the Rolling Process of DH36 Ship Plate Steel Using Thermal Simulation Technology

Using the self-developed large sample plane strain thermal simulation test machine, thermal simulation and optimization of Baosteel DH36 ship plate steel rolling process were carried out, the rheological curve of the material in the deformation process was measured , and the simulated sample The microstructure , round bar tensile and Charpy impact analyzes were carried out . The results show that the large sample plane strain simulation technology can not only meet the requirements of conventional thermal simulation system analysis , but also the simulated samples can be used for mechanical performance analysis . The experimental data show that the simulated ship plate steel has excellent mechanical properties .
Key words ship plate steel ; rolling process ; large sample plane strain ; thermal simulation ; mechanical property analysis

The quality of hot-rolled products is comprehensively evaluated by its microstructure and mechanical properties . They are not only related to chemical composition , but also have a great relationship with the stress state and temperature system during rolling . The most important influencing factors are Is the depression system , temperature and time . It is impossible to study the complex relationship between process parameters and final product quality on the spot rolling mill . The only practical way is to develop a suitable simulation method . Simulation includes numerical simulation and physical simulation . Numerical simulation of the hot rolling process requires constitutive equations describing all relevant parameters and their solutions , such as austenitization , grain growth , particle dissolution and precipitation , work hardening , recovery and recrystallization softening, and phase transformation of the final structure Mathematical model of the process . Many scientific workers have established some relevant mathematical models , but the research object is only part of the process of ordinary carbon steel . In order to predict complex thermomechanical treatment results of multi-alloy and micro-alloy technology steels , laboratory physical simulation is the best method and means.
, the main methods for simulating the hot rolling process in the laboratory are the laboratory rolling mill and the thermal simulation system of the Gleeble series . It is impossible to analyze the mechanical properties , and there is a big difference between the simulation of small samples and the field production. The experimental rolling mills are all operated manually , and the parameters are not easy to control , especially the parameters of temperature and time, which are more important to the deformation, cannot be realized at all ; and the key data in the process of heating , deformation and cooling cannot be collected . To solve the above problems , the hot rolling simulation of strip steel was studied , and a thermal simulation system for plane strain of large samples was developed . The deformation process of this system is close to that of on-site rolling, and the microstructure and mechanical properties of the deformed sample can be analyzed .
With the rapid development of the shipbuilding industry , the demand for high-strength marine steel plates has also increased rapidly , so the research on high-strength steel for ships has become one of the hot spots . Ship steel generally adopts controlled rolling and controlled cooling process to control the microstructure of the steel and produce carbonitride precipitation strengthening , and obtain the best mechanical properties such as high strength , high toughness , high weldability and good formability in the hot rolled state Coordinated engineering structural materials . Combined with the development process of ship plate steel , this paper simulates and optimizes the process on the newly developed thermal simulation system , and obtains the best comprehensive performance by adjusting the process parameters .
1 Experimental materials and scheme
the DH36 ship plate steel sample cut from the continuous casting slab of Baosteel Wide and Heavy Plate Plant , with a size of 60 mm X 60 mm X 100 mm . The chemical composition is shown in Table 1 . The sample is deformed 6 times on the self-developed large sample plane strain thermal simulation testing machine . The first pass simulates rolling in the recrystallization zone , Refinement of prior austenite grain size ; subsequent 5 passes simulate rolling in the non-recrystallized zone , Analysis of the finish rolling process of ship plate steel . According to Baosteel ship plate steel processing technology , Two different processes are used to simulate and optimize the process of DH36 ship plate steel , Its process scheme is shown in Figure 1 . In both processes, the final cooling temperature of water cooling is 500°C, followed by air cooling •

Table 1 Chemical composition ( mass fraction ) of sample steel
Table 1 Chemical composition of steel %

C	Si	mn	P	S	o	h	N	als
0.12	0.35	1.12	0.0080	0.0034	0.0019	0.00013	0.0027	0.034

in conclusion

1. The developed large-sample plane-strain thermal simulation experiment system can continuously simulate the hot rolling process with a large amount of deformation , which can meet the simulation requirements of the strip finish rolling process . At the same time, the deformation area is large , and the deformed sample can not only meet the requirements of microstructure analysis , but also meet the requirements of tensile , impact and other mechanical properties experiments , and can truly combine composition , process , structure and performance. , is the ideal experimental equipment for strip steel process simulation and optimization , and development of new varieties .
2. The rolling deformation in the recrystallization zone is more than 30% , which is conducive to the refinement of austenite grains and the subsequent uniformity and refinement of the structure . This is conducive to the comprehensive mechanical properties of ship plate steel .
3. When the original austenite structure is fine , the reduction of the temperature in the non-recrystallized zone and the increase of the reduction are beneficial to the refinement and homogenization of the structure , and can significantly improve its mechanical proper ties ; when the original austenite structure is coarse , no The reduction of the temperature in the recrystallization zone and the increase of the reduction amount , due to the occurrence of deformation-induced ferrite transformation , the ferrite structure is preferentially precipitated at the original austenite grain boundary and the deformation zone , forming a network structure , so that the cooling After the organization is uneven , it is not good for the comprehensive performance .
4. Deform in the recrystallization zone to refine the original austenite grains to a certain extent, then give more than 50% deformation in the non-recrystallization zone at 860 ~ 780 C , and immediately cool at a cooling rate of about 15C.s — 1 , to obtain uniform and fine distribution of bainite and acicular ferrite , The DH36 ship plate steel produced under the process conditions has excellent comprehensive mechanical properties .

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