Maximum Hardness In Heat-affected Zone Research Articles

Study of the Effect of Thermal Cutting on the Microstructure and Chemical Composition of the Edges of Workpieces Made of Steel Brands S345, S390

The results of the experimental evaluation of the response of low-alloy steels on the thermal cycle of plasma and oxy-fuel cutting to determine their applicability for preparation of workpiece edges without subsequent machining are given in this article.It is shown that changing of the chemical composition of the metal in the cut zone happens due to the increase of the carbon content and reduction of the content of silicon, manganese and chromium. It occurs more significantly during the oxy-fuel cutting of the steel S390. At steel plasma cutting the content of the main alloying elements except carbon practically does not differ from the regulatory requirements for both brands, and the value of carbon equivalent for them does not exceed 0,45%.It was determined that structural changes in the edge zone are available but they are not critical from the point of view of their weldability. The depth of the heat affected zone (HAZ) varies from 0.54 to 2.3mm depending on the steel brand and the cutting method. The maximum hardness in HAZ of the edge is 325-380 HV10.The obtained results confirm the possibility of revising of domestic regulatory requirements for the manufacture of steel constructions in the part of preparation of edges for welding using thermal cutting technologies which are too conservative at the moment.

１３Ｃｒ鋳鋼溶接熱影響部の低温割れについて―１３Ｃｒ鋳鋼の溶接性 Ｉ

Slit type weld cracking test was performed to investigate the effect of preheating temperature on the cracking of the weld heat affected zone (HAZ) in 13Cr-Ni and 13Cr-Ni-Mo cast steels. The obtained results are as follows.(1) Cracking starting temperature of HAZ was decreased with the increased in preheating temperature. When the preheating temperature was increased from room temperature (RT) towerds 250-350°C, cold cracking starting temperature decreased from 115-160°C to RT or lower.(2) Maximum hardness of HAZ were almost no variations even when preheating temperature was increased, but width of harding area of HAZ increased in respons to increasing of the preheating temperature.

熔接構造用HT60に関する研究

This paper reports the investigation of weldable high tensile structural steels, having 60-70kg/mm2 tensile strength, with a satisfactory notch toughness and weldability. The main conclusions are obtai-ned as follows;(1) In the present results upon the effects of alloying elements for Mn-V type steel, comparatively satisfying results are obtained for Modifyed Vanity Type Steel, contain about 0.5% Ni.(2) Concerning the range of chemical composition of commercial steel, it is difficult to satisfy both the high tensile strength and lower Maximum Hardness of Heat-Affected zone.(3) High Tensile, High Notch-Tough Steel, ("2H" Steel) obtained after special heattreatment has a tensile strength over 60kg/mm2 and higher yield ratio of 85% and excellent notch-toughness and weIdability as shown in table 4. Therefore this "2H" Steel is the most practical steel for use welding construction.

マンガンシリコン系高張力鋼のスリット型亀裂性試験

Using slit type specimens, crack tests were performed to evaluate the cracking tendency of structural high tensile Mn-Si steels.It was found that as the maximum hardness in heat-affected zone (Hmax.) increased the cracking tendency of weld became marked. Cracks usually originated from the root of weld and grew along the heat-affected zone, then turning into the deposit. Hmax. seemed to increase proportionally with C and Mn contents but hardly increased with Si content for the range investigated. To prevent the weld crack C should be kept as low as possible; Mn below about 1.2%. There was not any indication that Si content promoted the craking tendency of weld. Of various types of electrodes applied for the test, the low hydrogen type proved to possess sufficient anti-cracking property.