方管斷面設(shè)計(jì)時(shí)要考慮兩個(gè)主要因素：一個(gè)是斷面的安全性；另一個(gè)是斷面的經(jīng)濟(jì)性。為了斷面安全，我們要求H型鋼的腰厚與高度之比應(yīng)不小于1/45。對(duì)作柱用的H型鋼，是用扭轉(zhuǎn)半徑與其質(zhì)量之比來表示其經(jīng)濟(jì)性。性理論用來計(jì)算靜態(tài)結(jié)構(gòu)，如倉(cāng)庫(kù)、房屋、橋梁等是可行的，但對(duì)運(yùn)動(dòng)構(gòu)件如車輪等就不太適用，這時(shí)人們往往采用塑性理論。它主要用于靜載荷平面梁和受到彎曲應(yīng)力的框架結(jié)構(gòu)，其要求如下：對(duì)于高層建筑，還需要進(jìn)行更細(xì)致的計(jì)算。塑性設(shè)計(jì)方法在動(dòng)載荷情況下，通常是按許用應(yīng)力不小于動(dòng)載荷再乘以許用應(yīng)力的安全系數(shù)的方法進(jìn)行許用應(yīng)力的計(jì)算。在一個(gè)軸受彎曲的情況下，可用公式a=W動(dòng)/W許進(jìn)行計(jì)算。用塑性方法代替性方法計(jì)算強(qiáng)度，可以提高構(gòu)件的承載能力14%。

There are two main factors to be considered in the design of square pipe section: one is the safety of the section, the other is the economy of the section. For the sake of section safety, the ratio of waist thickness to height of H-beam should be no less than 1/45. For H-section steel used as column, its economy is expressed by the ratio of torsion radius to its mass. Sex theory can be used to calculate static structures such as warehouses, houses and bridges, but it is not suitable for moving components such as wheels. At this time, people often use plastic theory. It is mainly used for static load plane beams and frame structures subjected to bending stress. Its requirements are as follows: for high-rise buildings, more detailed calculation is needed. In the case of dynamic load, the allowable stress is usually calculated by multiplying the allowable stress by the safety factor of the allowable stress. In the case of bending of an axle, the formula a=W/W may be used for calculation. By using the plastic method to calculate the strength, the bearing capacity of the component can be increased by 14%.

由于方管成型在機(jī)組設(shè)備和冷彎工藝上有著共同性，模輥的組合化是生產(chǎn)標(biāo)準(zhǔn)化，系列化型材的必然選擇。這幾年國(guó)內(nèi)機(jī)組上組合模輥發(fā)展很快，也出現(xiàn)了許多技術(shù)創(chuàng)新，大大降低了模輥投入成本，提高了機(jī)組效益?？墒腔旧鲜菍?duì)原有模輥的局部改進(jìn)，加了一些墊圈，組合方式缺乏科學(xué)性，結(jié)構(gòu)大同小異，換輥時(shí)間長(zhǎng)。

Because square tube forming has commonality in unit equipment and cold bending process, the combination of die roll is the inevitable choice for standardization of production and serialization of profiles. In recent years, the combined die rolls on domestic units have developed rapidly, and many technological innovations have emerged, which greatly reduces the input cost of die rolls and improves the unit efficiency. However, it is basically a partial improvement of the original die roll, with some washers added. The combination mode is lack of scientific nature, the structure is much the same, and the roll change time is long.