Common defects of titanium tube
Inner surface defect
In the fold
Features: the internal surface of the titanium tube presents a straight line or spiral or semi-spiral zigzag defect.
1) titanium billet: loose center, segregation; Serious residual shrinkage cavity; Non - metallic inclusion exceeds standard.
2) uneven heating, too high or too low temperature, too long heating time.
3) perforated area: severe wear on the top; Improper adjustment of puncher parameters; Perforating roll aging, etc.
Inspection: internal folding is not allowed on the surface of the titanium tube, and the internal folding at the tube end should be grinded or cut again. The actual wall thickness at the grinding point should not be less than the minimum required by the standard. The pass length is cancelled.
Characteristics: titanium tube surface spot scar, generally not rooting easy peeling.
1) graphite lubricant with impurities.
2) the iron ear at the back end of the pipe is pressed into the inner wall of the titanium pipe, etc.
Inspection: the surface of the titanium tube is not allowed to exist, the tube end should be repaired and cut again, the grinding depth should not exceed the standard requirements of negative deviation, the actual wall thickness should not be less than the minimum standard requirements; Scab will be rejected.
3 become warped skin
Characteristics: the surface of titanium tube presents a straight line or intermittent nail - shaped upturned small skin. Often appeared in the capillary head, and easy to peel off.
1) improper adjustment parameters of the punch.
2) titanium sticking to the top.
3) oxidation skin accumulation inside waste tube, etc.
Detection: the surface of titanium tube is allowed to have warped skin without roots that can be easily peeled off (or burned off during heat treatment). The warped skin with roots should be ground or removed.
Characteristics: there are linear scratches with certain width and depth on the surface of titanium tube.
1) low rolling temperature, stick with metal mandels.
2) graphite contains impurities and so on.
1) the casing and general pipe are allowed to have an inner straight with a depth not exceeding 5% (maximum pressure vessel depth of 0.4mm).
Shendu should be grinding and excising the chendu straight.
2) the inner straight with sharp edges should be polished smooth.
Characteristics: there are linear protrusions with certain width and depth on the surface of titanium tube.
Causes: mandrel wear seriously, grinding not smooth or too deep.
1) it is allowed that the height of casing and pipeline pipe shall not exceed 8% of the wall thickness, and the maximum height shall not exceed 0.8mm, which will not affect the existence of the inner edge of the diameter. Out of tolerance should be repaired and cut again.
2) internal edges whose height is not more than 8% of the wall thickness (maximum height is 0.8mm) are allowed for common pipes and pipelines. Overtolerance should be milled and recut.
3) for l2-level (N5) flaw detection, titanium tube shall not exceed 5% (maximum height is 0.5mm). Overtolerance should be milled and recut.
4) the sharp inner edge of the edge line should be polished and smooth.
Features: the surface of the titanium tube presents regular protrusion and no damage on the outer surface.
Causes: even roll grinding too large or off meat.
Inspection: inspect the inner edges according to the requirements.
Pull a concave
Features: the surface of titanium tube shows regular or irregular pits and no damage on the outer surface.
1) improper adjustment of continuous rolling, the rolling speed of each roller does not match.
2) uneven heating or excessively low temperature of the tube billet.
3) deviation of rolling center line, collision between titanium tube and roller after continuous rolling, etc. (note: this reason was put forward in January, 2001, and the principle is still being discussed).
Detection: no more than the negative deviation of the wall thickness, the actual wall thickness is greater than the minimum required value of the wall thickness is allowed to exist. Overshoot pull concave should be excised. (note: serious development of tension depression is called tension fracture, such injury should be strictly tested).
Internal thread (this defect only occurs in the axel unit)
Features: there are spiral traces on the surface of titanium tube, which are often found on the thin-walled tube surface, with obvious uneven feel. Causes:
1) inherent defects of diagonal rolling process. This defect is more prominent when the technical parameters of assel mill are not adjusted properly.
2) unreasonable distribution of deformation amount, assel wall reduction amount is too large.
3) improper configuration of axel rolling roll.
Inspection: the defect depth of titanium pipe thread is no more than 0.3mm and within certain tolerance range.
Fold the outside
Features: spiral laminar folding on the outer surface of titanium tube.
1) there are folds or cracks on the surface of the billet.
2) the subcutaneous pores and inclusions of the billet are serious.
3) the surface cleaning of tube billet is not good, or there are ears, wrong side, etc.
4) during the rolling process, the surface of the titanium tube is lifted and scratched. After rolling, it is pressed to the base of the titanium tube to form outer folding.
Inspection: it is not allowed to exist: slight grinding can be carried out, the actual value of wall thickness and outer diameter after grinding shall not be less than the minimum value required by the standard.
Characteristics: spiral or massive lamination and fracture on the surface of titanium tube.
Causes: serious nonmetallic inclusion, residual shrinkage cavity or serious loose etc.
Detection: not allowed to exist
Characteristics: titanium tube surface appeared spot scar.
1) roll adhesion titanium, aging, serious wear or roll abrasion.
2) there is foreign matter or serious wear on the conveying roller table.
1) external scarring distribution should be grinded or removed.
2) on the tube segment with external scar, if the external scar area exceeds 10%, it should be cut or polished.
3) external scarring with a depth exceeding 5% of the wall thickness should be polished.
4) the actual value of wall thickness and outside diameter at the grinding place shall not be less than the minimum value required by the standard.
Characteristics: the surface of titanium tube presents uneven pitting.
1) the titanium tube stays in the furnace for too long or is heated for too long, making the surface of the oxide iron sheet too thick, which is not clean and rolled into the surface of the titanium tube.
2) the high-pressure water phosphorus removal equipment does not work normally, and the phosphorus removal is not clean.
1) pockmarks with local negative deviation of wall thickness are allowed to exist.
2) the area of pockmarked surface shall not exceed 20% of the area of pockmarked pipe section.
3) the out-of-tolerance pit surface can be repaired or removed, and the actual value of wall thickness and outer diameter at the grinding place shall not be less than the minimum value required by the standard.
4) serious pockmarked waste.
The green line
Characteristics: the outer surface of titanium tube shows symmetrical or asymmetric linear rolling mark.
1) the diameter sizing machine is badly misaligned or worn.
2) unreasonable design of roll pass of sizing machine.
3) rolling titanium at low temperature.
4) roll processing is not good, roll edge chamfering is too small.
5) poor roll assembly, excessive gap, etc.
1) the allowable height of the outer surface of the casing should not exceed 0.2mm and the green line should be worn.
2) the high-pressure container pipes are not allowed to have green lines. Green lines must be removed if there is feeling. Grinding place should be smooth without edges.
3) the normal titanium pipe (structure, fluid, hydraulic support, etc.) is allowed to have a height less than 0.4mm green line, and the out-of-tolerance should be polished.
4) the sharp green lines should be polished to be smooth.
5) the actual value of wall thickness and outer diameter at the grinding place shall not exceed the minimum value required by the standard.
Characteristics: continuous or discontinuous hair-like fine lines appear on the outer surface of titanium tube.
1) the billet has subcutaneous pores or inclusions.
2) the surface cleaning of tube billet is not complete, and there are small cracks.
3) excessive wear and aging of rollers.
4) roll processing accuracy is not good.
Detection: visible hairline on the outer surface of titanium tube is not allowed. If it exists, it should be completely removed, and the actual wall thickness and outer diameter should not be less than the minimum required by the standard.
The reticular crack
Characteristics: the titanium tube has a fish-scale fissure on the outer surface with large pitch.
1) high content of harmful elements (such as arsenic) in the tube billet.
2) aging of punch roll and titanium adhesion.
3) guide plate adhesion titanium, etc.
Detection: should be completely removed. The actual wall thickness and outside diameter after cleaning shall not be less than the minimum required by the standard.
Features: titanium tube surface spiral or linear groove shape defects, most can see the bottom.
1) mechanical scratches are mainly caused by roll table, cold bed, straightening and transportation.
2) roll processing is not good or wear is serious or there is foreign matter in roll seam clamp.
1) local scratches not exceeding 0.5mm are allowed on the outer surface of the titanium tube, and scratches exceeding 0.5mm should be polished. The actual value of wall thickness and outside diameter at the grinding place shall not be less than the minimum value required by the standard.
2) scratches with sharp edges should be polished smooth.
Features: the outer surface of the titanium tube is concave and convex, but the thickness of the titanium tube is not damaged.
1) it is knocked flat in lifting.
2) flatten when biting.
3) after the sizing machine, the roller table is dented, etc.
Detection: local dent can exist without exceeding the negative deviation of outer diameter and the surface is smooth. Excision when out of tolerance.
Features: irregular scars on the outer surface of titanium tube due to collision.
Causes: can be produced in the cold zone and hot zone of various collision.
1) local bruising with a depth not exceeding 0.4mm is allowed on the outer surface.
2) if the damage exceeds 0.4mm, the grinding shall be smooth and the actual values of the outer diameter and wall thickness at the grinding place shall not be less than the minimum required by the standard.
Characteristics: the titanium tube surface is helical concave.
1) improper adjustment of the roller Angle of the straightener and excessive reduction.
2) serious wear of straightening roll.
Test: titanium tube outer surface is allowed to have no obvious edges and corners and the inner surface is not protruding, and the outer diameter size meets the tolerance requirements of the orthopedic. Excision of excess - standard orthopedics should be performed.
Features: titanium tube wall along the longitudinal partial or through length of the concave and convex wrinkles, the outer surface into a strip depression.
1) too small width coefficient selection.
2) improper adjustment of the mill leads to misalignment of the pass or inconsistent rolling center line.
3) improper distribution of each stand of continuous rolling mill.
Because of the above reasons, the metal enters into the gap of roll or the pipe loses its stability during the rolling process of titanium pipe, resulting in the wrinkling of the pipe wall.
Detection: not allowed to exist. Should be excised or disallowed.
Characteristics: the surface of titanium tube has the phenomenon of pulling and cracking, which is mainly produced on the thin-walled tube.
1) due to the uneven heating temperature of the billet, the deformation part is good, the part with low temperature pull rolling, when the pull is larger, the pipe will be pulled crack.
2) the influence of capillary wall thickness: when the capillary wall thickness supplied by the puncher is small, the metal deformation of the tandem mill is reduced compared with the designed deformation, resulting in the pulling rolling of the tandem mill and tearing when the pulling force is large.
3) severe inclusions exist locally in the pipe blank.
Detection: not allowed to exist. Should be excised or disallowed
Uneven wall thickness
Features: the wall thickness of titanium tube is not uniform on the same section, and there is a big difference between the maximum wall thickness and the minimum wall thickness.
1) uneven heating of tube billets.
2) the punch rolling line is not adjusted, the centering roll is not stable.
3) wear of the top or eccentric back hole of the top.
4) fill and correct the centering hole of the billet.
5) the bending and cutting Angle of the tube billet are too large.
Inspection: measure each branch and remove the uneven end of the wall thickness.
Wall thickness error
Features: the wall thickness of titanium tube is out of tolerance in one direction. Those with excess deviation are referred to as ultra-thin wall thickness.
1) uneven heating of tube billets.
2) improper adjustment of punch.
Inspection: measure by measure, the overshoot of the end should be excised, the overshoot of the whole length should be rescinded or rejected.
Outside diameter out-of-tolerance
Characteristics: the titanium tube outer diameter exceeds the standard, the excess positive difference is called the outside diameter is large, the excess negative difference is called the outside diameter is small.
1) excessive wear on the sizing machine pass or unreasonable design of the new pass.
2) unstable final rolling temperature.
Inspection: measure by measure, exceeding the standard should be given to change the sentence or reject.
Characteristics: the titanium tube is not straight along the length direction or has a goose-head bend at the end of the titanium tube, which is called "goose-head bend".
1) local water cooling during manual thermal inspection.
2) improper adjustment during straightening, serious wear of straightening roll.
3) improper sizing machining, assembly and adjustment.
4) bending during hoisting and transportation.
Inspection: when the bending degree exceeds the standard, it can be straightened twice, otherwise it will be rejected. "Goose-head bends" that cannot be straightened should be excised.
The length of the super poor
Features: the length of titanium tube exceeds the requirements, the over-positive difference is called long ruler, the over-negative difference is called short ruler.
1) tube billet length exceeds standard.
2) rolling instability.
3) bad control when cutting.
Inspection: long tube recut or rejudged, short tube rejudged or rejected