D-type graphite cast iron bar and preparation method thereof

[0034] Embodiment 1: A kind of D-type graphite cast iron profile, selects HT250 material HT250 material The mass percentages of carbon, silicon, manganese, and titanium elements in the profile are:

[0035] Carbon: 3.45%;

[0036] Silicon: 2.55%;

[0037] Manganese: 0.55%;

[0038] Phosphorus: 0.075%;

[0039] Sulfur: 0.046%;

[0040] Titanium: 0.25%;

[0041] The rest is iron.

[0042] HT250 material The profile preparation method specifically comprises the following steps:

[0043] The cross-section of this profile is small, and the liquid center hardly exists outside the drawing exit. Before production, the traction head is strictly made according to the size of the production profile, and the rough manufacture of the traction head, or the gap between the graphite sleeve and the graphite sleeve is too large or too small. If it is too small, it will not be able to vent, and if it is too large, it will easily leak molten iron, which will easily cause production failure.

[0044] Therefore, it is selected to be produced on the No. 5 production line of Hebei Henggong Machinery Equipment Technology Co., Ltd. After the combination of the crystallizer and the holding furnace is installed, the raw burner is used to bake the holding furnace for about 3-5 hours. The temperature is about 500-600 degrees, and it is red. To reduce temperature fluctuations and the oxidation of molten iron injected in advance.

[0045] (1) Melting of molten iron. Use 6-ton and 10-ton intermediate-frequency induction furnaces to smelt pig iron and scrap steel for molten iron. After the pig iron and scrap steel are completely melted, detect the content of each element in the molten iron, and adjust the content of each element to meet the formula requirements. The temperature is 1440°C.

[0046] (2) Inoculation treatment of molten iron, when the tapped iron reaches the set amount, thoroughly remove the slag and measure the temperature; add an inoculant with 0.5% of the total weight of the molten iron after the temperature is suitable, and put the inoculant in the molten iron treatment transfer bag to complete the slag removal After stirring and dissolving, pour it into the holding furnace for drawing.

[0047] (3) Measure the temperature after scraping off the slag, and control the temperature between 1390°C. If the temperature is suitable, transfer it to the holding furnace for pouring. After pouring, measure the temperature of the molten iron in the holding furnace and control it at 1360°C. After the first ladle of molten iron is injected into the holding furnace Stay for 3 minutes, so that the injected molten iron wraps the traction head, and solidifies the crystal to a certain strength, so that the traction of the dummy rod traction unit is pulled down, with a stable empirical step length of about 55-60mm/step, and The pull-stop-pull method starts steadily. During the drawing process, pay attention to observing the outlet temperature of the circulating water every hour. When it is higher than 50°C, replenish water to cool down.

[0048] The pouring process should be stable, and the injection speed should not be too fast or too slow. If it is too slow, it will easily cause the temperature and liquid level to drop. A pull failure occurs.

[0049] (4) In order to achieve the goal of stable production and high quality, the interval of molten iron in the replenishment furnace must be strictly controlled within 9-11 minutes. In line with the principle of frequent replenishment and less replenishment, the "freshness" of the molten iron in the holding furnace can be maintained. Only in this way can the pressure fluctuation in the holding furnace be reduced to the greatest extent, and the molten iron in the furnace can be ensured to have a strong spontaneous nucleation ability. The molten iron is rapidly and uniformly cooled to form a profile with stable rigidity and strength, and the outer contour size is stable, the appearance is smooth, and the inner structure is dense.

[0050] After the start is stable and the red-hot profile is rolled up, judge whether it is necessary to increase the speed according to the color displayed by the step of pulling out, and determine the normal production parameters of pulling and staying on the main control panel.

[0051] Embodiment 2-3: a kind of D-type graphite cast iron profile, wherein the mass fraction of carbon is inconsistent with that of Example 1, and the mass fractions of other components are the same as in Example 1, and the corresponding components of a D-type graphite cast iron profile The quality scores are shown in Table 1.

[0052] Embodiment 4-5: A kind of D-type graphite cast iron profile, wherein the mass fraction of silicon is inconsistent with that in Example 1, and the mass fractions of other components are the same as in Example 1, and the corresponding components of a D-type graphite cast iron profile The quality scores are shown in Table 2.