The dynamic CCT curve of low carbon high niobium steel is determined and drawn as well as the effects of cooling rate on microstructure are studied through static simulating rolling compression test of low carbon high niobium steel with MMS-200 thermomechanical simulator. The results showed that the microstructure was mainly composed of polygonal ferrite (PF), a little pearlite (P) and small quantity of acicular ferrite (AF) observed when cooling rate was 0.5 ℃/s; the microstructure was mainly composed of acicular ferrite (AF) and pearlite disappeared, but certain proportion of polygonal ferrite (PF) was still visible when cooling rate was 1.0 ℃/s; the transformation structure was completely granular bainite (GB) when cooling rate was increased to 2 ℃/s; the transformation structure was mainly composed of granular bainite (GB) and a small amount of ferrite bainite (FB) when cooling rate was increased to 5 ℃/s; the transformation structure was mainly composed of ferrite bainite (FB) and a small amount of martensite (M) when cooling rate was increased to 30 ℃/s.

The IF (Interstitial Free) steel plate is welded into steel pipe for manufacturing condenser pipe of household appliances by a user. There are local spot defects on the surface of steel pipe when it is subjected to conventional hydrostatic test. Such tests on chemical compositions, microstructure of defect and non-metallic inclusions of spot defects as well as mechanical properties and metallographic microstructure of the steel plate with base metal are carried out with such means as metalloscope and scanning electron microscope. The results showed that there were abnormal microstructures at the spot defects. The abnormal microstructures contain such alloying elements as Cr and Ni, which are different from the chemical compositions of matrix. When foreign matter is pressed into welded pipe, its local stress is concentrated. During hydrostatic test, the leak points of pressuring are at the foreign matter which is weakly combined with matrix. In order to avoid such surface defects, it is necessary to strengthen quality monitoring during the whole production and processing processes of welded pipe to prevent foreign matters from pressing into matrix to destroy its continuity so that the steel quality is reduced.

During the stamping process of components and parts of computer case, there is blackening phenomenon on the surface of galvanized fingerprint resistant plate of Baotou Steel so that the appearance quality after spraying by user is seriously affected. The microscopic morphology of galvanized plate after stamping is analyzed by microscope and scanning electron microscope (SEM) aiming at the defect. The results showed that the passivation film on the surface of galvanized plate of Baotou Steel dropped out during stamping process as well as the exposed Zn oxidized and turned black. It is effectively solved by adjusting film thickness and proportion of poly tetra fluoro ethylene in passivating liquid.

In the paper, it is introduced a new type of wear resistant and low temperature resistant pearlitic rail with excellent performances is developed through designing material compositions and studying heat treatment process aiming at the operating environment of railway in alpine regions and performance requirements for service of rail. The test results showed that the improvement of impact energy of test steel at -40 ℃ was not obvious by adding 0.10% Ni on the basis of the chemical composition of 0.66%C-0.45%Si-1.10%Mn, but impact performance was more stable than that of test steel without Ni. After the heat treatment of test steel is started and temperature is increased to 780 ℃, the abnormal microstructure, martensite could be prevented to be generated as well as microstructure is pearlite and a small amount of ferrite and impact energy at -40 ℃ could reach 20.1 J.

The targeted optimization and improvement measures are proposed by summarizing and analyzing the existing quality problems of ER70S-6 welding wire steel. The emphasis is strictly controlling such key indicators as chemical composition range, gaseous nitrogen content, dimensional accuracy and microstructure of ER70S-6 welding wire steel. After tackling the problems, rates of reaching the standard for internal control of C, Si, Mn, and N contents are improved, class C accuracy of dimensional deviation is improved as well as abnormal duplex grain structure is eliminated. The drawing results of users showed that the quality of optimized welding wire steel were further improved, which could meet the requirements of high speed drawing with drawing speed of over 28 m/s.

In the process of producing HRB500E rebar for domestic manufacturers, there are often low strength-to-yield ratio or a small amount of nonconformity. In this paper, the comparative experiment of niobium vanadium composite rebar and vanadium nitrogen rebar manufactured with industrial trial production is carried out. The results showed that the strength-to-yield ratio of rebar was increased by 0.03 with the niobium vanadium composite process, ferrite transformation was delayed due to presence of niobium, pearlite content was increased by about 10 percentage points so that tensile strength was increased; vanadium nitrogen alloy was relatively reduced due to the addition of niobium so that its precipitation strengthening and fine grain strengthening effects were reduced as well as yield strength of rebar was slightly decreased. The practices show that the strength-to-yield ratio of rebar and seismic resistance of HRB500E rebar are significantly improved with the niobium vanadium composite process.

There are often such phenomena as spillage, firing, scratch of foreign objects and blockage as well as such failures as off tracking, slipping, scratch and tearing for conveyor belt of iron and steel enterprises. Moreover, the causes of various failures are analyzed, advantages and disadvantages of using various switches for belt failure detection are compared, a method of detecting various failures with images is proposed as well as adaptability of 2D and 3D image detection methods are compared. At last, the architecture of establishing intelligent belt detection platform for iron and steel enterprises is briefly described.

In this paper, the sealing device for patchhole of oxygen lance is redesigned based on the infinite space submerged turbulent jet theory and characteristic test of dominant frequency of oscillation for double-hole jet aiming at such phenomena as spill over of flue gas and flare-up often occurred at nitrogen sealing at oxygen lance of gasification cooling flue for converter. The new nitrogen sealing device adopts the design of seal chamber and double row of inclined holes are set on nitrogen seal seat as well as the aperture and angle of inclined hole are reasonably designed combining with theoretical calculations. It is applied on new 1^# converter of Steel-making Plant of Baotou Steel, in which the phenomenon of “smoking” in process of converting at oxygen lance as well as the frequency of cleaning and changing nitrogen seal cap for operators are reduced so that recovery amount of coal gas is improved. The engineering applications show that the modified sealing device is with such advantages as reasonable design, simple equipment and safe operations.

When dry mechanical pump system is used to vacuumize for such vacuum refining systems as VD, VOD and RH, a large amount of dust generated in liquid steel will enter vacuum pipe with process gas. In order to protect vacuum pump, the precipitator needs to be installed in front of mechanical vacuum pump to remove dust in process gas. It is common to add a cyclone dust collector in front of bag filter so that occupied area is large as well as costs and operating costs are high. The precipitator introduced in this article is with the integrated structure of cyclone and bag. These two parts are installed in two compartments mode within one precipitator so that occupied area is small and costs are low. The integrated precipitator is with such characteristics as high dust removal efficiency, small pressure loss as well as convenient and rapid maintenance and repair through optimizing structural design so that long-term safe operations of dry mechanical vacuum pump are ensured.

In this paper, the combined process of low-nitrogen combustion+calcium-based desulfuration with fixed bed is proposed for flue gas treatment of heating furnace thorough comparing current common desulfurization technology with active carbon, SDS sodium-based desulfurization technology, calcium-based desulfurization technology with fixed bed and dry desulfurization technology with highly active calcium powder in metallurgical industry as well as selecting the desulfurization and denitrification technologies suitable for conventional walking beam reheating furnace of steel rolling mill by taking the ultra-low emission transformation for conventional walking beam reheating furnace of steel rolling mill as an example. After on-site implementation, the nitrogen oxides, sulfur dioxide and particulate matter in flue gas could all meet the ultra-low emission requirements so that the combined process could provide reference for enterprises in the same industry.