1　Introduction

During the hot rolling process of metal products,a layer of oxide(commonly called scale) forms on the surface due to the interactions between the metal elements and oxygen.The scale can cause a lot of problems for further processes such as stamping,coating,and cold rolling.

To eliminate the negative effects caused by scales,they must be eliminated,and the most commonly adopted method is acid pickling,which uses pickling agents,such as HCl,HNO3,or HF,to dissolve and eliminate scales from the surface of metal products.However,acid pickling cannot avoid its fatal draw-backs,including acid fog pollution,high cost for treating spent acid,uneven descaling quality,and over-pickling of the substrate[1].To solve these pro-blems,several studies have been performed to develop novel processes to replace acid pickling.They include plasma descaling,ultrasonic descaling,brush roller descaling,laser descaling,high-pressure water jet containing abrasive descaling[2],hydrogen reduction descaling,and their combinations.These types of descaling processes use mechanical inter-action,electric fields,or sound-wave effects to eliminate descales instead of chemical reactions.The overall energy consumption can be attributed to the electric power consumed during the processes[3].

当前钢结构施工期间存在较多的项目环节，项目成本、质量、安全管理、进度管理以及控制等方面均存在问题。具体而言，在工程项目的推进过程中，施工环节存在较多的不确定性影响因素，工程变动难免会影响造价成本，为企业带来了一定的经济损失。安装期间，由于技术人员没有掌握正确的施工技术，也会影响工程的推进效果，甚至延误工期，造成不良经济损失。运输与安装钢结构构件时，也会因损坏以及污染等问题延长施工进度，技术人员需要重新调配构件，导致工期延误。工程项目推进期间，施工人员需要进行现场操作，会受多种因素的影响导致技术以及安全等问题，从而影响钢结构的施工效果。

Among the three categories,the method that uses the least energy is the cutting method,followed by the abrasive and the discharging methods.According to the evaluation of the recent descaling technology development,the cutting and discharging methods still depict problems such as low efficiency and high proportion of residual scale;thus,these methods cannot be industrialized currently.Under this background,the Baosteel mechanical descaling(BMD) technology,an optimized abrasive method,has emerged as the best alternative for acid pickling or other descaling processes.

2　Domestic and international development in descaling technology

2.1　International development

Considerable effort has been made to develop novel descaling technologies by companies in coun-tries such as the United States,Japan,Germany,and Italy.The Eco Pickled Surface (EPS) technology by the American company The Material Works,Ltd.(TMW) has drawn significant attention.This process uses the slurry mixture as the descaling medium,and the mixture is propelled to a given velocity by a rotating impeller.Further,the slurry mixture hits and grinds the steel surface to eliminate the scales[4-5].

The slurry mixture comprises abrasives and water that can be recycled and reused after performing the separation and infiltration processes.Thus far,a maximum of 10 production lines of EPS have been promoted.In addition,the Chinese companies,TISCO and Ansteel-Jingu,have both introduced complete equipment from TMW.

This process is significantly reliant on high-pressure water,and this water is provided by a pressurization system comprising pumps,high-pressure tubes,and valves.This complex system increases the overall energy consumption to make it extremely high.Meanwhile,the available energy directly used for descaling only occupies a small portion of the whole energy consumed.The afore-mentioned factors cause this process to be expen-sive.Moreover,the nozzles are arranged separately,which makes the jet flow unlikely to be uniform across the steel surface;thus,the surface quality is not guaranteed.In addition,the extremely high pressure may cause the abrasives to become embedded in the steel substrate,especially in case of some low-strength steels.

其二，离情别绪，酬唱赠答，表现亲情和友情的作品。多数是情致浓郁，缠绵温润，充分体现出词人的深情厚谊。例如《忆王孙·秋山送别》，从“登山临水送将归”至“惟有年年秋雁飞”，抒写了伤别之苦、刻画了离别之恨、极写了送别之际，表达了词人的真情厚谊和孤苦落寞的情怀。

全国水利风景区建设与管理工作会召开。3月19日，全国水利风景区建设与管理工作会在京召开。水利部部长陈雷强调，要深刻认识加强水利风景区建设与管理的重要意义，全面落实各项建设与管理措施，努力开创水利风景区建设与管理新局面。水利部副部长胡四一主持会议并作总结讲话，水利部党组成员、办公厅主任陈小江宣读了第九批国家水利风景区名单。水利部总工程师汪洪出席会议。

2.2　Domestic development

The Changsha Research Institute of Mining and Metallurgy Co.,Ltd.and Hu’nan Nonferrous Heavy Machinery Co.,Ltd.,as typical domestic companies,have developed distinct abrasive water jet descaling technologies.This technology uses high-pressure water (up to 30-50 MPa) to propel abrasive particles against the steel,thereby achieving a cleaning surface.

The Danieli Corporation has also developed a hydrogen reduction process that uses hydrogen to reduce the oxide from the iron.However,the reduced surface has to be mechanically brushed to completely eliminate the scales.Further,this process is frequently hindered by the residual scale problem,and it illustrates a large demand for a pure H2 atmosphere.These defects make it difficult to industrialize this process.

2.3　Existing problems

Despite much development in descaling tech-nology,none of the processes mentioned has been extensively promoted.The reasons are as follows:

(1) The international technology,such as the TMW’s EPS technology or the spinning jetting technology,could achieve the descaling process to some extent.However,the cost and stability of these technologies make them to be unacceptable for the domestic customers.

（1）根据动态效应分析得到的结论：水资源消耗对自身的动态冲击作用最大，城镇化程度越高的省份，水资源消耗对自身的冲击越小；人口城镇化程度较高的省份，对水资源消耗影响的动态效应表现为负向冲击作用，反之则表现为正向冲击作用，且人口城镇化程度越高，其作用就越小；经济城镇化较低的省份会对水资源消耗产生正向冲击作用，反之会产生负向冲击作用，且经济城镇化程度越高的省份，负向冲击作用就越大；全国大部省份的产业城镇化对水资源消耗都有正向冲击作用，只有少部分省份的产业城镇化会对水资源消耗起到负向冲击作用。

(2) The domestic technologies,whether it be the plasma cleaning or the high-pressure abrasive water jet,have difficult problems to overcome before they are suitable for industrialization.The problems,including excessively complex systems,unstable quality,or having trouble in equipment manufac-turing,result in barriers for the promotion of the usage of domestic technologies.

Based on the discussed reasons,Baosteel started the self-development of its own descaling process in 2008.After several years of research,an eco-friendly de-scaling process was developed,which could completely satisfy the strict environmental requirements and meet the indicators of commercial production.

3　Principle and development process of the BMD technology

3.1　Process of the BMD technology

To eliminate the problems that were observed during acid pickling,the BMD technology was developed.It is a promising descaling technology that depicts the advantages of “zero pollution,higher quality,and lower cost” and offers an ideal alternative for acid pickling.The process flows are illustrated in Fig.1.

不同层次的师范教育类院校，在制定师范专业人才培养方案时，教育实践所占比重都比较大。实践教学类的课程，是学生掌握必备的教师职业技能，形成良好的职业道德品质的重要保证。因此，规范、合理、充分地安排好这类课程，是教师教育培养的关键所在，是培养未来教师必不可少的一个条件。基础教育的发展，对教师的专业素养和职业技能的要求逐渐提高，社会对教师职业的专业化水平也日趋重视。新的历史条件下，师范教育类院校的人才培养模式应顺应社会、人才发展的需求，相应的教育实践改革也势在必行。如何对师范生进行专业教学实训、职业技能培训、职业素质培养等教学活动，强化教育体验，是教育实践改革的关键。

As illustrated in Fig.1,the specific processes are as follows:

(2) The BMD-processed products,which are depicted in Figs.3-5,illustrate a surface of randomly

(2) The used abrasives and water along with the scales are initially collected by the recycling system.Further,the usable abrasives are separated and transferred to the abrasive supplying system,while the rest (water-carrying fine particles of scales and broken abrasives,which are usually called suspension) are sent to the infiltration system.

乳酸链球菌素是一种抗菌素,由乳酸菌属的乳酸链球菌制得,乳酸链球菌素不能抑制革兰氏阴性菌、酵母和霉菌,能抑制葡萄球菌属、链球菌属、小球菌属和乳杆菌属的某些菌种；对于抑制LAB和其它革兰氏阳性细菌,特别是梭菌和细菌芽孢极其有效[5]。乳酸链球菌素就作为一种防腐剂在食品中使用。能产生细菌素的乳酸菌作为一种新型发酵剂被广泛用于发酵肉制品工业,能有效地抑制引起食品腐败的细菌和孢子,延长食品的货架期[6]。

(3) The suspension flows to the infiltration system that can filter the particles and deliver the filtered water back to the ejecting system.

核桃是我国能在国际市场上站稳脚跟的少数农副产品之一，特别是核桃油价格可达66元/kg，加之，核桃生产成本低，投入与产出比是1∶5，核桃果加工成仁能增值0.25倍，加工成油能增值2.5倍，加工成饲料能增值8倍，且收获期长达60多年，产量稳定，所以，核桃产业具有广阔的发展前景。

(4) The abrasive supplying system accepts usable abrasives from the recycling system and concurrently completes the sorting and cleaning processes before feeding the abrasives back to the ejecting system.In addition,the number of abrasives are continuously monitored and automatically added once desired.

3.2　Research and development process of the BMD technology

The BMD technology research was initiated in 2009 and progressed through four stages within a period of 8 years,which is as follows:

(1) 2009-2011:Survey and analysis of various descaling technologies,tentative tests,and principle tests.

(2) 2011-2012:Small-scale experimental platform building and testing.

(3) 2012-2014:Medium-scale experimental plat-form building and testing and the certification of two customers.

(4) 2014-2016:Industrial test line building,continuous production test-simulating commercial lines,certification,and continuous supply for typical customers.

轨道监测数据自动化处理与分析系统的设计……………………………………… 张定忠，黄赟，王新胜（8-264）

The BMD medium platform and industrial test are depicted in Fig.2.

Currently,the BMD-technology developing team is engaged in building the first BMD commercial line,and it was formally put into production in February 2018.The specifications of this line are as follows:

(1) Coil line:capable of continuously descaling on both sides of the strip.

(2) Descaling quality:Sa3.0 of both the wide sides;uniform across the strip width;the surface roughness is user-specified.

(3) Coil specifications:maximum thickness is 11 mm,maximum width is 1 800 mm,maximum yield strength is 750 MPa.

(4) Production capacity:≥100 000 t per year (two shifts with weekends and holidays).

(5) Product users:manufacturers using steel plates for commercial vehicle chassis,beams (cross and longitudinal),and construction machines.

3.3　Quality detection of the BMD product

The characteristics of the BMD surface are as follows:

(1) The descaling grade is Sa3.0,and the proportion of the residual scale is at the same level as that observed in the acid pickled surface.The BMD product can be substituted in place of the acid pickled product and is suitable for subsequent processes such as stamping,coating,and cold rolling.

(1) The abrasives and water are fed into the ejecting system in which they are rapidly mixed and ejected towards the strip surface.Through con-tinuous hitting and grinding,the scales are rapidly eliminated.

distributed peaks and pits,which are quite uniform when observed at a lower magnification.The surface roughness value(Ra value,0.8 mm step length) can be adjusted to fall within the range of 2.5-10.0 μm,and the fluctuation range of the roughness of single piece BMD sample can be controlled within the range of ±0.5 μm.The varying and adjustable surface provides a favorable base for coating.

珠江由西江、北江、东江及三角洲河网组成，东江干流发源于江西省寻邬县桠髻岭，在广东境内流经龙川、河源、紫金、博罗、惠阳至东莞石龙，石龙以下进入三角洲河网区。东江三角洲通过狮子洋与西、北江三角洲相连，相对独立。干流由源头至石龙长约520 km，至狮子洋总长约562 km。石龙以上广东省境内约23 540 km2，约占流域总面积的87.06%，石龙以下的东江三角洲面积约为1 380 km2。

(3) The BMD product can be delivered either with oil or as a dry surface depending on the requirement of the user.

The BMD surface was observed using scanning electron microscope(SEM):

4　Promotion and certification of the BMD product

Since the development of the BMD technology,the BMD products have been promoted to many domestic automakers and auto-part manufacturers with whom Baosteel completed a series of tests and certifications that were required before obtaining mass distribution approval.The promotion and certification details are depicted in Table 1.

4.1　Customer certification of the BMD product

4.2.5　Metallographic microstructure

To simulate the stamping performance of the BMD product during commercialized production,a stamping test was arranged in cooperation with an automobile manufacturer in Anhui province.To maintain the stamping conditions,the test for the BMD plates was conducted after completing the routine production of other plates.

The test results depicted that the BMD plate was comparable to the acid pickled plate in terms of coating performance and that it was superior to the hot rolled/shot-blasted plates.

(2) Equipment:hydraulic stamping machine (3 000 t).

(3) Application of stamped parts:special-shaped longitudinal beams used for trucks.

4.1.2　Quality inspection after stamping

Before the test,it is critical to designate the monitoring site where the most complex deformation occurs and is the most probable to produce defects such as scratches or burrs.Combining the mold structure,the deformation feature of the plates was analyzed,and an area that undergoes both bending and tensile deformation was selected.This area indicated by the arrow in Fig.6 was defined as the key area to judge the stamping performance of the BMD product.In addition,the mold surface corresponding to this area was carefully checked to ensure that the mold was in a normal condition.

After 120 pieces of the BMD plates were continuously stamped,the surface state and quality of the plates were carefully inspected (as depicted in Fig.6).The results are as follows:

(1) No scratching of plates was observed,even in the area undergoing both bending and tensile deformation.

(2) The wear of the stamping die was unrecognizable,which indicated that the BMD plate with oil was favorable for prolonging the service life of the stamping die.

(3) The inspection worker concluded that the BMD plates were appropriate for stamping and that the forming accuracies were qualified.

4.1.3　Roll-forming performance of the BMD product

The coil specifications are as follows:

(1) Two coils of QSTE650TM steel (7 mm thickness) treated by the BMD process.

(2) Surface condition:oiled.

After the roll-forming process,the vehicle manu-facturer concluded the following:

(1) The surface state was qualified,i.e.,no burr or scratching was observed.

(2) The forming accuracy was qualified before and after the separation of the part,e.g.,the truck’s chassis longitudinal beam.

To determine whether the BMD-processed surface was appropriate to complete the coating process of a customer,a coating test was performed,which can be given as follows:

4.1.4　Coating performance of the BMD product

(1) The hot rolled black plates were taken from the same coil and were treated using the BMD,acid pickling,and shot blast process.Thus,four categories of samples were prepared (3 treated and 1 untreated plates).

(2) The four samples were coated using a similar process to that of the practical production (degreasing→cleaning→surface conditioning→phosphating→electrocoating).

(3) The coating performance was tested according to the national standard,and the results are depicted in Figs.7-9.

To completely compare the corrosion resistance of the BMD samples after coated,the author placed four categories of coated samples in the same salt spray test box.Further,the coated samples were scratched on the surface and kept for 720 h,and the results are shown in Fig.9.

(1) Objects:120 pieces of the BMD plates with a moderate coating of oil.

4.2　Cold rolling test for the BMD product

4.2.1　Purpose of the experiment

宋早雪［4］解释道，所谓“337条款”，即美国1930年《关税法》第337条款的俗称，主要用于调查进口产品中侵犯不正当竞争和知识产权的问题，其中约有90%的相关调查为专利侵权。

A cold rolling test was arranged to compare the BMD plate with the acid pickled plate in terms of cold rolling performance.Combining the perform-ance data of Baosteel’s cold rolled products,the effect of the BMD on substrate properties was studied.

4.2.2　Rolling mill

结果显示，亲密关系丧失组和死亡凸显组中的高自尊者的职业期望显著低于对照组的高自尊者，表明死亡凸显和亲密关系丧失会显著降低高自尊者的职业期望，详见表 4、表 5。

To completely compare different features after rolling,Baosteel’s own cold rolling testing machine was used,as follows:

(1) The two-high rolling mill.

(2) The roll diameter is 250 mm,the maximum rolling force is 1 t,and the tension is 0-2.7 t.

(3) The newly replaced rollers with the surface roughness of Ra≈0.1 μm.

1) 黑水角阀结构。该阀门主要由阀体、阀盖、阀杆、阀芯、阀座和扩散段等组成，结构如图1所示。角阀工作时，介质从左侧入口流入，流经阀芯与阀座之间形成的节流口，再依次经过阀座和扩散段后从下侧流出，即侧进底出，通过阀杆的上下移动改变阀芯与阀座之间的相对位置从而改变黑水流量。

4.2.3　Plates for experiment

The plates’ classification and the two-high rolling mill used in the experiment are illustrated in Table 2 and Fig.10,respectively.The accessory materials include oil-water emulsion (name of the original liquid:RH- 4T) and dry leveling mundificant.

4.2.4　Surface roughness and topography after cold rolling

女子的死而复生，在整个云浮族中，犹如投下了一枚重磅炸弹，人们奔走相告，沉浸在巨大的兴奋和虔敬中。他们议论着，这名女子，躺在安魂殿的那段时间里，一定是有天神曾经光顾过的。天神以大愿力复活了她，能够受到天神如此眷顾的人，注定不会是一个凡人！

The Ra values of the cold rolled plates were measured using the portable roughness measuring instrument and the laser confocal scanning microscope.Furthermore,the surface topography of

the plates was studied and recorded by the laser confocal microscope.The Ra values are depicted in Table 3,and the surface topography is illustrated in Figs.11 and 12.

4.1.1　Stamping performance of the BMD product

To investigate the effect of the BMD process on the microstructure of cold rolled plates and its difference from acid pickling,the microstructure detection was performed using the following procedure:

(1) For each plate of the four categories (as depicted in Table 2),the two cross-section samples are eliminated and prepared to be metallographic specimens.These two samples are destined to perform the observation of the following two directions:perpendicular to and along the rolling direction.The direction perpendicular to the rolling direction is called PRD.The direction along the rolling direction is called ARD.

(2) The specimens are ground,polished,and eroded in accordance with the standard.

(3) Further,the specimens are examined using a high magnification microscope.

The results are depicted in Figs.13-15.

4.2.6　Experiment summary

Based on the cold rolling test and detection,it is concluded that:

(1) There is only a slight difference between the surface topographies of the cold rolled BMD plate and the cold rolled acid pickled plate.However,the cold rolled BMD plate performs better in terms of the uniformity of Ra values in different directions(perpendicular to and along the rolling direction).

(2) The microstructure of the cold rolled BMD plates agrees with that of the cold rolled acid pickled plates,which indicates that these two plates possess the same mechanical properties.

5　Conclusions

(1) Over a period of 8 years of self-development and testing,the BMD evolved from a technique concept to a novel descaling process,and the BMD is promising due to the advantages of “zero pollution,higher quality,and lower cost”.

(2) The BMD products have passed various certifi-cation tests,including surface quality detection,stamping/rolling forming testing,cold rolling testing,and paint performance comparison.All these results indicate that the BMD product is appropriate for the subsequent manufacturing processes and is ready to be promoted.

(3) Years of technology accumulation and the analysis in this study demonstrate that the newly developed BMD process is a feasible alternative for acid pickling.The result agrees with the green manufacturing idea,which is emphasized by the Chinese government.Meanwhile,the BMD process provides a perfect solution for domestic and inter-national companies that seek to innovate the descaling process and reform their existing production lines.

References

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[2]　ZHANG Q S.The discussion on the development of new descaling technology for cold rolling in China[J].Liaoning Metallurgy,1989(6):50-54.

[3]　FAN Q and FAN Z R.New cleaning machine for metal surface[J].Surface Technology,2000,29(3):41- 42.

[4]　SUN L F,ZHANG X W and WANG G R.Acid-free descaling technique for cold rolled strips[J].CFHI Technology,2014(2):1-3.

[5]　VOGES K.Eco-pickled surface:An environmentally advantageous alternative to conventional acid pickling[J].Engineering and Technology,2008(2):56-66.