As we all know, plastic doors and windows have become substitutes for steel windows and wood windows because of their good thermal insulation, sound insulation and corrosion resistance. However, due to the immaturity of the market, the price of raw materials has soared while the price of profiles has plummeted, which makes many profile manufacturers have to sacrifice the quality of profiles to reduce costs, add a lot of calcium carbonate to profiles or use cheap raw material additives, and use inferior hardware accessories, ultra-thin ribs and rough plastic window manufacturing technology. After such low-performance products enter the market, it will give users and the whole industry. So how can we improve the overall performance of plastic windows and make high-performance plastic windows? I want to elaborate from the following aspects:

First, the inherent quality of profiles and their reasonable structural design are the prerequisites for manufacturing high-performance plastic windows. First of all, we must have a good formula, high-quality raw materials and advanced production technology to ensure the quality of profiles. In addition, from the profile structure, there are single-cavity and multi-cavity PVC plastic profiles, and the inner cavity can be designed with ribs, ribs, bosses and so on. The cavities can be divided into double-cavity, three-cavity or multi-cavity, so that on the one hand, it can better play the role of heat insulation, on the other hand, it can make each cavity have different uses, some are used to fix the steel lining to improve its rigidity, some are used to set it as a drainage cavity, some have internal ribs to prevent the deformation of the profile, and some have internal ribs to improve the rigidity of the profile. ?

At present, most domestic profiles copy the structure of European profiles, but due to the limitation of market acceptance, the wall thickness is reduced, which will inevitably affect the quality of windows. Due to the actual situation of processing, installation and use, it is difficult to meet the domestic market demand. Therefore, it is urgent to combine the characteristics of European and American profiles, digest and absorb, and develop profiles suitable for China's national conditions. In this respect, our company has made a bold attempt, absorbing some advantages of European profiles while retaining the advantages of American profiles, and using its complex structure and multiple ribs to make up for the wall thickness and increase the moment of inertia. In addition, from the design point of view, the profile should also fully consider several properties such as water tightness, air tightness and wind pressure resistance. ?

Secondly, the overall quality of plastic doors and windows is greatly influenced by the quality and installation accuracy of hardware fittings. Due to the different shapes and sizes of PVC plastic door and window profiles in domestic enterprises, the hardware fittings can not be unified, and it is difficult to mass-produce each variety of accessories and form scale effect. In addition, the overall consumption level of domestic doors and windows is still very low, and the price of PVC plastic doors and windows is limited, which makes the price of PVC plastic doors and windows hardware fittings too low, which makes manufacturers have to reduce costs and make them cheaper to meet the market. Fortunately, the new standard of plastic window hardware is being formulated, hoping to standardize the hardware market. Excellent hardware fittings can improve the overall performance of windows. For example, when multi-point locking is used for casement windows, the sealing performance and wind pressure resistance are much higher than that of single-point locking, and the use performance of corner hinges or adjustable hinges is much stronger than that of ordinary or saddle hinges, which can effectively prevent the fan from sagging. In addition, the gyro with silicified water separator in the middle is much better than the ordinary gyro in air tightness. ?

The reasonable design of the windshield of European sliding window can also greatly improve the sealing performance of the window. In terms of glass mosaic, the bonding method of glass glue for American sliding window is much stronger than that of rubber strip for European sliding window. Its advantages are:

1. Glass glue connects glass and window sash into a whole, which improves the wind pressure resistance of window sash; ?

2. The sealing performance of the glass glue is much better than that of the rubber strip, because the rubber strip is greatly affected by temperature and has poor aging resistance, and there is no problem that the fan is deformed due to improper installation of the glass pad; ?

In a word, the use of hardware fittings with reasonable design and high quality can greatly improve the overall performance of windows. ?

Thirdly, reasonable assembly technology is the key to manufacture plastic windows with excellent performance. At present, there are two common ways to assemble plastic doors and windows in China, one is full welding and the other is welding-rotating. All-welding molding is mainly used for European windows. The technological method is as follows: after cutting the profile according to the specifications of doors and windows, V-shaped grooves and U-shaped saws are carried out at both ends of the profile, and drainage seams, lock holes and matching grooves are milled, and then welded into window (door) frames and window (door) fans. Finally, the frame and fan are closed with hardware fittings. Its advantages are that it is suitable for mass production, rainwater is not easy to invade the inner cavity of the profile, and the steel lining is not corroded by rainwater; Its disadvantage is that the workload is greater than welding-screwing, the production efficiency is low, and the welding quality is not easy to control. Wear the steel lining while it is hot after welding, otherwise it will be difficult to wear it. ?

The process method of welding-screwing molding is as follows: firstly, the door and window profiles are cut according to the specifications of doors and windows, and then the two ends of the profiles are milled and cut into shapes matching the shapes of the window (door) frame and the glass retaining arm outside the window (door), and each drainage seam, keyhole and matching groove are milled; Then the window (door) frame is welded and molded, then the profile is installed on the window (door) frame or fan with screws, finally the hardware fittings are installed, the frame and fan are closed, and the finished product is made by filling with glass and glass battens. ?

Compared with full welding, it has the advantages of quick blanking, simple assembly, no need to cut the V-shaped mouth and the ∧-shaped end, just milling the end and putting the steel lining before welding or tightening, which is very convenient and easy. Four-corner welding machine can be used, which has high working efficiency, and the strength of T-joint is higher than that of welding, and the position of profile can be adjusted, which is convenient for correction. Its disadvantage is that the position and size of screw holes are greatly influenced by human factors, so it is necessary to use end face milling machine, milling cutter, sealant, glass glue or sealing gasket to prevent rain from corroding steel lining, and special "cross" screw holes should be designed on profiles. ?

Welding technology is the key to determine the quality of doors and windows, whether it is full welding or welding rotation. So how to control the welding process?

(1) First, choose the profile that meets the technical standard of GB/T88 14- 1998 "Rigid PVC Profile for Door and Window Frames". The 12 index in the regulation is interrelated and influenced each other. Among them, tensile strength, low temperature drop hammer impact and simply supported beam impact strength have direct influence on fillet strength. When the physical and mechanical properties are unqualified, the fillet strength of the profile is difficult to pass. ?

(2) Control of welding process parameters?

There are five main process parameters for welding PVC plastic doors and windows. These five process parameters and control ranges are as follows:

Welding quality: 2-4mm at each end (2.5mm recommended)?

Welding temperature: 245-265℃ (surface temperature of heating plate)?

Heating time: 20-35s?

Heating welding pressure: 0.45-0.75mpa?

Welding holding time: 25-45s (cooling time)?

These five parameters form a group, and each parameter can be changed. Although there is a lot of choice in the arrangement and combination of parameters, according to practical experience, the welding allowance is generally fixed at 2.5mm (domestic equipment is generally set at 3.0 mm); The heating and welding pressure is 0.5mpa；; The welding heat preservation time is 30s；; Therefore, the adjustable variable parameters in production are reduced to only welding temperature and heating time. These two items also have great influence on fillet strength. Control the welding temperature and heating time, and strive to make the welding end faces of the two profiles become welding slag after the welding margin is completely extruded from the weld, so that the temperature of the welding end faces is just in the ideal 185℃ or in the optimized welding area of the profiles (180℃- 190℃), so as to achieve the best welding angle.

During the strength test of fillet weld, it can be found that there are three kinds of cracking modes of fillet weld:?

The first is to attack along the center of the weld; ?

The second is that a part of the weld center is attacked, and the other part is cracked on the profile at a certain distance from the weld center; ?

The third is that all cracks are on the profile near the weld, but the weld is not cracked. ?

Among these three forms, the first and second forms are the most common, and the third form is rare. When cracks appear in the first form, if the profile is qualified, it must be that the temperature of the weld center is not within the range of excellent plasticizing temperature zone. When the temperature here is higher than 200℃ or lower than 170℃, cracks will appear in the weld center with the lowest mechanical properties. The fillet weld strength of this type of cracks is mostly lower than 3000N, but there are a few exceptions. For example, some profiles have large section size and wall thickness, and crack from the weld, but the strength can still reach above 3000N, which is actually a quality problem that cannot be ignored. The second kind of crack can judge that the welding process and technical parameters are basically correct. The melting temperature of most weld centers is in the excellent plasticizing zone, with good mechanical properties and high strength. The third kind of crack is extremely rare. When it happens, if the mechanical properties of the profile are qualified, the weld is the most ideal and the strength is high. But in fact, if the weld angular strength is less than 3000N, the tensile strength, bending elastic modulus, low-temperature drop hammer impact or simple support of the profile will be low. ?

The previous introduction is how to improve the fillet strength of windows, and air tightness is also a problem that cannot be ignored in the three major properties of windows. The so-called air tightness is the air permeability under the pressure difference between the inside and outside of normally closed doors and windows. There are three unfavorable factors affecting air tightness:?

1) The existence of force difference?

2) the gap?

3) There is a temperature difference. ?

Knowing the reasons that affect air tightness, it is not difficult to find a solution. There are some common solutions in actual production:?

1. Internal and external drainage holes (joints) should not be opposite, but should be staggered from side to side by 50-100 mm; ?

2. The sealing strip of casement window can't bend and deform, and can't form a hard angle; ?

3. The top of the sliding window should be sealed in place, in good contact with the profile, to ensure a certain amount of compression, and the anti-theft windproof block should really play its role; ?

4. The handle is installed reasonably to ensure that the stress around the window sash is uniform and the seal is good; ?

5. Sealing fittings and assembly shall ensure the lap size of window frames. ?

Just like air tightness, there are three reasons that affect the water tightness of windows:?

1) has cracks and holes. ?

2) It rains. ?

3) Pressure difference?

Only when three conditions exist at the same time can leakage occur, and the existence of rainwater is an objective fact and is not affected by human factors. Therefore, the drainage system should be arranged reasonably, and attention should be paid to opening internal and external drainage holes (joints) at the lowest position of the profile as far as possible to avoid water accumulation in the profile. In addition, according to the principle of communication device, rainwater leakage is caused by the fact that the external air pressure is greater than the indoor air pressure+indoor and outdoor water level difference. One of the solutions is to seal the room so that rainwater can't overflow the profile and enter the room. Another method is to increase the height of indoor flashing when designing profiles. Every time the height increases by 10mm, the amount of water that can be blocked per unit area is 1kg. This can effectively prevent water from pouring into the room. ?

The above is my humble opinion, and I hope my colleagues will criticize and correct me.

(originally published in Daming profile 200 1-2)

Selection of plastic steel window:

How to choose plastic steel window Plastic steel window is the fourth generation of new windows developed from wood window, steel window and aluminum alloy window in recent years. It is made of polyvinyl chloride (PVC) and chlorinated polyethylene blended resin as the main body, with a certain proportion of additives, through extrusion processing. In order to increase the rigidity of the profile, the inner cavity of the plastic profile is filled with steel lining (reinforcing rib) which can increase the tensile and bending capacity, and then the window frame is made by cutting, drilling and melting, so it is called plastic steel window.

Classification of ceramic tiles

It not only has the characteristics of plastic products, but also has greatly improved physical and chemical properties and anti-aging ability. Its decoration is comparable to that of aluminum alloy windows, and it has the characteristics of thermal insulation, making the room more comfortable, quiet and modern. In addition, it has the advantages of acid resistance, alkali resistance, corrosion resistance, dustproof, flame retardant and self-extinguishing, high strength, no deformation, harmonious tone and so on. Moreover, it does not need duty paint coating, and it is durable, and its air tightness and water tightness are 2-5 times greater than those of ordinary similar doors and windows.

Opening mode of plastic steel window

The main opening modes of plastic steel windows are push-pull, outward opening, inward opening, inward opening and hanging. The new opening mode is push-pull suspension. Different opening methods have their own characteristics. Generally speaking, sliding windows have the advantages of simple facade, beautiful appearance, flexible use, safety and reliability, long service life, large daylighting rate, less land occupation and convenient screen window. The external window has the advantages of large opening area, sealing, ventilation, air permeability, heat insulation and excellent impermeability. At present, push-pull type is widely used, followed by open type.

Factors to be considered in purchasing plastic steel windows

1, choose the home market where consumers are satisfied or the after-sales service is reliable.

2, to shop around, for the same style, the same brand of goods, from the quality, price, service and other aspects of comprehensive consideration.

3. When choosing profiles, we must first understand the PVC profiles selected for plastic-steel windows. PVC profile is the decisive factor for the quality and grade of plastic steel windows. A good PVC profile should be multi-cavity designed in the example, with thick wall and anti-aging and anti-ultraviolet additives in the formula. From the appearance, it should be smooth and blue and white. The middle and low-grade profiles are yellow in white and have poor sun protection ability. After several years of use, it will turn yellow until it ages, deforms and becomes brittle. The reason is that the calcium content in the profile formula is too high. Considering that most houses have large windows (such as balcony sealing) and many high-rise buildings, the wall thickness of profiles should be greater than 2.5 mm, and the inner cavity should be a profile with three-cavity structure (with closed drainage cavity, isolation cavity and reinforcement cavity) to ensure that the windows will not be deformed for decades. In addition, such profiles are not easy to change color and age.

4. Observe the surface of the model steel window for obvious scratches, debonding, cracks at welding corners, etc.

5. For houses with loud outdoor noise, it is best to choose plastic steel windows and insulating glass, which has excellent sealing and sound insulation effect.

6. When the model steel window is closed, there is no gap between the fan and the window frame. Push-pull plastic steel window should slide freely, with soft voice and no dust falling off.

7. There should be a steel bar in the frame of the plastic steel window. The glass shall be installed flat and firm, without direct contact with the profile. If it is a double-layer glass, there should be no dust and water vapor in the interlayer, and the switch part should be tight and flexible.

8. When designing a window type, you can generally follow the following order: a. Function; B. practical and beautiful; C. ahead.

9. Invoices and contracts must indicate the name, specification, quantity, price and amount of plastic-steel windows.