Wear Characteristics of Wear-Resistant Hammer Heads Used in Cement Plant Limestone Crushing
2013-08-27
The silicon content in the chemical composition of limestone directly affects the service life of hammer heads—higher silicon levels lead to shorter lifespans. Ideally, the silicon content in limestone should remain below 2%. On the other hand, the compressive strength of limestone is closely linked to hammer head durability: the higher the compressive strength, the less brittle the material becomes, but paradoxically, this also reduces the hammer head's lifespan. Hammer head selection and manufacturing quality play a critical role in determining how long a hammer head will last. Historically, the materials used for crusher hammers in the cement industry were primarily high-manganese steels, with ZGMn13Cr2 being the preferred choice due to its excellent wear resistance. However, even this material struggles under conditions involving high-silicon content and extremely hard limestone—and when combined with unfavorable operating conditions, its lifespan can drop dramatically. For instance, a single set of hammers might fail after processing just 100,000 tons of material. With advancements in hammer technology, newer materials have emerged, such as ultra-high-manganese steel and dual-alloy composite wear-resistant hammers. Ultra-high-manganese steel, specifically ZGMn18Cr2MoRe, features an increased manganese content compared to the traditional ZGMn13Cr2. This enhancement aims to boost the material’s hardness during heat treatment, thereby improving wear resistance and extending the hammer’s service life. Yet, there’s a practical limit to how much manganese and alloy elements can be added, as increasing these components often compromises the material’s toughness. As a result, ultra-high-manganese hammers are not recommended for applications involving significant impact forces. Dual-alloy composite wear-resistant hammers come in three main designs: First, a layer of hard alloy is welded onto the working surface of the hammer, significantly enhancing its abrasion resistance. Second, during casting, the alloy content (particularly chromium) in the hammer’s working area is carefully controlled to maximize wear performance. Finally, hard alloy rods or blocks may be embedded directly into the hammer’s working zone for added durability. Ultimately, the quality of hammer head manufacturing depends heavily on factors like precise geometric dimensions, carefully calibrated alloy compositions and contents, as well as the depth and uniformity of the heat treatment process. Additionally, operational conditions during crushing activities have a profound impact on hammer life: for example, the particle size of the limestone greatly influences hammer durability; moisture content in the limestone directly affects wear rates; frequent blockages in the crusher’s discharge grate, coupled with continued operation despite these obstructions, can severely shorten hammer life; and finally, the presence of impurities in the raw limestone material can also significantly degrade hammer performance. Each of these factors plays a crucial role in determining the overall longevity of wear-resistant hammers.
The silicon content in the chemical composition of limestone directly affects the lifespan of hammer heads—higher silicon levels lead to shorter lifespans. Ideally, the silicon content in limestone should be kept below 2%. On the other hand, the compressive strength of limestone is closely linked to the durability of hammer heads: the higher the compressive strength, the less brittle the material becomes, yet the shorter the hammer head's lifespan tends to be.
The selection and manufacturing quality of hammer heads significantly impact their service life. Previously, the material commonly used for crusher hammers in the cement industry was high-manganese steel—specifically, the superior grade ZGMn13Cr2, which achieves a hardness of HRc23 after heat treatment. However, when these hammers are subjected to limestone with high silicon content and extreme strength, combined with unfavorable operating conditions, their lifespan tends to be relatively short. For instance, a set of hammers from 2022 might struggle to exceed a production output of 100,000 tons.
With the continuous emergence of new technologies in hammer heads, ultra-high-manganese steel hammers and dual-alloy composite wear-resistant hammers have appeared one after another. Ultra-high-manganese steel refers to ZGMn18Cr2MoRe, which features a higher manganese content compared to ZGMn13Cr2. The goal is to enhance the heat-treated hardness of the hammer head, improve its wear resistance, and ultimately extend its service life. However, since there’s a practical limit to how much manganese and alloy elements can be increased—because while these elements boost material hardness and wear resistance, they also reduce toughness—the hammers are not recommended for use under conditions involving significant impact forces.
Dual-alloy composite wear-resistant hammer heads typically come in three forms: First, a layer of hard alloy is built up by welding onto the working surface of the hammer head, significantly enhancing its abrasion resistance. Second, during the casting process, the alloy content—particularly chromium—in the working area of the hammer head is carefully controlled to boost its durability. Third, hard alloy rods or blocks are embedded directly into the working section of the hammer head.
The manufacturing quality of hammer heads is primarily influenced by factors such as geometric dimensions, alloy composition and content, as well as the hardness and depth achieved through heat treatment. Additionally, the operational conditions during crushing significantly impact the lifespan of hammer heads: for instance, the particle size of limestone has a substantial effect on hammer head durability; the moisture content of limestone also plays a critical role in determining how long the hammer heads last. Furthermore, the frequency with which the crusher discharge grate openings become clogged—and the duration of continued operation after clogging occurs—are key determinants of hammer head longevity. Lastly, the presence of impurities in the limestone raw material can greatly affect the wear resistance and overall lifespan of the hammer heads.
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