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公司名称:泊头市 卓远机械设备制造有限公司
注册地址:河北省 泊头市交河开发区
传真号码:0317-8031093
联系方式:15369812793 (微信同号)褚连胜
邮政编码:062151
企业邮箱: 1358827475@qq.com
账号开户银行:中国银行泊头支行
账号:100399943203
农行账号:6228481739059615270
Company name: botou zhuoyuan mechanical equipment manufacturing co.,LTD
Registered address: jiaohe development zone, botou city, hebei province
Fax number: 0317-8031093
Contact information: 15369812793 (WeChat with the same number)  liansheng chu
Postcode: 062151
Enterprise email:1358827475@qq.com
Account Opening Bank: Botou Branch of Bank of China
Account number: 100399943203
Agricultural bank account number: 6228481739059615270

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机床床 身为什么会产生热裂

时间:2016-2-28 11:10:44 浏览量:699

机床床身在凝固期间因砂型、砂芯、浇注系 统和冒口等阻碍而不能自由收缩时,在铸件 内产生的应力或应变超过金属在该温度下的断裂强度或断裂应变,既生产热裂纹。热裂纹 分为外裂和内裂,外裂常 产生在机床铸件截面厚度有突变或局部凝固慢的热节部位;内裂生 产铸件内部最后凝固的部位,常在缩 孔附近或其尾部。热裂纹 的外观特征是裂纹沿晶界扩展,外形曲折,表面呈氧化色,不光滑。

影响热 裂的主要因素有以下几方面:1、铸件材质。2、结晶温 度范围较窄的金属不易热裂;结晶温 度范围较宽的金属易热裂。3、灰铸铁 在冷凝过程中有石墨膨胀,收缩比 白口铸铁和碳钢小,不易热 裂而白口铸铁和碳钢热裂倾向较大。硫和铁形成熔点只有985℃的低熔点化合物,并在晶 界上呈网状态分布,使钢产生热脆。4、铸件结构。铸件各 部位厚度相差较大薄处冷却较快轻度增加较快阻碍厚处收缩,结果在 强度较低的厚处或厚薄相交处出现热裂。铸型阻 力铸型退让性差铸件高温收缩受阻也易热裂。5、浇冒口系统设置不当。如铸件 速度收缩可能受到浇注系统阻碍,与冒口 相邻的铸件部分冷凝速度比附近部分慢,形成铸件上薄弱区,也都会造成热裂。热裂纹 不仅降低了铸件的力学性能还引起应力集中使用时会因裂纹扩张而导致铸件断裂。


When the machine tool bed can't shrink freely due to the obstruction of sand mould, sand core, gating system and riser during solidification, the stress or strain produced in the casting exceeds the fracture strength or fracture strain of metal at that temperature, which produces hot cracks. Hot cracks are divided into external cracks and internal cracks. External cracks often occur in hot spots where the cross-section thickness of machine tool castings changes abruptly or local solidification slows down. The final solidification part of internal crack castings is usually near the shrinkage hole or its tail. The appearance of hot cracks is characterized by crack propagation along grain boundaries, zigzag shape, oxidation color and non-smooth surface.

The main factors affecting hot cracking are as follows: 1. Casting material. 2. Metals with narrow crystallization temperature range are not easy to crack; metals with wide crystallization temperature range are easy to crack. 3. Gray cast iron has graphite expansion in the process of condensation, shrinkage is smaller than white cast iron and carbon steel, and it is not easy to hot crack, while white cast iron and carbon steel tend to hot crack. Sulphur and iron form low melting point compounds with a melting point of only 985 C, which distribute in a network state at grain boundaries, thus brittle steel. 4. Casting structure. The thickness difference of each part of the castings is bigger, the cooling of the thin part is faster, the slight increase is faster, and the shrinkage of the thick part is hindered. As a result, hot cracks occur at the thicker part or the intersection of the thicker part and the thinner part of the castings. High temperature shrinkage of castings with poor yielding resistance is blocked and hot cracking is easy to occur. 5. improper setting of gating and riser system. If the casting speed shrinkage may be hindered by the gating system, the condensation speed of the part adjacent to the riser is slower than that of the adjacent part, forming a weak area on the casting and causing hot cracking. Hot crack not only reduces the mechanical properties of castings, but also causes crack expansion and fracture of castings when stress concentration is used.


Company name: botou zhuoyuan mechanical equipment manufacturing co.,LTD
Registered address: jiaohe development zone, botou city, hebei province
Fax number: 0317-8031093
Contact information: 15369812793 (WeChat with the same number)  liansheng chu
Postcode: 062151
Enterprise email:1358827475@qq.com
Account Opening Bank: Botou Branch of Bank of China
Account number: 100399943203
Agricultural bank account number: 6228481739059615270

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