1.Cause analysis and improvement measures
It is analyzed that the main causes of casting scrap are: uncontrolled melting process, high pouring temperature, low w(C), w(Si), lower CE than eutectic point and insufficient local cooling of casting.Therefore, the following improvement measures are taken:
(1) Control the CE in4.4%Above, where the median of the w(C) quantity3.7%, w(Si)>2.1%In order to guarantee the mechanical properties of the castings,0.15%For Cu, the casting temperature shall not exceed 1 360 C.
(2) The processing quantity of the end face of the upper box 537 mm is increased from 15 mm to 25 mm, and 3 risers with the dimension_100mm x 17 mm are added to the upper box surface. 12_22 mm ceramic pipes are set on the flange surface of_2 590 mm, and 6_22 mm ceramic pipes are added at the R75mm transition between the hot section 3 and 4. The outer circular cold iron with the thickness of_018 mm is increased from 50 mm to 80 mm.The arrangement of 600 mm right side cold iron is changed from horizontal to vertical, increasing the number of cold iron, thus increasing the cooling area, while the remaining processes remain unchanged as shown in the figure.
2.Results of process improvements
After process improvement, 2 pieces are produced continuously, numbering 0094276002 and 0094276003 respectively.
The test results show that: the full-size scribe inspection, ultrasonic testing, magnetic particle testing, appearance, leakage testing, mechanical properties, metallographic structure, etc. are all qualified, which prevents the generation of shrinkage defects and shrinkage defects of the casting, and meets the various acceptance requirements of the casting and achieves satisfactory results.
The chemical composition of 0094276002 casting is w(C).3.72%W (Si)2.17%, w (Mn)0.18%W(P)0.024%W(S)0.01%, w (Mg)0.06%W (CE)4.44%And the pouring temperature is 1 361 C.Mechanical properties of the enclosed cast block, the metallographic structure of the enclosed cast block is shown in Table 2 and the metallographic structure picture is shown in the figure.