASS test), copper accelerated acetate spray test (CASS test); corrosion paste corrosion test (CORR test) and solution drop corrosion test; immersion test, intermittent corrosion test and so on.
There are many ways to call a screw. Everyone may call it different. Some call it screw, some call it screw, some call it standard part, and some call it fastener. Although there are so many names, but the meaning is the same, are all screws. Screw is the general term for fasteners. The principle of screw is to use the physical and mathematical principles of the oblique circular rotation and friction force of objects to fasten the objects step by step.
Screw in daily life and industrial production and manufacturing, is indispensable, screw is also known as the meter of industry. It can be seen that screws are widely used. The application scope of screw is: electronic products, mechanical products, digital products, electrical equipment, mechanical and electrical machinery products. Screws are also used in ships, vehicles, water conservancy projects, and even chemical experiments. Anyway, screws are used in many places. Such as the precision screws used in digital products. DVD, micro screws for cameras, glasses, clocks, electronics, etc.; general screws for TV, electrical products, musical instruments, furniture, etc.; large screws and nuts are used for engineering, construction and bridges; large screws and nuts are used for traffic appliances, aircraft, tramcars and automobiles. Screw plays an important role in industry. As long as there is industry on earth, the function of screw is always important.
There are many types of screws, whether they are small screws for glasses or large screws for large-scale heavy and electric engineering. The accuracy of screw is usually 6G (grade 2, American specification "IFI" is 2A thread), and the rough screw used in construction engineering is 1g grade.
The application range of screws is so wide, so the screw Market is certainly relatively large, the demand is certainly relatively huge, and there are certainly more screw manufacturers in the screw industry. Purchasers in the selection of professional screw manufacturers, we must first understand some professional basic knowledge of screws, such as screw classification standard specification and American screw specification table.
If we want to use a screw, the first thing we need to do is to understand the performance of the screw, which is its characteristics, so that we can use the screw in the most correct place. Because there are many kinds of screws, in these screws, the performance of each screw is different, so the screw has different uses. In order to avoid our wrong use of screws, we must have a certain understanding of the performance of screws, so that we can use screws in the most correct place.
First of all, let's take a look at the self tapping screws. For self tapping screws, the diameter is 0.8mm to 12mm. For this kind of screw is generally with a very high hardness, self tapping screw to go through the screw in test, that is, screw the screw into a test plate, and then check whether the hardness of the screw meets the standard. If it does not meet the standard, we need to analyze the problem? In order to find a solution.
There is also a kind of drilling tail screw. As the name implies, the tail of the screw is generally in the shape of a drill tail. The hardness of this screw is also very strong. Compared with ordinary screws, it not only has a better ability to maintain, but also has a very strong effect in connecting objects. For screws with this performance, it generally does not need auxiliary processing and can be directly applied to the object It is not only convenient to use, but also can greatly improve the efficiency of work. This kind of drill tail screw can be said to be the first choice of staff in various fields.
From the above we can find that when we use screws, it is very important to understand the performance of various screws.
Stainless steel screws are made of metal. There are four ways to prevent metal corrosion, namely, the nature of the material itself, the environment in which it is used, the interface between data and environment, and the improvement of the design of metal structure. If stainless steel screws are manufactured with complete anti-corrosion alloy, unless there is special demand, it is not practical in terms of economy, or the appearance of the screw will produce corrosion The complete isolation of the environmental elements of erosion is not feasible in practice and may be very difficult. The improvement of metal structure design can improve the influence of special conditions in some conditions. However, most stainless steel screws can not be fully modified and their maintenance function is not permanent. Therefore, this method can not basically deal with the problem. As long as the anti-corrosion treatment on the interface, that is, the external anti-corrosion treatment, is the most widely used method.
The anti-corrosion treatment of stainless steel screw surface refers to the application of maintenance layer on the metal surface by various methods. Its function is to isolate the metal from the corrosive environment, so as to prevent the corrosion process, or reduce the contact between the corrosive medium and the metal surface, so as to avoid or reduce the corrosion.
The maintenance layer shall be able to meet the following requests:
1. Corrosion resistance, wear resistance, high hardness
2. The structure is tight and intact with small pores.
3. It has strong separation from the base metal and good adhesion.
4. They are evenly distributed and have a certain thickness.
Maintenance layer is usually divided into metal coating and non-metallic coating. Metal coating refers to the use of metal or alloy with strong corrosion resistance to form a maintenance layer on the surface of metal which is easy to corrode. This kind of coating is also called coating. There are many methods and varieties of metal coating, among which electroplating is the most common, followed by molten metal immersion (hot dip) and chemical surface treatment. Non metallic coating refers to the use of organic polymer materials such as paint, and inorganic materials such as ceramics to form a maintenance layer on the surface of metal equipment or parts. The maintenance layer can completely isolate the base metal from the environmental medium, and avoid the corrosion of the base metal in the stainless steel standard part medium due to contact corrosion.
Moisture proof measures
If the iron screw is wet or soaked in liquid. In or be affected by damp and so on, in this case, it is very likely to rust. So,
In order to prevent the screws from rusting, we have to protect the screws from moisture and moisture. So how to deal with the screw moisture proof and moisture proof! Screw moisture and moisture methods are as follows: (1) vibration machinery as far as possible to use solvent-free paint. (2) It is better to choose the impregnating varnish without oxidation components, such as epoxy urethane base or epoxy - based impregnating varnish. (3) When using cyanuric acid impregnating varnish, the curing temperature and curing time should be adjusted. The curing temperature should be slightly higher than 130 ℃ (e.g. 135 ℃) and the curing time should be longer than 180 min. moreover, the process must be strictly implemented. Especially in the high temperature and humidity season, the rotary vibration screen is not necessarily sufficient for the paint drying (curing) time specified in the paint factory samples from the perspective of rust prevention, The motor has a specific internal shape. (4) Paint without volatile acid is used. (5) Choose the paint with good hydrolysis resistance.