High-quality Structural Steel Research Articles

Improving the Quality of Rolled Metal Products Using a Set of Quality Management Statistical Methods

In the face of the increasing need of shaped and bar iron for buildings and installations construction, production of modern domestic vessels at one of the Kuzbass metallurgical enterprises, mastering the production of hot-rolled bulb bars made from highquality structural steel, which is based on existing technology, has begun. To ensure the production quality, control quality techniques for “asymmetric bulb bar” experimental rolled steel made from A32 and D32 steel grades is proposed. It enabled us to identify the systemic and most significant unsatisfactory features in production process, to develop measures to eliminate them and prevent possible defects in mass production of rolled products. These techniques are based on the application of quality management statistical methods. The implementation of a quality control techniques and recommended measures to prevent possible defects made it possible to improve the quality of metal, ensure production stability and competitiveness in the metal market.

Influence of the Reduction in the First Matched Groove Pair of a Three-High Stand on Billet Damage

The influence of the one-time reduction in the first pair of matched grooves in a three-high stand on the cracking at the end of the billet is simulated. The traditional six-pass procedure in the three-high stand is compared with the new six-pass procedure and the eight-pass procedure proposed in the present work. The comparison shows that, by milder reduction in the first pair of matched grooves, the effective stress may be decreased, along with the likelihood of cracking at the end of the billet. The damage at the ends of the multiple billets in the three-high roughing stand may be minimized by means of further decrease in deformation in the first passes on rolling multiple continuous-cast billets made of high-quality structural steel, along with decrease in the initial rolling temperature and division of the billet into measured lengths on a band saw.

An investigation of the prediction accuracy for volume based HCF models using scaled geometries and scaled loading

The prediction accuracy for the volume based Weibull- and V∗ high cycle fatigue models is investigated and compared to the point method. A high number of fatigue tests are performed in rotating bending for single notched cylindrical specimens manufactured in a 12% Cr-steel, a high quality structural steel. The specimens are designed with different highly stressed volume and stress gradient by scaling the geometry, but with the same stresses at the corresponding scaled points. Thus, the maximum stress in the notch is the same. Experiments are performed for three specimen sizes at several stress levels. The volume based Weibull- and V∗-models, as well as the point stress method are fitted to the experimental results. Based on the results, the V∗-model is favored for design purposes.

Resource-saving bar production on existing mills

Simulation of rolling in simple bar grooves permits analysis of the flow of surface layers of the billet and its influence on the stress–strain state of the metal in rolling; the conclusions are experimentally confirmed. The new groove system developed on the basis of those recommendations for the roughing rollers in the 250-2 continuous small-bar mill at OAO EVRAZ ZSMK is tested in industrial conditions. This system increases the product yield (reduces the rejection rate) by 3% in the production of bar from high-quality structural steel. The improvement in production efficiency due to the increase in productivity when slit rolling is introduced at the existing 250-1 continuous small-bar mill at OAO EVRAZ ZSMK is estimated. A method is proposed for determining the splitting conditions as a function of the required gain in productivity. Recommendations are made regarding the calculation of the rolling speed in the roughing and finishing cells. The change in total extrusion and rolling speed in the groups of cells during the production of rebar 10, rebar 12, and rebar 14 is recorded.