軋制工藝乳化液的行為及作用機(jī)理的基礎(chǔ)研究
發(fā)布時(shí)間：2018-08-01 14:57
【摘要】：乳化液以其優(yōu)異的潤(rùn)滑及冷卻性能被廣泛應(yīng)用于機(jī)械、金屬材料加工等領(lǐng)域,在軋制過(guò)程中采用乳化液進(jìn)行潤(rùn)滑及冷卻能夠有效降低軋制力、減小摩擦、控制磨損、改善軋材的表面質(zhì)量及機(jī)械性能,對(duì)軋制生產(chǎn)過(guò)程節(jié)能降耗、提高產(chǎn)品質(zhì)量具有重要意義。金屬軋制工藝一般采用水包油型(O/W)乳化液作為介質(zhì),通過(guò)將其噴射在軋制入口區(qū)并隨著軋制過(guò)程帶入變形區(qū)起到潤(rùn)滑及傳熱作用;乳化液在金屬表面上的吸附成膜過(guò)程(Plate-out)以及噴射前的穩(wěn)定性能對(duì)軋制變形區(qū)潤(rùn)滑及傳熱效果的發(fā)揮至關(guān)重要,這些不僅與乳化液的組成成分有關(guān),同時(shí)也受軋制工藝參數(shù)的影響。為了對(duì)軋制工藝潤(rùn)滑及傳熱過(guò)程進(jìn)行調(diào)節(jié)和控制,從而降低軋制能耗、提高產(chǎn)品質(zhì)量,有必要針對(duì)軋制過(guò)程中乳化液的行為及變化規(guī)律開(kāi)展研究,以期為乳化液成分優(yōu)化及軋制工藝控制提供指導(dǎo)。本文以非離子型表面活性劑制備的水包油型乳化液為研究對(duì)象,采用實(shí)驗(yàn)、介觀(guān)/分子模擬和模型計(jì)算相結(jié)合的方法,以乳化液在軋制過(guò)程中的潤(rùn)滑及傳熱為核心,結(jié)合乳化液的穩(wěn)定性及“Plate-out”性能,系統(tǒng)研究了乳化液在軋制過(guò)程中的行為及作用機(jī)理,為乳化液成分設(shè)計(jì)以及軋制工藝過(guò)程優(yōu)化提供理論依據(jù)。具體研究結(jié)果如下:(1)采用靜置實(shí)驗(yàn)及耗散粒子動(dòng)力學(xué)方法對(duì)乳化液的穩(wěn)定性能進(jìn)行了研究,獲得了穩(wěn)定性能與乳化劑HLB值、濃度、機(jī)械攪拌強(qiáng)度、攪拌時(shí)間之間的關(guān)系,分析了油水界面膜特性對(duì)乳化液穩(wěn)定性的作用機(jī)理。當(dāng)非離子型乳化劑HLB值為13,濃度為1.6%時(shí),制備得到的乳化液最穩(wěn)定。油水界面膜厚度隨著乳化劑HLB值的增大而增大,但乳化液的穩(wěn)定性與界面膜厚度之間并非線(xiàn)性關(guān)系,當(dāng)界面張力最低時(shí)乳化液最穩(wěn)定;油滴粒徑隨著HLB值增大而增大,這與乳化劑的分子結(jié)構(gòu)以及親水基團(tuán)與親油基團(tuán)的體積比有關(guān)。(2)對(duì)乳化液“Plate-out”性能進(jìn)行了研究,提出了一種彈性控制乳化液“Plate-out”性能的方法,即在乳化液制備過(guò)程中添加短鏈醇類(lèi)添加劑(丙三醇、1,2-丙二醇、乙二醇、正丙醇),作用于油滴在金屬表面的“Plate-out”行為,從而影響其“Plate-out”性能。采用分子動(dòng)力學(xué)方法構(gòu)建添加劑分子的吸附模型以及“Plate-out”多層吸附構(gòu)型,研究了添加劑分子在“Plate-out”過(guò)程中的行為及作用機(jī)理;發(fā)現(xiàn)添加醇類(lèi)添加劑的乳化液“Plate-out”油膜量大小遵循如下規(guī)律:丙三醇1,2-丙二醇乙二醇正丙醇,但該規(guī)律與添加劑分子在金屬表面的吸附能大小及制備的乳化液油滴粒徑分布之間沒(méi)有必然聯(lián)系。通過(guò)對(duì)“Plate-out”多層吸附膜的分子動(dòng)力學(xué)模擬發(fā)現(xiàn):添加劑分子是通過(guò)影響油滴在吸附油膜上的再吸附過(guò)程對(duì)“Plate-out”性能產(chǎn)生作用,這與油相成分在添加劑體系中的均方根位移以及添加劑分子間的內(nèi)聚能計(jì)算結(jié)果相一致。(3)基于微凸體扁平化理論及平均流動(dòng)模型,建立了軋制變形區(qū)混合潤(rùn)滑模型,并通過(guò)該模型對(duì)不同軋制條件下的界面潤(rùn)滑特性(軋制力、流體壓力分布,真實(shí)接觸面積、油膜厚度變化)進(jìn)行了計(jì)算分析。結(jié)果表明:表面粗糙度、軋制速度、潤(rùn)滑劑粘度的增大均有利于提高軋輥與軋件接觸界面的油膜厚度、降低界面真實(shí)接觸面積,但對(duì)軋制力分布特征沒(méi)有明顯影響;而壓下率的提高不僅提高了真實(shí)接觸面積、降低了油膜厚度,而且增大了軋制力。(4)基于限制層剪切模型從分子尺度研究了潤(rùn)滑劑在剪切過(guò)程中的行為以及對(duì)正壓力、摩擦力和摩擦系數(shù)的影響。結(jié)果表明:限制層間壓力的提高有利于將剪切動(dòng)量從墻面向潤(rùn)滑膜中間區(qū)域傳遞,雖然油膜壓力的提升增大了層間摩擦力,但可以有效地降低摩擦系數(shù)。穩(wěn)定的層狀吸附結(jié)構(gòu)一般出現(xiàn)在距離墻面3nm內(nèi),當(dāng)油膜厚度超過(guò)6nm時(shí),中間區(qū)域?qū)⒈憩F(xiàn)出潤(rùn)滑劑液相特性;油膜厚度與摩擦系數(shù)之間存在一個(gè)臨界值厚度?(8,只有當(dāng)實(shí)際油膜厚度??(8時(shí),摩擦系數(shù)隨膜厚的增大而逐漸減小。剪切速度的提高有利于增大正壓力,降低摩擦系數(shù);溫度的升高不僅提高了正壓力,同時(shí)還降低了吸附膜的固化程度和剪切力,從而有效降低了摩擦系數(shù)。油水混勻體系潤(rùn)滑膜潤(rùn)滑過(guò)程中,油相傾向于吸附在壁面而水則傾向于聚集在中間區(qū)域;含水油膜比純油潤(rùn)滑更能降低摩擦力,當(dāng)油水體積比為1:1時(shí),摩擦系數(shù)達(dá)到最低。(5)為了考慮變形區(qū)內(nèi)部任意點(diǎn)的微凸體扁平化及油膜厚度變化對(duì)界面?zhèn)鳠徇^(guò)程的影響,將本文建立的混合潤(rùn)滑模型引入界面?zhèn)鳠崮Ｐ?對(duì)軋制變形區(qū)的界面?zhèn)鳠嵯禂?shù)及其變化特征進(jìn)行了計(jì)算分析。結(jié)果表明:微凸體界面?zhèn)鳠嵯禂?shù)分布存在兩個(gè)峰值,一個(gè)出現(xiàn)在入口區(qū),另一個(gè)出現(xiàn)在中性面位置;越接近出口處,潤(rùn)滑油傳熱系數(shù)越高,當(dāng)潤(rùn)滑油導(dǎo)熱系數(shù)較高時(shí),其傳熱系數(shù)甚至超過(guò)微凸體接觸傳熱系數(shù);在考慮金屬表面氧化層熱阻時(shí),界面?zhèn)鳠嵯禂?shù)將以數(shù)量級(jí)程度降低;變形區(qū)內(nèi)部界面?zhèn)鳠嵯禂?shù)分布可以劃分為三個(gè)變化區(qū)間,其變化趨勢(shì)主要受壓力分布、真實(shí)接觸面積以及油膜厚度變化的影響。
[Abstract]:The emulsion is widely used in the fields of machinery and metal material processing for its excellent lubrication and cooling properties. The use of emulsion to lubricate and cool the emulsion in the rolling process can effectively reduce the rolling force, reduce friction, control wear, improve the surface quality and mechanical energy of the rolled material, save energy and reduce consumption and improve the quality of the product. In the rolling process of metal, the O/W emulsion is usually used as a medium, and it is lubricated and heat transfer through the injection of the emulsion into the rolling entrance area and with the rolling process into the deformation zone; the adsorption forming process of the emulsion on the metal surface (Plate-out) and the stability performance before the injection are on the rolling deformation zone. The effect of lubrication and heat transfer is very important. These are not only related to the composition of the emulsion, but also influenced by the rolling process parameters. In order to adjust and control the rolling process lubrication and heat transfer process, so as to reduce the rolling energy consumption and improve the quality of the products, it is necessary to focus on the behavior and change rules of the emulsion during the rolling process. The law is carried out to provide guidance for the optimization of emulsion composition and the control of the rolling process. In this paper, the water emulsion emulsified liquid prepared by non ionic surfactants was studied by experiments, mesoscopic / molecular simulation and model calculation, with the lubrication and heat transfer of emulsion in the rolling process as the core, and the emulsification combined with emulsification. The stability and "Plate-out" properties of the liquid are studied. The behavior and mechanism of the emulsion in the rolling process are systematically studied. The theoretical basis for the design of emulsion composition and the optimization of the rolling process are provided. The results are as follows: (1) the stability of the emulsion is studied by the static experiment and the dissipative particle dynamic mechanics method. The relationship between the stability performance and the HLB value of emulsifier, the concentration, the mechanical stirring strength and the stirring time were obtained. The mechanism of the action of the oil and water interfacial film characteristics to the stability of the emulsion was analyzed. When the HLB value of the non ionic emulsifier was 13 and the concentration was 1.6%, the emulsion prepared was the most stable. The thickness of the oil and water boundary mask increased with the increase of the emulsifier HLB value. But it increases, but the stability of the emulsion has a nonlinear relationship with the thickness of the boundary film. The emulsion is most stable when the interfacial tension is the lowest; the droplet diameter increases with the increase of HLB value, which is related to the molecular structure of the emulsifier and the volume ratio of the hydrophilic group to the oil Pro Group. (2) the performance of the emulsion "Plate-out" is studied. A method to control the "Plate-out" properties of emulsion, namely, the addition of short chain alcohols (glycerol, 1,2- propanediol, ethylene glycol, propanol) in the preparation of emulsion, is used to influence the "Plate-out" behavior of the oil droplets on the metal surface, thus affecting its "Plate-out" properties. The molecular dynamics method is used to construct the addition. The behavior and mechanism of additive molecules in the process of "Plate-out" are studied by the adsorptive model of the agent and the "Plate-out" multilayer adsorption configuration. It is found that the size of the "Plate-out" oil film added to the emulsion additive is followed by the following rules: glycerol 1,2- propyl two alcohol glycol propanol, but the law and the additive molecule There is no inevitable relationship between the size of the adsorption energy on the metal surface and the distribution of the droplet size distribution of the emulsion. Through the molecular dynamics simulation of the "Plate-out" multilayer adsorption membrane, it is found that the additive molecules affect the performance of "Plate-out" by the readsorption process of the oil droplets on the adsorbed oil film, which is in the composition of the oil phase. The root mean square displacement in the additive system and the calculation results of the cohesive energy between the additives are in agreement. (3) a mixed lubrication model of the rolling deformation zone is established based on the theory of the flattening of the micro convex body and the average flow model. Through this model, the sliding characteristics of the interface under different rolling conditions (rolling force, the distribution of fluid pressure, real contact) The results show that the surface roughness, rolling speed, and the increase of the viscosity of the lubricant can improve the oil film thickness of the contact interface of the roller and the rolling parts, reduce the actual contact area of the interface, but have no obvious influence on the rolling force distribution, and the increase of the pressing rate not only improves the true connection of the rolling force. The contact area reduces the thickness of the oil film and increases the rolling force. (4) the effect of the lubricant on the shear process and the effect on the positive pressure, friction force and friction coefficient are studied from the molecular scale based on the limiting layer shear model. The results show that the increase of the confining interlayer pressure is beneficial to the shear momentum from the wall to the middle area of the lubricating film. Transfer, although the increase of the oil film pressure increases the interlayer friction, it can effectively reduce the friction coefficient. The stable layered adsorption structure usually appears in the distance wall 3nm. When the thickness of the oil film is over 6nm, the intermediate region will show the liquid properties of the lubricant; there is a critical thickness between the oil film thickness and the friction coefficient (8, only) When the actual oil film thickness is 8, the friction coefficient decreases with the increase of the thickness of the film. The increase of the shear speed is beneficial to increase the positive pressure and reduce the friction coefficient; the increase of the temperature not only increases the positive pressure, but also reduces the curing degree and shear force of the adsorption film, thus effectively reducing the friction coefficient. The lubricating film of the oil and water mixing system is effectively reduced. In the process of lubrication, the oil phase tends to adsorb on the wall and water tends to gather in the middle area; the water bearing oil film can lower the friction force more than the pure oil lubrication. When the oil and water volume ratio is 1:1, the friction coefficient reaches the lowest. (5) in order to consider the influence of the flat flatting of the micro convex body at any point inside the deformation zone and the change of the oil film thickness to the interface heat transfer process The mixed lubrication model established in this paper is introduced into the interface heat transfer model and the interfacial heat transfer coefficient and its change characteristics of the rolling deformation zone are calculated and analyzed. The results show that there are two peaks in the distribution of the heat transfer coefficient at the interface of the micro convex body, one appears in the entrance area and the other is now on the neutral surface; the closer to the outlet, the heat transfer heat transfer. The higher coefficient is, when the coefficient of thermal conductivity is high, the heat transfer coefficient of the lubricating oil is even higher than that of the micro convex body. When the thermal resistance of the oxide layer on the metal surface is considered, the heat transfer coefficient of the interface will be reduced in order of magnitude. The distribution of heat transfer coefficient in the internal interface of the deformation zone can be divided into three changing intervals, and the trend of the change is mainly affected by the pressure distribution. The influence of real contact area and oil film thickness changes.
【學(xué)位授予單位】：重慶大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類(lèi)號(hào)】：TG335
[Abstract]:The emulsion is widely used in the fields of machinery and metal material processing for its excellent lubrication and cooling properties. The use of emulsion to lubricate and cool the emulsion in the rolling process can effectively reduce the rolling force, reduce friction, control wear, improve the surface quality and mechanical energy of the rolled material, save energy and reduce consumption and improve the quality of the product. In the rolling process of metal, the O/W emulsion is usually used as a medium, and it is lubricated and heat transfer through the injection of the emulsion into the rolling entrance area and with the rolling process into the deformation zone; the adsorption forming process of the emulsion on the metal surface (Plate-out) and the stability performance before the injection are on the rolling deformation zone. The effect of lubrication and heat transfer is very important. These are not only related to the composition of the emulsion, but also influenced by the rolling process parameters. In order to adjust and control the rolling process lubrication and heat transfer process, so as to reduce the rolling energy consumption and improve the quality of the products, it is necessary to focus on the behavior and change rules of the emulsion during the rolling process. The law is carried out to provide guidance for the optimization of emulsion composition and the control of the rolling process. In this paper, the water emulsion emulsified liquid prepared by non ionic surfactants was studied by experiments, mesoscopic / molecular simulation and model calculation, with the lubrication and heat transfer of emulsion in the rolling process as the core, and the emulsification combined with emulsification. The stability and "Plate-out" properties of the liquid are studied. The behavior and mechanism of the emulsion in the rolling process are systematically studied. The theoretical basis for the design of emulsion composition and the optimization of the rolling process are provided. The results are as follows: (1) the stability of the emulsion is studied by the static experiment and the dissipative particle dynamic mechanics method. The relationship between the stability performance and the HLB value of emulsifier, the concentration, the mechanical stirring strength and the stirring time were obtained. The mechanism of the action of the oil and water interfacial film characteristics to the stability of the emulsion was analyzed. When the HLB value of the non ionic emulsifier was 13 and the concentration was 1.6%, the emulsion prepared was the most stable. The thickness of the oil and water boundary mask increased with the increase of the emulsifier HLB value. But it increases, but the stability of the emulsion has a nonlinear relationship with the thickness of the boundary film. The emulsion is most stable when the interfacial tension is the lowest; the droplet diameter increases with the increase of HLB value, which is related to the molecular structure of the emulsifier and the volume ratio of the hydrophilic group to the oil Pro Group. (2) the performance of the emulsion "Plate-out" is studied. A method to control the "Plate-out" properties of emulsion, namely, the addition of short chain alcohols (glycerol, 1,2- propanediol, ethylene glycol, propanol) in the preparation of emulsion, is used to influence the "Plate-out" behavior of the oil droplets on the metal surface, thus affecting its "Plate-out" properties. The molecular dynamics method is used to construct the addition. The behavior and mechanism of additive molecules in the process of "Plate-out" are studied by the adsorptive model of the agent and the "Plate-out" multilayer adsorption configuration. It is found that the size of the "Plate-out" oil film added to the emulsion additive is followed by the following rules: glycerol 1,2- propyl two alcohol glycol propanol, but the law and the additive molecule There is no inevitable relationship between the size of the adsorption energy on the metal surface and the distribution of the droplet size distribution of the emulsion. Through the molecular dynamics simulation of the "Plate-out" multilayer adsorption membrane, it is found that the additive molecules affect the performance of "Plate-out" by the readsorption process of the oil droplets on the adsorbed oil film, which is in the composition of the oil phase. The root mean square displacement in the additive system and the calculation results of the cohesive energy between the additives are in agreement. (3) a mixed lubrication model of the rolling deformation zone is established based on the theory of the flattening of the micro convex body and the average flow model. Through this model, the sliding characteristics of the interface under different rolling conditions (rolling force, the distribution of fluid pressure, real contact) The results show that the surface roughness, rolling speed, and the increase of the viscosity of the lubricant can improve the oil film thickness of the contact interface of the roller and the rolling parts, reduce the actual contact area of the interface, but have no obvious influence on the rolling force distribution, and the increase of the pressing rate not only improves the true connection of the rolling force. The contact area reduces the thickness of the oil film and increases the rolling force. (4) the effect of the lubricant on the shear process and the effect on the positive pressure, friction force and friction coefficient are studied from the molecular scale based on the limiting layer shear model. The results show that the increase of the confining interlayer pressure is beneficial to the shear momentum from the wall to the middle area of the lubricating film. Transfer, although the increase of the oil film pressure increases the interlayer friction, it can effectively reduce the friction coefficient. The stable layered adsorption structure usually appears in the distance wall 3nm. When the thickness of the oil film is over 6nm, the intermediate region will show the liquid properties of the lubricant; there is a critical thickness between the oil film thickness and the friction coefficient (8, only) When the actual oil film thickness is 8, the friction coefficient decreases with the increase of the thickness of the film. The increase of the shear speed is beneficial to increase the positive pressure and reduce the friction coefficient; the increase of the temperature not only increases the positive pressure, but also reduces the curing degree and shear force of the adsorption film, thus effectively reducing the friction coefficient. The lubricating film of the oil and water mixing system is effectively reduced. In the process of lubrication, the oil phase tends to adsorb on the wall and water tends to gather in the middle area; the water bearing oil film can lower the friction force more than the pure oil lubrication. When the oil and water volume ratio is 1:1, the friction coefficient reaches the lowest. (5) in order to consider the influence of the flat flatting of the micro convex body at any point inside the deformation zone and the change of the oil film thickness to the interface heat transfer process The mixed lubrication model established in this paper is introduced into the interface heat transfer model and the interfacial heat transfer coefficient and its change characteristics of the rolling deformation zone are calculated and analyzed. The results show that there are two peaks in the distribution of the heat transfer coefficient at the interface of the micro convex body, one appears in the entrance area and the other is now on the neutral surface; the closer to the outlet, the heat transfer heat transfer. The higher coefficient is, when the coefficient of thermal conductivity is high, the heat transfer coefficient of the lubricating oil is even higher than that of the micro convex body. When the thermal resistance of the oxide layer on the metal surface is considered, the heat transfer coefficient of the interface will be reduced in order of magnitude. The distribution of heat transfer coefficient in the internal interface of the deformation zone can be divided into three changing intervals, and the trend of the change is mainly affected by the pressure distribution. The influence of real contact area and oil film thickness changes.
【學(xué)位授予單位】：重慶大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類(lèi)號(hào)】：TG335
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